const PLC_DIRECTORY = "https://plc.directory";

export default {
  async fetch(request, env, ctx) {
    const url = new URL(request.url);
    const cache = caches.default;

    // Regex to extract Type, DID, and CID
    const pathRegex = /^\/img\/([^/]+)\/plain\/(did:[^/]+)\/([^@/]+)(?:@([^/]+))?$/;
    const match = url.pathname.match(pathRegex);

    if (!match) return new Response("400: Invalid Path", { status: 400 });
    const [_, type, did, cid] = match;

    // 1. TRY OFFICIAL CDN FIRST (Best for resized/transformed images)
    const bskyCdnUrl = `https://cdn.bsky.app${url.pathname}`;
    let response = await fetch(bskyCdnUrl, { cf: { cacheTtl: 3600 } });
    
    // If CDN works (200 OK), return it immediately
    if (response.ok) {
      const cdnRes = new Response(response.body, response);
      cdnRes.headers.set("X-Proxy-Source", "Bluesky-CDN");
      return cdnRes;
    }

    // 2. GLOBAL CACHE CHECK (For the Fallback)
    let cachedResponse = await cache.match(request);
    if (cachedResponse) return cachedResponse;

    // 3. PDS FALLBACK LOGIC
    try {
      const pdsUrl = await resolvePds(did);
      if (!pdsUrl) throw new Error("PDS not found for this DID");

      // A. Try the CID from the URL directly on the PDS (Works if it's the original)
      let blobRes = await fetchBlob(pdsUrl, did, cid);

      // B. TRANSFORMED IMAGE FIX: If 404, the CID is a thumbnail. 
      // We look up the 'Original' CID from the user's Profile Record.
      if (blobRes.status === 404 && (type === 'avatar' || type === 'banner')) {
        console.log(`Thumbnail CID not found. Fetching original for ${type}...`);
        const originalCid = await findOriginalCidFromProfile(pdsUrl, did, type);
        
        if (originalCid && originalCid !== cid) {
          blobRes = await fetchBlob(pdsUrl, did, originalCid);
        }
      }

      if (blobRes.ok) {
        const finalRes = new Response(blobRes.body, blobRes);
        finalRes.headers.set("Cache-Control", "public, s-maxage=604800");
        finalRes.headers.set("X-Proxy-Source", "PDS-Discovery");
        
        ctx.waitUntil(cache.put(request, finalRes.clone()));
        return finalRes;
      }

      return new Response(`404: Asset not found on CDN or PDS.`, { status: 404 });

    } catch (err) {
      return new Response(`502: Failover Error: ${err.message}`, { status: 502 });
    }
  }
};

/** * Helpers 
 **/

async function fetchBlob(pdsUrl, did, cid) {
  return fetch(`${pdsUrl}/xrpc/com.atproto.sync.getBlob?did=${encodeURIComponent(did)}&cid=${encodeURIComponent(cid)}`);
}

async function resolvePds(did) {
  const res = await fetch(`${PLC_DIRECTORY}/${did}`, { cf: { cacheTtl: 3600 } });
  if (!res.ok) return null;
  const doc = await res.json();
  const pds = doc.service?.find(s => s.id === "#atproto_pds" || s.type === "AtprotoPersonalDataServer");
  return pds?.serviceEndpoint;
}

async function findOriginalCidFromProfile(pdsUrl, did, type) {
  // Collection: app.bsky.actor.profile, Key: self
  const recordUrl = `${pdsUrl}/xrpc/com.atproto.repo.getRecord?repo=${encodeURIComponent(did)}&collection=app.bsky.actor.profile&rkey=self`;
  const res = await fetch(recordUrl);
  if (!res.ok) return null;
  const data = await res.json();
  
  // Navigate the JSON to find the blob reference for 'avatar' or 'banner'
  return data.value?.[type]?.ref?.$link;
}