deltachat/

receive_imf.rs

//! Internet Message Format reception pipeline.

use std::cmp;
use std::collections::{BTreeMap, BTreeSet};
use std::iter;
use std::str::FromStr as _;
use std::sync::LazyLock;

use anyhow::{Context as _, Result, ensure};
use deltachat_contact_tools::{
    ContactAddress, addr_cmp, addr_normalize, may_be_valid_addr, sanitize_bidi_characters,
    sanitize_single_line,
};
use mailparse::SingleInfo;
use regex::Regex;

use crate::chat::{
    self, Chat, ChatId, ChatIdBlocked, ChatVisibility, is_contact_in_chat, save_broadcast_secret,
};
use crate::config::Config;
use crate::constants::{self, Blocked, Chattype, DC_CHAT_ID_TRASH, EDITED_PREFIX};
use crate::contact::{self, Contact, ContactId, Origin, mark_contact_id_as_verified};
use crate::context::Context;
use crate::debug_logging::maybe_set_logging_xdc_inner;
use crate::download::{DownloadState, msg_is_downloaded_for};
use crate::ephemeral::{Timer as EphemeralTimer, stock_ephemeral_timer_changed};
use crate::events::EventType;
use crate::headerdef::{HeaderDef, HeaderDefMap};
use crate::imap::{GENERATED_PREFIX, markseen_on_imap_table};
use crate::key::{DcKey, Fingerprint};
use crate::key::{
    load_self_public_key, load_self_public_key_opt, self_fingerprint, self_fingerprint_opt,
};
use crate::log::{LogExt as _, warn};
use crate::message::{
    self, Message, MessageState, MessengerMessage, MsgId, Viewtype, insert_tombstone,
    rfc724_mid_exists,
};
use crate::mimeparser::{
    AvatarAction, GossipedKey, MimeMessage, PreMessageMode, SystemMessage, parse_message_ids,
};
use crate::param::{Param, Params};
use crate::peer_channels::{add_gossip_peer_from_header, insert_topic_stub, iroh_topic_from_str};
use crate::reaction::{Reaction, set_msg_reaction};
use crate::rusqlite::OptionalExtension;
use crate::securejoin::{
    self, get_secure_join_step, handle_securejoin_handshake, observe_securejoin_on_other_device,
};
use crate::simplify;
use crate::smtp::msg_has_pending_smtp_job;
use crate::stats::STATISTICS_BOT_EMAIL;
use crate::stock_str;
use crate::sync::Sync::*;
use crate::tools::{
    self, buf_compress, normalize_text, remove_subject_prefix, validate_broadcast_secret,
};
use crate::{chatlist_events, ensure_and_debug_assert, ensure_and_debug_assert_eq, location};
use crate::{logged_debug_assert, mimeparser};

/// This is the struct that is returned after receiving one email (aka MIME message).
///
/// One email with multiple attachments can end up as multiple chat messages, but they
/// all have the same chat_id, state and sort_timestamp.
#[derive(Debug)]
pub struct ReceivedMsg {
    /// Chat the message is assigned to.
    pub chat_id: ChatId,

    /// Received message state.
    pub state: MessageState,

    /// Whether the message is hidden.
    pub hidden: bool,

    /// Message timestamp for sorting.
    pub sort_timestamp: i64,

    /// IDs of inserted rows in messages table.
    pub msg_ids: Vec<MsgId>,

    /// Whether IMAP messages should be immediately deleted.
    pub needs_delete_job: bool,
}

/// Decision on which kind of chat the message
/// should be assigned in.
///
/// This is done before looking up contact IDs
/// so we know in advance whether to lookup
/// key-contacts or email address contacts.
///
/// Once this decision is made,
/// it should not be changed so we
/// don't assign the message to an encrypted
/// group after looking up key-contacts
/// or vice versa.
#[derive(Debug)]
enum ChatAssignment {
    /// Trash the message.
    Trash,

    /// Group chat with a Group ID.
    ///
    /// Lookup key-contacts and
    /// assign to encrypted group.
    GroupChat { grpid: String },

    /// Mailing list or broadcast channel.
    ///
    /// Mailing lists don't have members.
    /// Broadcast channels have members
    /// on the sender side,
    /// but their addresses don't go into
    /// the `To` field.
    ///
    /// In any case, the `To`
    /// field should be ignored
    /// and no contact IDs should be looked
    /// up except the `from_id`
    /// which may be an email address contact
    /// or a key-contact.
    MailingListOrBroadcast,

    /// Group chat without a Group ID.
    ///
    /// This is not encrypted.
    AdHocGroup,

    /// Assign the message to existing chat
    /// with a known `chat_id`.
    ExistingChat {
        /// ID of existing chat
        /// which the message should be assigned to.
        chat_id: ChatId,

        /// Whether existing chat is blocked.
        /// This is loaded together with a chat ID
        /// reduce the number of database calls.
        ///
        /// We may want to unblock the chat
        /// after adding the message there
        /// if the chat is currently blocked.
        chat_id_blocked: Blocked,
    },

    /// 1:1 chat with a single contact.
    ///
    /// The chat may be encrypted or not,
    /// it does not matter.
    /// It is not possible to mix
    /// email address contacts
    /// with key-contacts in a single 1:1 chat anyway.
    OneOneChat,
}

/// Emulates reception of a message from the network.
///
/// This method returns errors on a failure to parse the mail or extract Message-ID. It's only used
/// for tests and REPL tool, not actual message reception pipeline.
#[cfg(any(test, feature = "internals"))]
pub async fn receive_imf(
    context: &Context,
    imf_raw: &[u8],
    seen: bool,
) -> Result<Option<ReceivedMsg>> {
    let mail = mailparse::parse_mail(imf_raw).context("can't parse mail")?;
    let rfc724_mid = crate::imap::prefetch_get_message_id(&mail.headers)
        .unwrap_or_else(crate::imap::create_message_id);
    receive_imf_from_inbox(context, &rfc724_mid, imf_raw, seen).await
}

/// Emulates reception of a message from "INBOX".
///
/// Only used for tests and REPL tool, not actual message reception pipeline.
#[cfg(any(test, feature = "internals"))]
pub(crate) async fn receive_imf_from_inbox(
    context: &Context,
    rfc724_mid: &str,
    imf_raw: &[u8],
    seen: bool,
) -> Result<Option<ReceivedMsg>> {
    receive_imf_inner(context, rfc724_mid, imf_raw, seen).await
}

async fn get_to_and_past_contact_ids(
    context: &Context,
    mime_parser: &MimeMessage,
    chat_assignment: &mut ChatAssignment,
    parent_message: &Option<Message>,
    incoming_origin: Origin,
) -> Result<(Vec<Option<ContactId>>, Vec<Option<ContactId>>)> {
    // `None` means that the chat is encrypted,
    // but we were not able to convert the address
    // to key-contact, e.g.
    // because there was no corresponding
    // Autocrypt-Gossip header.
    //
    // This way we still preserve remaining
    // number of contacts and their positions
    // so we can match the contacts to
    // e.g. Chat-Group-Member-Timestamps
    // header.
    let to_ids: Vec<Option<ContactId>>;
    let past_ids: Vec<Option<ContactId>>;

    // ID of the chat to look up the addresses in.
    //
    // Note that this is not necessarily the chat we want to assign the message to.
    // In case of an outgoing private reply to a group message we may
    // lookup the address of receipient in the list of addresses used in the group,
    // but want to assign the message to 1:1 chat.
    let chat_id = match chat_assignment {
        ChatAssignment::Trash => None,
        ChatAssignment::GroupChat { grpid } => {
            if let Some((chat_id, _blocked)) = chat::get_chat_id_by_grpid(context, grpid).await? {
                Some(chat_id)
            } else {
                None
            }
        }
        ChatAssignment::AdHocGroup => {
            // If we are going to assign a message to ad hoc group,
            // we can just convert the email addresses
            // to e-mail address contacts and don't need a `ChatId`
            // to lookup key-contacts.
            None
        }
        ChatAssignment::ExistingChat { chat_id, .. } => Some(*chat_id),
        ChatAssignment::MailingListOrBroadcast => None,
        ChatAssignment::OneOneChat => {
            if !mime_parser.incoming {
                parent_message.as_ref().map(|m| m.chat_id)
            } else {
                None
            }
        }
    };

    let member_fingerprints = mime_parser.chat_group_member_fingerprints();
    let to_member_fingerprints;
    let past_member_fingerprints;

    if !member_fingerprints.is_empty() {
        if member_fingerprints.len() >= mime_parser.recipients.len() {
            (to_member_fingerprints, past_member_fingerprints) =
                member_fingerprints.split_at(mime_parser.recipients.len());
        } else {
            warn!(
                context,
                "Unexpected length of the fingerprint header, expected at least {}, got {}.",
                mime_parser.recipients.len(),
                member_fingerprints.len()
            );
            to_member_fingerprints = &[];
            past_member_fingerprints = &[];
        }
    } else {
        to_member_fingerprints = &[];
        past_member_fingerprints = &[];
    }

    match chat_assignment {
        ChatAssignment::GroupChat { .. } => {
            to_ids = add_or_lookup_key_contacts(
                context,
                &mime_parser.recipients,
                &mime_parser.gossiped_keys,
                to_member_fingerprints,
                Origin::Hidden,
            )
            .await?;

            if let Some(chat_id) = chat_id {
                past_ids = lookup_key_contacts_fallback_to_chat(
                    context,
                    &mime_parser.past_members,
                    past_member_fingerprints,
                    Some(chat_id),
                )
                .await?;
            } else {
                past_ids = add_or_lookup_key_contacts(
                    context,
                    &mime_parser.past_members,
                    &mime_parser.gossiped_keys,
                    past_member_fingerprints,
                    Origin::Hidden,
                )
                .await?;
            }
        }
        ChatAssignment::Trash => {
            to_ids = Vec::new();
            past_ids = Vec::new();
        }
        ChatAssignment::ExistingChat { chat_id, .. } => {
            let chat = Chat::load_from_db(context, *chat_id).await?;
            if chat.is_encrypted(context).await? {
                to_ids = add_or_lookup_key_contacts(
                    context,
                    &mime_parser.recipients,
                    &mime_parser.gossiped_keys,
                    to_member_fingerprints,
                    Origin::Hidden,
                )
                .await?;
                past_ids = lookup_key_contacts_fallback_to_chat(
                    context,
                    &mime_parser.past_members,
                    past_member_fingerprints,
                    Some(*chat_id),
                )
                .await?;
            } else {
                to_ids = add_or_lookup_contacts_by_address_list(
                    context,
                    &mime_parser.recipients,
                    if !mime_parser.incoming {
                        Origin::OutgoingTo
                    } else if incoming_origin.is_known() {
                        Origin::IncomingTo
                    } else {
                        Origin::IncomingUnknownTo
                    },
                )
                .await?;

                past_ids = add_or_lookup_contacts_by_address_list(
                    context,
                    &mime_parser.past_members,
                    Origin::Hidden,
                )
                .await?;
            }
        }
        ChatAssignment::AdHocGroup => {
            to_ids = add_or_lookup_contacts_by_address_list(
                context,
                &mime_parser.recipients,
                if !mime_parser.incoming {
                    Origin::OutgoingTo
                } else if incoming_origin.is_known() {
                    Origin::IncomingTo
                } else {
                    Origin::IncomingUnknownTo
                },
            )
            .await?;

            past_ids = add_or_lookup_contacts_by_address_list(
                context,
                &mime_parser.past_members,
                Origin::Hidden,
            )
            .await?;
        }
        // Sometimes, messages are sent just to a single recipient
        // in a broadcast (e.g. securejoin messages).
        // In this case, we need to look them up like in a 1:1 chat:
        ChatAssignment::OneOneChat | ChatAssignment::MailingListOrBroadcast => {
            let pgp_to_ids = add_or_lookup_key_contacts(
                context,
                &mime_parser.recipients,
                &mime_parser.gossiped_keys,
                to_member_fingerprints,
                Origin::Hidden,
            )
            .await?;
            if pgp_to_ids
                .first()
                .is_some_and(|contact_id| contact_id.is_some())
            {
                // There is a single recipient and we have
                // mapped it to a key contact.
                // This is an encrypted 1:1 chat.
                to_ids = pgp_to_ids
            } else {
                let ids = if mime_parser.was_encrypted() {
                    let mut recipient_fps = mime_parser
                        .signature
                        .as_ref()
                        .map(|(_, recipient_fps)| recipient_fps.iter().cloned().collect::<Vec<_>>())
                        .unwrap_or_default();
                    // If there are extra recipient fingerprints, it may be a non-chat "implicit
                    // Bcc" message. Fall back to in-chat lookup if so.
                    if !recipient_fps.is_empty() && recipient_fps.len() <= 2 {
                        let self_fp = load_self_public_key(context).await?.dc_fingerprint();
                        recipient_fps.retain(|fp| *fp != self_fp);
                        if recipient_fps.is_empty() {
                            vec![Some(ContactId::SELF)]
                        } else {
                            add_or_lookup_key_contacts(
                                context,
                                &mime_parser.recipients,
                                &mime_parser.gossiped_keys,
                                &recipient_fps,
                                Origin::Hidden,
                            )
                            .await?
                        }
                    } else {
                        lookup_key_contacts_fallback_to_chat(
                            context,
                            &mime_parser.recipients,
                            to_member_fingerprints,
                            chat_id,
                        )
                        .await?
                    }
                } else {
                    vec![]
                };
                if mime_parser.was_encrypted() && !ids.contains(&None)
                // Prefer creating PGP chats if there are any key-contacts. At least this prevents
                // from replying unencrypted. Otherwise downgrade to a non-replyable ad-hoc group.
                || ids
                    .iter()
                    .any(|&c| c.is_some() && c != Some(ContactId::SELF))
                {
                    to_ids = ids;
                } else {
                    if mime_parser.was_encrypted() {
                        warn!(
                            context,
                            "No key-contact looked up. Downgrading to AdHocGroup."
                        );
                        *chat_assignment = ChatAssignment::AdHocGroup;
                    }
                    to_ids = add_or_lookup_contacts_by_address_list(
                        context,
                        &mime_parser.recipients,
                        if !mime_parser.incoming {
                            Origin::OutgoingTo
                        } else if incoming_origin.is_known() {
                            Origin::IncomingTo
                        } else {
                            Origin::IncomingUnknownTo
                        },
                    )
                    .await?;
                }
            }

            past_ids = add_or_lookup_contacts_by_address_list(
                context,
                &mime_parser.past_members,
                Origin::Hidden,
            )
            .await?;
        }
    };

    Ok((to_ids, past_ids))
}

/// Receive a message and add it to the database.
///
/// Returns an error on database failure or if the message is broken,
/// e.g. has nonstandard MIME structure.
///
/// If possible, creates a database entry to prevent the message from being
/// downloaded again, sets `chat_id=DC_CHAT_ID_TRASH` and returns `Ok(Some(…))`.
/// If the message is so wrong that we didn't even create a database entry,
/// returns `Ok(None)`.
pub(crate) async fn receive_imf_inner(
    context: &Context,
    rfc724_mid: &str,
    imf_raw: &[u8],
    seen: bool,
) -> Result<Option<ReceivedMsg>> {
    ensure!(
        !context
            .get_config_bool(Config::SimulateReceiveImfError)
            .await?
    );
    if std::env::var(crate::DCC_MIME_DEBUG).is_ok() {
        info!(
            context,
            "receive_imf: incoming message mime-body:\n{}",
            String::from_utf8_lossy(imf_raw),
        );
    }

    let trash = || async {
        let msg_ids = vec![insert_tombstone(context, rfc724_mid).await?];
        Ok(Some(ReceivedMsg {
            chat_id: DC_CHAT_ID_TRASH,
            state: MessageState::Undefined,
            hidden: false,
            sort_timestamp: 0,
            msg_ids,
            needs_delete_job: false,
        }))
    };

    let mut mime_parser = match MimeMessage::from_bytes(context, imf_raw).await {
        Err(err) => {
            warn!(context, "receive_imf: can't parse MIME: {err:#}.");
            if rfc724_mid.starts_with(GENERATED_PREFIX) {
                // We don't have an rfc724_mid, there's no point in adding a trash entry
                return Ok(None);
            }
            return trash().await;
        }
        Ok(mime_parser) => mime_parser,
    };

    let rfc724_mid_orig = &mime_parser
        .get_rfc724_mid()
        .unwrap_or(rfc724_mid.to_string());

    if let Some((_, recipient_fps)) = &mime_parser.signature
        && !recipient_fps.is_empty()
        && let Some(self_pubkey) = load_self_public_key_opt(context).await?
        && !recipient_fps.contains(&self_pubkey.dc_fingerprint())
    {
        warn!(
            context,
            "Message {rfc724_mid_orig:?} is not intended for us (TRASH)."
        );
        return trash().await;
    }
    info!(
        context,
        "Receiving message {rfc724_mid_orig:?}, seen={seen}...",
    );

    // These checks must be done before processing of SecureJoin and other special messages.
    if mime_parser.pre_message == mimeparser::PreMessageMode::Post {
        // Post-Message just replaces the attachment and modifies Params, not the whole message.
        // This is done in the `handle_post_message` method.
    } else if let Some(msg_id) = message::rfc724_mid_exists(context, rfc724_mid_orig).await? {
        info!(
            context,
            "Message {rfc724_mid} is already in some chat or deleted."
        );
        if mime_parser.incoming {
            return Ok(None);
        }
        // For the case if we missed a successful SMTP response. Be optimistic that the message is
        // delivered also.
        let self_addr = context.get_primary_self_addr().await?;
        context
            .sql
            .execute(
                "DELETE FROM smtp \
                WHERE rfc724_mid=?1 AND (recipients LIKE ?2 OR recipients LIKE ('% ' || ?2))",
                (rfc724_mid_orig, &self_addr),
            )
            .await?;
        if !msg_has_pending_smtp_job(context, msg_id).await? {
            msg_id.set_delivered(context).await?;
        }
        return Ok(None);
    }

    let prevent_rename = should_prevent_rename(&mime_parser);

    // get From: (it can be an address list!) and check if it is known (for known From:'s we add
    // the other To:/Cc: in the 3rd pass)
    // or if From: is equal to SELF (in this case, it is any outgoing messages,
    // we do not check Return-Path any more as this is unreliable, see
    // <https://github.com/deltachat/deltachat-core/issues/150>)
    //
    // If this is a mailing list email (i.e. list_id_header is some), don't change the displayname because in
    // a mailing list the sender displayname sometimes does not belong to the sender email address.
    // For example, GitHub sends messages from `notifications@github.com`,
    // but uses display name of the user whose action generated the notification
    // as the display name.
    let fingerprint = mime_parser.signature.as_ref().map(|(fp, _)| fp);
    let (from_id, _from_id_blocked, incoming_origin) = match from_field_to_contact_id(
        context,
        &mime_parser.from,
        fingerprint,
        prevent_rename,
        false,
    )
    .await?
    {
        Some(contact_id_res) => contact_id_res,
        None => {
            warn!(
                context,
                "receive_imf: From field does not contain an acceptable address."
            );
            return Ok(None);
        }
    };

    // Lookup parent message.
    //
    // This may be useful to assign the message to
    // group chats without Chat-Group-ID
    // when a message is sent by Thunderbird.
    //
    // This can be also used to lookup
    // key-contact by email address
    // when receiving a private 1:1 reply
    // to a group chat message.
    let parent_message = get_parent_message(
        context,
        mime_parser.get_header(HeaderDef::References),
        mime_parser.get_header(HeaderDef::InReplyTo),
    )
    .await?;

    let mut chat_assignment =
        decide_chat_assignment(context, &mime_parser, &parent_message, rfc724_mid, from_id).await?;
    let (to_ids, past_ids) = get_to_and_past_contact_ids(
        context,
        &mime_parser,
        &mut chat_assignment,
        &parent_message,
        incoming_origin,
    )
    .await?;

    let received_msg;
    if let Some(_step) = get_secure_join_step(&mime_parser) {
        let res = if mime_parser.incoming {
            handle_securejoin_handshake(context, &mut mime_parser, from_id)
                .await
                .with_context(|| {
                    format!(
                        "Error in Secure-Join '{}' message handling",
                        mime_parser.get_header(HeaderDef::SecureJoin).unwrap_or("")
                    )
                })?
        } else if let Some(to_id) = to_ids.first().copied().flatten() {
            // handshake may mark contacts as verified and must be processed before chats are created
            observe_securejoin_on_other_device(context, &mime_parser, to_id)
                .await
                .with_context(|| {
                    format!(
                        "Error in Secure-Join '{}' watching",
                        mime_parser.get_header(HeaderDef::SecureJoin).unwrap_or("")
                    )
                })?
        } else {
            securejoin::HandshakeMessage::Propagate
        };

        match res {
            securejoin::HandshakeMessage::Done | securejoin::HandshakeMessage::Ignore => {
                let msg_id = insert_tombstone(context, rfc724_mid).await?;
                received_msg = Some(ReceivedMsg {
                    chat_id: DC_CHAT_ID_TRASH,
                    state: MessageState::InSeen,
                    hidden: false,
                    sort_timestamp: mime_parser.timestamp_sent,
                    msg_ids: vec![msg_id],
                    needs_delete_job: res == securejoin::HandshakeMessage::Done,
                });
            }
            securejoin::HandshakeMessage::Propagate => {
                received_msg = None;
            }
        }
    } else {
        received_msg = None;
    }

    let verified_encryption = has_verified_encryption(context, &mime_parser, from_id).await?;

    if verified_encryption == VerifiedEncryption::Verified {
        mark_recipients_as_verified(context, from_id, &mime_parser).await?;
    }

    let is_old_contact_request;
    let received_msg = if let Some(received_msg) = received_msg {
        is_old_contact_request = false;
        received_msg
    } else {
        let is_dc_message = if mime_parser.has_chat_version() {
            MessengerMessage::Yes
        } else if let Some(parent_message) = &parent_message {
            match parent_message.is_dc_message {
                MessengerMessage::No => MessengerMessage::No,
                MessengerMessage::Yes | MessengerMessage::Reply => MessengerMessage::Reply,
            }
        } else {
            MessengerMessage::No
        };

        let allow_creation = if mime_parser.decryption_error.is_some() {
            false
        } else {
            !mime_parser.parts.iter().all(|part| part.is_reaction)
        };

        let to_id = if mime_parser.incoming {
            ContactId::SELF
        } else {
            to_ids.first().copied().flatten().unwrap_or(ContactId::SELF)
        };

        let (chat_id, chat_id_blocked, is_created) = do_chat_assignment(
            context,
            &chat_assignment,
            from_id,
            &to_ids,
            &past_ids,
            to_id,
            allow_creation,
            &mut mime_parser,
            parent_message,
        )
        .await?;
        is_old_contact_request = chat_id_blocked == Blocked::Request && !is_created;

        // Add parts
        add_parts(
            context,
            &mut mime_parser,
            imf_raw,
            &to_ids,
            &past_ids,
            rfc724_mid_orig,
            from_id,
            seen,
            prevent_rename,
            chat_id,
            chat_id_blocked,
            is_dc_message,
            is_created,
        )
        .await
        .context("add_parts error")?
    };

    if !from_id.is_special() {
        contact::update_last_seen(context, from_id, mime_parser.timestamp_sent).await?;
    }

    // Update gossiped timestamp for the chat if someone else or our other device sent
    // Autocrypt-Gossip header to avoid sending Autocrypt-Gossip ourselves
    // and waste traffic.
    let chat_id = received_msg.chat_id;
    if !chat_id.is_special() {
        for gossiped_key in mime_parser.gossiped_keys.values() {
            context
                .sql
                .transaction(move |transaction| {
                    let fingerprint = gossiped_key.public_key.dc_fingerprint().hex();
                    transaction.execute(
                        "INSERT INTO gossip_timestamp (chat_id, fingerprint, timestamp)
                         VALUES                       (?, ?, ?)
                         ON CONFLICT                  (chat_id, fingerprint)
                         DO UPDATE SET timestamp=MAX(timestamp, excluded.timestamp)",
                        (chat_id, &fingerprint, mime_parser.timestamp_sent),
                    )?;

                    Ok(())
                })
                .await?;
        }
    }

    let insert_msg_id = if let Some(msg_id) = received_msg.msg_ids.last() {
        *msg_id
    } else {
        MsgId::new_unset()
    };

    save_locations(context, &mime_parser, chat_id, from_id, insert_msg_id).await?;

    if let Some(ref sync_items) = mime_parser.sync_items {
        if from_id == ContactId::SELF {
            if mime_parser.was_encrypted() {
                context
                    .execute_sync_items(sync_items, mime_parser.timestamp_sent)
                    .await;

                // Receiving encrypted message from self updates primary transport.
                let from_addr = &mime_parser.from.addr;

                let transport_changed = context
                    .sql
                    .transaction(|transaction| {
                        let transport_exists = transaction.query_row(
                            "SELECT COUNT(*) FROM transports WHERE addr=?",
                            (from_addr,),
                            |row| {
                                let count: i64 = row.get(0)?;
                                Ok(count > 0)
                            },
                        )?;

                        let transport_changed = if transport_exists {
                            transaction.execute(
                                "
UPDATE config SET value=? WHERE keyname='configured_addr' AND value!=?1
                                ",
                                (from_addr,),
                            )? > 0
                        } else {
                            warn!(
                                context,
                                "Received sync message from unknown address {from_addr:?}."
                            );
                            false
                        };
                        Ok(transport_changed)
                    })
                    .await?;
                if transport_changed {
                    info!(context, "Primary transport changed to {from_addr:?}.");
                    context.sql.uncache_raw_config("configured_addr").await;
                    context.self_public_key.lock().await.take();

                    context.emit_event(EventType::TransportsModified);
                }
            } else {
                warn!(context, "Sync items are not encrypted.");
            }
        } else {
            warn!(context, "Sync items not sent by self.");
        }
    }

    if let Some(ref status_update) = mime_parser.webxdc_status_update {
        let can_info_msg;
        let instance = if mime_parser
            .parts
            .first()
            .is_some_and(|part| part.typ == Viewtype::Webxdc)
        {
            can_info_msg = false;
            if mime_parser.pre_message == PreMessageMode::Post
                && let Some(msg_id) = message::rfc724_mid_exists(context, rfc724_mid_orig).await?
            {
                // The messsage is a post-message and pre-message exists.
                // Assign status update to existing message because just received post-message will be trashed.
                Some(
                    Message::load_from_db(context, msg_id)
                        .await
                        .context("Failed to load webxdc instance that we just checked exists")?,
                )
            } else {
                Some(
                    Message::load_from_db(context, insert_msg_id)
                        .await
                        .context("Failed to load just created webxdc instance")?,
                )
            }
        } else if let Some(field) = mime_parser.get_header(HeaderDef::InReplyTo) {
            if let Some(instance) =
                message::get_by_rfc724_mids(context, &parse_message_ids(field)).await?
            {
                can_info_msg = instance.download_state() == DownloadState::Done;
                Some(instance)
            } else {
                can_info_msg = false;
                None
            }
        } else {
            can_info_msg = false;
            None
        };

        if let Some(instance) = instance {
            if let Err(err) = context
                .receive_status_update(
                    from_id,
                    &instance,
                    received_msg.sort_timestamp,
                    can_info_msg,
                    status_update,
                )
                .await
            {
                warn!(context, "receive_imf cannot update status: {err:#}.");
            }
        } else {
            warn!(
                context,
                "Received webxdc update, but cannot assign it to message."
            );
        }
    }

    if let Some(avatar_action) = &mime_parser.user_avatar
        && !matches!(from_id, ContactId::UNDEFINED | ContactId::SELF)
        && context
            .update_contacts_timestamp(from_id, Param::AvatarTimestamp, mime_parser.timestamp_sent)
            .await?
        && let Err(err) = contact::set_profile_image(context, from_id, avatar_action).await
    {
        warn!(context, "receive_imf cannot update profile image: {err:#}.");
    };

    // Ignore footers from mailinglists as they are often created or modified by the mailinglist software.
    if let Some(footer) = &mime_parser.footer
        && !mime_parser.is_mailinglist_message()
        && !matches!(from_id, ContactId::UNDEFINED | ContactId::SELF)
        && context
            .update_contacts_timestamp(from_id, Param::StatusTimestamp, mime_parser.timestamp_sent)
            .await?
        && let Err(err) = contact::set_status(context, from_id, footer.to_string()).await
    {
        warn!(context, "Cannot update contact status: {err:#}.");
    }

    // Get user-configured server deletion
    let delete_server_after = context.get_config_delete_server_after().await?;

    if !received_msg.msg_ids.is_empty() {
        let target = if received_msg.needs_delete_job || delete_server_after == Some(0) {
            Some("".to_string())
        } else {
            None
        };
        if target.is_some() || rfc724_mid_orig != rfc724_mid {
            let target_subst = match &target {
                Some(_) => "target=?1,",
                None => "",
            };
            context
                .sql
                .execute(
                    &format!("UPDATE imap SET {target_subst} rfc724_mid=?2 WHERE rfc724_mid=?3"),
                    (
                        target.as_deref().unwrap_or_default(),
                        rfc724_mid_orig,
                        rfc724_mid,
                    ),
                )
                .await?;
            context.scheduler.interrupt_inbox().await;
        }
        if target.is_none() && !mime_parser.mdn_reports.is_empty() && mime_parser.has_chat_version()
        {
            // This is a Delta Chat MDN. Mark as read.
            markseen_on_imap_table(context, rfc724_mid_orig).await?;
        }
        if !mime_parser.incoming && !context.get_config_bool(Config::TeamProfile).await? {
            let mut updated_chats = BTreeMap::new();
            let mut archived_chats_maybe_noticed = false;
            for report in &mime_parser.mdn_reports {
                for msg_rfc724_mid in report
                    .original_message_id
                    .iter()
                    .chain(&report.additional_message_ids)
                {
                    let Some(msg_id) = rfc724_mid_exists(context, msg_rfc724_mid).await? else {
                        continue;
                    };
                    let Some(msg) = Message::load_from_db_optional(context, msg_id).await? else {
                        continue;
                    };
                    if msg.state < MessageState::InFresh || msg.state >= MessageState::InSeen {
                        continue;
                    }
                    if !mime_parser.was_encrypted() && msg.get_showpadlock() {
                        warn!(context, "MDN: Not encrypted. Ignoring.");
                        continue;
                    }
                    message::update_msg_state(context, msg_id, MessageState::InSeen).await?;
                    if let Err(e) = msg_id.start_ephemeral_timer(context).await {
                        error!(context, "start_ephemeral_timer for {msg_id}: {e:#}.");
                    }
                    if !mime_parser.has_chat_version() {
                        continue;
                    }
                    archived_chats_maybe_noticed |= msg.state < MessageState::InNoticed
                        && msg.chat_visibility == ChatVisibility::Archived;
                    updated_chats
                        .entry(msg.chat_id)
                        .and_modify(|pos| *pos = cmp::max(*pos, (msg.timestamp_sort, msg.id)))
                        .or_insert((msg.timestamp_sort, msg.id));
                }
            }
            for (chat_id, (timestamp_sort, msg_id)) in updated_chats {
                context
                    .sql
                    .execute(
                        "
UPDATE msgs SET state=? WHERE
    state=? AND
    hidden=0 AND
    chat_id=? AND
    (timestamp,id)<(?,?)",
                        (
                            MessageState::InNoticed,
                            MessageState::InFresh,
                            chat_id,
                            timestamp_sort,
                            msg_id,
                        ),
                    )
                    .await
                    .context("UPDATE msgs.state")?;
                if chat_id.get_fresh_msg_cnt(context).await? == 0 {
                    // Removes all notifications for the chat in UIs.
                    context.emit_event(EventType::MsgsNoticed(chat_id));
                } else {
                    context.emit_msgs_changed_without_msg_id(chat_id);
                }
                chatlist_events::emit_chatlist_item_changed(context, chat_id);
            }
            if archived_chats_maybe_noticed {
                context.on_archived_chats_maybe_noticed();
            }
        }
    }

    if mime_parser.is_call() {
        context
            .handle_call_msg(insert_msg_id, &mime_parser, from_id)
            .await?;
    } else if received_msg.hidden {
        // No need to emit an event about the changed message
    } else if !chat_id.is_trash() {
        let fresh = received_msg.state == MessageState::InFresh
            && mime_parser.is_system_message != SystemMessage::CallAccepted
            && mime_parser.is_system_message != SystemMessage::CallEnded;
        let is_bot = context.get_config_bool(Config::Bot).await?;
        let is_pre_message = matches!(mime_parser.pre_message, PreMessageMode::Pre { .. });
        let skip_bot_notify = is_bot && is_pre_message;
        let is_empty = !is_pre_message
            && mime_parser.parts.first().is_none_or(|p| {
                p.typ == Viewtype::Text && p.msg.is_empty() && p.param.get(Param::Quote).is_none()
            });
        let important = mime_parser.incoming
            && !is_empty
            && fresh
            && !is_old_contact_request
            && !skip_bot_notify;

        for msg_id in &received_msg.msg_ids {
            chat_id.emit_msg_event(context, *msg_id, important);
        }
    }
    context.new_msgs_notify.notify_one();

    mime_parser
        .handle_reports(context, from_id, &mime_parser.parts)
        .await;

    if let Some(is_bot) = mime_parser.is_bot {
        // If the message is auto-generated and was generated by Delta Chat,
        // mark the contact as a bot.
        if mime_parser.get_header(HeaderDef::ChatVersion).is_some() {
            from_id.mark_bot(context, is_bot).await?;
        }
    }

    Ok(Some(received_msg))
}

/// Converts "From" field to contact id.
///
/// Also returns whether it is blocked or not and its origin.
///
/// * `prevent_rename`: if true, the display_name of this contact will not be changed. Useful for
///   mailing lists: In some mailing lists, many users write from the same address but with different
///   display names. We don't want the display name to change every time the user gets a new email from
///   a mailing list.
///
/// * `find_key_contact_by_addr`: if true, we only know the e-mail address
///   of the contact, but not the fingerprint,
///   yet want to assign the message to some key-contact.
///   This can happen during prefetch.
///   If we get it wrong, the message will be placed into the correct
///   chat after downloading.
///
/// Returns `None` if From field does not contain a valid contact address.
pub async fn from_field_to_contact_id(
    context: &Context,
    from: &SingleInfo,
    fingerprint: Option<&Fingerprint>,
    prevent_rename: bool,
    find_key_contact_by_addr: bool,
) -> Result<Option<(ContactId, bool, Origin)>> {
    let fingerprint = fingerprint.as_ref().map(|fp| fp.hex()).unwrap_or_default();
    let display_name = if prevent_rename {
        Some("")
    } else {
        from.display_name.as_deref()
    };
    let from_addr = match ContactAddress::new(&from.addr) {
        Ok(from_addr) => from_addr,
        Err(err) => {
            warn!(
                context,
                "Cannot create a contact for the given From field: {err:#}."
            );
            return Ok(None);
        }
    };

    if fingerprint.is_empty() && find_key_contact_by_addr {
        let addr_normalized = addr_normalize(&from_addr);

        // Try to assign to some key-contact.
        if let Some((from_id, origin)) = context
            .sql
            .query_row_optional(
                "SELECT id, origin FROM contacts
                 WHERE addr=?1 COLLATE NOCASE
                 AND fingerprint<>'' -- Only key-contacts
                 AND id>?2 AND origin>=?3 AND blocked=?4
                 ORDER BY last_seen DESC
                 LIMIT 1",
                (
                    &addr_normalized,
                    ContactId::LAST_SPECIAL,
                    Origin::IncomingUnknownFrom,
                    Blocked::Not,
                ),
                |row| {
                    let id: ContactId = row.get(0)?;
                    let origin: Origin = row.get(1)?;
                    Ok((id, origin))
                },
            )
            .await?
        {
            return Ok(Some((from_id, false, origin)));
        }
    }

    let (from_id, _) = Contact::add_or_lookup_ex(
        context,
        display_name.unwrap_or_default(),
        &from_addr,
        &fingerprint,
        Origin::IncomingUnknownFrom,
    )
    .await?;

    if from_id == ContactId::SELF {
        Ok(Some((ContactId::SELF, false, Origin::OutgoingBcc)))
    } else {
        let contact = Contact::get_by_id(context, from_id).await?;
        let from_id_blocked = contact.blocked;
        let incoming_origin = contact.origin;

        context
            .sql
            .execute(
                "UPDATE contacts SET addr=? WHERE id=?",
                (from_addr, from_id),
            )
            .await?;

        Ok(Some((from_id, from_id_blocked, incoming_origin)))
    }
}

#[expect(clippy::arithmetic_side_effects)]
async fn decide_chat_assignment(
    context: &Context,
    mime_parser: &MimeMessage,
    parent_message: &Option<Message>,
    rfc724_mid: &str,
    from_id: ContactId,
) -> Result<ChatAssignment> {
    let mut should_trash = if !mime_parser.mdn_reports.is_empty() {
        info!(context, "Message is an MDN (TRASH).");
        true
    } else if mime_parser.delivery_report.is_some() {
        info!(context, "Message is a DSN (TRASH).");
        markseen_on_imap_table(context, rfc724_mid).await.ok();
        true
    } else if mime_parser.get_header(HeaderDef::ChatEdit).is_some()
        || mime_parser.get_header(HeaderDef::ChatDelete).is_some()
        || mime_parser.get_header(HeaderDef::IrohNodeAddr).is_some()
        || mime_parser.sync_items.is_some()
    {
        info!(context, "Chat edit/delete/iroh/sync message (TRASH).");
        true
    } else if mime_parser.is_system_message == SystemMessage::CallAccepted
        || mime_parser.is_system_message == SystemMessage::CallEnded
    {
        info!(context, "Call state changed (TRASH).");
        true
    } else if let Some(ref decryption_error) = mime_parser.decryption_error
        && !mime_parser.incoming
    {
        // Outgoing undecryptable message.
        let last_time = context
            .get_config_i64(Config::LastCantDecryptOutgoingMsgs)
            .await?;
        let now = tools::time();
        let update_config = if last_time.saturating_add(24 * 60 * 60) <= now {
            let txt = format!(
                "⚠️ It seems you are using Delta Chat on multiple devices that cannot decrypt each other's outgoing messages. To fix this, on the older device use \"Settings / Add Second Device\" and follow the instructions. (Error: {decryption_error}, {rfc724_mid})."
            );
            let mut msg = Message::new_text(txt.to_string());
            chat::add_device_msg(context, None, Some(&mut msg))
                .await
                .log_err(context)
                .ok();
            true
        } else {
            last_time > now
        };
        if update_config {
            context
                .set_config_internal(Config::LastCantDecryptOutgoingMsgs, Some(&now.to_string()))
                .await?;
        }
        info!(context, "Outgoing undecryptable message (TRASH).");
        true
    } else if mime_parser
        .get_header(HeaderDef::XMozillaDraftInfo)
        .is_some()
    {
        // Mozilla Thunderbird does not set \Draft flag on "Templates", but sets
        // X-Mozilla-Draft-Info header, which can be used to detect both drafts and templates
        // created by Thunderbird.

        // Most mailboxes have a "Drafts" folder where constantly new emails appear but we don't actually want to show them
        info!(context, "Email is probably just a draft (TRASH).");
        true
    } else if mime_parser.webxdc_status_update.is_some() && mime_parser.parts.len() == 1 {
        if let Some(part) = mime_parser.parts.first() {
            if part.typ == Viewtype::Text && part.msg.is_empty() {
                info!(context, "Message is a status update only (TRASH).");
                markseen_on_imap_table(context, rfc724_mid).await.ok();
                true
            } else {
                false
            }
        } else {
            false
        }
    } else {
        false
    };

    should_trash |= if mime_parser.pre_message == PreMessageMode::Post {
        // if pre message exist, then trash after replacing, otherwise treat as normal message
        let pre_message_exists = msg_is_downloaded_for(context, rfc724_mid).await?;
        info!(
            context,
            "Message {rfc724_mid} is a post-message ({}).",
            if pre_message_exists {
                "pre-message exists already, so trash after replacing attachment"
            } else {
                "no pre-message -> Keep"
            }
        );
        pre_message_exists
    } else if let PreMessageMode::Pre {
        post_msg_rfc724_mid,
        ..
    } = &mime_parser.pre_message
    {
        let post_msg_exists = if let Some((msg_id, not_downloaded)) =
            message::rfc724_mid_exists_ex(context, post_msg_rfc724_mid, "download_state<>0").await?
        {
            context
                .sql
                .execute(
                    "UPDATE msgs SET pre_rfc724_mid=? WHERE id=?",
                    (rfc724_mid, msg_id),
                )
                .await?;
            !not_downloaded
        } else {
            false
        };
        info!(
            context,
            "Message {rfc724_mid} is a pre-message for {post_msg_rfc724_mid} (post_msg_exists:{post_msg_exists})."
        );
        post_msg_exists
    } else {
        false
    };

    // Decide on the type of chat we assign the message to.
    //
    // The chat may not exist yet, i.e. there may be
    // no database row and ChatId yet.
    let mut num_recipients = 0;
    let mut has_self_addr = false;

    if let Some((sender_fingerprint, intended_recipient_fingerprints)) = mime_parser
        .signature
        .as_ref()
        .filter(|(_sender_fingerprint, fps)| !fps.is_empty())
    {
        // The message is signed and has intended recipient fingerprints.

        // If the message has intended recipient fingerprint and is not trashed already,
        // then it is intended for us.
        has_self_addr = true;

        num_recipients = intended_recipient_fingerprints
            .iter()
            .filter(|fp| *fp != sender_fingerprint)
            .count();
    } else {
        // Message has no intended recipient fingerprints
        // or is not signed, count the `To` field recipients.
        for recipient in &mime_parser.recipients {
            has_self_addr |= context.is_self_addr(&recipient.addr).await?;
            if addr_cmp(&recipient.addr, &mime_parser.from.addr) {
                continue;
            }
            num_recipients += 1;
        }
        if from_id != ContactId::SELF && !has_self_addr {
            num_recipients += 1;
        }
    }
    let mut can_be_11_chat_log = String::new();
    let mut l = |cond: bool, s: String| {
        can_be_11_chat_log += &s;
        cond
    };
    let can_be_11_chat = l(
        num_recipients <= 1,
        format!("num_recipients={num_recipients}."),
    ) && (l(from_id != ContactId::SELF, format!(" from_id={from_id}."))
        || !(l(
            mime_parser.recipients.is_empty(),
            format!(" Raw recipients len={}.", mime_parser.recipients.len()),
        ) || l(has_self_addr, format!(" has_self_addr={has_self_addr}.")))
        || l(
            mime_parser.was_encrypted(),
            format!(" was_encrypted={}.", mime_parser.was_encrypted()),
        ));

    let chat_assignment_log;
    let chat_assignment = if should_trash {
        chat_assignment_log = "".to_string();
        ChatAssignment::Trash
    } else if mime_parser.get_mailinglist_header().is_some() {
        chat_assignment_log = "Mailing list header found.".to_string();
        ChatAssignment::MailingListOrBroadcast
    } else if let Some(grpid) = mime_parser.get_chat_group_id() {
        if mime_parser.was_encrypted() {
            chat_assignment_log = "Encrypted group message.".to_string();
            ChatAssignment::GroupChat {
                grpid: grpid.to_string(),
            }
        } else if let Some(parent) = &parent_message {
            if let Some((chat_id, chat_id_blocked)) =
                lookup_chat_by_reply(context, mime_parser, parent).await?
            {
                // Try to assign to a chat based on In-Reply-To/References.
                chat_assignment_log = "Unencrypted group reply.".to_string();
                ChatAssignment::ExistingChat {
                    chat_id,
                    chat_id_blocked,
                }
            } else {
                chat_assignment_log = "Unencrypted group reply.".to_string();
                ChatAssignment::AdHocGroup
            }
        } else {
            // Could be a message from old version
            // with opportunistic encryption.
            //
            // We still want to assign this to a group
            // even if it had only two members.
            //
            // Group ID is ignored, however.
            chat_assignment_log = "Unencrypted group message, no parent.".to_string();
            ChatAssignment::AdHocGroup
        }
    } else if let Some(parent) = &parent_message {
        if let Some((chat_id, chat_id_blocked)) =
            lookup_chat_by_reply(context, mime_parser, parent).await?
        {
            // Try to assign to a chat based on In-Reply-To/References.
            chat_assignment_log = "Reply w/o grpid.".to_string();
            ChatAssignment::ExistingChat {
                chat_id,
                chat_id_blocked,
            }
        } else if mime_parser.get_header(HeaderDef::ChatGroupName).is_some() {
            chat_assignment_log = "Reply with Chat-Group-Name.".to_string();
            ChatAssignment::AdHocGroup
        } else if can_be_11_chat {
            chat_assignment_log = format!("Non-group reply. {can_be_11_chat_log}");
            ChatAssignment::OneOneChat
        } else {
            chat_assignment_log = format!("Non-group reply. {can_be_11_chat_log}");
            ChatAssignment::AdHocGroup
        }
    } else if mime_parser.get_header(HeaderDef::ChatGroupName).is_some() {
        chat_assignment_log = "Message with Chat-Group-Name, no parent.".to_string();
        ChatAssignment::AdHocGroup
    } else if can_be_11_chat {
        chat_assignment_log = format!("Non-group message, no parent. {can_be_11_chat_log}");
        ChatAssignment::OneOneChat
    } else {
        chat_assignment_log = format!("Non-group message, no parent. {can_be_11_chat_log}");
        ChatAssignment::AdHocGroup
    };

    if !chat_assignment_log.is_empty() {
        info!(
            context,
            "{chat_assignment_log} Chat assignment = {chat_assignment:?}."
        );
    }
    Ok(chat_assignment)
}

/// Assigns the message to a chat.
///
/// Creates a new chat if necessary.
///
/// Returns the chat ID,
/// whether it is blocked
/// and if the chat was created by this function
/// (as opposed to being looked up among existing chats).
#[expect(clippy::too_many_arguments)]
async fn do_chat_assignment(
    context: &Context,
    chat_assignment: &ChatAssignment,
    from_id: ContactId,
    to_ids: &[Option<ContactId>],
    past_ids: &[Option<ContactId>],
    to_id: ContactId,
    allow_creation: bool,
    mime_parser: &mut MimeMessage,
    parent_message: Option<Message>,
) -> Result<(ChatId, Blocked, bool)> {
    let is_bot = context.get_config_bool(Config::Bot).await?;

    let mut chat_id = None;
    let mut chat_id_blocked = Blocked::Not;
    let mut chat_created = false;

    if mime_parser.incoming {
        let test_normal_chat = ChatIdBlocked::lookup_by_contact(context, from_id).await?;

        let create_blocked_default = if is_bot {
            Blocked::Not
        } else {
            Blocked::Request
        };
        let create_blocked = if let Some(ChatIdBlocked { id: _, blocked }) = test_normal_chat {
            match blocked {
                Blocked::Request => create_blocked_default,
                Blocked::Not => Blocked::Not,
                Blocked::Yes => {
                    if Contact::is_blocked_load(context, from_id).await? {
                        // User has blocked the contact.
                        // Block the group contact created as well.
                        Blocked::Yes
                    } else {
                        // 1:1 chat is blocked, but the contact is not.
                        // This happens when 1:1 chat is hidden
                        // during scanning of a group invitation code.
                        create_blocked_default
                    }
                }
            }
        } else {
            create_blocked_default
        };

        match &chat_assignment {
            ChatAssignment::Trash => {
                chat_id = Some(DC_CHAT_ID_TRASH);
            }
            ChatAssignment::GroupChat { grpid } => {
                // Try to assign to a chat based on Chat-Group-ID.
                if let Some((id, blocked)) = chat::get_chat_id_by_grpid(context, grpid).await? {
                    chat_id = Some(id);
                    chat_id_blocked = blocked;
                } else if (allow_creation || test_normal_chat.is_some())
                    && let Some((new_chat_id, new_chat_id_blocked)) = create_group(
                        context,
                        mime_parser,
                        create_blocked,
                        from_id,
                        to_ids,
                        past_ids,
                        grpid,
                    )
                    .await?
                {
                    chat_id = Some(new_chat_id);
                    chat_id_blocked = new_chat_id_blocked;
                    chat_created = true;
                }
            }
            ChatAssignment::MailingListOrBroadcast => {
                if let Some(mailinglist_header) = mime_parser.get_mailinglist_header()
                    && let Some((new_chat_id, new_chat_id_blocked, new_chat_created)) =
                        create_or_lookup_mailinglist_or_broadcast(
                            context,
                            allow_creation,
                            create_blocked,
                            mailinglist_header,
                            from_id,
                            mime_parser,
                        )
                        .await?
                {
                    chat_id = Some(new_chat_id);
                    chat_id_blocked = new_chat_id_blocked;
                    chat_created = new_chat_created;

                    apply_mailinglist_changes(context, mime_parser, new_chat_id).await?;
                }
            }
            ChatAssignment::ExistingChat {
                chat_id: new_chat_id,
                chat_id_blocked: new_chat_id_blocked,
            } => {
                chat_id = Some(*new_chat_id);
                chat_id_blocked = *new_chat_id_blocked;
            }
            ChatAssignment::AdHocGroup => {
                if let Some((new_chat_id, new_chat_id_blocked, new_created)) =
                    lookup_or_create_adhoc_group(
                        context,
                        mime_parser,
                        to_ids,
                        allow_creation || test_normal_chat.is_some(),
                        create_blocked,
                    )
                    .await?
                {
                    chat_id = Some(new_chat_id);
                    chat_id_blocked = new_chat_id_blocked;
                    chat_created = new_created;
                }
            }
            ChatAssignment::OneOneChat => {}
        }

        // if the chat is somehow blocked but we want to create a non-blocked chat,
        // unblock the chat
        if chat_id_blocked != Blocked::Not
            && create_blocked != Blocked::Yes
            && !matches!(chat_assignment, ChatAssignment::MailingListOrBroadcast)
            && let Some(chat_id) = chat_id
        {
            chat_id.set_blocked(context, create_blocked).await?;
            chat_id_blocked = create_blocked;
        }

        if chat_id.is_none() {
            // Try to create a 1:1 chat.
            let contact = Contact::get_by_id(context, from_id).await?;
            let create_blocked = match contact.is_blocked() {
                true => Blocked::Yes,
                false if is_bot => Blocked::Not,
                false => Blocked::Request,
            };

            if let Some(chat) = test_normal_chat {
                chat_id = Some(chat.id);
                chat_id_blocked = chat.blocked;
            } else if allow_creation {
                let chat = ChatIdBlocked::get_for_contact(context, from_id, create_blocked)
                    .await
                    .context("Failed to get (new) chat for contact")?;
                chat_id = Some(chat.id);
                chat_id_blocked = chat.blocked;
                chat_created = true;
            }

            if let Some(chat_id) = chat_id
                && chat_id_blocked != Blocked::Not
            {
                if chat_id_blocked != create_blocked {
                    chat_id.set_blocked(context, create_blocked).await?;
                }
                if create_blocked == Blocked::Request && parent_message.is_some() {
                    // we do not want any chat to be created implicitly.  Because of the origin-scale-up,
                    // the contact requests will pop up and this should be just fine.
                    ContactId::scaleup_origin(context, &[from_id], Origin::IncomingReplyTo).await?;
                    info!(
                        context,
                        "Message is a reply to a known message, mark sender as known.",
                    );
                }
            }
        }
    } else {
        // Outgoing

        // Older Delta Chat versions with core <=1.152.2 only accepted
        // self-sent messages in Saved Messages with own address in the `To` field.
        // New Delta Chat versions may use empty `To` field
        // with only a single `hidden-recipients` group in this case.
        let self_sent = to_ids.len() <= 1 && to_id == ContactId::SELF;

        match &chat_assignment {
            ChatAssignment::Trash => {
                chat_id = Some(DC_CHAT_ID_TRASH);
            }
            ChatAssignment::GroupChat { grpid } => {
                if let Some((id, blocked)) = chat::get_chat_id_by_grpid(context, grpid).await? {
                    chat_id = Some(id);
                    chat_id_blocked = blocked;
                } else if allow_creation
                    && let Some((new_chat_id, new_chat_id_blocked)) = create_group(
                        context,
                        mime_parser,
                        Blocked::Not,
                        from_id,
                        to_ids,
                        past_ids,
                        grpid,
                    )
                    .await?
                {
                    chat_id = Some(new_chat_id);
                    chat_id_blocked = new_chat_id_blocked;
                    chat_created = true;
                }
            }
            ChatAssignment::ExistingChat {
                chat_id: new_chat_id,
                chat_id_blocked: new_chat_id_blocked,
            } => {
                chat_id = Some(*new_chat_id);
                chat_id_blocked = *new_chat_id_blocked;
            }
            ChatAssignment::MailingListOrBroadcast => {
                // Check if the message belongs to a broadcast channel
                // (it can't be a mailing list, since it's outgoing)
                if let Some(mailinglist_header) = mime_parser.get_mailinglist_header() {
                    let listid = mailinglist_header_listid(mailinglist_header)?;
                    if let Some((id, ..)) = chat::get_chat_id_by_grpid(context, &listid).await? {
                        chat_id = Some(id);
                    } else {
                        // Looks like we missed the sync message that was creating this broadcast channel
                        let name =
                            compute_mailinglist_name(mailinglist_header, &listid, mime_parser);
                        if let Some(secret) = mime_parser
                            .get_header(HeaderDef::ChatBroadcastSecret)
                            .filter(|s| validate_broadcast_secret(s))
                        {
                            chat_created = true;
                            chat_id = Some(
                                chat::create_out_broadcast_ex(
                                    context,
                                    Nosync,
                                    listid,
                                    name,
                                    secret.to_string(),
                                )
                                .await?,
                            );
                        } else {
                            warn!(
                                context,
                                "Not creating outgoing broadcast with id {listid}, because secret is unknown"
                            );
                        }
                    }
                }
            }
            ChatAssignment::AdHocGroup => {
                if let Some((new_chat_id, new_chat_id_blocked, new_chat_created)) =
                    lookup_or_create_adhoc_group(
                        context,
                        mime_parser,
                        to_ids,
                        allow_creation,
                        Blocked::Not,
                    )
                    .await?
                {
                    chat_id = Some(new_chat_id);
                    chat_id_blocked = new_chat_id_blocked;
                    chat_created = new_chat_created;
                }
            }
            ChatAssignment::OneOneChat => {}
        }

        if !to_ids.is_empty() {
            if chat_id.is_none() && allow_creation {
                let to_contact = Contact::get_by_id(context, to_id).await?;
                if let Some(list_id) = to_contact.param.get(Param::ListId) {
                    if let Some((id, blocked)) =
                        chat::get_chat_id_by_grpid(context, list_id).await?
                    {
                        chat_id = Some(id);
                        chat_id_blocked = blocked;
                    }
                } else {
                    let chat = ChatIdBlocked::get_for_contact(context, to_id, Blocked::Not).await?;
                    chat_id = Some(chat.id);
                    chat_id_blocked = chat.blocked;
                    chat_created = true;
                }
            }
            if chat_id.is_none()
                && mime_parser.has_chat_version()
                && let Some(chat) = ChatIdBlocked::lookup_by_contact(context, to_id).await?
            {
                chat_id = Some(chat.id);
                chat_id_blocked = chat.blocked;
            }
        }

        if chat_id.is_none() && self_sent {
            // from_id==to_id==ContactId::SELF - this is a self-sent messages,
            // maybe an Autocrypt Setup Message
            let chat = ChatIdBlocked::get_for_contact(context, ContactId::SELF, Blocked::Not)
                .await
                .context("Failed to get (new) chat for contact")?;

            chat_id = Some(chat.id);
            chat_id_blocked = chat.blocked;

            if Blocked::Not != chat.blocked {
                chat.id.unblock_ex(context, Nosync).await?;
            }
        }

        // automatically unblock chat when the user sends a message
        if chat_id_blocked != Blocked::Not
            && let Some(chat_id) = chat_id
        {
            chat_id.unblock_ex(context, Nosync).await?;
            chat_id_blocked = Blocked::Not;
        }
    }
    let chat_id = chat_id.unwrap_or_else(|| {
        info!(context, "No chat id for message (TRASH).");
        DC_CHAT_ID_TRASH
    });
    Ok((chat_id, chat_id_blocked, chat_created))
}

/// Creates a `ReceivedMsg` from given parts which might consist of
/// multiple messages (if there are multiple attachments).
/// Every entry in `mime_parser.parts` produces a new row in the `msgs` table.
#[expect(clippy::too_many_arguments)]
async fn add_parts(
    context: &Context,
    mime_parser: &mut MimeMessage,
    imf_raw: &[u8],
    to_ids: &[Option<ContactId>],
    past_ids: &[Option<ContactId>],
    rfc724_mid: &str,
    from_id: ContactId,
    seen: bool,
    prevent_rename: bool,
    mut chat_id: ChatId,
    mut chat_id_blocked: Blocked,
    is_dc_message: MessengerMessage,
    is_chat_created: bool,
) -> Result<ReceivedMsg> {
    let to_id = if mime_parser.incoming {
        ContactId::SELF
    } else {
        to_ids.first().copied().flatten().unwrap_or(ContactId::SELF)
    };

    // if contact renaming is prevented (for mailinglists and bots),
    // we use name from From:-header as override name
    if prevent_rename && let Some(name) = &mime_parser.from.display_name {
        for part in &mut mime_parser.parts {
            part.param.set(Param::OverrideSenderDisplayname, name);
        }
    }

    let mut chat = Chat::load_from_db(context, chat_id).await?;

    if mime_parser.incoming && !chat_id.is_trash() {
        // It can happen that the message is put into a chat
        // but the From-address is not a member of this chat.
        if !chat::is_contact_in_chat(context, chat_id, from_id).await? {
            // Mark the sender as overridden.
            // The UI will prepend `~` to the sender's name,
            // indicating that the sender is not part of the group.
            let from = &mime_parser.from;
            let name: &str = from.display_name.as_ref().unwrap_or(&from.addr);
            for part in &mut mime_parser.parts {
                part.param.set(Param::OverrideSenderDisplayname, name);
            }

            if chat.typ == Chattype::InBroadcast {
                warn!(
                    context,
                    "Not assigning msg '{rfc724_mid}' to broadcast {chat_id}: wrong sender: {from_id}."
                );
                let direct_chat =
                    ChatIdBlocked::get_for_contact(context, from_id, Blocked::Request).await?;
                chat_id = direct_chat.id;
                chat_id_blocked = direct_chat.blocked;
                chat = Chat::load_from_db(context, chat_id).await?;
            }
        }
    }

    // Sort message to the bottom if we are not in the chat
    // so if we are added via QR code scan
    // the message about our addition goes after all the info messages.
    // Info messages are sorted by local smeared_timestamp()
    // which advances quickly during SecureJoin,
    // while "member added" message may have older timestamp
    // corresponding to the sender clock.
    // In practice inviter clock may even be slightly in the past.
    let sort_to_bottom = !chat.is_self_in_chat(context).await?;

    let is_location_kml = mime_parser.location_kml.is_some();
    let mut group_changes = match chat.typ {
        _ if chat.id.is_special() => GroupChangesInfo::default(),
        Chattype::Single => GroupChangesInfo::default(),
        Chattype::Mailinglist => GroupChangesInfo::default(),
        Chattype::OutBroadcast => {
            apply_out_broadcast_changes(context, mime_parser, &mut chat, from_id).await?
        }
        Chattype::Group => {
            apply_group_changes(
                context,
                mime_parser,
                &mut chat,
                from_id,
                to_ids,
                past_ids,
                is_chat_created,
            )
            .await?
        }
        Chattype::InBroadcast => {
            apply_in_broadcast_changes(context, mime_parser, &mut chat, from_id).await?
        }
    };

    let rfc724_mid_orig = &mime_parser
        .get_rfc724_mid()
        .unwrap_or(rfc724_mid.to_string());

    // Extract ephemeral timer from the message
    let mut ephemeral_timer = if let Some(value) = mime_parser.get_header(HeaderDef::EphemeralTimer)
    {
        match EphemeralTimer::from_str(value) {
            Ok(timer) => timer,
            Err(err) => {
                warn!(context, "Can't parse ephemeral timer \"{value}\": {err:#}.");
                EphemeralTimer::Disabled
            }
        }
    } else {
        EphemeralTimer::Disabled
    };

    let state = if !mime_parser.incoming {
        MessageState::OutDelivered
    } else if seen
        || !mime_parser.mdn_reports.is_empty()
        || chat_id_blocked == Blocked::Yes
        || group_changes.silent
    // No check for `hidden` because only reactions are such and they should be `InFresh`.
    {
        MessageState::InSeen
    } else if mime_parser.from.addr == STATISTICS_BOT_EMAIL {
        MessageState::InNoticed
    } else {
        MessageState::InFresh
    };
    let in_fresh = state == MessageState::InFresh;

    let sort_timestamp = chat_id
        .calc_sort_timestamp(context, mime_parser.timestamp_sent, sort_to_bottom)
        .await?;

    // Apply ephemeral timer changes to the chat.
    //
    // Only apply the timer when there are visible parts (e.g., the message does not consist only
    // of `location.kml` attachment).  Timer changes without visible received messages may be
    // confusing to the user.
    if !chat_id.is_special()
        && !mime_parser.parts.is_empty()
        && chat_id.get_ephemeral_timer(context).await? != ephemeral_timer
    {
        let chat_contacts =
            BTreeSet::<ContactId>::from_iter(chat::get_chat_contacts(context, chat_id).await?);
        let is_from_in_chat =
            !chat_contacts.contains(&ContactId::SELF) || chat_contacts.contains(&from_id);

        info!(
            context,
            "Received new ephemeral timer value {ephemeral_timer:?} for chat {chat_id}, checking if it should be applied."
        );
        if !is_from_in_chat {
            warn!(
                context,
                "Ignoring ephemeral timer change to {ephemeral_timer:?} for chat {chat_id} because sender {from_id} is not a member.",
            );
        } else if is_dc_message == MessengerMessage::Yes
            && get_previous_message(context, mime_parser)
                .await?
                .map(|p| p.ephemeral_timer)
                == Some(ephemeral_timer)
            && mime_parser.is_system_message != SystemMessage::EphemeralTimerChanged
        {
            // The message is a Delta Chat message, so we know that previous message according to
            // References header is the last message in the chat as seen by the sender. The timer
            // is the same in both the received message and the last message, so we know that the
            // sender has not seen any change of the timer between these messages. As our timer
            // value is different, it means the sender has not received some timer update that we
            // have seen or sent ourselves, so we ignore incoming timer to prevent a rollback.
            warn!(
                context,
                "Ignoring ephemeral timer change to {ephemeral_timer:?} for chat {chat_id} to avoid rollback.",
            );
        } else if chat_id
            .update_timestamp(
                context,
                Param::EphemeralSettingsTimestamp,
                mime_parser.timestamp_sent,
            )
            .await?
        {
            if let Err(err) = chat_id
                .inner_set_ephemeral_timer(context, ephemeral_timer)
                .await
            {
                warn!(
                    context,
                    "Failed to modify timer for chat {chat_id}: {err:#}."
                );
            } else {
                info!(
                    context,
                    "Updated ephemeral timer to {ephemeral_timer:?} for chat {chat_id}."
                );
                if mime_parser.is_system_message != SystemMessage::EphemeralTimerChanged {
                    chat::add_info_msg_with_cmd(
                        context,
                        chat_id,
                        &stock_ephemeral_timer_changed(context, ephemeral_timer, from_id).await,
                        SystemMessage::Unknown,
                        Some(sort_timestamp),
                        mime_parser.timestamp_sent,
                        None,
                        None,
                        None,
                    )
                    .await?;
                }
            }
        } else {
            warn!(
                context,
                "Ignoring ephemeral timer change to {ephemeral_timer:?} because it is outdated."
            );
        }
    }

    let mut better_msg = if mime_parser.is_system_message == SystemMessage::LocationStreamingEnabled
    {
        Some(stock_str::msg_location_enabled_by(context, from_id).await)
    } else if mime_parser.is_system_message == SystemMessage::EphemeralTimerChanged {
        let better_msg = stock_ephemeral_timer_changed(context, ephemeral_timer, from_id).await;

        // Do not delete the system message itself.
        //
        // This prevents confusion when timer is changed
        // to 1 week, and then changed to 1 hour: after 1
        // hour, only the message about the change to 1
        // week is left.
        ephemeral_timer = EphemeralTimer::Disabled;

        Some(better_msg)
    } else {
        None
    };

    drop(chat); // Avoid using stale `chat` object.

    let sort_timestamp = tweak_sort_timestamp(
        context,
        mime_parser,
        group_changes.silent,
        chat_id,
        sort_timestamp,
    )
    .await?;

    let mime_in_reply_to = mime_parser
        .get_header(HeaderDef::InReplyTo)
        .unwrap_or_default();
    let mime_references = mime_parser
        .get_header(HeaderDef::References)
        .unwrap_or_default();

    // fine, so far.  now, split the message into simple parts usable as "short messages"
    // and add them to the database (mails sent by other messenger clients should result
    // into only one message; mails sent by other clients may result in several messages
    // (eg. one per attachment))
    let icnt = mime_parser.parts.len();

    let subject = mime_parser.get_subject().unwrap_or_default();

    let is_system_message = mime_parser.is_system_message;

    // if indicated by the parser,
    // we save the full mime-message and add a flag
    // that the ui should show button to display the full message.

    // We add "Show Full Message" button to the last message bubble (part) if this flag evaluates to
    // `true` finally.
    let mut save_mime_modified = false;

    let mime_headers = if mime_parser.is_mime_modified {
        let headers = if !mime_parser.decoded_data.is_empty() {
            mime_parser.decoded_data.clone()
        } else {
            imf_raw.to_vec()
        };
        tokio::task::block_in_place(move || buf_compress(&headers))?
    } else {
        Vec::new()
    };

    let mut created_db_entries = Vec::with_capacity(mime_parser.parts.len());

    if let Some(m) = group_changes.better_msg {
        match &better_msg {
            None => better_msg = Some(m),
            Some(_) => {
                if !m.is_empty() {
                    group_changes.extra_msgs.push((m, is_system_message, None))
                }
            }
        }
    }

    let chat_id = if better_msg
        .as_ref()
        .is_some_and(|better_msg| better_msg.is_empty())
    {
        DC_CHAT_ID_TRASH
    } else {
        chat_id
    };

    for (group_changes_msg, cmd, added_removed_id) in group_changes.extra_msgs {
        chat::add_info_msg_with_cmd(
            context,
            chat_id,
            &group_changes_msg,
            cmd,
            Some(sort_timestamp),
            mime_parser.timestamp_sent,
            None,
            None,
            added_removed_id,
        )
        .await?;
    }

    if let Some(node_addr) = mime_parser.get_header(HeaderDef::IrohNodeAddr) {
        match mime_parser.get_header(HeaderDef::InReplyTo) {
            Some(in_reply_to) => match rfc724_mid_exists(context, in_reply_to).await? {
                Some(instance_id) => {
                    if let Err(err) =
                        add_gossip_peer_from_header(context, instance_id, node_addr).await
                    {
                        warn!(context, "Failed to add iroh peer from header: {err:#}.");
                    }
                }
                None => {
                    warn!(
                        context,
                        "Cannot add iroh peer because WebXDC instance does not exist."
                    );
                }
            },
            None => {
                warn!(
                    context,
                    "Cannot add iroh peer because the message has no In-Reply-To."
                );
            }
        }
    }

    handle_edit_delete(context, mime_parser, from_id).await?;
    handle_post_message(context, mime_parser, from_id, state).await?;

    if mime_parser.is_system_message == SystemMessage::CallAccepted
        || mime_parser.is_system_message == SystemMessage::CallEnded
    {
        if let Some(field) = mime_parser.get_header(HeaderDef::InReplyTo) {
            if let Some(call) =
                message::get_by_rfc724_mids(context, &parse_message_ids(field)).await?
            {
                context
                    .handle_call_msg(call.get_id(), mime_parser, from_id)
                    .await?;
            } else {
                warn!(context, "Call: Cannot load parent.")
            }
        } else {
            warn!(context, "Call: Not a reply.")
        }
    }

    let hidden = mime_parser.parts.iter().all(|part| part.is_reaction);
    let mut parts = mime_parser.parts.iter().peekable();
    while let Some(part) = parts.next() {
        let hidden = part.is_reaction;
        if part.is_reaction {
            let reaction_str = simplify::remove_footers(part.msg.as_str());
            let is_incoming_fresh = mime_parser.incoming && !seen;
            set_msg_reaction(
                context,
                mime_in_reply_to,
                chat_id,
                from_id,
                sort_timestamp,
                Reaction::new(reaction_str.as_str()),
                is_incoming_fresh,
            )
            .await?;
        }

        let mut param = part.param.clone();
        if is_system_message != SystemMessage::Unknown {
            param.set_int(Param::Cmd, is_system_message as i32);
        }

        let (msg, typ): (&str, Viewtype) = if let Some(better_msg) = &better_msg {
            (better_msg, Viewtype::Text)
        } else {
            (&part.msg, part.typ)
        };
        let part_is_empty =
            typ == Viewtype::Text && msg.is_empty() && part.param.get(Param::Quote).is_none();

        if let Some(contact_id) = group_changes.added_removed_id {
            param.set(Param::ContactAddedRemoved, contact_id.to_u32().to_string());
        }

        save_mime_modified |= mime_parser.is_mime_modified && !part_is_empty && !hidden;
        let save_mime_modified = save_mime_modified && parts.peek().is_none();

        let ephemeral_timestamp = if in_fresh {
            0
        } else {
            match ephemeral_timer {
                EphemeralTimer::Disabled => 0,
                EphemeralTimer::Enabled { duration } => {
                    mime_parser.timestamp_rcvd.saturating_add(duration.into())
                }
            }
        };

        if let PreMessageMode::Pre {
            metadata: Some(metadata),
            ..
        } = &mime_parser.pre_message
        {
            param.apply_post_msg_metadata(metadata);
        };

        // If you change which information is skipped if the message is trashed,
        // also change `MsgId::trash()` and `delete_expired_messages()`
        let trash = chat_id.is_trash() || (is_location_kml && part_is_empty && !save_mime_modified);

        let row_id = context
            .sql
            .call_write(|conn| {
                let mut stmt = conn.prepare_cached(
                    "
INSERT INTO msgs
  (
    rfc724_mid, pre_rfc724_mid, chat_id,
    from_id, to_id, timestamp, timestamp_sent, 
    timestamp_rcvd, type, state, msgrmsg, 
    txt, txt_normalized, subject, param, hidden,
    bytes, mime_headers, mime_compressed, mime_in_reply_to,
    mime_references, mime_modified, error, ephemeral_timer,
    ephemeral_timestamp, download_state, hop_info
  )
  VALUES (
    ?, ?, ?, ?, ?,
    ?, ?, ?, ?,
    ?, ?, ?, ?,
    ?, ?, ?, ?, ?, 1,
    ?, ?, ?, ?,
    ?, ?, ?, ?
  )",
                )?;
                let params = params![
                    if let PreMessageMode::Pre {
                        post_msg_rfc724_mid,
                        ..
                    } = &mime_parser.pre_message
                    {
                        post_msg_rfc724_mid
                    } else {
                        rfc724_mid_orig
                    },
                    if let PreMessageMode::Pre { .. } = &mime_parser.pre_message {
                        rfc724_mid_orig
                    } else {
                        ""
                    },
                    if trash { DC_CHAT_ID_TRASH } else { chat_id },
                    if trash { ContactId::UNDEFINED } else { from_id },
                    if trash { ContactId::UNDEFINED } else { to_id },
                    sort_timestamp,
                    if trash { 0 } else { mime_parser.timestamp_sent },
                    if trash { 0 } else { mime_parser.timestamp_rcvd },
                    if trash {
                        Viewtype::Unknown
                    } else if let PreMessageMode::Pre { .. } = mime_parser.pre_message {
                        Viewtype::Text
                    } else {
                        typ
                    },
                    if trash {
                        MessageState::Undefined
                    } else {
                        state
                    },
                    if trash {
                        MessengerMessage::No
                    } else {
                        is_dc_message
                    },
                    if trash || hidden { "" } else { msg },
                    if trash || hidden {
                        None
                    } else {
                        normalize_text(msg)
                    },
                    if trash || hidden { "" } else { &subject },
                    if trash {
                        "".to_string()
                    } else {
                        param.to_string()
                    },
                    !trash && hidden,
                    if trash { 0 } else { part.bytes as isize },
                    if save_mime_modified && !(trash || hidden) {
                        mime_headers.clone()
                    } else {
                        Vec::new()
                    },
                    if trash { "" } else { mime_in_reply_to },
                    if trash { "" } else { mime_references },
                    !trash && save_mime_modified,
                    if trash {
                        ""
                    } else {
                        part.error.as_deref().unwrap_or_default()
                    },
                    if trash { 0 } else { ephemeral_timer.to_u32() },
                    if trash { 0 } else { ephemeral_timestamp },
                    if trash {
                        DownloadState::Done
                    } else if mime_parser.decryption_error.is_some() {
                        DownloadState::Undecipherable
                    } else if let PreMessageMode::Pre { .. } = mime_parser.pre_message {
                        DownloadState::Available
                    } else {
                        DownloadState::Done
                    },
                    if trash { "" } else { &mime_parser.hop_info },
                ];
                let row_id = MsgId::new(stmt.insert(params)?.try_into()?);
                Ok(row_id)
            })
            .await?;
        ensure_and_debug_assert!(!row_id.is_special(), "Rowid {row_id} is special");
        created_db_entries.push(row_id);
    }

    // Maybe set logging xdc and add gossip topics for webxdcs.
    for (part, msg_id) in mime_parser.parts.iter().zip(&created_db_entries) {
        if mime_parser.pre_message != PreMessageMode::Post
            && part.typ == Viewtype::Webxdc
            && let Some(topic) = mime_parser.get_header(HeaderDef::IrohGossipTopic)
        {
            let topic = iroh_topic_from_str(topic)?;
            insert_topic_stub(context, *msg_id, topic).await?;
        }

        maybe_set_logging_xdc_inner(
            context,
            part.typ,
            chat_id,
            part.param.get(Param::Filename),
            *msg_id,
        )
        .await?;
    }

    let unarchive = match mime_parser.get_header(HeaderDef::ChatGroupMemberRemoved) {
        Some(addr) => context.is_self_addr(addr).await?,
        None => true,
    };
    if unarchive {
        chat_id.unarchive_if_not_muted(context, state).await?;
    }

    info!(
        context,
        "Message has {icnt} parts and is assigned to chat #{chat_id}, timestamp={sort_timestamp}."
    );

    if !chat_id.is_trash() && !hidden {
        let mut chat = Chat::load_from_db(context, chat_id).await?;
        let mut update_param = false;

        // In contrast to most other update-timestamps,
        // use `sort_timestamp` instead of `sent_timestamp` for the subject-timestamp comparison.
        // This way, `LastSubject` actually refers to the most recent message _shown_ in the chat.
        if chat
            .param
            .update_timestamp(Param::SubjectTimestamp, sort_timestamp)?
        {
            // write the last subject even if empty -
            // otherwise a reply may get an outdated subject.
            let subject = mime_parser.get_subject().unwrap_or_default();

            chat.param.set(Param::LastSubject, subject);
            update_param = true;
        }

        if chat.is_unpromoted() {
            chat.param.remove(Param::Unpromoted);
            update_param = true;
        }
        if update_param {
            chat.update_param(context).await?;
        }
    }

    Ok(ReceivedMsg {
        chat_id,
        state,
        hidden,
        sort_timestamp,
        msg_ids: created_db_entries,
        needs_delete_job: false,
    })
}

/// Checks for "Chat-Edit" and "Chat-Delete" headers,
/// and edits/deletes existing messages accordingly.
async fn handle_edit_delete(
    context: &Context,
    mime_parser: &MimeMessage,
    from_id: ContactId,
) -> Result<()> {
    if let Some(rfc724_mid) = mime_parser.get_header(HeaderDef::ChatEdit) {
        if let Some(original_msg_id) = rfc724_mid_exists(context, rfc724_mid).await? {
            if let Some(mut original_msg) =
                Message::load_from_db_optional(context, original_msg_id).await?
            {
                if original_msg.from_id == from_id {
                    if let Some(part) = mime_parser.parts.first() {
                        let edit_msg_showpadlock = part
                            .param
                            .get_bool(Param::GuaranteeE2ee)
                            .unwrap_or_default();
                        if edit_msg_showpadlock || !original_msg.get_showpadlock() {
                            let new_text =
                                part.msg.strip_prefix(EDITED_PREFIX).unwrap_or(&part.msg);
                            chat::save_text_edit_to_db(context, &mut original_msg, new_text)
                                .await?;
                        } else {
                            warn!(context, "Edit message: Not encrypted.");
                        }
                    }
                } else {
                    warn!(context, "Edit message: Bad sender.");
                }
            } else {
                warn!(context, "Edit message: Database entry does not exist.");
            }
        } else {
            warn!(
                context,
                "Edit message: rfc724_mid {rfc724_mid:?} not found."
            );
        }
    } else if let Some(rfc724_mid_list) = mime_parser.get_header(HeaderDef::ChatDelete)
        && let Some(part) = mime_parser.parts.first()
    {
        // See `message::delete_msgs_ex()`, unlike edit requests, DC doesn't send unencrypted
        // deletion requests, so there's no need to support them.
        if part.param.get_bool(Param::GuaranteeE2ee).unwrap_or(false) {
            let mut modified_chat_ids = BTreeSet::new();
            let mut msg_ids = Vec::new();

            let rfc724_mid_vec: Vec<&str> = rfc724_mid_list.split_whitespace().collect();
            for rfc724_mid in rfc724_mid_vec {
                let rfc724_mid = rfc724_mid.trim_start_matches('<').trim_end_matches('>');
                if let Some(msg_id) = message::rfc724_mid_exists(context, rfc724_mid).await? {
                    if let Some(msg) = Message::load_from_db_optional(context, msg_id).await? {
                        if msg.from_id == from_id {
                            message::delete_msg_locally(context, &msg).await?;
                            msg_ids.push(msg.id);
                            modified_chat_ids.insert(msg.chat_id);
                        } else {
                            warn!(context, "Delete message: Bad sender.");
                        }
                    } else {
                        warn!(context, "Delete message: Database entry does not exist.");
                    }
                } else {
                    warn!(context, "Delete message: {rfc724_mid:?} not found.");
                    // Insert a tombstone so that the message will be ignored if it arrives later within a period specified in prune_tombstones().
                    insert_tombstone(context, rfc724_mid).await?;
                }
            }
            message::delete_msgs_locally_done(context, &msg_ids, modified_chat_ids).await?;
        } else {
            warn!(context, "Delete message: Not encrypted.");
        }
    }
    Ok(())
}

async fn handle_post_message(
    context: &Context,
    mime_parser: &MimeMessage,
    from_id: ContactId,
    state: MessageState,
) -> Result<()> {
    let PreMessageMode::Post = &mime_parser.pre_message else {
        return Ok(());
    };
    // if Pre-Message exist, replace attachment
    // only replacing attachment ensures that doesn't overwrite the text if it was edited before.
    let rfc724_mid = mime_parser
        .get_rfc724_mid()
        .context("expected Post-Message to have a message id")?;

    let Some(msg_id) = message::rfc724_mid_exists(context, &rfc724_mid).await? else {
        warn!(
            context,
            "handle_post_message: {rfc724_mid}: Database entry does not exist."
        );
        return Ok(());
    };
    let Some(original_msg) = Message::load_from_db_optional(context, msg_id).await? else {
        // else: message is processed like a normal message
        warn!(
            context,
            "handle_post_message: {rfc724_mid}: Pre-message was not downloaded yet so treat as normal message."
        );
        return Ok(());
    };
    let Some(part) = mime_parser.parts.first() else {
        return Ok(());
    };

    // Do nothing if safety checks fail, the worst case is the message modifies the chat if the
    // sender is a member.
    if from_id != original_msg.from_id {
        warn!(context, "handle_post_message: {rfc724_mid}: Bad sender.");
        return Ok(());
    }
    let post_msg_showpadlock = part
        .param
        .get_bool(Param::GuaranteeE2ee)
        .unwrap_or_default();
    if !post_msg_showpadlock && original_msg.get_showpadlock() {
        warn!(context, "handle_post_message: {rfc724_mid}: Not encrypted.");
        return Ok(());
    }

    if !part.typ.has_file() {
        warn!(
            context,
            "handle_post_message: {rfc724_mid}: First mime part's message-viewtype has no file."
        );
        return Ok(());
    }

    if part.typ == Viewtype::Webxdc
        && let Some(topic) = mime_parser.get_header(HeaderDef::IrohGossipTopic)
    {
        let topic = iroh_topic_from_str(topic)?;
        insert_topic_stub(context, msg_id, topic).await?;
    }

    let mut new_params = original_msg.param.clone();
    new_params
        .merge_in_params(part.param.clone())
        .remove(Param::PostMessageFileBytes)
        .remove(Param::PostMessageViewtype);
    // Don't update `chat_id`: even if it differs from pre-message's one somehow so the result
    // depends on message download order, we don't want messages jumping across chats.
    context
        .sql
        .execute(
            "
UPDATE msgs SET param=?, type=?, bytes=?, error=?, state=max(state,?), download_state=?
WHERE id=?
            ",
            (
                new_params.to_string(),
                part.typ,
                part.bytes as isize,
                part.error.as_deref().unwrap_or_default(),
                state,
                DownloadState::Done as u32,
                original_msg.id,
            ),
        )
        .await?;

    if context.get_config_bool(Config::Bot).await? {
        if original_msg.hidden {
            // No need to emit an event about the changed message
        } else if !original_msg.chat_id.is_trash() {
            let fresh = original_msg.state == MessageState::InFresh;
            let important = mime_parser.incoming && fresh;

            original_msg
                .chat_id
                .emit_msg_event(context, original_msg.id, important);
            context.new_msgs_notify.notify_one();
        }
    } else {
        context.emit_msgs_changed(original_msg.chat_id, original_msg.id);
    }

    Ok(())
}

async fn tweak_sort_timestamp(
    context: &Context,
    mime_parser: &mut MimeMessage,
    silent: bool,
    chat_id: ChatId,
    sort_timestamp: i64,
) -> Result<i64> {
    // Ensure replies to messages are sorted after the parent message.
    //
    // This is useful in a case where sender clocks are not
    // synchronized and parent message has a Date: header with a
    // timestamp higher than reply timestamp.
    //
    // This does not help if parent message arrives later than the
    // reply.
    let parent_timestamp = mime_parser.get_parent_timestamp(context).await?;
    let mut sort_timestamp = parent_timestamp.map_or(sort_timestamp, |parent_timestamp| {
        std::cmp::max(sort_timestamp, parent_timestamp)
    });

    // If the message should be silent,
    // set the timestamp to be no more than the same as last message
    // so that the chat is not sorted to the top of the chatlist.
    if silent {
        let last_msg_timestamp = if let Some(t) = chat_id.get_timestamp(context).await? {
            t
        } else {
            chat_id.created_timestamp(context).await?
        };
        sort_timestamp = std::cmp::min(sort_timestamp, last_msg_timestamp);
    }
    Ok(sort_timestamp)
}

/// Saves attached locations to the database.
///
/// Emits an event if at least one new location was added.
async fn save_locations(
    context: &Context,
    mime_parser: &MimeMessage,
    chat_id: ChatId,
    from_id: ContactId,
    msg_id: MsgId,
) -> Result<()> {
    if chat_id.is_special() {
        // Do not save locations for trashed messages.
        return Ok(());
    }

    let mut send_event = false;

    if let Some(message_kml) = &mime_parser.message_kml
        && let Some(newest_location_id) =
            location::save(context, chat_id, from_id, &message_kml.locations, true).await?
    {
        location::set_msg_location_id(context, msg_id, newest_location_id).await?;
        send_event = true;
    }

    if let Some(location_kml) = &mime_parser.location_kml
        && let Some(addr) = &location_kml.addr
    {
        let contact = Contact::get_by_id(context, from_id).await?;
        if contact.get_addr().to_lowercase() == addr.to_lowercase() {
            if location::save(context, chat_id, from_id, &location_kml.locations, false)
                .await?
                .is_some()
            {
                send_event = true;
            }
        } else {
            warn!(
                context,
                "Address in location.kml {:?} is not the same as the sender address {:?}.",
                addr,
                contact.get_addr()
            );
        }
    }
    if send_event {
        context.emit_location_changed(Some(from_id)).await?;
    }
    Ok(())
}

async fn lookup_chat_by_reply(
    context: &Context,
    mime_parser: &MimeMessage,
    parent: &Message,
) -> Result<Option<(ChatId, Blocked)>> {
    // If the message is encrypted and has group ID,
    // lookup by reply should never be needed
    // as we can directly assign the message to the chat
    // by its group ID.
    ensure_and_debug_assert!(
        mime_parser.get_chat_group_id().is_none() || !mime_parser.was_encrypted(),
        "Encrypted message has group ID {}",
        mime_parser.get_chat_group_id().unwrap_or_default(),
    );

    // Try to assign message to the same chat as the parent message.
    let Some(parent_chat_id) = ChatId::lookup_by_message(parent) else {
        return Ok(None);
    };

    // If this was a private message just to self, it was probably a private reply.
    // It should not go into the group then, but into the private chat.
    if is_probably_private_reply(context, mime_parser, parent_chat_id).await? {
        return Ok(None);
    }

    // If the parent chat is a 1:1 chat, and the sender added
    // a new person to TO/CC, then the message should not go to the 1:1 chat, but to a
    // newly created ad-hoc group.
    let parent_chat = Chat::load_from_db(context, parent_chat_id).await?;
    if parent_chat.typ == Chattype::Single && mime_parser.recipients.len() > 1 {
        return Ok(None);
    }

    // Do not assign unencrypted messages to encrypted chats.
    if parent_chat.is_encrypted(context).await? && !mime_parser.was_encrypted() {
        return Ok(None);
    }

    info!(
        context,
        "Assigning message to {parent_chat_id} as it's a reply to {}.", parent.rfc724_mid
    );
    Ok(Some((parent_chat.id, parent_chat.blocked)))
}

async fn lookup_or_create_adhoc_group(
    context: &Context,
    mime_parser: &MimeMessage,
    to_ids: &[Option<ContactId>],
    allow_creation: bool,
    create_blocked: Blocked,
) -> Result<Option<(ChatId, Blocked, bool)>> {
    if mime_parser.decryption_error.is_some() {
        warn!(
            context,
            "Not creating ad-hoc group for message that cannot be decrypted."
        );
        return Ok(None);
    }

    // Lookup address-contact by the From address.
    let fingerprint = None;
    let find_key_contact_by_addr = false;
    let prevent_rename = should_prevent_rename(mime_parser);
    let (from_id, _from_id_blocked, _incoming_origin) = from_field_to_contact_id(
        context,
        &mime_parser.from,
        fingerprint,
        prevent_rename,
        find_key_contact_by_addr,
    )
    .await?
    .context("Cannot lookup address-contact by the From field")?;

    let grpname = mime_parser
        .get_header(HeaderDef::ChatGroupName)
        .map(|s| s.to_string())
        .unwrap_or_else(|| {
            mime_parser
                .get_subject()
                .map(|s| remove_subject_prefix(&s))
                .unwrap_or_else(|| "👥📧".to_string())
        });
    let to_ids: Vec<ContactId> = to_ids.iter().filter_map(|x| *x).collect();
    let mut contact_ids = BTreeSet::<ContactId>::from_iter(to_ids.iter().copied());
    contact_ids.insert(from_id);
    if mime_parser.was_encrypted() {
        contact_ids.remove(&ContactId::SELF);
    }
    let trans_fn = |t: &mut rusqlite::Transaction| {
        t.pragma_update(None, "query_only", "0")?;
        t.execute(
            "CREATE TEMP TABLE temp.contacts (
                id INTEGER PRIMARY KEY
            ) STRICT",
            (),
        )
        .context("CREATE TEMP TABLE temp.contacts")?;
        let mut stmt = t.prepare("INSERT INTO temp.contacts(id) VALUES (?)")?;
        for &id in &contact_ids {
            stmt.execute((id,)).context("INSERT INTO temp.contacts")?;
        }
        let val = t
            .query_row(
                "SELECT c.id, c.blocked
                FROM chats c INNER JOIN msgs m ON c.id=m.chat_id
                WHERE m.hidden=0 AND c.grpid='' AND c.name=?
                AND (SELECT COUNT(*) FROM chats_contacts
                     WHERE chat_id=c.id
                     AND add_timestamp >= remove_timestamp)=?
                AND (SELECT COUNT(*) FROM chats_contacts
                     WHERE chat_id=c.id
                     AND contact_id NOT IN (SELECT id FROM temp.contacts)
                     AND add_timestamp >= remove_timestamp)=0
                ORDER BY m.timestamp DESC",
                (&grpname, contact_ids.len()),
                |row| {
                    let id: ChatId = row.get(0)?;
                    let blocked: Blocked = row.get(1)?;
                    Ok((id, blocked))
                },
            )
            .optional()
            .context("Select chat with matching name and members")?;
        t.execute("DROP TABLE temp.contacts", ())
            .context("DROP TABLE temp.contacts")?;
        Ok(val)
    };
    let query_only = true;
    if let Some((chat_id, blocked)) = context.sql.transaction_ex(query_only, trans_fn).await? {
        info!(
            context,
            "Assigning message to ad-hoc group {chat_id} with matching name and members."
        );
        return Ok(Some((chat_id, blocked, false)));
    }
    if !allow_creation {
        return Ok(None);
    }
    Ok(create_adhoc_group(
        context,
        mime_parser,
        create_blocked,
        from_id,
        &to_ids,
        &grpname,
    )
    .await
    .context("Could not create ad hoc group")?
    .map(|(chat_id, blocked)| (chat_id, blocked, true)))
}

/// If this method returns true, the message shall be assigned to the 1:1 chat with the sender.
/// If it returns false, it shall be assigned to the parent chat.
async fn is_probably_private_reply(
    context: &Context,
    mime_parser: &MimeMessage,
    parent_chat_id: ChatId,
) -> Result<bool> {
    // Message cannot be a private reply if it has an explicit Chat-Group-ID header.
    if mime_parser.get_chat_group_id().is_some() {
        return Ok(false);
    }

    // Usually we don't want to show private replies in the parent chat, but in the
    // 1:1 chat with the sender.
    //
    // There is one exception: Classical MUA replies to two-member groups
    // should be assigned to the group chat. We restrict this exception to classical emails, as chat-group-messages
    // contain a Chat-Group-Id header and can be sorted into the correct chat this way.

    if mime_parser.recipients.len() != 1 {
        return Ok(false);
    }

    if !mime_parser.has_chat_version() {
        let chat_contacts = chat::get_chat_contacts(context, parent_chat_id).await?;
        if chat_contacts.len() == 2 && chat_contacts.contains(&ContactId::SELF) {
            return Ok(false);
        }
    }

    Ok(true)
}

/// This function tries to extract the group-id from the message and create a new group
/// chat with this ID. If there is no group-id and there are more
/// than two members, a new ad hoc group is created.
///
/// On success the function returns the created (chat_id, chat_blocked) tuple.
async fn create_group(
    context: &Context,
    mime_parser: &mut MimeMessage,
    create_blocked: Blocked,
    from_id: ContactId,
    to_ids: &[Option<ContactId>],
    past_ids: &[Option<ContactId>],
    grpid: &str,
) -> Result<Option<(ChatId, Blocked)>> {
    let to_ids_flat: Vec<ContactId> = to_ids.iter().filter_map(|x| *x).collect();
    let mut chat_id = None;
    let mut chat_id_blocked = Default::default();

    if !mime_parser.is_mailinglist_message()
            && !grpid.is_empty()
            && mime_parser.get_header(HeaderDef::ChatGroupName).is_some()
            // otherwise, a pending "quit" message may pop up
            && mime_parser.get_header(HeaderDef::ChatGroupMemberRemoved).is_none()
    {
        // Group does not exist but should be created.
        let grpname = mime_parser
            .get_header(HeaderDef::ChatGroupName)
            .context("Chat-Group-Name vanished")?
            // Workaround for the "Space added before long group names after MIME
            // serialization/deserialization #3650" issue. DC itself never creates group names with
            // leading/trailing whitespace.
            .trim();
        let new_chat_id = ChatId::create_multiuser_record(
            context,
            Chattype::Group,
            grpid,
            grpname,
            create_blocked,
            None,
            mime_parser.timestamp_sent,
        )
        .await
        .with_context(|| format!("Failed to create group '{grpname}' for grpid={grpid}"))?;

        chat_id = Some(new_chat_id);
        chat_id_blocked = create_blocked;

        // Create initial member list.
        if let Some(mut chat_group_member_timestamps) = mime_parser.chat_group_member_timestamps() {
            let mut new_to_ids = to_ids.to_vec();
            if !new_to_ids.contains(&Some(from_id)) {
                new_to_ids.insert(0, Some(from_id));
                chat_group_member_timestamps.insert(0, mime_parser.timestamp_sent);
            }

            update_chats_contacts_timestamps(
                context,
                new_chat_id,
                None,
                &new_to_ids,
                past_ids,
                &chat_group_member_timestamps,
            )
            .await?;
        } else {
            let mut members = vec![ContactId::SELF];
            if !from_id.is_special() {
                members.push(from_id);
            }
            members.extend(to_ids_flat);

            // Add all members with 0 timestamp
            // because we don't know the real timestamp of their addition.
            // This will allow other senders who support
            // `Chat-Group-Member-Timestamps` to overwrite
            // timestamps later.
            let timestamp = 0;

            chat::add_to_chat_contacts_table(context, timestamp, new_chat_id, &members).await?;
        }

        context.emit_event(EventType::ChatModified(new_chat_id));
        chatlist_events::emit_chatlist_changed(context);
        chatlist_events::emit_chatlist_item_changed(context, new_chat_id);
    }

    if let Some(chat_id) = chat_id {
        Ok(Some((chat_id, chat_id_blocked)))
    } else if mime_parser.decryption_error.is_some() {
        // It is possible that the message was sent to a valid,
        // yet unknown group, which was rejected because
        // Chat-Group-Name, which is in the encrypted part, was
        // not found. We can't create a properly named group in
        // this case, so assign error message to 1:1 chat with the
        // sender instead.
        Ok(None)
    } else {
        // The message was decrypted successfully, but contains a late "quit" or otherwise
        // unwanted message.
        info!(context, "Message belongs to unwanted group (TRASH).");
        Ok(Some((DC_CHAT_ID_TRASH, Blocked::Not)))
    }
}

#[expect(clippy::arithmetic_side_effects)]
async fn update_chats_contacts_timestamps(
    context: &Context,
    chat_id: ChatId,
    ignored_id: Option<ContactId>,
    to_ids: &[Option<ContactId>],
    past_ids: &[Option<ContactId>],
    chat_group_member_timestamps: &[i64],
) -> Result<bool> {
    let expected_timestamps_count = to_ids.len() + past_ids.len();

    if chat_group_member_timestamps.len() != expected_timestamps_count {
        warn!(
            context,
            "Chat-Group-Member-Timestamps has wrong number of timestamps, got {}, expected {}.",
            chat_group_member_timestamps.len(),
            expected_timestamps_count
        );
        return Ok(false);
    }

    let mut modified = false;

    context
        .sql
        .transaction(|transaction| {
            let mut add_statement = transaction.prepare(
                "INSERT INTO chats_contacts (chat_id, contact_id, add_timestamp)
                 VALUES                     (?1,      ?2,         ?3)
                 ON CONFLICT (chat_id, contact_id)
                 DO
                   UPDATE SET add_timestamp=?3
                   WHERE ?3>add_timestamp AND ?3>=remove_timestamp",
            )?;

            for (contact_id, ts) in iter::zip(
                to_ids.iter(),
                chat_group_member_timestamps.iter().take(to_ids.len()),
            ) {
                if let Some(contact_id) = contact_id
                    && Some(*contact_id) != ignored_id
                {
                    // It could be that member was already added,
                    // but updated addition timestamp
                    // is also a modification worth notifying about.
                    modified |= add_statement.execute((chat_id, contact_id, ts))? > 0;
                }
            }

            let mut remove_statement = transaction.prepare(
                "INSERT INTO chats_contacts (chat_id, contact_id, remove_timestamp)
                 VALUES                     (?1,      ?2,         ?3)
                 ON CONFLICT (chat_id, contact_id)
                 DO
                   UPDATE SET remove_timestamp=?3
                   WHERE ?3>remove_timestamp AND ?3>add_timestamp",
            )?;

            for (contact_id, ts) in iter::zip(
                past_ids.iter(),
                chat_group_member_timestamps.iter().skip(to_ids.len()),
            ) {
                if let Some(contact_id) = contact_id {
                    // It could be that member was already removed,
                    // but updated removal timestamp
                    // is also a modification worth notifying about.
                    modified |= remove_statement.execute((chat_id, contact_id, ts))? > 0;
                }
            }

            Ok(())
        })
        .await?;

    Ok(modified)
}

/// The return type of [apply_group_changes].
/// Contains information on which system messages
/// should be shown in the chat.
#[derive(Default)]
struct GroupChangesInfo {
    /// Optional: A better message that should replace the original system message.
    /// If this is an empty string, the original system message should be trashed.
    better_msg: Option<String>,
    /// Added/removed contact `better_msg` refers to.
    added_removed_id: Option<ContactId>,
    /// If true, the user should not be notified about the group change.
    silent: bool,
    /// A list of additional group changes messages that should be shown in the chat.
    extra_msgs: Vec<(String, SystemMessage, Option<ContactId>)>,
}

/// Apply group member list, name, avatar and protection status changes from the MIME message.
///
/// Returns [GroupChangesInfo].
///
/// * `to_ids` - contents of the `To` and `Cc` headers.
/// * `past_ids` - contents of the `Chat-Group-Past-Members` header.
async fn apply_group_changes(
    context: &Context,
    mime_parser: &mut MimeMessage,
    chat: &mut Chat,
    from_id: ContactId,
    to_ids: &[Option<ContactId>],
    past_ids: &[Option<ContactId>],
    is_chat_created: bool,
) -> Result<GroupChangesInfo> {
    let from_is_key_contact = Contact::get_by_id(context, from_id).await?.is_key_contact();
    ensure!(from_is_key_contact || chat.grpid.is_empty());
    let to_ids_flat: Vec<ContactId> = to_ids.iter().filter_map(|x| *x).collect();
    ensure!(chat.typ == Chattype::Group);
    ensure!(!chat.id.is_special());

    let mut send_event_chat_modified = false;
    let (mut removed_id, mut added_id) = (None, None);
    let mut better_msg = None;
    let mut silent = false;
    let chat_contacts =
        BTreeSet::<ContactId>::from_iter(chat::get_chat_contacts(context, chat.id).await?);
    let is_from_in_chat =
        !chat_contacts.contains(&ContactId::SELF) || chat_contacts.contains(&from_id);

    if let Some(removed_addr) = mime_parser.get_header(HeaderDef::ChatGroupMemberRemoved) {
        if !is_from_in_chat {
            better_msg = Some(String::new());
        } else if let Some(removed_fpr) =
            mime_parser.get_header(HeaderDef::ChatGroupMemberRemovedFpr)
        {
            removed_id = lookup_key_contact_by_fingerprint(context, removed_fpr).await?;
        } else {
            // Removal message sent by a legacy Delta Chat client.
            removed_id =
                lookup_key_contact_by_address(context, removed_addr, Some(chat.id)).await?;
        }
        if let Some(id) = removed_id {
            better_msg = if id == from_id {
                silent = true;
                Some(stock_str::msg_group_left_local(context, from_id).await)
            } else {
                Some(stock_str::msg_del_member_local(context, id, from_id).await)
            };
        } else {
            warn!(context, "Removed {removed_addr:?} has no contact id.")
        }
    } else if let Some(added_addr) = mime_parser.get_header(HeaderDef::ChatGroupMemberAdded) {
        if !is_from_in_chat {
            better_msg = Some(String::new());
        } else if let Some(key) = mime_parser.gossiped_keys.get(added_addr) {
            if !chat_contacts.contains(&from_id) {
                chat::add_to_chat_contacts_table(
                    context,
                    mime_parser.timestamp_sent,
                    chat.id,
                    &[from_id],
                )
                .await?;
            }

            // TODO: if gossiped keys contain the same address multiple times,
            // we may lookup the wrong contact.
            // This can be fixed by looking at ChatGroupMemberAddedFpr,
            // just like we look at ChatGroupMemberRemovedFpr.
            // The result of the error is that info message
            // may contain display name of the wrong contact.
            let fingerprint = key.public_key.dc_fingerprint().hex();
            if let Some(contact_id) =
                lookup_key_contact_by_fingerprint(context, &fingerprint).await?
            {
                added_id = Some(contact_id);
                better_msg =
                    Some(stock_str::msg_add_member_local(context, contact_id, from_id).await);
            } else {
                warn!(context, "Added {added_addr:?} has no contact id.");
            }
        } else {
            warn!(context, "Added {added_addr:?} has no gossiped key.");
        }
    }

    apply_chat_name_avatar_and_description_changes(
        context,
        mime_parser,
        from_id,
        is_from_in_chat,
        chat,
        &mut send_event_chat_modified,
        &mut better_msg,
    )
    .await?;

    if is_from_in_chat {
        // Avoid insertion of `from_id` into a group with inappropriate encryption state.
        if from_is_key_contact != chat.grpid.is_empty()
            && chat.member_list_is_stale(context).await?
        {
            info!(context, "Member list is stale.");
            let mut new_members: BTreeSet<ContactId> =
                BTreeSet::from_iter(to_ids_flat.iter().copied());
            new_members.insert(ContactId::SELF);
            if !from_id.is_special() {
                new_members.insert(from_id);
            }
            if mime_parser.was_encrypted() && chat.grpid.is_empty() {
                new_members.remove(&ContactId::SELF);
            }
            context
                .sql
                .transaction(|transaction| {
                    // Remove all contacts and tombstones.
                    transaction.execute(
                        "DELETE FROM chats_contacts
                         WHERE chat_id=?",
                        (chat.id,),
                    )?;

                    // Insert contacts with default timestamps of 0.
                    let mut statement = transaction.prepare(
                        "INSERT INTO chats_contacts (chat_id, contact_id)
                         VALUES                     (?,       ?)",
                    )?;
                    for contact_id in &new_members {
                        statement.execute((chat.id, contact_id))?;
                    }

                    Ok(())
                })
                .await?;
            send_event_chat_modified = true;
        } else if let Some(ref chat_group_member_timestamps) =
            mime_parser.chat_group_member_timestamps()
        {
            send_event_chat_modified |= update_chats_contacts_timestamps(
                context,
                chat.id,
                Some(from_id),
                to_ids,
                past_ids,
                chat_group_member_timestamps,
            )
            .await?;
        } else {
            let mut new_members: BTreeSet<ContactId>;
            // True if a Delta Chat client has explicitly and really added our primary address to an
            // already existing group.
            let self_added =
                if let Some(added_addr) = mime_parser.get_header(HeaderDef::ChatGroupMemberAdded) {
                    addr_cmp(&context.get_primary_self_addr().await?, added_addr)
                        && !chat_contacts.contains(&ContactId::SELF)
                } else {
                    false
                };
            if self_added {
                new_members = BTreeSet::from_iter(to_ids_flat.iter().copied());
                new_members.insert(ContactId::SELF);
                if !from_id.is_special() && from_is_key_contact != chat.grpid.is_empty() {
                    new_members.insert(from_id);
                }
            } else {
                new_members = chat_contacts.clone();
            }

            // Allow non-Delta Chat MUAs to add members.
            if mime_parser.get_header(HeaderDef::ChatVersion).is_none() {
                // Don't delete any members locally, but instead add absent ones to provide group
                // membership consistency for all members:
                new_members.extend(to_ids_flat.iter());
            }

            // Apply explicit addition if any.
            if let Some(added_id) = added_id {
                new_members.insert(added_id);
            }

            // Apply explicit removal if any.
            if let Some(removed_id) = removed_id {
                new_members.remove(&removed_id);
            }

            if mime_parser.was_encrypted() && chat.grpid.is_empty() {
                new_members.remove(&ContactId::SELF);
            }

            if new_members != chat_contacts {
                chat::update_chat_contacts_table(
                    context,
                    mime_parser.timestamp_sent,
                    chat.id,
                    &new_members,
                )
                .await?;
                send_event_chat_modified = true;
            }
        }

        chat.id
            .update_timestamp(
                context,
                Param::MemberListTimestamp,
                mime_parser.timestamp_sent,
            )
            .await?;
    }

    let new_chat_contacts = BTreeSet::<ContactId>::from_iter(
        chat::get_chat_contacts(context, chat.id)
            .await?
            .iter()
            .copied(),
    );

    // These are for adding info messages about implicit membership changes.
    let mut added_ids: BTreeSet<ContactId> = new_chat_contacts
        .difference(&chat_contacts)
        .copied()
        .collect();
    let mut removed_ids: BTreeSet<ContactId> = chat_contacts
        .difference(&new_chat_contacts)
        .copied()
        .collect();
    let id_was_already_added = if let Some(added_id) = added_id {
        !added_ids.remove(&added_id)
    } else {
        false
    };
    if let Some(removed_id) = removed_id {
        removed_ids.remove(&removed_id);
    }

    let group_changes_msgs = if !chat_contacts.contains(&ContactId::SELF)
        && new_chat_contacts.contains(&ContactId::SELF)
    {
        Vec::new()
    } else {
        group_changes_msgs(context, &added_ids, &removed_ids, chat.id).await?
    };

    if id_was_already_added && group_changes_msgs.is_empty() && !is_chat_created {
        info!(context, "No-op 'Member added' message (TRASH)");
        better_msg = Some(String::new());
    }

    if send_event_chat_modified {
        context.emit_event(EventType::ChatModified(chat.id));
        chatlist_events::emit_chatlist_item_changed(context, chat.id);
    }
    Ok(GroupChangesInfo {
        better_msg,
        added_removed_id: if added_id.is_some() {
            added_id
        } else {
            removed_id
        },
        silent,
        extra_msgs: group_changes_msgs,
    })
}

/// Applies incoming changes to the group's or broadcast channel's name and avatar.
///
/// - `send_event_chat_modified` is set to `true` if ChatModified event should be sent
/// - `better_msg` is filled with an info message about name change, if necessary
async fn apply_chat_name_avatar_and_description_changes(
    context: &Context,
    mime_parser: &MimeMessage,
    from_id: ContactId,
    is_from_in_chat: bool,
    chat: &mut Chat,
    send_event_chat_modified: &mut bool,
    better_msg: &mut Option<String>,
) -> Result<()> {
    // ========== Apply chat name changes ==========

    let group_name_timestamp = mime_parser
        .get_header(HeaderDef::ChatGroupNameTimestamp)
        .and_then(|s| s.parse::<i64>().ok());

    if let Some(old_name) = mime_parser
        .get_header(HeaderDef::ChatGroupNameChanged)
        .map(|s| s.trim())
        .or(match group_name_timestamp {
            Some(0) => None,
            Some(_) => Some(chat.name.as_str()),
            None => None,
        })
        && let Some(grpname) = mime_parser
            .get_header(HeaderDef::ChatGroupName)
            .map(|grpname| grpname.trim())
            .filter(|grpname| grpname.len() < 200)
    {
        let grpname = &sanitize_single_line(grpname);

        let chat_group_name_timestamp = chat.param.get_i64(Param::GroupNameTimestamp).unwrap_or(0);
        let group_name_timestamp = group_name_timestamp.unwrap_or(mime_parser.timestamp_sent);
        // To provide group name consistency, compare names if timestamps are equal.
        if is_from_in_chat
            && (chat_group_name_timestamp, grpname) < (group_name_timestamp, &chat.name)
            && chat
                .id
                .update_timestamp(context, Param::GroupNameTimestamp, group_name_timestamp)
                .await?
            && grpname != &chat.name
        {
            info!(context, "Updating grpname for chat {}.", chat.id);
            context
                .sql
                .execute(
                    "UPDATE chats SET name=?, name_normalized=? WHERE id=?",
                    (grpname, normalize_text(grpname), chat.id),
                )
                .await?;
            *send_event_chat_modified = true;
        }
        if mime_parser
            .get_header(HeaderDef::ChatGroupNameChanged)
            .is_some()
        {
            if is_from_in_chat {
                let old_name = &sanitize_single_line(old_name);
                better_msg.get_or_insert(
                    if matches!(chat.typ, Chattype::InBroadcast | Chattype::OutBroadcast) {
                        stock_str::msg_broadcast_name_changed(context, old_name, grpname)
                    } else {
                        stock_str::msg_grp_name(context, old_name, grpname, from_id).await
                    },
                );
            } else {
                // Attempt to change group name by non-member, trash it.
                *better_msg = Some(String::new());
            }
        }
    }

    // ========== Apply chat description changes ==========

    if let Some(new_description) = mime_parser
        .get_header(HeaderDef::ChatGroupDescription)
        .map(|d| d.trim())
    {
        let new_description = sanitize_bidi_characters(new_description.trim());
        let old_description = chat::get_chat_description(context, chat.id).await?;

        let old_timestamp = chat
            .param
            .get_i64(Param::GroupDescriptionTimestamp)
            .unwrap_or(0);
        let timestamp_in_header = mime_parser
            .get_header(HeaderDef::ChatGroupDescriptionTimestamp)
            .and_then(|s| s.parse::<i64>().ok());

        let new_timestamp = timestamp_in_header.unwrap_or(mime_parser.timestamp_sent);
        // To provide consistency, compare descriptions if timestamps are equal.
        if is_from_in_chat
            && (old_timestamp, &old_description) < (new_timestamp, &new_description)
            && chat
                .id
                .update_timestamp(context, Param::GroupDescriptionTimestamp, new_timestamp)
                .await?
            && new_description != old_description
        {
            info!(context, "Updating description for chat {}.", chat.id);
            context
                .sql
                .execute(
                    "INSERT OR REPLACE INTO chats_descriptions(chat_id, description) VALUES(?, ?)",
                    (chat.id, &new_description),
                )
                .await?;
            *send_event_chat_modified = true;
        }
        if mime_parser
            .get_header(HeaderDef::ChatGroupDescriptionChanged)
            .is_some()
        {
            if is_from_in_chat {
                better_msg
                    .get_or_insert(stock_str::msg_chat_description_changed(context, from_id).await);
            } else {
                // Attempt to change group description by non-member, trash it.
                *better_msg = Some(String::new());
            }
        }
    }

    // ========== Apply chat avatar changes ==========

    if let (Some(value), None) = (mime_parser.get_header(HeaderDef::ChatContent), &better_msg)
        && value == "group-avatar-changed"
        && let Some(avatar_action) = &mime_parser.group_avatar
    {
        if is_from_in_chat {
            // this is just an explicit message containing the group-avatar,
            // apart from that, the group-avatar is send along with various other messages
            better_msg.get_or_insert(
                if matches!(chat.typ, Chattype::InBroadcast | Chattype::OutBroadcast) {
                    stock_str::msg_broadcast_img_changed(context)
                } else {
                    match avatar_action {
                        AvatarAction::Delete => {
                            stock_str::msg_grp_img_deleted(context, from_id).await
                        }
                        AvatarAction::Change(_) => {
                            stock_str::msg_grp_img_changed(context, from_id).await
                        }
                    }
                },
            );
        } else {
            // Attempt to change group avatar by non-member, trash it.
            *better_msg = Some(String::new());
        }
    }

    if let Some(avatar_action) = &mime_parser.group_avatar
        && is_from_in_chat
        && chat
            .param
            .update_timestamp(Param::AvatarTimestamp, mime_parser.timestamp_sent)?
    {
        info!(context, "Group-avatar change for {}.", chat.id);
        match avatar_action {
            AvatarAction::Change(profile_image) => {
                chat.param.set(Param::ProfileImage, profile_image);
            }
            AvatarAction::Delete => {
                chat.param.remove(Param::ProfileImage);
            }
        };
        chat.update_param(context).await?;
        *send_event_chat_modified = true;
    }

    Ok(())
}

/// Returns a list of strings that should be shown as info messages, informing about group membership changes.
#[expect(clippy::arithmetic_side_effects)]
async fn group_changes_msgs(
    context: &Context,
    added_ids: &BTreeSet<ContactId>,
    removed_ids: &BTreeSet<ContactId>,
    chat_id: ChatId,
) -> Result<Vec<(String, SystemMessage, Option<ContactId>)>> {
    let mut group_changes_msgs: Vec<(String, SystemMessage, Option<ContactId>)> = Vec::new();
    if !added_ids.is_empty() {
        warn!(
            context,
            "Implicit addition of {added_ids:?} to chat {chat_id}."
        );
    }
    if !removed_ids.is_empty() {
        warn!(
            context,
            "Implicit removal of {removed_ids:?} from chat {chat_id}."
        );
    }
    group_changes_msgs.reserve(added_ids.len() + removed_ids.len());
    for contact_id in added_ids {
        group_changes_msgs.push((
            stock_str::msg_add_member_local(context, *contact_id, ContactId::UNDEFINED).await,
            SystemMessage::MemberAddedToGroup,
            Some(*contact_id),
        ));
    }
    for contact_id in removed_ids {
        group_changes_msgs.push((
            stock_str::msg_del_member_local(context, *contact_id, ContactId::UNDEFINED).await,
            SystemMessage::MemberRemovedFromGroup,
            Some(*contact_id),
        ));
    }

    Ok(group_changes_msgs)
}

static LIST_ID_REGEX: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"^(.+)<(.+)>$").unwrap());

fn mailinglist_header_listid(list_id_header: &str) -> Result<String> {
    Ok(match LIST_ID_REGEX.captures(list_id_header) {
        Some(cap) => cap.get(2).context("no match??")?.as_str().trim(),
        None => list_id_header
            .trim()
            .trim_start_matches('<')
            .trim_end_matches('>'),
    }
    .to_string())
}

/// Create or lookup a mailing list or incoming broadcast channel chat.
///
/// `list_id_header` contains the Id that must be used for the mailing list
/// and has the form `Name <Id>`, `<Id>` or just `Id`.
/// Depending on the mailing list type, `list_id_header`
/// was picked from `ListId:`-header or the `Sender:`-header.
///
/// `mime_parser` is the corresponding message
/// and is used to figure out the mailing list name from different header fields.
///
/// Returns the chat ID,
/// whether it is blocked
/// and if the chat was created by this function
/// (as opposed to being looked up among existing chats).
async fn create_or_lookup_mailinglist_or_broadcast(
    context: &Context,
    allow_creation: bool,
    create_blocked: Blocked,
    list_id_header: &str,
    from_id: ContactId,
    mime_parser: &MimeMessage,
) -> Result<Option<(ChatId, Blocked, bool)>> {
    let listid = mailinglist_header_listid(list_id_header)?;

    if let Some((chat_id, blocked)) = chat::get_chat_id_by_grpid(context, &listid).await? {
        return Ok(Some((chat_id, blocked, false)));
    }

    let chattype = if mime_parser.was_encrypted() {
        Chattype::InBroadcast
    } else {
        Chattype::Mailinglist
    };

    let name = if chattype == Chattype::InBroadcast {
        mime_parser
            .get_header(HeaderDef::ChatGroupName)
            .unwrap_or("Broadcast Channel")
    } else {
        &compute_mailinglist_name(list_id_header, &listid, mime_parser)
    };

    if allow_creation {
        // Broadcast channel / mailinglist does not exist but should be created
        let param = mime_parser.list_post.as_ref().map(|list_post| {
            let mut p = Params::new();
            p.set(Param::ListPost, list_post);
            p.to_string()
        });

        let chat_id = ChatId::create_multiuser_record(
            context,
            chattype,
            &listid,
            name,
            if chattype == Chattype::InBroadcast {
                // If we joined the broadcast, we have scanned a QR code.
                // Even if 1:1 chat does not exist or is in a contact request,
                // create the channel as unblocked.
                Blocked::Not
            } else {
                create_blocked
            },
            param,
            mime_parser.timestamp_sent,
        )
        .await
        .with_context(|| format!("failed to create mailinglist '{name}' for grpid={listid}",))?;

        if chattype == Chattype::InBroadcast {
            chat::add_to_chat_contacts_table(
                context,
                mime_parser.timestamp_sent,
                chat_id,
                &[from_id],
            )
            .await?;
        }

        context.emit_event(EventType::ChatModified(chat_id));
        chatlist_events::emit_chatlist_changed(context);
        chatlist_events::emit_chatlist_item_changed(context, chat_id);

        Ok(Some((chat_id, create_blocked, true)))
    } else {
        info!(context, "Creating list forbidden by caller.");
        Ok(None)
    }
}

fn compute_mailinglist_name(
    list_id_header: &str,
    listid: &str,
    mime_parser: &MimeMessage,
) -> String {
    let mut name = match LIST_ID_REGEX
        .captures(list_id_header)
        .and_then(|caps| caps.get(1))
    {
        Some(cap) => cap.as_str().trim().to_string(),
        None => "".to_string(),
    };

    // for mailchimp lists, the name in `ListId` is just a long number.
    // a usable name for these lists is in the `From` header
    // and we can detect these lists by a unique `ListId`-suffix.
    if listid.ends_with(".list-id.mcsv.net")
        && let Some(display_name) = &mime_parser.from.display_name
    {
        name.clone_from(display_name);
    }

    // additional names in square brackets in the subject are preferred
    // (as that part is much more visible, we assume, that names is shorter and comes more to the point,
    // than the sometimes longer part from ListId)
    let subject = mime_parser.get_subject().unwrap_or_default();
    static SUBJECT: LazyLock<Regex> =
        LazyLock::new(|| Regex::new(r"^.{0,5}\[(.+?)\](\s*\[.+\])?").unwrap()); // remove square brackets around first name
    if let Some(cap) = SUBJECT.captures(&subject) {
        name = cap[1].to_string() + cap.get(2).map_or("", |m| m.as_str());
    }

    // if we do not have a name yet and `From` indicates, that this is a notification list,
    // a usable name is often in the `From` header (seen for several parcel service notifications).
    // same, if we do not have a name yet and `List-Id` has a known suffix (`.xt.local`)
    //
    // this pattern is similar to mailchimp above, however,
    // with weaker conditions and does not overwrite existing names.
    if name.is_empty()
        && (mime_parser.from.addr.contains("noreply")
            || mime_parser.from.addr.contains("no-reply")
            || mime_parser.from.addr.starts_with("notifications@")
            || mime_parser.from.addr.starts_with("newsletter@")
            || listid.ends_with(".xt.local"))
        && let Some(display_name) = &mime_parser.from.display_name
    {
        name.clone_from(display_name);
    }

    // as a last resort, use the ListId as the name
    // but strip some known, long hash prefixes
    if name.is_empty() {
        // 51231231231231231231231232869f58.xing.com -> xing.com
        static PREFIX_32_CHARS_HEX: LazyLock<Regex> =
            LazyLock::new(|| Regex::new(r"([0-9a-fA-F]{32})\.(.{6,})").unwrap());
        if let Some(cap) = PREFIX_32_CHARS_HEX
            .captures(listid)
            .and_then(|caps| caps.get(2))
        {
            name = cap.as_str().to_string();
        } else {
            name = listid.to_string();
        }
    }

    sanitize_single_line(&name)
}

/// Set ListId param on the contact and ListPost param the chat.
/// Only called for incoming messages since outgoing messages never have a
/// List-Post header, anyway.
async fn apply_mailinglist_changes(
    context: &Context,
    mime_parser: &MimeMessage,
    chat_id: ChatId,
) -> Result<()> {
    let Some(mailinglist_header) = mime_parser.get_mailinglist_header() else {
        return Ok(());
    };

    let mut chat = Chat::load_from_db(context, chat_id).await?;
    if chat.typ != Chattype::Mailinglist {
        return Ok(());
    }
    let listid = &chat.grpid;

    let new_name = compute_mailinglist_name(mailinglist_header, listid, mime_parser);
    if chat.name != new_name
        && chat_id
            .update_timestamp(
                context,
                Param::GroupNameTimestamp,
                mime_parser.timestamp_sent,
            )
            .await?
    {
        info!(context, "Updating listname for chat {chat_id}.");
        context
            .sql
            .execute(
                "UPDATE chats SET name=?, name_normalized=? WHERE id=?",
                (&new_name, normalize_text(&new_name), chat_id),
            )
            .await?;
        context.emit_event(EventType::ChatModified(chat_id));
    }

    let Some(list_post) = &mime_parser.list_post else {
        return Ok(());
    };

    let list_post = match ContactAddress::new(list_post) {
        Ok(list_post) => list_post,
        Err(err) => {
            warn!(context, "Invalid List-Post: {:#}.", err);
            return Ok(());
        }
    };
    let (contact_id, _) = Contact::add_or_lookup(context, "", &list_post, Origin::Hidden).await?;
    let mut contact = Contact::get_by_id(context, contact_id).await?;
    if contact.param.get(Param::ListId) != Some(listid) {
        contact.param.set(Param::ListId, listid);
        contact.update_param(context).await?;
    }

    if let Some(old_list_post) = chat.param.get(Param::ListPost) {
        if list_post.as_ref() != old_list_post {
            // Apparently the mailing list is using a different List-Post header in each message.
            // Make the mailing list read-only because we wouldn't know which message the user wants to reply to.
            chat.param.remove(Param::ListPost);
            chat.update_param(context).await?;
        }
    } else {
        chat.param.set(Param::ListPost, list_post);
        chat.update_param(context).await?;
    }

    Ok(())
}

async fn apply_out_broadcast_changes(
    context: &Context,
    mime_parser: &MimeMessage,
    chat: &mut Chat,
    from_id: ContactId,
) -> Result<GroupChangesInfo> {
    ensure!(chat.typ == Chattype::OutBroadcast);

    let mut send_event_chat_modified = false;
    let mut better_msg = None;
    let mut added_removed_id: Option<ContactId> = None;

    if from_id == ContactId::SELF {
        let is_from_in_chat = true;
        apply_chat_name_avatar_and_description_changes(
            context,
            mime_parser,
            from_id,
            is_from_in_chat,
            chat,
            &mut send_event_chat_modified,
            &mut better_msg,
        )
        .await?;
    }

    if let Some(added_fpr) = mime_parser.get_header(HeaderDef::ChatGroupMemberAddedFpr) {
        if from_id == ContactId::SELF {
            let added_id = lookup_key_contact_by_fingerprint(context, added_fpr).await?;
            if let Some(added_id) = added_id {
                if chat::is_contact_in_chat(context, chat.id, added_id).await? {
                    info!(context, "No-op broadcast addition (TRASH)");
                    better_msg.get_or_insert("".to_string());
                } else {
                    chat::add_to_chat_contacts_table(
                        context,
                        mime_parser.timestamp_sent,
                        chat.id,
                        &[added_id],
                    )
                    .await?;
                    let msg =
                        stock_str::msg_add_member_local(context, added_id, ContactId::UNDEFINED)
                            .await;
                    better_msg.get_or_insert(msg);
                    added_removed_id = Some(added_id);
                    send_event_chat_modified = true;
                }
            } else {
                warn!(context, "Failed to find contact with fpr {added_fpr}");
            }
        }
    } else if let Some(removed_fpr) = mime_parser.get_header(HeaderDef::ChatGroupMemberRemovedFpr) {
        send_event_chat_modified = true;
        let removed_id = lookup_key_contact_by_fingerprint(context, removed_fpr).await?;
        if removed_id == Some(from_id) {
            // The sender of the message left the broadcast channel
            // Silently remove them without notifying the user
            chat::remove_from_chat_contacts_table_without_trace(context, chat.id, from_id).await?;
            info!(context, "Broadcast leave message (TRASH)");
            better_msg = Some("".to_string());
        } else if from_id == ContactId::SELF
            && let Some(removed_id) = removed_id
        {
            chat::remove_from_chat_contacts_table_without_trace(context, chat.id, removed_id)
                .await?;

            better_msg.get_or_insert(
                stock_str::msg_del_member_local(context, removed_id, ContactId::SELF).await,
            );
            added_removed_id = Some(removed_id);
        }
    }

    if send_event_chat_modified {
        context.emit_event(EventType::ChatModified(chat.id));
        chatlist_events::emit_chatlist_item_changed(context, chat.id);
    }
    Ok(GroupChangesInfo {
        better_msg,
        added_removed_id,
        silent: false,
        extra_msgs: vec![],
    })
}

async fn apply_in_broadcast_changes(
    context: &Context,
    mime_parser: &MimeMessage,
    chat: &mut Chat,
    from_id: ContactId,
) -> Result<GroupChangesInfo> {
    ensure!(chat.typ == Chattype::InBroadcast);

    if let Some(part) = mime_parser.parts.first()
        && let Some(error) = &part.error
    {
        warn!(
            context,
            "Not applying broadcast changes from message with error: {error}"
        );
        return Ok(GroupChangesInfo::default());
    }

    let mut send_event_chat_modified = false;
    let mut better_msg = None;

    let is_from_in_chat = is_contact_in_chat(context, chat.id, from_id).await?;
    apply_chat_name_avatar_and_description_changes(
        context,
        mime_parser,
        from_id,
        is_from_in_chat,
        chat,
        &mut send_event_chat_modified,
        &mut better_msg,
    )
    .await?;

    if let Some(added_addr) = mime_parser.get_header(HeaderDef::ChatGroupMemberAdded)
        && context.is_self_addr(added_addr).await?
    {
        let msg = if chat.is_self_in_chat(context).await? {
            // Self is already in the chat.
            // Probably Alice has two devices and her second device added us again;
            // just hide the message.
            info!(context, "No-op broadcast 'Member added' message (TRASH)");
            "".to_string()
        } else {
            stock_str::msg_you_joined_broadcast(context)
        };

        better_msg.get_or_insert(msg);
        send_event_chat_modified = true;
    }

    if let Some(removed_fpr) = mime_parser.get_header(HeaderDef::ChatGroupMemberRemovedFpr) {
        // We are not supposed to receive a notification when someone else than self is removed:
        if removed_fpr != self_fingerprint(context).await? {
            logged_debug_assert!(context, false, "Ignoring unexpected removal message");
            return Ok(GroupChangesInfo::default());
        }
        chat::delete_broadcast_secret(context, chat.id).await?;

        if from_id == ContactId::SELF {
            better_msg.get_or_insert(stock_str::msg_you_left_broadcast(context));
        } else {
            better_msg.get_or_insert(
                stock_str::msg_del_member_local(context, ContactId::SELF, from_id).await,
            );
        }

        chat::remove_from_chat_contacts_table_without_trace(context, chat.id, ContactId::SELF)
            .await?;
        send_event_chat_modified = true;
    } else if !chat.is_self_in_chat(context).await? {
        chat::add_to_chat_contacts_table(
            context,
            mime_parser.timestamp_sent,
            chat.id,
            &[ContactId::SELF],
        )
        .await?;
        send_event_chat_modified = true;
    }

    if let Some(secret) = mime_parser.get_header(HeaderDef::ChatBroadcastSecret) {
        if validate_broadcast_secret(secret) {
            save_broadcast_secret(context, chat.id, secret).await?;
        } else {
            warn!(context, "Not saving invalid broadcast secret");
        }
    }

    if send_event_chat_modified {
        context.emit_event(EventType::ChatModified(chat.id));
        chatlist_events::emit_chatlist_item_changed(context, chat.id);
    }
    Ok(GroupChangesInfo {
        better_msg,
        added_removed_id: None,
        silent: false,
        extra_msgs: vec![],
    })
}

/// Creates ad-hoc group and returns chat ID on success.
async fn create_adhoc_group(
    context: &Context,
    mime_parser: &MimeMessage,
    create_blocked: Blocked,
    from_id: ContactId,
    to_ids: &[ContactId],
    grpname: &str,
) -> Result<Option<(ChatId, Blocked)>> {
    let mut member_ids: Vec<ContactId> = to_ids
        .iter()
        .copied()
        .filter(|&id| id != ContactId::SELF)
        .collect();
    if from_id != ContactId::SELF && !member_ids.contains(&from_id) {
        member_ids.push(from_id);
    }
    if !mime_parser.was_encrypted() {
        member_ids.push(ContactId::SELF);
    }

    if mime_parser.is_mailinglist_message() {
        return Ok(None);
    }
    if mime_parser
        .get_header(HeaderDef::ChatGroupMemberRemoved)
        .is_some()
    {
        info!(
            context,
            "Message removes member from unknown ad-hoc group (TRASH)."
        );
        return Ok(Some((DC_CHAT_ID_TRASH, Blocked::Not)));
    }

    let new_chat_id: ChatId = ChatId::create_multiuser_record(
        context,
        Chattype::Group,
        "", // Ad hoc groups have no ID.
        grpname,
        create_blocked,
        None,
        mime_parser.timestamp_sent,
    )
    .await?;

    info!(
        context,
        "Created ad-hoc group id={new_chat_id}, name={grpname:?}."
    );
    chat::add_to_chat_contacts_table(
        context,
        mime_parser.timestamp_sent,
        new_chat_id,
        &member_ids,
    )
    .await?;

    context.emit_event(EventType::ChatModified(new_chat_id));
    chatlist_events::emit_chatlist_changed(context);
    chatlist_events::emit_chatlist_item_changed(context, new_chat_id);

    Ok(Some((new_chat_id, create_blocked)))
}

#[derive(Debug, PartialEq, Eq)]
enum VerifiedEncryption {
    Verified,
    NotVerified(String), // The string contains the reason why it's not verified
}

/// Checks whether the message is allowed to appear in a protected chat.
///
/// This means that it is encrypted and signed with a verified key.
async fn has_verified_encryption(
    context: &Context,
    mimeparser: &MimeMessage,
    from_id: ContactId,
) -> Result<VerifiedEncryption> {
    use VerifiedEncryption::*;

    if !mimeparser.was_encrypted() {
        return Ok(NotVerified("This message is not encrypted".to_string()));
    };

    if from_id == ContactId::SELF {
        return Ok(Verified);
    }

    let from_contact = Contact::get_by_id(context, from_id).await?;

    let Some(fingerprint) = from_contact.fingerprint() else {
        return Ok(NotVerified(
            "The message was sent without encryption".to_string(),
        ));
    };

    if from_contact.get_verifier_id(context).await?.is_none() {
        return Ok(NotVerified(
            "The message was sent by non-verified contact".to_string(),
        ));
    }

    let signed_with_verified_key = mimeparser
        .signature
        .as_ref()
        .is_some_and(|(signature, _)| *signature == fingerprint);
    if signed_with_verified_key {
        Ok(Verified)
    } else {
        Ok(NotVerified(
            "The message was sent with non-verified encryption".to_string(),
        ))
    }
}

async fn mark_recipients_as_verified(
    context: &Context,
    from_id: ContactId,
    mimeparser: &MimeMessage,
) -> Result<()> {
    let verifier_id = Some(from_id).filter(|&id| id != ContactId::SELF);

    // We don't yet send the _verified property in autocrypt headers.
    // Until we do, we instead accept the Chat-Verified header as indication all contacts are verified.
    // TODO: Ignore ChatVerified header once we reset existing verifications.
    let chat_verified = mimeparser.get_header(HeaderDef::ChatVerified).is_some();

    for gossiped_key in mimeparser
        .gossiped_keys
        .values()
        .filter(|gossiped_key| gossiped_key.verified || chat_verified)
    {
        let fingerprint = gossiped_key.public_key.dc_fingerprint().hex();
        let Some(to_id) = lookup_key_contact_by_fingerprint(context, &fingerprint).await? else {
            continue;
        };

        if to_id == ContactId::SELF || to_id == from_id {
            continue;
        }

        mark_contact_id_as_verified(context, to_id, verifier_id).await?;
    }

    Ok(())
}

/// Returns the last message referenced from `References` header if it is in the database.
///
/// For Delta Chat messages it is the last message in the chat of the sender.
async fn get_previous_message(
    context: &Context,
    mime_parser: &MimeMessage,
) -> Result<Option<Message>> {
    if let Some(field) = mime_parser.get_header(HeaderDef::References)
        && let Some(rfc724mid) = parse_message_ids(field).last()
        && let Some(msg_id) = rfc724_mid_exists(context, rfc724mid).await?
    {
        return Message::load_from_db_optional(context, msg_id).await;
    }
    Ok(None)
}

/// Returns the last message referenced from References: header found in the database.
///
/// If none found, tries In-Reply-To: as a fallback for classic MUAs that don't set the
/// References: header.
async fn get_parent_message(
    context: &Context,
    references: Option<&str>,
    in_reply_to: Option<&str>,
) -> Result<Option<Message>> {
    let mut mids = Vec::new();
    if let Some(field) = in_reply_to {
        mids = parse_message_ids(field);
    }
    if let Some(field) = references {
        mids.append(&mut parse_message_ids(field));
    }
    message::get_by_rfc724_mids(context, &mids).await
}

pub(crate) async fn get_prefetch_parent_message(
    context: &Context,
    headers: &[mailparse::MailHeader<'_>],
) -> Result<Option<Message>> {
    get_parent_message(
        context,
        headers.get_header_value(HeaderDef::References).as_deref(),
        headers.get_header_value(HeaderDef::InReplyTo).as_deref(),
    )
    .await
}

/// Looks up contact IDs from the database given the list of recipients.
async fn add_or_lookup_contacts_by_address_list(
    context: &Context,
    address_list: &[SingleInfo],
    origin: Origin,
) -> Result<Vec<Option<ContactId>>> {
    let mut contact_ids = Vec::new();
    for info in address_list {
        let addr = &info.addr;
        if !may_be_valid_addr(addr) {
            contact_ids.push(None);
            continue;
        }
        let display_name = info.display_name.as_deref();
        if let Ok(addr) = ContactAddress::new(addr) {
            let (contact_id, _) =
                Contact::add_or_lookup(context, display_name.unwrap_or_default(), &addr, origin)
                    .await?;
            contact_ids.push(Some(contact_id));
        } else {
            warn!(context, "Contact with address {:?} cannot exist.", addr);
            contact_ids.push(None);
        }
    }

    Ok(contact_ids)
}

/// Looks up contact IDs from the database given the list of recipients.
async fn add_or_lookup_key_contacts(
    context: &Context,
    address_list: &[SingleInfo],
    gossiped_keys: &BTreeMap<String, GossipedKey>,
    fingerprints: &[Fingerprint],
    origin: Origin,
) -> Result<Vec<Option<ContactId>>> {
    let mut contact_ids = Vec::new();
    let mut fingerprint_iter = fingerprints.iter();
    for info in address_list {
        let fp = fingerprint_iter.next();
        let addr = &info.addr;
        if !may_be_valid_addr(addr) {
            contact_ids.push(None);
            continue;
        }
        let fingerprint: String = if let Some(fp) = fp {
            // Iterator has not ran out of fingerprints yet.
            fp.hex()
        } else if let Some(key) = gossiped_keys.get(addr) {
            key.public_key.dc_fingerprint().hex()
        } else if context.is_self_addr(addr).await? {
            contact_ids.push(Some(ContactId::SELF));
            continue;
        } else {
            contact_ids.push(None);
            continue;
        };
        let display_name = info.display_name.as_deref();
        if let Ok(addr) = ContactAddress::new(addr) {
            let (contact_id, _) = Contact::add_or_lookup_ex(
                context,
                display_name.unwrap_or_default(),
                &addr,
                &fingerprint,
                origin,
            )
            .await?;
            contact_ids.push(Some(contact_id));
        } else {
            warn!(context, "Contact with address {:?} cannot exist.", addr);
            contact_ids.push(None);
        }
    }

    ensure_and_debug_assert_eq!(contact_ids.len(), address_list.len(),);
    Ok(contact_ids)
}

/// Looks up a key-contact by email address.
///
/// If provided, `chat_id` must be an encrypted chat ID that has key-contacts inside.
/// Otherwise the function searches in all contacts, preferring accepted and most recently seen ones.
async fn lookup_key_contact_by_address(
    context: &Context,
    addr: &str,
    chat_id: Option<ChatId>,
) -> Result<Option<ContactId>> {
    if context.is_self_addr(addr).await? {
        if chat_id.is_none() {
            return Ok(Some(ContactId::SELF));
        }
        let is_self_in_chat = context
            .sql
            .exists(
                "SELECT COUNT(*) FROM chats_contacts WHERE chat_id=? AND contact_id=1",
                (chat_id,),
            )
            .await?;
        if is_self_in_chat {
            return Ok(Some(ContactId::SELF));
        }
    }
    let contact_id: Option<ContactId> = match chat_id {
        Some(chat_id) => {
            context
                .sql
                .query_row_optional(
                    "SELECT id FROM contacts
                     WHERE contacts.addr=?
                     AND EXISTS (SELECT 1 FROM chats_contacts
                                 WHERE contact_id=contacts.id
                                 AND chat_id=?)
                     AND fingerprint<>'' -- Should always be true
                     ",
                    (addr, chat_id),
                    |row| {
                        let contact_id: ContactId = row.get(0)?;
                        Ok(contact_id)
                    },
                )
                .await?
        }
        None => {
            context
                .sql
                .query_row_optional(
                    "SELECT id FROM contacts
                     WHERE addr=?
                     AND fingerprint<>''
                     ORDER BY
                         (
                             SELECT COUNT(*) FROM chats c
                             INNER JOIN chats_contacts cc
                             ON c.id=cc.chat_id
                             WHERE c.type=?
                                 AND c.id>?
                                 AND c.blocked=?
                                 AND cc.contact_id=contacts.id
                         ) DESC,
                         last_seen DESC, id DESC
                     ",
                    (
                        addr,
                        Chattype::Single,
                        constants::DC_CHAT_ID_LAST_SPECIAL,
                        Blocked::Not,
                    ),
                    |row| {
                        let contact_id: ContactId = row.get(0)?;
                        Ok(contact_id)
                    },
                )
                .await?
        }
    };
    Ok(contact_id)
}

async fn lookup_key_contact_by_fingerprint(
    context: &Context,
    fingerprint: &str,
) -> Result<Option<ContactId>> {
    logged_debug_assert!(
        context,
        !fingerprint.is_empty(),
        "lookup_key_contact_by_fingerprint: fingerprint is empty."
    );
    if fingerprint.is_empty() {
        // Avoid accidentally looking up a non-key-contact.
        return Ok(None);
    }
    if let Some(contact_id) = context
        .sql
        .query_row_optional(
            "SELECT id FROM contacts
             WHERE fingerprint=? AND fingerprint!=''",
            (fingerprint,),
            |row| {
                let contact_id: ContactId = row.get(0)?;
                Ok(contact_id)
            },
        )
        .await?
    {
        Ok(Some(contact_id))
    } else if let Some(self_fp) = self_fingerprint_opt(context).await? {
        if self_fp == fingerprint {
            Ok(Some(ContactId::SELF))
        } else {
            Ok(None)
        }
    } else {
        Ok(None)
    }
}

/// Adds or looks up key-contacts by fingerprints or by email addresses in the given chat.
///
/// `fingerprints` may be empty.
/// This is used as a fallback when email addresses are available,
/// but not the fingerprints, e.g. when core 1.157.3
/// client sends the `To` and `Chat-Group-Past-Members` header
/// but not the corresponding fingerprint list.
///
/// Lookup is restricted to the chat ID.
///
/// If contact cannot be found, `None` is returned.
/// This ensures that the length of the result vector
/// is the same as the number of addresses in the header
/// and it is possible to find corresponding
/// `Chat-Group-Member-Timestamps` items.
async fn lookup_key_contacts_fallback_to_chat(
    context: &Context,
    address_list: &[SingleInfo],
    fingerprints: &[Fingerprint],
    chat_id: Option<ChatId>,
) -> Result<Vec<Option<ContactId>>> {
    let mut contact_ids = Vec::new();
    let mut fingerprint_iter = fingerprints.iter();
    for info in address_list {
        let fp = fingerprint_iter.next();
        let addr = &info.addr;
        if !may_be_valid_addr(addr) {
            contact_ids.push(None);
            continue;
        }

        if let Some(fp) = fp {
            // Iterator has not ran out of fingerprints yet.
            let display_name = info.display_name.as_deref();
            let fingerprint: String = fp.hex();

            if let Ok(addr) = ContactAddress::new(addr) {
                let (contact_id, _) = Contact::add_or_lookup_ex(
                    context,
                    display_name.unwrap_or_default(),
                    &addr,
                    &fingerprint,
                    Origin::Hidden,
                )
                .await?;
                contact_ids.push(Some(contact_id));
            } else {
                warn!(context, "Contact with address {:?} cannot exist.", addr);
                contact_ids.push(None);
            }
        } else {
            let contact_id = lookup_key_contact_by_address(context, addr, chat_id).await?;
            contact_ids.push(contact_id);
        }
    }
    ensure_and_debug_assert_eq!(address_list.len(), contact_ids.len(),);
    Ok(contact_ids)
}

/// Returns true if the message should not result in renaming
/// of the sender contact.
fn should_prevent_rename(mime_parser: &MimeMessage) -> bool {
    (mime_parser.is_mailinglist_message() && !mime_parser.was_encrypted())
        || mime_parser.get_header(HeaderDef::Sender).is_some()
}

#[cfg(test)]
mod receive_imf_tests;