// IndexedDB cache of computed modes files, keyed by a hash of the configuration and options.

const DB = "cymplay", STORE = "modes";

function open(): Promise<IDBDatabase> {
  return new Promise((resolve, reject) => {
    const req = indexedDB.open(DB, 1);
    req.onupgradeneeded = () => req.result.createObjectStore(STORE);
    req.onsuccess = () => resolve(req.result);
    req.onerror = () => reject(req.error);
  });
}

export async function cacheKey(obj: unknown): Promise<string> {
  const bytes = new TextEncoder().encode(JSON.stringify(obj));
  const digest = await crypto.subtle.digest("SHA-256", bytes);
  return Array.from(new Uint8Array(digest).slice(0, 16), (b) => b.toString(16).padStart(2, "0")).join("");
}

export async function cacheGet(key: string): Promise<ArrayBuffer | null> {
  try {
    const db = await open();
    return await new Promise((resolve, reject) => {
      const req = db.transaction(STORE, "readonly").objectStore(STORE).get(key);
      req.onsuccess = () => resolve((req.result as ArrayBuffer) ?? null);
      req.onerror = () => reject(req.error);
    });
  } catch {
    return null;
  }
}

export async function cachePut(key: string, buffer: ArrayBuffer): Promise<void> {
  try {
    const db = await open();
    await new Promise<void>((resolve, reject) => {
      const tx = db.transaction(STORE, "readwrite");
      tx.objectStore(STORE).put(buffer, key);
      tx.oncomplete = () => resolve();
      tx.onerror = () => reject(tx.error);
    });
  } catch {
    /* caching is best effort */
  }
}

export async function cacheClear(): Promise<void> {
  try {
    const db = await open();
    await new Promise<void>((resolve, reject) => {
      const tx = db.transaction(STORE, "readwrite");
      tx.objectStore(STORE).clear();
      tx.oncomplete = () => resolve();
      tx.onerror = () => reject(tx.error);
    });
  } catch {
    /* ignore */
  }
}