feat: Use IMAP APPEND command to upload sync messages (#5845)

Why:
- With IMAP APPEND we can upload messages directly to the DeltaChat folder (for non-chatmail
  accounts).
- We can set the `\Seen` flag immediately so that if the user has other MUA, it doesn't alert about
  a new message if it's just a sync message (there were several such reports on the support
  forum). Though this also isn't useful for chatmail.
- We don't need SMTP envelope and overall remove some overhead on processing sync messages.

src/chat.rs

@@ -2245,7 +2245,7 @@ pub(crate) async fn sync(context: &Context, id: SyncId, action: SyncAction) -> R
     context
         .add_sync_item(SyncData::AlterChat { id, action })
         .await?;
-    context.scheduler.interrupt_smtp().await;
+    context.scheduler.interrupt_inbox().await;
     Ok(())
 }
 
@@ -2906,10 +2906,9 @@ async fn prepare_send_msg(
     create_send_msg_jobs(context, msg).await
 }
 
-/// Constructs jobs for sending a message and inserts them into the `smtp` table.
+/// Constructs jobs for sending a message and inserts them into the appropriate table.
 ///
-/// Returns row ids if jobs were created or an empty `Vec` otherwise, e.g. when sending to a
-/// group with only self and no BCC-to-self configured.
+/// Returns row ids if `smtp` table jobs were created or an empty `Vec` otherwise.
 ///
 /// The caller has to interrupt SMTP loop or otherwise process new rows.
 pub(crate) async fn create_send_msg_jobs(context: &Context, msg: &mut Message) -> Result<Vec<i64>> {
@@ -3003,12 +3002,6 @@ pub(crate) async fn create_send_msg_jobs(context: &Context, msg: &mut Message) -
         }
     }
 
-    if let Some(sync_ids) = rendered_msg.sync_ids_to_delete {
-        if let Err(err) = context.delete_sync_ids(sync_ids).await {
-            error!(context, "Failed to delete sync ids: {err:#}.");
-        }
-    }
-
     if attach_selfavatar {
         if let Err(err) = msg.chat_id.set_selfavatar_timestamp(context, now).await {
             error!(context, "Failed to set selfavatar timestamp: {err:#}.");
@@ -3025,19 +3018,30 @@ pub(crate) async fn create_send_msg_jobs(context: &Context, msg: &mut Message) -
     let chunk_size = context.get_max_smtp_rcpt_to().await?;
     let trans_fn = |t: &mut rusqlite::Transaction| {
         let mut row_ids = Vec::<i64>::new();
-        for recipients_chunk in recipients.chunks(chunk_size) {
-            let recipients_chunk = recipients_chunk.join(" ");
-            let row_id = t.execute(
-                "INSERT INTO smtp (rfc724_mid, recipients, mime, msg_id) \
-                VALUES            (?1,         ?2,         ?3,   ?4)",
-                (
-                    &rendered_msg.rfc724_mid,
-                    recipients_chunk,
-                    &rendered_msg.message,
-                    msg.id,
-                ),
+        if let Some(sync_ids) = rendered_msg.sync_ids_to_delete {
+            t.execute(
+                &format!("DELETE FROM multi_device_sync WHERE id IN ({sync_ids})"),
+                (),
             )?;
-            row_ids.push(row_id.try_into()?);
+            t.execute(
+                "INSERT INTO imap_send (mime, msg_id) VALUES (?, ?)",
+                (&rendered_msg.message, msg.id),
+            )?;
+        } else {
+            for recipients_chunk in recipients.chunks(chunk_size) {
+                let recipients_chunk = recipients_chunk.join(" ");
+                let row_id = t.execute(
+                    "INSERT INTO smtp (rfc724_mid, recipients, mime, msg_id) \
+                    VALUES            (?1,         ?2,         ?3,   ?4)",
+                    (
+                        &rendered_msg.rfc724_mid,
+                        recipients_chunk,
+                        &rendered_msg.message,
+                        msg.id,
+                    ),
+                )?;
+                row_ids.push(row_id.try_into()?);
+            }
         }
         Ok(row_ids)
     };
@@ -3793,7 +3797,7 @@ pub(crate) async fn add_contact_to_chat_ex(
                 .log_err(context)
                 .is_ok()
         {
-            context.scheduler.interrupt_smtp().await;
+            context.scheduler.interrupt_inbox().await;
         }
     }
     context.emit_event(EventType::ChatModified(chat_id));

src/config.rs

@@ -589,6 +589,12 @@ impl Context {
             && !self.get_config_bool(Config::Bot).await?)
     }
 
+    /// Returns whether sync messages should be uploaded to the mvbox.
+    pub(crate) async fn should_move_sync_msgs(&self) -> Result<bool> {
+        Ok(self.get_config_bool(Config::MvboxMove).await?
+            || !self.get_config_bool(Config::IsChatmail).await?)
+    }
+
     /// Returns whether MDNs should be requested.
     pub(crate) async fn should_request_mdns(&self) -> Result<bool> {
         match self.get_config_bool_opt(Config::MdnsEnabled).await? {
@@ -792,7 +798,7 @@ impl Context {
         {
             return Ok(());
         }
-        self.scheduler.interrupt_smtp().await;
+        self.scheduler.interrupt_inbox().await;
         Ok(())
     }
 
@@ -1175,7 +1181,7 @@ mod tests {
         let status = "Synced via usual message";
         alice0.set_config(Config::Selfstatus, Some(status)).await?;
         alice0.send_sync_msg().await?;
-        alice0.pop_sent_msg().await;
+        alice0.pop_sent_sync_msg().await;
         let status1 = "Synced via sync message";
         alice1.set_config(Config::Selfstatus, Some(status1)).await?;
         tcm.send_recv(alice0, alice1, "hi Alice!").await;
@@ -1199,7 +1205,7 @@ mod tests {
             .set_config(Config::Selfavatar, Some(file.to_str().unwrap()))
             .await?;
         alice0.send_sync_msg().await?;
-        alice0.pop_sent_msg().await;
+        alice0.pop_sent_sync_msg().await;
         let file = alice1.dir.path().join("avatar.jpg");
         let bytes = include_bytes!("../test-data/image/avatar1000x1000.jpg");
         tokio::fs::write(&file, bytes).await?;

src/imap.rs

@@ -32,6 +32,7 @@ use crate::contact::{Contact, ContactId, Modifier, Origin};
 use crate::context::Context;
 use crate::events::EventType;
 use crate::headerdef::{HeaderDef, HeaderDefMap};
+use crate::log::LogExt;
 use crate::login_param::{
     prioritize_server_login_params, ConfiguredLoginParam, ConfiguredServerLoginParam,
 };
@@ -1043,6 +1044,52 @@ impl Session {
         Ok(())
     }
 
+    /// Uploads sync messages from the `imap_send` table with `\Seen` flag set.
+    pub(crate) async fn send_sync_msgs(&mut self, context: &Context, folder: &str) -> Result<()> {
+        context.send_sync_msg().await?;
+        while let Some((id, mime, msg_id, attempts)) = context
+            .sql
+            .query_row_optional(
+                "SELECT id, mime, msg_id, attempts FROM imap_send ORDER BY id LIMIT 1",
+                (),
+                |row| {
+                    let id: i64 = row.get(0)?;
+                    let mime: String = row.get(1)?;
+                    let msg_id: MsgId = row.get(2)?;
+                    let attempts: i64 = row.get(3)?;
+                    Ok((id, mime, msg_id, attempts))
+                },
+            )
+            .await
+            .context("Failed to SELECT from imap_send")?
+        {
+            let res = self
+                .append(folder, Some("(\\Seen)"), None, mime)
+                .await
+                .with_context(|| format!("IMAP APPEND to {folder} failed for {msg_id}"))
+                .log_err(context);
+            if res.is_ok() {
+                msg_id.set_delivered(context).await?;
+            }
+            const MAX_ATTEMPTS: i64 = 2;
+            if res.is_ok() || attempts >= MAX_ATTEMPTS - 1 {
+                context
+                    .sql
+                    .execute("DELETE FROM imap_send WHERE id=?", (id,))
+                    .await
+                    .context("Failed to delete from imap_send")?;
+            } else {
+                context
+                    .sql
+                    .execute("UPDATE imap_send SET attempts=attempts+1 WHERE id=?", (id,))
+                    .await
+                    .context("Failed to update imap_send.attempts")?;
+                res?;
+            }
+        }
+        Ok(())
+    }
+
     /// Stores pending `\Seen` flags for messages in `imap_markseen` table.
     pub(crate) async fn store_seen_flags_on_imap(&mut self, context: &Context) -> Result<()> {
         let rows = context

src/mimefactory.rs

@@ -104,10 +104,8 @@ pub struct RenderedEmail {
     pub is_gossiped: bool,
     pub last_added_location_id: Option<u32>,
 
-    /// A comma-separated string of sync-IDs that are used by the rendered email
-    /// and must be deleted once the message is actually queued for sending
-    /// (deletion must be done by `delete_sync_ids()`).
-    /// If the rendered email is not queued for sending, the IDs must not be deleted.
+    /// A comma-separated string of sync-IDs that are used by the rendered email and must be deleted
+    /// from `multi_device_sync` once the message is actually queued for sending.
     pub sync_ids_to_delete: Option<String>,
 
     /// Message ID (Message in the sense of Email)

src/qr.rs

@@ -719,7 +719,7 @@ pub async fn set_config_from_qr(context: &Context, qr: &str) -> Result<()> {
             token::save(context, token::Namespace::InviteNumber, None, &invitenumber).await?;
             token::save(context, token::Namespace::Auth, None, &authcode).await?;
             context.sync_qr_code_tokens(None).await?;
-            context.scheduler.interrupt_smtp().await;
+            context.scheduler.interrupt_inbox().await;
         }
         Qr::ReviveVerifyGroup {
             invitenumber,
@@ -736,7 +736,7 @@ pub async fn set_config_from_qr(context: &Context, qr: &str) -> Result<()> {
             .await?;
             token::save(context, token::Namespace::Auth, Some(&grpid), &authcode).await?;
             context.sync_qr_code_tokens(Some(&grpid)).await?;
-            context.scheduler.interrupt_smtp().await;
+            context.scheduler.interrupt_inbox().await;
         }
         Qr::Login { address, options } => {
             configure_from_login_qr(context, &address, options).await?

src/scheduler.rs

@@ -568,6 +568,21 @@ async fn fetch_idle(
     };
 
     if folder_config == Config::ConfiguredInboxFolder {
+        let mvbox;
+        let syncbox = match ctx.should_move_sync_msgs().await? {
+            false => &watch_folder,
+            true => {
+                mvbox = ctx.get_config(Config::ConfiguredMvboxFolder).await?;
+                mvbox.as_deref().unwrap_or(&watch_folder)
+            }
+        };
+        session
+            .send_sync_msgs(ctx, syncbox)
+            .await
+            .context("fetch_idle: send_sync_msgs")
+            .log_err(ctx)
+            .ok();
+
         session
             .store_seen_flags_on_imap(ctx)
             .await

src/securejoin.rs

@@ -109,7 +109,7 @@ pub async fn get_securejoin_qr(context: &Context, group: Option<ChatId>) -> Resu
             context
                 .sync_qr_code_tokens(Some(chat.grpid.as_str()))
                 .await?;
-            context.scheduler.interrupt_smtp().await;
+            context.scheduler.interrupt_inbox().await;
         }
         format!(
             "OPENPGP4FPR:{}#a={}&g={}&x={}&i={}&s={}",
@@ -124,7 +124,7 @@ pub async fn get_securejoin_qr(context: &Context, group: Option<ChatId>) -> Resu
         // parameters used: a=n=i=s=
         if sync_token {
             context.sync_qr_code_tokens(None).await?;
-            context.scheduler.interrupt_smtp().await;
+            context.scheduler.interrupt_inbox().await;
         }
         format!(
             "OPENPGP4FPR:{}#a={}&n={}&i={}&s={}",

src/smtp.rs

@@ -485,7 +485,6 @@ pub(crate) async fn send_smtp_messages(context: &Context, connection: &mut Smtp)
     let ratelimited = if context.ratelimit.read().await.can_send() {
         // add status updates and sync messages to end of sending queue
         context.flush_status_updates().await?;
-        context.send_sync_msg().await?;
         false
     } else {
         true

src/sql/migrations.rs

@@ -991,6 +991,20 @@ CREATE INDEX msgs_status_updates_index2 ON msgs_status_updates (uid);
         .await?;
     }
 
+    inc_and_check(&mut migration_version, 119)?;
+    if dbversion < migration_version {
+        sql.execute_migration(
+            "CREATE TABLE imap_send (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                mime TEXT NOT NULL, -- Message content
+                msg_id INTEGER NOT NULL, -- ID of the message in the `msgs` table
+                attempts INTEGER NOT NULL DEFAULT 0 -- Number of failed attempts to send the message
+            )",
+            migration_version,
+        )
+        .await?;
+    }
+
     let new_version = sql
         .get_raw_config_int(VERSION_CFG)
         .await?

src/sync.rs

@@ -120,7 +120,7 @@ impl Context {
     /// Adds most recent qr-code tokens for the given group or self-contact to the list of items to
     /// be synced. If device synchronization is disabled,
     /// no tokens exist or the chat is unpromoted, the function does nothing.
-    /// The caller should perform `SchedulerState::interrupt_smtp()` on its own to trigger sending.
+    /// The caller should call `SchedulerState::interrupt_inbox()` on its own to trigger sending.
     pub(crate) async fn sync_qr_code_tokens(&self, grpid: Option<&str>) -> Result<()> {
         if !self.should_send_sync_msgs().await? {
             return Ok(());
@@ -153,7 +153,7 @@ impl Context {
             grpid: None,
         }))
         .await?;
-        self.scheduler.interrupt_smtp().await;
+        self.scheduler.interrupt_inbox().await;
         Ok(())
     }
 
@@ -233,17 +233,6 @@ impl Context {
             .body(json)
     }
 
-    /// Deletes IDs as returned by `build_sync_json()`.
-    pub(crate) async fn delete_sync_ids(&self, ids: String) -> Result<()> {
-        self.sql
-            .execute(
-                &format!("DELETE FROM multi_device_sync WHERE id IN ({ids});"),
-                (),
-            )
-            .await?;
-        Ok(())
-    }
-
     /// Takes a JSON string created by `build_sync_json()`
     /// and construct `SyncItems` from it.
     pub(crate) fn parse_sync_items(&self, serialized: String) -> Result<SyncItems> {
@@ -384,7 +373,12 @@ mod tests {
         );
 
         assert!(t.build_sync_json().await?.is_some());
-        t.delete_sync_ids(ids).await?;
+        t.sql
+            .execute(
+                &format!("DELETE FROM multi_device_sync WHERE id IN ({ids})"),
+                (),
+            )
+            .await?;
         assert!(t.build_sync_json().await?.is_none());
 
         let sync_items = t.parse_sync_items(serialized)?;
@@ -565,7 +559,7 @@ mod tests {
 
         // let alice's other device receive and execute the sync message,
         // also here, self-talk should stay hidden
-        let sent_msg = alice.pop_sent_msg().await;
+        let sent_msg = alice.pop_sent_sync_msg().await;
         let alice2 = TestContext::new_alice().await;
         alice2.set_config_bool(Config::SyncMsgs, true).await?;
         alice2.recv_msg_trash(&sent_msg).await;
@@ -593,7 +587,7 @@ mod tests {
             .set_config(Config::Displayname, Some("Alice Human"))
             .await?;
         alice.send_sync_msg().await?;
-        alice.pop_sent_msg().await;
+        alice.pop_sent_sync_msg().await;
         let msg = bob.recv_msg(&alice.pop_sent_msg().await).await;
         assert_eq!(msg.text, "hi");
 
@@ -628,7 +622,7 @@ mod tests {
         // group is promoted for compatibility (because the group could be created by older Core).
         // TODO: assert!(msg_id.is_none());
         assert!(msg_id.is_some());
-        let sent = alice.pop_sent_msg().await;
+        let sent = alice.pop_sent_sync_msg().await;
         let msg = alice.parse_msg(&sent).await;
         let mut sync_items = msg.sync_items.unwrap().items;
         assert_eq!(sync_items.len(), 1);

src/test_utils.rs

@@ -438,7 +438,7 @@ impl TestContext {
     /// Retrieves a sent message from the jobs table.
     ///
     /// This retrieves and removes a message which has been scheduled to send from the jobs
-    /// table.  Messages are returned in the order they have been sent.
+    /// table. Messages are returned in the reverse order of sending.
     ///
     /// Panics if there is no message or on any error.
     pub async fn pop_sent_msg(&self) -> SentMessage<'_> {
@@ -532,6 +532,46 @@ impl TestContext {
         })
     }
 
+    /// Retrieves a sent sync message from the db.
+    ///
+    /// This retrieves and removes a sync message which has been scheduled to send from the jobs
+    /// table. Messages are returned in the order they have been sent.
+    ///
+    /// Panics if there is no message or on any error.
+    pub async fn pop_sent_sync_msg(&self) -> SentMessage<'_> {
+        let (id, msg_id, payload) = self
+            .ctx
+            .sql
+            .query_row(
+                "SELECT id, msg_id, mime \
+                FROM imap_send \
+                ORDER BY id",
+                (),
+                |row| {
+                    let rowid: i64 = row.get(0)?;
+                    let msg_id: MsgId = row.get(1)?;
+                    let mime: String = row.get(2)?;
+                    Ok((rowid, msg_id, mime))
+                },
+            )
+            .await
+            .expect("query_row failed");
+        self.ctx
+            .sql
+            .execute("DELETE FROM imap_send WHERE id=?", (id,))
+            .await
+            .expect("failed to remove job");
+        update_msg_state(&self.ctx, msg_id, MessageState::OutDelivered)
+            .await
+            .expect("failed to update message state");
+        SentMessage {
+            payload,
+            sender_msg_id: msg_id,
+            sender_context: &self.ctx,
+            recipients: self.get_primary_self_addr().await.unwrap(),
+        }
+    }
+
     /// Parses a message.
     ///
     /// Parsing a message does not run the entire receive pipeline, but is not without
@@ -1141,7 +1181,7 @@ pub(crate) async fn mark_as_verified(this: &TestContext, other: &TestContext) {
 /// alice0's side that implies sending a sync message.
 pub(crate) async fn sync(alice0: &TestContext, alice1: &TestContext) {
     alice0.send_sync_msg().await.unwrap();
-    let sync_msg = alice0.pop_sent_msg().await;
+    let sync_msg = alice0.pop_sent_sync_msg().await;
     let no_msg = alice1.recv_msg_opt(&sync_msg).await;
     assert!(no_msg.is_none());
 }