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;
8
9type Result<T> = std::result::Result<T, Error>;
10
11#[derive(Debug, thiserror::Error)]
12pub enum Error {
13    #[error("Got a NO response when trying to select {0}, usually this means that it doesn't exist: {1}")]
14    NoFolder(String, String),
15
16    #[error("IMAP other error: {0}")]
17    Other(String),
18}
19
20impl From<anyhow::Error> for Error {
21    fn from(err: anyhow::Error) -> Error {
22        Error::Other(format!("{err:#}"))
23    }
24}
25
26impl ImapSession {
27    /// Issues a CLOSE command if selected folder needs expunge,
28    /// i.e. if Delta Chat marked a message there as deleted previously.
29    ///
30    /// CLOSE is considerably faster than an EXPUNGE
31    /// because no EXPUNGE responses are sent, see
32    /// <https://tools.ietf.org/html/rfc3501#section-6.4.2>
33    pub(super) async fn maybe_close_folder(&mut self, context: &Context) -> anyhow::Result<()> {
34        if let Some(folder) = &self.selected_folder {
35            if self.selected_folder_needs_expunge {
36                info!(context, "Expunge messages in \"{}\".", folder);
37
38                self.close().await.context("IMAP close/expunge failed")?;
39                info!(context, "close/expunge succeeded");
40                self.selected_folder = None;
41                self.selected_folder_needs_expunge = false;
42                self.new_mail = false;
43            }
44        }
45        Ok(())
46    }
47
48    /// Selects a folder, possibly updating uid_validity and, if needed,
49    /// expunging the folder to remove delete-marked messages.
50    /// Returns whether a new folder was selected.
51    async fn select_folder(&mut self, context: &Context, folder: &str) -> Result<NewlySelected> {
52        // if there is a new folder and the new folder is equal to the selected one, there's nothing to do.
53        // if there is _no_ new folder, we continue as we might want to expunge below.
54        if let Some(selected_folder) = &self.selected_folder {
55            if folder == selected_folder {
56                return Ok(NewlySelected::No);
57            }
58        }
59
60        // deselect existing folder, if needed (it's also done implicitly by SELECT, however, without EXPUNGE then)
61        self.maybe_close_folder(context).await?;
62
63        // select new folder
64        let res = if self.can_condstore() {
65            self.select_condstore(folder).await
66        } else {
67            self.select(folder).await
68        };
69
70        // <https://tools.ietf.org/html/rfc3501#section-6.3.1>
71        // says that if the server reports select failure we are in
72        // authenticated (not-select) state.
73
74        match res {
75            Ok(mailbox) => {
76                self.selected_folder = Some(folder.to_string());
77                self.selected_mailbox = Some(mailbox);
78                Ok(NewlySelected::Yes)
79            }
80            Err(async_imap::error::Error::No(response)) => {
81                Err(Error::NoFolder(folder.to_string(), response))
82            }
83            Err(err) => Err(Error::Other(err.to_string())),
84        }
85    }
86
87    /// Selects a folder. Tries to create it once and select again if the folder does not exist.
88    pub(super) async fn select_or_create_folder(
89        &mut self,
90        context: &Context,
91        folder: &str,
92    ) -> anyhow::Result<NewlySelected> {
93        match self.select_folder(context, folder).await {
94            Ok(newly_selected) => Ok(newly_selected),
95            Err(err) => match err {
96                Error::NoFolder(..) => {
97                    info!(context, "Failed to select folder {} because it does not exist, trying to create it.", folder);
98                    let create_res = self.create(folder).await;
99                    if let Err(ref err) = create_res {
100                        info!(context, "Couldn't select folder, then create() failed: {err:#}.");
101                        // Need to recheck, could have been created in parallel.
102                    }
103                    let select_res = self.select_folder(context, folder).await.with_context(|| format!("failed to select newely created folder {folder}"));
104                    if select_res.is_err() {
105                        create_res?;
106                    }
107                    select_res
108                }
109                _ => Err(err).with_context(|| format!("failed to select folder {folder} with error other than NO, not trying to create it")),
110            },
111        }
112    }
113
114    /// Selects a folder optionally creating it and takes care of UIDVALIDITY changes. Returns false
115    /// iff `folder` doesn't exist.
116    ///
117    /// When selecting a folder for the first time, sets the uid_next to the current
118    /// mailbox.uid_next so that no old emails are fetched.
119    ///
120    /// Updates `self.new_mail` if folder was previously unselected
121    /// and new mails are detected after selecting,
122    /// i.e. UIDNEXT advanced while the folder was closed.
123    pub(crate) async fn select_with_uidvalidity(
124        &mut self,
125        context: &Context,
126        folder: &str,
127        create: bool,
128    ) -> Result<bool> {
129        let newly_selected = if create {
130            self.select_or_create_folder(context, folder)
131                .await
132                .with_context(|| format!("failed to select or create folder {folder}"))?
133        } else {
134            match self.select_folder(context, folder).await {
135                Ok(newly_selected) => newly_selected,
136                Err(err) => match err {
137                    Error::NoFolder(..) => return Ok(false),
138                    _ => {
139                        return Err(err)
140                            .with_context(|| format!("failed to select folder {folder}"))?
141                    }
142                },
143            }
144        };
145        let mailbox = self
146            .selected_mailbox
147            .as_mut()
148            .with_context(|| format!("No mailbox selected, folder: {folder}"))?;
149
150        let old_uid_validity = get_uidvalidity(context, folder)
151            .await
152            .with_context(|| format!("failed to get old UID validity for folder {folder}"))?;
153        let old_uid_next = get_uid_next(context, folder)
154            .await
155            .with_context(|| format!("failed to get old UID NEXT for folder {folder}"))?;
156
157        let new_uid_validity = mailbox
158            .uid_validity
159            .with_context(|| format!("No UIDVALIDITY for folder {folder}"))?;
160        let new_uid_next = if let Some(uid_next) = mailbox.uid_next {
161            Some(uid_next)
162        } else {
163            warn!(
164                context,
165                "SELECT response for IMAP folder {folder:?} has no UIDNEXT, fall back to STATUS command."
166            );
167
168            // RFC 3501 says STATUS command SHOULD NOT be used
169            // on the currently selected mailbox because the same
170            // information can be obtained by other means,
171            // such as reading SELECT response.
172            //
173            // However, it also says that UIDNEXT is REQUIRED
174            // in the SELECT response and if we are here,
175            // it is actually not returned.
176            //
177            // In particular, Winmail Pro Mail Server 5.1.0616
178            // never returns UIDNEXT in SELECT response,
179            // but responds to "STATUS INBOX (UIDNEXT)" command.
180            let status = self
181                .inner
182                .status(folder, "(UIDNEXT)")
183                .await
184                .with_context(|| format!("STATUS (UIDNEXT) error for {folder:?}"))?;
185
186            if status.uid_next.is_none() {
187                // This happens with mail.163.com as of 2023-11-26.
188                // It does not return UIDNEXT on SELECT and returns invalid
189                // `* STATUS "INBOX" ()` response on explicit request for UIDNEXT.
190                warn!(context, "STATUS {folder} (UIDNEXT) did not return UIDNEXT.");
191            }
192            status.uid_next
193        };
194        mailbox.uid_next = new_uid_next;
195
196        if new_uid_validity == old_uid_validity {
197            if newly_selected == NewlySelected::Yes {
198                if let Some(new_uid_next) = new_uid_next {
199                    if new_uid_next < old_uid_next {
200                        warn!(
201                            context,
202                            "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...",
203                        );
204                        set_uid_next(context, folder, new_uid_next).await?;
205                        context.schedule_resync().await?;
206                    }
207
208                    // If UIDNEXT changed, there are new emails.
209                    self.new_mail |= new_uid_next != old_uid_next;
210                } else {
211                    warn!(context, "Folder {folder} was just selected but we failed to determine UIDNEXT, assume that it has new mail.");
212                    self.new_mail = true;
213                }
214            }
215
216            return Ok(true);
217        }
218
219        // UIDVALIDITY is modified, reset highest seen MODSEQ.
220        set_modseq(context, folder, 0).await?;
221
222        // ==============  uid_validity has changed or is being set the first time.  ==============
223
224        let new_uid_next = new_uid_next.unwrap_or_default();
225        set_uid_next(context, folder, new_uid_next).await?;
226        set_uidvalidity(context, folder, new_uid_validity).await?;
227        self.new_mail = true;
228
229        // Collect garbage entries in `imap` table.
230        context
231            .sql
232            .execute(
233                "DELETE FROM imap WHERE folder=? AND uidvalidity!=?",
234                (&folder, new_uid_validity),
235            )
236            .await?;
237
238        if old_uid_validity != 0 || old_uid_next != 0 {
239            context.schedule_resync().await?;
240        }
241        info!(
242            context,
243            "uid/validity change folder {}: new {}/{} previous {}/{}.",
244            folder,
245            new_uid_next,
246            new_uid_validity,
247            old_uid_next,
248            old_uid_validity,
249        );
250        Ok(true)
251    }
252}
253
254#[derive(PartialEq, Debug, Copy, Clone, Eq)]
255pub(crate) enum NewlySelected {
256    /// The folder was newly selected during this call to select_folder().
257    Yes,
258    /// No SELECT command was run because the folder already was selected
259    /// and self.config.selected_mailbox was not updated (so, e.g. it may contain an outdated uid_next)
260    No,
261}
deltachat/imap/select_folder.rs

deltachat/imap/
select_folder.rs
