feat: Enable fetching and caching of remote ActivityPub posts in the post details API.

src/app/api/posts/[id]/route.ts

@@ -1,6 +1,7 @@
 import { NextResponse } from 'next/server';
-import { db, posts, users, media } from '@/db';
+import { db, posts, users, media, remotePosts } from '@/db';
 import { eq, desc, and } from 'drizzle-orm';
+import { fetchRemotePost } from '@/lib/activitypub/fetchRemotePost';
 
 export async function GET(
     request: Request,
@@ -9,7 +10,11 @@ export async function GET(
     try {
         const { id } = await params;
 
-        // Fetch the main post
+        const nodeDomain = process.env.NEXT_PUBLIC_NODE_DOMAIN || 'localhost:3000';
+
+        let mainPost: any = null;
+        let replyPosts: any[] = [];
+
         const post = await db.query.posts.findFirst({
             where: eq(posts.id, id),
             with: {
@@ -21,11 +26,9 @@ export async function GET(
             },
         });
 
-        if (!post) {
-            return NextResponse.json({ error: 'Post not found' }, { status: 404 });
-        }
+        if (post) {
+            mainPost = post;
 
-        // Fetch replies to this post
             const replies = await db.query.posts.findMany({
                 where: and(
                     eq(posts.replyToId, id),
@@ -38,8 +41,7 @@ export async function GET(
                 orderBy: [desc(posts.createdAt)],
             });
 
-        let mainPost = post;
-        let replyPosts = replies;
+            let allPostIds = [post.id, ...replies.map(r => r.id)];
 
             try {
                 const { requireAuth } = await import('@/lib/auth');
@@ -47,7 +49,7 @@ export async function GET(
                 const { inArray } = await import('drizzle-orm');
 
                 const viewer = await requireAuth();
-            const allPostIds = [post.id, ...replies.map(r => r.id)];
+                allPostIds = [post.id, ...replies.map(r => r.id)];
 
                 if (allPostIds.length > 0) {
                     const viewerLikes = await db.query.likes.findMany({
@@ -76,10 +78,51 @@ export async function GET(
                         ...r,
                         isLiked: likedPostIds.has(r.id),
                         isReposted: repostedPostIds.has(r.id),
-                })) as any;
+                    })) as any[];
                 }
             } catch {
-            // Not authenticated or other error, skip flags
+            }
+        } else {
+            const cached = await db.query.remotePosts.findFirst({
+                where: eq(remotePosts.apId, id),
+            });
+
+            if (cached) {
+                mainPost = {
+                    id: cached.id,
+                    content: cached.content,
+                    createdAt: cached.publishedAt.toISOString(),
+                    likesCount: 0,
+                    repostsCount: 0,
+                    repliesCount: 0,
+                    author: {
+                        id: cached.authorHandle,
+                        handle: cached.authorHandle,
+                        displayName: cached.authorDisplayName || cached.authorHandle,
+                        avatarUrl: cached.authorAvatarUrl,
+                        bio: null,
+                        isRemote: true,
+                    },
+                    media: cached.mediaJson ? JSON.parse(cached.mediaJson) : null,
+                    linkPreviewUrl: cached.linkPreviewUrl,
+                    linkPreviewTitle: cached.linkPreviewTitle,
+                    linkPreviewDescription: cached.linkPreviewDescription,
+                    linkPreviewImage: cached.linkPreviewImage,
+                    isLiked: false,
+                    isReposted: false,
+                };
+            } else {
+                const postUrl = `https://${nodeDomain}/posts/${id}`;
+                const result = await fetchRemotePost(postUrl, nodeDomain);
+
+                if (result.post) {
+                    mainPost = result.post;
+                }
+            }
+        }
+
+        if (!mainPost) {
+            return NextResponse.json({ error: 'Post not found' }, { status: 404 });
         }
 
         return NextResponse.json({

src/lib/activitypub/fetchRemotePost.ts

@@ -0,0 +1,169 @@
+import { db, remotePosts } from '@/db';
+import { eq } from 'drizzle-orm';
+
+export interface ActivityPubNote {
+    '@context': string;
+    id: string;
+    type: 'Note';
+    attributedTo: string;
+    content: string;
+    published: string;
+    to: string[];
+    cc: string[];
+    inReplyTo?: string | null;
+    url: string;
+    attachment?: {
+        type: string;
+        mediaType: string;
+        url: string;
+        name?: string;
+    }[];
+}
+
+function parsePostIdFromUrl(url: string): string | null {
+    try {
+        const urlObj = new URL(url);
+        const pathParts = urlObj.pathname.split('/').filter(Boolean);
+
+        const postsIndex = pathParts.indexOf('posts');
+        if (postsIndex !== -1 && pathParts[postsIndex + 1]) {
+            return pathParts[postsIndex + 1];
+        }
+
+        const objectsIndex = pathParts.indexOf('objects');
+        if (objectsIndex !== -1 && pathParts[objectsIndex + 1]) {
+            return pathParts[objectsIndex + 1];
+        }
+
+        if (pathParts.includes('objects') && pathParts.includes('users')) {
+            const lastPart = pathParts[pathParts.length - 1];
+            return lastPart;
+        }
+
+        return null;
+    } catch {
+        return null;
+    }
+}
+
+async function fetchRemotePostFromUrl(url: string): Promise<ActivityPubNote | null> {
+    try {
+        const response = await fetch(url, {
+            headers: {
+                'Accept': 'application/activity+json, application/ld+json; profile="https://www.w3.org/ns/activitystreams"',
+                'User-Agent': 'Synapsis/1.0 (+https://synapsis.social)',
+            },
+        });
+
+        if (!response.ok) {
+            console.error(`Failed to fetch remote post: ${response.status}`);
+            return null;
+        }
+
+        return await response.json();
+    } catch (error) {
+        console.error('Error fetching remote post:', error);
+        return null;
+    }
+}
+
+async function cacheRemotePost(apNote: ActivityPubNote, nodeDomain: string): Promise<boolean> {
+    try {
+        const postId = parsePostIdFromUrl(apNote.url);
+        if (!postId) {
+            console.error('Could not parse post ID from:', apNote.url);
+            return false;
+        }
+
+        const existing = await db.query.remotePosts.findFirst({
+            where: eq(remotePosts.apId, apNote.id),
+        });
+
+        if (existing) {
+            console.log('Remote post already cached:', postId);
+            return true;
+        }
+
+        let mediaJson: string | null = null;
+        if (apNote.attachment && apNote.attachment.length > 0) {
+            mediaJson = JSON.stringify(apNote.attachment);
+        }
+
+        const authorUrl = new URL(apNote.attributedTo);
+        const authorHandle = authorUrl.pathname.split('/').pop() || apNote.attributedTo;
+        const authorDomain = authorUrl.hostname;
+
+        await db.insert(remotePosts).values({
+            id: crypto.randomUUID(),
+            apId: apNote.id,
+            authorHandle: authorHandle,
+            authorActorUrl: apNote.attributedTo,
+            authorDisplayName: apNote.attributedTo === authorHandle ? null : authorHandle,
+            authorAvatarUrl: null,
+            content: apNote.content || '',
+            publishedAt: apNote.published ? new Date(apNote.published) : new Date(),
+            linkPreviewUrl: null,
+            linkPreviewTitle: null,
+            linkPreviewDescription: null,
+            linkPreviewImage: null,
+            mediaJson: mediaJson,
+            fetchedAt: new Date(),
+        });
+
+        console.log('Cached remote post:', postId);
+        return true;
+    } catch (error) {
+        console.error('Error caching remote post:', error);
+        return false;
+    }
+}
+
+function cachedRemotePostToFrontend(remotePost: any) {
+    let media = null;
+    try {
+        if (remotePost.mediaJson) {
+            media = JSON.parse(remotePost.mediaJson);
+        }
+    } catch {
+    }
+
+    return {
+        id: remotePost.id,
+        content: remotePost.content,
+        createdAt: remotePost.publishedAt.toISOString(),
+        likesCount: 0,
+        repostsCount: 0,
+        repliesCount: 0,
+        author: {
+            id: remotePost.authorHandle,
+            handle: remotePost.authorHandle,
+            displayName: remotePost.authorDisplayName || remotePost.authorHandle,
+            avatarUrl: remotePost.authorAvatarUrl,
+            bio: null,
+            isRemote: true,
+        },
+        media: media || undefined,
+        linkPreviewUrl: remotePost.linkPreviewUrl,
+        linkPreviewTitle: remotePost.linkPreviewTitle,
+        linkPreviewDescription: remotePost.linkPreviewDescription,
+        linkPreviewImage: remotePost.linkPreviewImage,
+        isLiked: false,
+        isReposted: false,
+    };
+}
+
+export async function fetchRemotePost(postUrl: string, nodeDomain: string): Promise<{ post: any | null; isCached: boolean }> {
+    const apNote = await fetchRemotePostFromUrl(postUrl);
+    if (!apNote) {
+        return { post: null, isCached: false };
+    }
+
+    const cached = await cacheRemotePost(apNote, nodeDomain);
+    if (!cached) {
+        return { post: null, isCached: false };
+    }
+
+    const frontendPost = cachedRemotePostToFrontend(apNote);
+
+    return { post: frontendPost, isCached: true };
+}