import asset from "./persona-resource-manifest.json";

const source = `${asset.path}?v=${asset.sha256}`;
const cacheName = "tjwater-agent-persona-v1";

let pending: Promise<ArrayBuffer> | undefined;

async function readResource(response: Response): Promise<ArrayBuffer> {
  if (!response.ok) throw new Error(`Obsidian resource: ${response.status}`);
  const bytes = await response.arrayBuffer();
  const header = new Uint8Array(bytes, 0, Math.min(bytes.byteLength, 4));
  if (bytes.byteLength !== asset.byteLength || String.fromCharCode(...header) !== "RIVE") {
    throw new Error("Obsidian resource: invalid animation data");
  }
  if (globalThis.crypto?.subtle) {
    const digest = await crypto.subtle.digest("SHA-256", bytes);
    const hash = Array.from(new Uint8Array(digest), (byte) => byte.toString(16).padStart(2, "0")).join("");
    if (hash !== asset.sha256) throw new Error("Obsidian resource: version mismatch");
  }
  return bytes;
}

async function loadBytes(): Promise<ArrayBuffer> {
  let cache: Cache | undefined;
  try {
    cache = await globalThis.caches?.open(cacheName);
    const cached = await cache?.match(source);
    if (cached) return await readResource(cached);
  } catch {
    // Storage can be denied or contain incomplete data. Retry through the network.
  }

  const response = await fetch(source, { signal: AbortSignal.timeout(15_000) });
  const bytes = await readResource(response);
  if (cache) {
    try {
      await cache.put(source, new Response(bytes, {
        headers: { "Content-Type": "application/octet-stream" }
      }));
      const current = new URL(source, window.location.href);
      for (const request of await cache.keys()) {
        const url = new URL(request.url);
        if (url.origin === current.origin && url.pathname === asset.path && url.href !== current.href) {
          await cache.delete(request);
        }
      }
    } catch {
      // Quota or storage failures must not prevent the downloaded animation playing.
    }
  }
  return bytes;
}

// Share the immutable bytes, never a live renderer or View Model instance.
export function loadPersonaResource() {
  pending ??= loadBytes().catch((error: unknown) => {
    pending = undefined;
    throw error;
  });
  return pending;
}