feat: Update how messages load and sync, allow plugins to import messages

toju-app/src/app/store/messages/messages.reducer.ts

@@ -13,10 +13,18 @@ export interface MessagesState extends EntityState<Message> {
   loading: boolean;
   /** Whether a peer-to-peer sync cycle is in progress. */
   syncing: boolean;
+  /** Whether a scroll-up older-page fetch is currently in flight. */
+  loadingOlder: boolean;
   /** Most recent error message from message operations. */
   error: string | null;
   /** ID of the room whose messages are currently loaded. */
   currentRoomId: string | null;
+  /**
+   * Conversation keys (`${roomId}:${channelId}`) that have been paginated
+   * all the way back to the start of the local DB history. Used by the
+   * scroll-up handler to stop issuing further DB pages.
+   */
+  exhaustedConversations: Record<string, true>;
 }
 
 export const messagesAdapter: EntityAdapter<Message> = createEntityAdapter<Message>({
@@ -27,8 +35,10 @@ export const messagesAdapter: EntityAdapter<Message> = createEntityAdapter<Messa
 export const initialState: MessagesState = messagesAdapter.getInitialState({
   loading: false,
   syncing: false,
+  loadingOlder: false,
   error: null,
-  currentRoomId: null
+  currentRoomId: null,
+  exhaustedConversations: {}
 });
 
 export const messagesReducer = createReducer(
@@ -41,7 +51,8 @@ export const messagesReducer = createReducer(
         ...state,
         loading: true,
         error: null,
-        currentRoomId: roomId
+        currentRoomId: roomId,
+        exhaustedConversations: {}
       });
     }
 
@@ -66,6 +77,30 @@ export const messagesReducer = createReducer(
     error
   })),
 
+  // Load older messages - paginate backwards from the DB on scroll-up.
+  on(MessagesActions.loadOlderMessages, (state) => ({
+    ...state,
+    loadingOlder: true,
+    error: null
+  })),
+
+  on(MessagesActions.loadOlderMessagesSuccess, (state, { conversationKey, messages, reachedEnd }) =>
+    messagesAdapter.upsertMany(messages, {
+      ...state,
+      loadingOlder: false,
+      exhaustedConversations: reachedEnd
+        ? { ...state.exhaustedConversations,
+          [conversationKey]: true }
+        : state.exhaustedConversations
+    })
+  ),
+
+  on(MessagesActions.loadOlderMessagesFailure, (state, { error }) => ({
+    ...state,
+    loadingOlder: false,
+    error
+  })),
+
   // Send message
   on(MessagesActions.sendMessage, (state) => ({
     ...state,
@@ -202,7 +237,10 @@ export const messagesReducer = createReducer(
 
     return messagesAdapter.upsertMany(merged, {
       ...state,
-      syncing: false
+      syncing: false,
+      // Peer sync may have inserted messages older than our current oldest;
+      // reopen pagination so the scroll-up handler revisits the DB.
+      exhaustedConversations: {}
     });
   }),
 
@@ -221,7 +259,8 @@ export const messagesReducer = createReducer(
   on(MessagesActions.clearMessages, (state) =>
     messagesAdapter.removeAll({
       ...state,
-      currentRoomId: null
+      currentRoomId: null,
+      exhaustedConversations: {}
     })
   )
 );