deltachat/imap/
select_folder.rs

1//! # IMAP folder selection module.
2
3use anyhow::Context as _;
4
5use super::session::Session as ImapSession;
6use super::{get_uid_next, get_uidvalidity, set_modseq, set_uid_next, set_uidvalidity};
7use crate::context::Context;
8use crate::ensure_and_debug_assert;
9use crate::log::warn;
10
11type Result<T> = std::result::Result<T, Error>;
12
13#[derive(Debug, thiserror::Error)]
14pub enum Error {
15    #[error(
16        "Got a NO response when trying to select {0}, usually this means that it doesn't exist: {1}"
17    )]
18    NoFolder(String, String),
19
20    #[error("IMAP other error: {0}")]
21    Other(String),
22}
23
24impl From<anyhow::Error> for Error {
25    fn from(err: anyhow::Error) -> Error {
26        Error::Other(format!("{err:#}"))
27    }
28}
29
30impl ImapSession {
31    /// Issues a CLOSE command if selected folder needs expunge,
32    /// i.e. if Delta Chat marked a message there as deleted previously.
33    ///
34    /// CLOSE is considerably faster than an EXPUNGE
35    /// because no EXPUNGE responses are sent, see
36    /// <https://tools.ietf.org/html/rfc3501#section-6.4.2>
37    pub(super) async fn maybe_close_folder(&mut self, context: &Context) -> anyhow::Result<()> {
38        if let Some(folder) = &self.selected_folder
39            && self.selected_folder_needs_expunge
40        {
41            info!(context, "Expunge messages in {folder:?}.");
42
43            self.close().await.context("IMAP close/expunge failed")?;
44            info!(context, "Close/expunge succeeded.");
45            self.selected_folder = None;
46            self.selected_folder_needs_expunge = false;
47            self.new_mail = false;
48        }
49        Ok(())
50    }
51
52    /// Selects a folder, possibly updating uid_validity and, if needed,
53    /// expunging the folder to remove delete-marked messages.
54    /// Returns whether a new folder was selected.
55    async fn select_folder(&mut self, context: &Context, folder: &str) -> Result<NewlySelected> {
56        // if there is a new folder and the new folder is equal to the selected one, there's nothing to do.
57        // if there is _no_ new folder, we continue as we might want to expunge below.
58        if let Some(selected_folder) = &self.selected_folder
59            && folder == selected_folder
60        {
61            return Ok(NewlySelected::No);
62        }
63
64        // deselect existing folder, if needed (it's also done implicitly by SELECT, however, without EXPUNGE then)
65        self.maybe_close_folder(context).await?;
66
67        // select new folder
68        let res = self.select(folder).await;
69
70        let transport_id = self.transport_id();
71
72        // <https://tools.ietf.org/html/rfc3501#section-6.3.1>
73        // says that if the server reports select failure we are in
74        // authenticated (not-select) state.
75
76        match res {
77            Ok(mailbox) => {
78                info!(
79                    context,
80                    "Transport {transport_id}: Selected folder {folder:?}."
81                );
82                self.selected_folder = Some(folder.to_string());
83                self.selected_mailbox = Some(mailbox);
84                Ok(NewlySelected::Yes)
85            }
86            Err(async_imap::error::Error::No(response)) => {
87                Err(Error::NoFolder(folder.to_string(), response))
88            }
89            Err(err) => Err(Error::Other(err.to_string())),
90        }
91    }
92
93    /// Selects a folder optionally creating it and takes care of UIDVALIDITY changes. Returns false
94    /// iff `folder` doesn't exist.
95    ///
96    /// When selecting a folder for the first time, sets the uid_next to the current
97    /// mailbox.uid_next so that no old emails are fetched.
98    ///
99    /// Updates `self.new_mail` if folder was previously unselected
100    /// and new mails are detected after selecting,
101    /// i.e. UIDNEXT advanced while the folder was closed.
102    pub(crate) async fn select_with_uidvalidity(
103        &mut self,
104        context: &Context,
105        folder: &str,
106    ) -> anyhow::Result<bool> {
107        let newly_selected = match self.select_folder(context, folder).await {
108            Ok(newly_selected) => newly_selected,
109            Err(err) => match err {
110                Error::NoFolder(..) => return Ok(false),
111                _ => {
112                    return Err(err)
113                        .with_context(|| format!("Failed to select folder {folder:?}"))?;
114                }
115            },
116        };
117        let transport_id = self.transport_id();
118
119        // Folders should not be selected when transport_id is not assigned yet
120        // because we cannot save UID validity then.
121        ensure_and_debug_assert!(
122            transport_id > 0,
123            "Cannot select folder when transport ID is unknown"
124        );
125
126        let mailbox = self
127            .selected_mailbox
128            .as_mut()
129            .with_context(|| format!("No mailbox selected, folder: {folder:?}"))?;
130
131        let old_uid_validity = get_uidvalidity(context, transport_id, folder)
132            .await
133            .with_context(|| format!("Failed to get old UID validity for folder {folder:?}"))?;
134        let old_uid_next = get_uid_next(context, transport_id, folder)
135            .await
136            .with_context(|| format!("Failed to get old UID NEXT for folder {folder:?}"))?;
137
138        let new_uid_validity = mailbox
139            .uid_validity
140            .with_context(|| format!("No UIDVALIDITY for folder {folder}"))?;
141        let new_uid_next = if let Some(uid_next) = mailbox.uid_next {
142            Some(uid_next)
143        } else {
144            warn!(
145                context,
146                "SELECT response for IMAP folder {folder:?} has no UIDNEXT, fall back to STATUS command."
147            );
148
149            // RFC 3501 says STATUS command SHOULD NOT be used
150            // on the currently selected mailbox because the same
151            // information can be obtained by other means,
152            // such as reading SELECT response.
153            //
154            // However, it also says that UIDNEXT is REQUIRED
155            // in the SELECT response and if we are here,
156            // it is actually not returned.
157            //
158            // In particular, Winmail Pro Mail Server 5.1.0616
159            // never returns UIDNEXT in SELECT response,
160            // but responds to "STATUS INBOX (UIDNEXT)" command.
161            let status = self
162                .inner
163                .status(folder, "(UIDNEXT)")
164                .await
165                .with_context(|| format!("STATUS (UIDNEXT) error for {folder:?}"))?;
166
167            if status.uid_next.is_none() {
168                // This happens with mail.163.com as of 2023-11-26.
169                // It does not return UIDNEXT on SELECT and returns invalid
170                // `* STATUS "INBOX" ()` response on explicit request for UIDNEXT.
171                warn!(context, "STATUS {folder} (UIDNEXT) did not return UIDNEXT.");
172            }
173            status.uid_next
174        };
175        mailbox.uid_next = new_uid_next;
176
177        if new_uid_validity == old_uid_validity {
178            if newly_selected == NewlySelected::Yes {
179                if let Some(new_uid_next) = new_uid_next {
180                    if new_uid_next < old_uid_next {
181                        warn!(
182                            context,
183                            "The server illegally decreased the uid_next of folder {folder:?} from {old_uid_next} to {new_uid_next} without changing validity ({new_uid_validity}), resyncing UIDs...",
184                        );
185                        set_uid_next(context, transport_id, folder, new_uid_next).await?;
186                        self.resync_request_sender.try_send(()).ok();
187                    }
188
189                    // If UIDNEXT changed, there are new emails.
190                    self.new_mail |= new_uid_next != old_uid_next;
191                } else {
192                    warn!(
193                        context,
194                        "Folder {folder} was just selected but we failed to determine UIDNEXT, assume that it has new mail."
195                    );
196                    self.new_mail = true;
197                }
198            }
199
200            return Ok(true);
201        }
202
203        // UIDVALIDITY is modified, reset highest seen MODSEQ.
204        set_modseq(context, transport_id, folder, 0).await?;
205
206        // ==============  uid_validity has changed or is being set the first time.  ==============
207
208        let new_uid_next = new_uid_next.unwrap_or_default();
209        set_uid_next(context, transport_id, folder, new_uid_next).await?;
210        set_uidvalidity(context, transport_id, folder, new_uid_validity).await?;
211        self.new_mail = true;
212
213        // Collect garbage entries in `imap` table.
214        context
215            .sql
216            .execute(
217                "DELETE FROM imap WHERE transport_id=? AND folder=? AND uidvalidity!=?",
218                (transport_id, &folder, new_uid_validity),
219            )
220            .await?;
221
222        if old_uid_validity != 0 || old_uid_next != 0 {
223            self.resync_request_sender.try_send(()).ok();
224        }
225        info!(
226            context,
227            "transport {transport_id}: UID validity for folder {folder} changed from {old_uid_validity}/{old_uid_next} to {new_uid_validity}/{new_uid_next}.",
228        );
229        Ok(true)
230    }
231}
232
233#[derive(PartialEq, Debug, Copy, Clone, Eq)]
234pub(crate) enum NewlySelected {
235    /// The folder was newly selected during this call to select_folder().
236    Yes,
237    /// No SELECT command was run because the folder already was selected
238    /// and self.config.selected_mailbox was not updated (so, e.g. it may contain an outdated uid_next)
239    No,
240}
deltachat/imap/select_folder.rs

deltachat/imap/
select_folder.rs
