Support Reddit gallery posts

src/reddit/api.ts

@@ -63,6 +63,20 @@ export interface RedditPost {
       resolutions: Array<{ url: string; width: number; height: number }>;
     }>;
   };
+  is_gallery?: boolean;
+  gallery_data?: {
+    items: Array<{ media_id: string; id?: number }>;
+  };
+  media_metadata?: Record<string, {
+    status?: string;
+    m?: string;
+    s?: {
+      u?: string;
+      gif?: string;
+      x?: number;
+      y?: number;
+    };
+  }>;
   created_utc: number;
   over_18: boolean;
   spoiler: boolean;
@@ -252,6 +266,8 @@ export class RedditApiClient {
   }
 
   private hasImage(post: RedditPost): boolean {
+    if (this.getGalleryImageUrl(post)) return true;
+
     // Check post_hint
     if (post.post_hint === 'image') return true;
 
@@ -272,6 +288,9 @@ export class RedditApiClient {
   }
 
   getImageUrl(post: RedditPost): string | null {
+    const galleryImageUrl = this.getGalleryImageUrl(post);
+    if (galleryImageUrl) return galleryImageUrl;
+
     // Prefer high-quality preview images (already processed by Reddit)
     if (post.preview?.images?.[0]?.source?.url) {
       // Reddit encodes URLs in preview, need to decode HTML entities
@@ -312,6 +331,24 @@ export class RedditApiClient {
     return null;
   }
 
+  /** Return the first valid gallery image in Reddit's declared display order. */
+  private getGalleryImageUrl(post: RedditPost): string | null {
+    if (!post.is_gallery || !post.media_metadata) return null;
+
+    const orderedMediaIds = post.gallery_data?.items.map((item) => item.media_id)
+      ?? Object.keys(post.media_metadata);
+    for (const mediaId of orderedMediaIds) {
+      const media = post.media_metadata[mediaId];
+      if (!media || (media.status && media.status !== 'valid')) continue;
+      if (media.m && !media.m.startsWith('image/')) continue;
+
+      const sourceUrl = media.s?.u ?? media.s?.gif;
+      if (sourceUrl) return this.decodeRedditUrl(sourceUrl);
+    }
+
+    return null;
+  }
+
   private decodeRedditUrl(url: string): string {
     return url.replace(/&amp;/g, '&');
   }

tests/reddit-api.test.ts

@@ -69,6 +69,51 @@ describe('RedditApiClient', () => {
       expect(url).toBe('http://i.redd.it/image.jpg');
     });
 
+    it('extracts the first valid image from a Reddit gallery in display order', () => {
+      const post = validPostFactory({
+        url: 'https://www.reddit.com/gallery/t3_gallery',
+        is_gallery: true,
+        gallery_data: {
+          items: [
+            { media_id: 'second-in-metadata' },
+            { media_id: 'first-in-metadata' },
+          ],
+        },
+        media_metadata: {
+          'first-in-metadata': {
+            status: 'valid',
+            m: 'image/jpg',
+            s: { u: 'https://i.redd.it/first.jpg' },
+          },
+          'second-in-metadata': {
+            status: 'valid',
+            m: 'image/jpg',
+            s: { u: 'https://preview.redd.it/second.jpg?width=1080&format=pjpg' },
+          },
+        },
+      });
+
+      expect(client.getImageUrl(post)).toBe(
+        'https://preview.redd.it/second.jpg?width=1080&format=pjpg',
+      );
+    });
+
+    it('ignores invalid and non-image gallery media', () => {
+      const post = validPostFactory({
+        url: 'https://www.reddit.com/gallery/t3_gallery',
+        is_gallery: true,
+        gallery_data: {
+          items: [{ media_id: 'invalid' }, { media_id: 'video' }],
+        },
+        media_metadata: {
+          invalid: { status: 'failed', m: 'image/jpg', s: { u: 'https://i.redd.it/invalid.jpg' } },
+          video: { status: 'valid', m: 'video/mp4', s: { u: 'https://v.redd.it/video.mp4' } },
+        },
+      });
+
+      expect(client.getImageUrl(post)).toBeNull();
+    });
+
     it('accepts posts with i.redd.it URLs', () => {
       const post = validPostFactory({ url: 'https://i.redd.it/abc123.jpg' });
       const url = client.getImageUrl(post);
@@ -615,6 +660,42 @@ describe('RedditApiClient', () => {
       expect(result[0].title).toBe('Image post 1');
     });
 
+    it('keeps Reddit gallery posts whose images are stored in media metadata', async () => {
+      const galleryPost: RedditPost = {
+        id: 't3_gallery',
+        name: 't3_gallery',
+        subreddit: 'test',
+        author: 'gallery-user',
+        title: 'Gallery post',
+        url: 'https://www.reddit.com/gallery/t3_gallery',
+        permalink: '/r/test/comments/t3_gallery/gallery_post',
+        thumbnail: 'nsfw',
+        is_self: false,
+        is_gallery: true,
+        gallery_data: { items: [{ media_id: 'media-1' }] },
+        media_metadata: {
+          'media-1': {
+            status: 'valid',
+            m: 'image/jpg',
+            s: { u: 'https://preview.redd.it/gallery-image.jpg' },
+          },
+        },
+        created_utc: 1000000,
+        over_18: true,
+        spoiler: false,
+      };
+      const mockAxios = {
+        get: vi.fn().mockResolvedValue({
+          data: { data: { children: [{ data: galleryPost }] } },
+        }),
+      };
+      vi.mocked(axios.create).mockReturnValue(mockAxios as unknown as AxiosInstance);
+      const client2 = new RedditApiClient(getTestConfig(), logger);
+
+      await expect(client2.getNewPosts('test')).resolves.toEqual([galleryPost]);
+      expect(client2.getImageUrl(galleryPost)).toBe('https://preview.redd.it/gallery-image.jpg');
+    });
+
     it('filters out deleted authors', async () => {
       const mockResponse = {
         data: { data: { children: [