export interface WasmResource {
  id: string;
  fileName: string;
  url: string;
  sha256: string;
  required: boolean;
}

export interface WebEngineManifest {
  schemaVersion: number;
  protocolVersion: number;
  engineVersion: string;
  engine: "mock" | "blender-wasm";
  memory: {
    initialPages: number;
    maximumPages: number;
    shared: boolean;
  };
  wasm: WasmResource[];
}

export async function loadWebEngineManifest(url = "/engine-manifest.json"): Promise<WebEngineManifest> {
  const response = await fetch(url, { cache: "no-store" });
  if (!response.ok) throw new Error(`Engine manifest request failed: ${response.status}`);
  const manifest = await response.json() as Partial<WebEngineManifest>;
  if (manifest.schemaVersion !== 1 || manifest.protocolVersion !== 1) {
    throw new Error("Unsupported engine manifest version");
  }
  if (!manifest.engine || !manifest.memory || !Array.isArray(manifest.wasm)) {
    throw new Error("Invalid engine manifest shape");
  }
  return manifest as WebEngineManifest;
}

export async function verifyWasmResource(resource: WasmResource): Promise<void> {
  const response = await fetch(resource.url, { cache: "no-store" });
  if (!response.ok) throw new Error(`WASM resource request failed: ${resource.id}`);
  const bytes = await response.arrayBuffer();
  const digest = await crypto.subtle.digest("SHA-256", bytes);
  const actual = [...new Uint8Array(digest)].map((byte) => byte.toString(16).padStart(2, "0")).join("");
  if (actual !== resource.sha256.toLowerCase()) {
    throw new Error(`WASM resource hash mismatch: ${resource.id}`);
  }
}