Add DC_EVENT_MSG_DELETE_TIMEOUT_CHANGED

This event tells the client when the next message will be deleted. When
this event is received, the client should start a timer and update
current chat or chatlist when timeout expires.

deltachat-ffi/deltachat.h

@@ -4405,6 +4405,17 @@ int64_t          dc_lot_get_timestamp     (const dc_lot_t* lot);
  */
 #define DC_EVENT_MSG_READ                 2015
 
+/**
+ * Time left until the next message deletion has changed.
+ *
+ * The only parameter is the number of seconds left until next message
+ * deletion. It is rounded up. If the timer is 0, it means there are no
+ * messages to be deleted in the future.
+ *
+ * @param data1 (int) Timer in seconds
+ * @param data2 (int) 0
+ */
+#define DC_EVENT_MSG_DELETE_TIMEOUT_CHANGED 2016
 
 /**
  * Chat changed.  The name or the image of a chat group was changed or members were added or removed.

deltachat-ffi/src/lib.rs

@@ -167,6 +167,9 @@ impl ContextWrapper {
                         msg_id.to_u32() as uintptr_t,
                     );
                 }
+                Event::MsgDeleteTimeoutChanged { timer } => {
+                    ffi_cb(self, event_id, timer as uintptr_t, 0);
+                }
                 Event::ChatModified(chat_id) => {
                     ffi_cb(self, event_id, chat_id.to_u32() as uintptr_t, 0);
                 }

src/chat.rs

@@ -1,6 +1,6 @@
 //! # Chat module
 
-use std::convert::TryFrom;
+use std::convert::{TryFrom, TryInto};
 use std::path::{Path, PathBuf};
 use std::time::{Duration, SystemTime};
 
@@ -931,6 +931,7 @@ impl Chat {
         } else {
             error!(context, "Cannot send message, not configured.",);
         }
+        update_autodelete_timeout(context);
 
         Ok(MsgId::new(msg_id))
     }
@@ -1600,11 +1601,48 @@ pub fn marknoticed_all_chats(context: &Context) -> Result<(), Error> {
     Ok(())
 }
 
+/// Emits an event to update the time until the next local deletion.
+///
+/// This takes into account only per-chat timeouts, because global device
+/// timeouts are at least one hour long and deletion is triggered often enough
+/// by user actions.
+pub fn update_autodelete_timeout(context: &Context) {
+    let autodelete_timestamp: Option<i64> = match context.sql.query_get_value_result(
+        "SELECT autodelete_timestamp \
+         FROM msgs \
+         WHERE autodelete_timestamp != 0 \
+         ORDER BY autodelete_timestamp ASC \
+         LIMIT 1",
+        rusqlite::NO_PARAMS,
+    ) {
+        Err(err) => {
+            warn!(context, "Can't calculate next autodelete timeout: {}", err);
+            return;
+        }
+        Ok(autodelete_timestamp) => autodelete_timestamp,
+    };
+
+    let timer = if let Some(next_autodelete) = autodelete_timestamp {
+        let now = time();
+        if now > next_autodelete {
+            1
+        } else {
+            (next_autodelete - now)
+                .try_into()
+                .unwrap_or(u32::MAX)
+                .saturating_add(1)
+        }
+    } else {
+        0
+    };
+    emit_event!(context, Event::MsgDeleteTimeoutChanged { timer });
+}
+
 /// Deletes messages which are expired according to "delete_device_after" setting.
 ///
 /// Returns true if any message is deleted, so event can be emitted. If nothing
 /// has been deleted, returns false.
-pub fn delete_device_expired_messages(context: &Context) -> Result<bool, Error> {
+pub(crate) fn delete_device_expired_messages(context: &Context) -> Result<bool, Error> {
     let now = time();
 
     let threshold_timestamp = match context.get_config_delete_device_after() {
@@ -1650,7 +1688,11 @@ pub fn delete_device_expired_messages(context: &Context) -> Result<bool, Error>
         ],
     )?;
 
-    Ok(rows_modified > 0)
+    let updated = rows_modified > 0;
+    if updated {
+        update_autodelete_timeout(context);
+    }
+    Ok(updated)
 }
 
 pub fn get_chat_media(

src/events.rs

@@ -132,6 +132,14 @@ pub enum Event {
     #[strum(props(id = "2015"))]
     MsgRead { chat_id: ChatId, msg_id: MsgId },
 
+    /// Time left until the next message deletion has changed.
+    ///
+    /// The only parameter is the number of seconds left until next message
+    /// deletion. It is rounded up. If the timer is 0, it means there are no
+    /// messages to be deleted in the future.
+    #[strum(props(id = "2016"))]
+    MsgDeleteTimeoutChanged { timer: u32 },
+
     /// Chat changed.  The name or the image of a chat group was changed or members were added or removed.
     /// Or the verify state of a chat has changed.
     /// See dc_set_chat_name(), dc_set_chat_profile_image(), dc_add_contact_to_chat()

src/message.rs

@@ -6,7 +6,7 @@ use deltachat_derive::{FromSql, ToSql};
 use lazy_static::lazy_static;
 use serde::{Deserialize, Serialize};
 
-use crate::chat::{self, Chat, ChatId};
+use crate::chat::{self, update_autodelete_timeout, Chat, ChatId};
 use crate::constants::*;
 use crate::contact::*;
 use crate::context::*;
@@ -157,10 +157,10 @@ impl MsgId {
                 WHERE (autodelete_timestamp == 0 OR autodelete_timestamp > ?) \
                 AND id = ?",
                 params![autodelete_timestamp, autodelete_timestamp, self],
-            )
+            )?;
-        } else {
+            update_autodelete_timeout(context);
-            Ok(())
         }
+        Ok(())
     }
 
     /// Bad evil escape hatch.