Disable unavailable subreddits after Reddit 404

tests/monitor.test.ts

@@ -1,6 +1,11 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest';
 import { MonitorService } from '../src/services/monitor.js';
-import { RedditRateLimitError, type RedditApiClient, type RedditPost } from '../src/reddit/api.js';
+import {
+  RedditRateLimitError,
+  RedditSubredditUnavailableError,
+  type RedditApiClient,
+  type RedditPost,
+} from '../src/reddit/api.js';
 import type { PostsRepository, MessagesRepository } from '../src/database/repositories.js';
 import { createMockLogger } from '../tests/mockLogger.js';
 import { getTestConfig } from '../tests/testUtils.js';
@@ -87,6 +92,25 @@ describe('MonitorService', () => {
     expect(result.length).toBe(0);
   });
 
+  it('disables a subreddit when Reddit returns a terminal listing 404', async () => {
+    const redditApi = createMockRedditApi();
+    vi.mocked(redditApi.getNewPosts).mockRejectedValueOnce(new RedditSubredditUnavailableError('banned-sub'));
+    const pollingControl = {
+      disableUnavailableSubreddit: vi.fn(),
+      isSubredditEnabled: vi.fn(() => true),
+    };
+    const config = getTestConfig({ reddit: { subreddits: [{ name: 'banned-sub', type: 'image' }] } });
+    monitor = new MonitorService(
+      redditApi, createMockPostsRepo(), createMockMessagesRepo(), config, logger, 0, pollingControl,
+    );
+
+    await expect(monitor.getUnprocessedPosts()).resolves.toEqual([]);
+    expect(pollingControl.disableUnavailableSubreddit).toHaveBeenCalledWith('banned-sub');
+    expect(logger.logs).toContainEqual(expect.objectContaining({
+      level: 'warn', message: expect.stringContaining('Disabled r/banned-sub: Reddit returned HTTP 404'),
+    }));
+  });
+
   it('uses shared post history so another account cannot rediscover a post', async () => {
     const post: RedditPost = {
       id: 't3_shared', subreddit: 'sub1', author: 'user1', title: 'Post',