sync message deletion to other devices (#6573)

this PR synchronises deletion of messages across devices and adds a test
for it

---------

Co-authored-by: Hocuri <hocuri@gmx.de>

src/sync.rs

@@ -17,6 +17,7 @@ use crate::sync::SyncData::{AddQrToken, AlterChat, DeleteQrToken};
 use crate::token::Namespace;
 use crate::tools::time;
 use crate::{message, stock_str, token};
+use std::collections::HashSet;
 
 /// Whether to send device sync messages. Aimed for usage in the internal API.
 #[derive(Debug, PartialEq)]
@@ -66,6 +67,9 @@ pub(crate) enum SyncData {
         src: String,  // RFC724 id (i.e. "Message-Id" header)
         dest: String, // RFC724 id (i.e. "Message-Id" header)
     },
+    DeleteMessages {
+        msgs: Vec<String>, // RFC724 id (i.e. "Message-Id" header)
+    },
 }
 
 #[derive(Debug, Serialize, Deserialize)]
@@ -258,6 +262,7 @@ impl Context {
                     AlterChat { id, action } => self.sync_alter_chat(id, action).await,
                     SyncData::Config { key, val } => self.sync_config(key, val).await,
                     SyncData::SaveMessage { src, dest } => self.save_message(src, dest).await,
+                    SyncData::DeleteMessages { msgs } => self.sync_message_deletion(msgs).await,
                 },
                 SyncDataOrUnknown::Unknown(data) => {
                     warn!(self, "Ignored unknown sync item: {data}.");
@@ -297,6 +302,26 @@ impl Context {
         }
         Ok(())
     }
+
+    async fn sync_message_deletion(&self, msgs: &Vec<String>) -> Result<()> {
+        let mut modified_chat_ids = HashSet::new();
+        let mut msg_ids = Vec::new();
+        for rfc724_mid in msgs {
+            if let Some((msg_id, _)) = message::rfc724_mid_exists(self, rfc724_mid).await? {
+                if let Some(msg) = Message::load_from_db_optional(self, msg_id).await? {
+                    message::delete_msg_locally(self, &msg).await?;
+                    msg_ids.push(msg.id);
+                    modified_chat_ids.insert(msg.chat_id);
+                } else {
+                    warn!(self, "Sync message delete: Database entry does not exist.");
+                }
+            } else {
+                warn!(self, "Sync message delete: {rfc724_mid:?} not found.");
+            }
+        }
+        message::delete_msgs_locally_done(self, &msg_ids, modified_chat_ids).await?;
+        Ok(())
+    }
 }
 
 #[cfg(test)]