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

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

@@ -43,7 +43,8 @@ import { TimeSyncService } from '../../core/services/time-sync.service';
 import {
   DELETED_MESSAGE_CONTENT,
   Message,
-  Reaction
+  Reaction,
+  Room
 } from '../../shared-kernel';
 import { hydrateMessages } from './messages.helpers';
 import { canEditMessage } from '../../domains/chat/domain/rules/message.rules';
@@ -67,8 +68,9 @@ export class MessagesEffects {
   loadMessages$ = createEffect(() =>
     this.actions$.pipe(
       ofType(MessagesActions.loadMessages),
-      switchMap(({ roomId }) =>
-        from(this.db.getMessages(roomId, INITIAL_ROOM_MESSAGE_LIMIT, 0)).pipe(
+      withLatestFrom(this.store.select(selectCurrentRoom)),
+      switchMap(([{ roomId }, currentRoom]) =>
+        from(this.loadInitialMessages(roomId, currentRoom)).pipe(
           mergeMap(async (messages) => {
             const hydrated = await hydrateMessages(messages, this.db);
 
@@ -88,6 +90,58 @@ export class MessagesEffects {
     )
   );
 
+  /** Paginates older messages from the local DB for scroll-up history loading. */
+  loadOlderMessages$ = createEffect(() =>
+    this.actions$.pipe(
+      ofType(MessagesActions.loadOlderMessages),
+      mergeMap(({ roomId, channelId, beforeTimestamp, limit }) =>
+        from(
+          this.db.getMessages(roomId, limit, 0, channelId, beforeTimestamp)
+        ).pipe(
+          mergeMap(async (messages) => {
+            const hydrated = await hydrateMessages(messages, this.db);
+
+            for (const message of hydrated) {
+              this.attachments.rememberMessageRoom(message.id, message.roomId);
+            }
+
+            return MessagesActions.loadOlderMessagesSuccess({
+              conversationKey: `${roomId}:${channelId}`,
+              messages: hydrated,
+              reachedEnd: hydrated.length < limit
+            });
+          }),
+          catchError((error) =>
+            of(MessagesActions.loadOlderMessagesFailure({ error: error.message }))
+          )
+        )
+      )
+    )
+  );
+
+  private async loadInitialMessages(roomId: string, currentRoom: Room | null): Promise<Message[]> {
+    const textChannels = currentRoom?.id === roomId
+      ? (currentRoom.channels ?? []).filter((channel) => channel.type === 'text')
+      : [];
+
+    if (textChannels.length <= 1) {
+      return this.db.getMessages(roomId, INITIAL_ROOM_MESSAGE_LIMIT, 0, textChannels[0]?.id);
+    }
+
+    const channelMessageSets = await Promise.all(
+      textChannels.map((channel) => this.db.getMessages(roomId, INITIAL_ROOM_MESSAGE_LIMIT, 0, channel.id))
+    );
+    const messagesById = new Map<string, Message>();
+
+    for (const messages of channelMessageSets) {
+      for (const message of messages) {
+        messagesById.set(message.id, message);
+      }
+    }
+
+    return [...messagesById.values()].sort((first, second) => first.timestamp - second.timestamp);
+  }
+
   /** Constructs a new message, persists it locally, and broadcasts to all peers. */
   sendMessage$ = createEffect(() =>
     this.actions$.pipe(