add get_chat_list_item_by_id method

why? because desktop currently fetches the chatlist multiple times, even though it just needs the chatlistitem for one chat

Note: @r10s was worried before that exposing the method to get a single
updated chatlistitem could lead to race conditions
where the chatlist item is newer than the chatlist order.
But I don't think this will change anything for desktop besides making it a little faster.
(because currently desktop fetches the whole chatlist
instead of just the entry it needs when an entry updates)

deltachat-jsonrpc/src/api/mod.rs

@@ -4,7 +4,7 @@ use deltachat::{
         self, add_contact_to_chat, forward_msgs, get_chat_media, get_chat_msgs, marknoticed_chat,
         remove_contact_from_chat, Chat, ChatId, ChatItem, ProtectionStatus,
     },
-    chatlist::Chatlist,
+    chatlist::{get_chatlistitem_for_chat, Chatlist},
     config::Config,
     constants::DC_MSG_ID_DAYMARKER,
     contact::{may_be_valid_addr, Contact, ContactId, Origin},
@@ -439,12 +439,27 @@ impl CommandApi {
         for i in 0..list.len() {
             l.push(ChatListEntry(
                 list.get_chat_id(i)?.to_u32(),
-                list.get_msg_id(i)?.unwrap_or_default().to_u32(),
+                list.get_msg_id(i)?.map(|msg_id| msg_id.to_u32()),
             ));
         }
         Ok(l)
     }
 
+    /// Get a chat list entry for a specific chat,
+    /// you should prefer using `get_chatlist_entries` unless you need this function for your virtual list needs like desktop
+    async fn get_chatlist_entry_by_chat(
+        &self,
+        account_id: u32,
+        chat_id: u32,
+    ) -> Result<ChatListEntry> {
+        let ctx = self.get_context(account_id).await?;
+        let (chat_id, message_id) = get_chatlistitem_for_chat(&ctx, ChatId::new(chat_id)).await?;
+        Ok(ChatListEntry(
+            chat_id.to_u32(),
+            message_id.map(|msg_id| msg_id.to_u32()),
+        ))
+    }
+
     async fn get_chatlist_items_by_entries(
         &self,
         account_id: u32,

deltachat-jsonrpc/src/api/types/chat_list.rs

@@ -16,7 +16,7 @@ use typescript_type_def::TypeDef;
 use super::color_int_to_hex_string;
 
 #[derive(Deserialize, Serialize, TypeDef)]
-pub struct ChatListEntry(pub u32, pub u32);
+pub struct ChatListEntry(pub u32, pub Option<u32>);
 
 #[derive(Serialize, TypeDef)]
 #[serde(tag = "type")]
@@ -59,10 +59,7 @@ pub(crate) async fn get_chat_list_item_by_id(
     entry: &ChatListEntry,
 ) -> Result<ChatListItemFetchResult> {
     let chat_id = ChatId::new(entry.0);
-    let last_msgid = match entry.1 {
-        0 => None,
-        _ => Some(MsgId::new(entry.1)),
-    };
+    let last_msgid = entry.1.map(|msg_id| MsgId::new(msg_id));
 
     let fresh_message_counter = chat_id.get_fresh_msg_cnt(ctx).await?;
 

src/chatlist.rs

@@ -362,6 +362,38 @@ pub async fn get_archived_cnt(context: &Context) -> Result<usize> {
     Ok(count)
 }
 
+/// Returns a single chatlistitem (chatId and messageid), used by desktop to partially update the chatlist on specific events
+pub async fn get_chatlistitem_for_chat(
+    context: &Context,
+    chat_id: ChatId,
+) -> Result<(ChatId, Option<MsgId>)> {
+    // Similar result as normal chatlist, only one item though and:
+    // archived and blocked chats are included
+    context
+        .sql
+        .query_row(
+            "SELECT c.id, m.id
+                FROM chats c
+                LEFT JOIN msgs m
+                    ON c.id=m.chat_id
+                    AND m.id=(
+                            SELECT id
+                                FROM msgs
+                            WHERE chat_id=c.id
+                                AND (hidden=0 OR state=?1)
+                                ORDER BY timestamp DESC, id DESC LIMIT 1)
+                WHERE c.id=?2
+                GROUP BY c.id",
+            paramsv![MessageState::OutDraft, chat_id],
+            |row: &rusqlite::Row| {
+                let chat_id: ChatId = row.get(0)?;
+                let msg_id: Option<MsgId> = row.get(1)?;
+                Ok((chat_id, msg_id))
+            },
+        )
+        .await
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;