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 = if self.can_condstore() {
69            self.select_condstore(folder).await
70        } else {
71            self.select(folder).await
72        };
73
74        // <https://tools.ietf.org/html/rfc3501#section-6.3.1>
75        // says that if the server reports select failure we are in
76        // authenticated (not-select) state.
77
78        match res {
79            Ok(mailbox) => {
80                info!(context, "Selected folder {folder:?}.");
81                self.selected_folder = Some(folder.to_string());
82                self.selected_mailbox = Some(mailbox);
83                Ok(NewlySelected::Yes)
84            }
85            Err(async_imap::error::Error::No(response)) => {
86                Err(Error::NoFolder(folder.to_string(), response))
87            }
88            Err(err) => Err(Error::Other(err.to_string())),
89        }
90    }
91
92    /// Selects a folder optionally creating it and takes care of UIDVALIDITY changes. Returns false
93    /// iff `folder` doesn't exist.
94    ///
95    /// When selecting a folder for the first time, sets the uid_next to the current
96    /// mailbox.uid_next so that no old emails are fetched.
97    ///
98    /// Updates `self.new_mail` if folder was previously unselected
99    /// and new mails are detected after selecting,
100    /// i.e. UIDNEXT advanced while the folder was closed.
101    pub(crate) async fn select_with_uidvalidity(
102        &mut self,
103        context: &Context,
104        folder: &str,
105    ) -> anyhow::Result<bool> {
106        let newly_selected = match self.select_folder(context, folder).await {
107            Ok(newly_selected) => newly_selected,
108            Err(err) => match err {
109                Error::NoFolder(..) => return Ok(false),
110                _ => {
111                    return Err(err)
112                        .with_context(|| format!("Failed to select folder {folder:?}"))?;
113                }
114            },
115        };
116        let transport_id = self.transport_id();
117
118        // Folders should not be selected when transport_id is not assigned yet
119        // because we cannot save UID validity then.
120        ensure_and_debug_assert!(
121            transport_id > 0,
122            "Cannot select folder when transport ID is unknown"
123        );
124
125        let mailbox = self
126            .selected_mailbox
127            .as_mut()
128            .with_context(|| format!("No mailbox selected, folder: {folder:?}"))?;
129
130        let old_uid_validity = get_uidvalidity(context, transport_id, folder)
131            .await
132            .with_context(|| format!("Failed to get old UID validity for folder {folder:?}"))?;
133        let old_uid_next = get_uid_next(context, transport_id, folder)
134            .await
135            .with_context(|| format!("Failed to get old UID NEXT for folder {folder:?}"))?;
136
137        let new_uid_validity = mailbox
138            .uid_validity
139            .with_context(|| format!("No UIDVALIDITY for folder {folder}"))?;
140        let new_uid_next = if let Some(uid_next) = mailbox.uid_next {
141            Some(uid_next)
142        } else {
143            warn!(
144                context,
145                "SELECT response for IMAP folder {folder:?} has no UIDNEXT, fall back to STATUS command."
146            );
147
148            // RFC 3501 says STATUS command SHOULD NOT be used
149            // on the currently selected mailbox because the same
150            // information can be obtained by other means,
151            // such as reading SELECT response.
152            //
153            // However, it also says that UIDNEXT is REQUIRED
154            // in the SELECT response and if we are here,
155            // it is actually not returned.
156            //
157            // In particular, Winmail Pro Mail Server 5.1.0616
158            // never returns UIDNEXT in SELECT response,
159            // but responds to "STATUS INBOX (UIDNEXT)" command.
160            let status = self
161                .inner
162                .status(folder, "(UIDNEXT)")
163                .await
164                .with_context(|| format!("STATUS (UIDNEXT) error for {folder:?}"))?;
165
166            if status.uid_next.is_none() {
167                // This happens with mail.163.com as of 2023-11-26.
168                // It does not return UIDNEXT on SELECT and returns invalid
169                // `* STATUS "INBOX" ()` response on explicit request for UIDNEXT.
170                warn!(context, "STATUS {folder} (UIDNEXT) did not return UIDNEXT.");
171            }
172            status.uid_next
173        };
174        mailbox.uid_next = new_uid_next;
175
176        if new_uid_validity == old_uid_validity {
177            if newly_selected == NewlySelected::Yes {
178                if let Some(new_uid_next) = new_uid_next {
179                    if new_uid_next < old_uid_next {
180                        warn!(
181                            context,
182                            "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...",
183                        );
184                        set_uid_next(context, transport_id, folder, new_uid_next).await?;
185                        self.resync_request_sender.try_send(()).ok();
186                    }
187
188                    // If UIDNEXT changed, there are new emails.
189                    self.new_mail |= new_uid_next != old_uid_next;
190                } else {
191                    warn!(
192                        context,
193                        "Folder {folder} was just selected but we failed to determine UIDNEXT, assume that it has new mail."
194                    );
195                    self.new_mail = true;
196                }
197            }
198
199            return Ok(true);
200        }
201
202        // UIDVALIDITY is modified, reset highest seen MODSEQ.
203        set_modseq(context, transport_id, folder, 0).await?;
204
205        // ==============  uid_validity has changed or is being set the first time.  ==============
206
207        let new_uid_next = new_uid_next.unwrap_or_default();
208        set_uid_next(context, transport_id, folder, new_uid_next).await?;
209        set_uidvalidity(context, transport_id, folder, new_uid_validity).await?;
210        self.new_mail = true;
211
212        // Collect garbage entries in `imap` table.
213        context
214            .sql
215            .execute(
216                "DELETE FROM imap WHERE transport_id=? AND folder=? AND uidvalidity!=?",
217                (transport_id, &folder, new_uid_validity),
218            )
219            .await?;
220
221        if old_uid_validity != 0 || old_uid_next != 0 {
222            self.resync_request_sender.try_send(()).ok();
223        }
224        info!(
225            context,
226            "transport {transport_id}: UID validity for folder {folder} changed from {old_uid_validity}/{old_uid_next} to {new_uid_validity}/{new_uid_next}.",
227        );
228        Ok(true)
229    }
230}
231
232#[derive(PartialEq, Debug, Copy, Clone, Eq)]
233pub(crate) enum NewlySelected {
234    /// The folder was newly selected during this call to select_folder().
235    Yes,
236    /// No SELECT command was run because the folder already was selected
237    /// and self.config.selected_mailbox was not updated (so, e.g. it may contain an outdated uid_next)
238    No,
239}
deltachat/imap/select_folder.rs

deltachat/imap/
select_folder.rs
