Sort message replies after parent message

src/dc_receive_imf.rs

@@ -698,6 +698,20 @@ async fn add_parts(
     let in_fresh = state == MessageState::InFresh;
     let rcvd_timestamp = time();
     let sort_timestamp = calc_sort_timestamp(context, *sent_timestamp, *chat_id, in_fresh).await;
+
+    // Ensure replies to messages are sorted after the parent message.
+    //
+    // This is useful in a case where sender clocks are not
+    // synchronized and parent message has a Date: header with a
+    // timestamp higher than reply timestamp.
+    //
+    // This does not help if parent message arrives later than the
+    // reply.
+    let parent_timestamp = mime_parser.get_parent_timestamp(context).await?;
+    let sort_timestamp = parent_timestamp.map_or(sort_timestamp, |parent_timestamp| {
+        std::cmp::max(sort_timestamp, parent_timestamp)
+    });
+
     *sent_timestamp = std::cmp::min(*sent_timestamp, rcvd_timestamp);
 
     // unarchive chat

src/mimeparser.rs

@@ -1044,6 +1044,28 @@ impl MimeMessage {
             message::handle_ndn(context, failure_report, error).await
         }
     }
+
+    /// Returns timestamp of the parent message.
+    ///
+    /// If there is no parent message or it is not found in the
+    /// database, returns None.
+    pub async fn get_parent_timestamp(&self, context: &Context) -> Result<Option<i64>> {
+        let parent_timestamp = if let Some(field) = self
+            .get(HeaderDef::InReplyTo)
+            .and_then(|msgid| parse_message_id(msgid).ok())
+        {
+            context
+                .sql
+                .query_get_value_result(
+                    "SELECT timestamp FROM msgs WHERE rfc724_mid=?",
+                    paramsv![field],
+                )
+                .await?
+        } else {
+            None
+        };
+        Ok(parent_timestamp)
+    }
 }
 
 async fn update_gossip_peerstates(
@@ -1413,6 +1435,39 @@ mod tests {
         assert!(mimeparser.chat_disposition_notification_to.is_none());
     }
 
+    #[async_std::test]
+    async fn test_get_parent_timestamp() {
+        let context = TestContext::new().await;
+        let raw = b"From: foo@example.org\n\
+                    Content-Type: text/plain\n\
+                    Chat-Version: 1.0\n\
+                    In-Reply-To: <Gr.beZgAF2Nn0-.oyaJOpeuT70@example.org>\n\
+                    \n\
+                    Some reply\n\
+                    ";
+        let mimeparser = MimeMessage::from_bytes(&context.ctx, &raw[..])
+            .await
+            .unwrap();
+        assert_eq!(
+            mimeparser.get_parent_timestamp(&context.ctx).await.unwrap(),
+            None
+        );
+        let timestamp = 1570435529;
+        context
+            .ctx
+            .sql
+            .execute(
+                "INSERT INTO msgs (rfc724_mid, timestamp) VALUES(?,?)",
+                paramsv!["Gr.beZgAF2Nn0-.oyaJOpeuT70@example.org", timestamp],
+            )
+            .await
+            .expect("Failed to write to the database");
+        assert_eq!(
+            mimeparser.get_parent_timestamp(&context.ctx).await.unwrap(),
+            Some(timestamp)
+        );
+    }
+
     #[async_std::test]
     async fn test_mimeparser_with_context() {
         let context = TestContext::new().await;