/**
 * IndexedDB wrapper for the POS offline order queue.
 * All reads/writes happen in a single "order_queue" object store.
 */

export type OfflineQueueItem = {
  /** Local UUID – primary key */
  id: string;
  /** "create_order" or "add_items_to_order" */
  type: "create_order" | "add_items";
  cafeId: string;
  /**
   * For add_items: the real server order ID.
   * For create_order: null (no server ID yet).
   */
  targetOrderId: string | null;
  /** Raw body to POST/PUT */
  payload: unknown;
  createdAt: string;
  retries: number;
  status: "pending" | "failed";
};

const DB_NAME = "meezi_pos_offline";
const DB_VERSION = 1;
const STORE = "order_queue";

let _db: IDBDatabase | null = null;

function openDb(): Promise<IDBDatabase> {
  if (_db) return Promise.resolve(_db);
  return new Promise((resolve, reject) => {
    const req = indexedDB.open(DB_NAME, DB_VERSION);
    req.onupgradeneeded = (e) => {
      const db = (e.target as IDBOpenDBRequest).result;
      if (!db.objectStoreNames.contains(STORE)) {
        db.createObjectStore(STORE, { keyPath: "id" });
      }
    };
    req.onsuccess = () => {
      _db = req.result;
      resolve(_db);
    };
    req.onerror = () => reject(req.error);
  });
}

export async function enqueueOfflineItem(
  item: Omit<OfflineQueueItem, "retries" | "status">
): Promise<void> {
  const db = await openDb();
  return new Promise((resolve, reject) => {
    const tx = db.transaction(STORE, "readwrite");
    tx.objectStore(STORE).put({ ...item, retries: 0, status: "pending" });
    tx.oncomplete = () => resolve();
    tx.onerror = () => reject(tx.error);
  });
}

export async function getQueueCount(): Promise<number> {
  try {
    const db = await openDb();
    return new Promise((resolve, reject) => {
      const tx = db.transaction(STORE, "readonly");
      const req = tx.objectStore(STORE).count();
      req.onsuccess = () => resolve(req.result);
      req.onerror = () => reject(req.error);
    });
  } catch {
    return 0;
  }
}

export async function getAllQueueItems(): Promise<OfflineQueueItem[]> {
  try {
    const db = await openDb();
    return new Promise((resolve, reject) => {
      const tx = db.transaction(STORE, "readonly");
      const req = tx.objectStore(STORE).getAll();
      req.onsuccess = () => resolve(req.result as OfflineQueueItem[]);
      req.onerror = () => reject(req.error);
    });
  } catch {
    return [];
  }
}

export async function removeQueueItem(id: string): Promise<void> {
  const db = await openDb();
  return new Promise((resolve, reject) => {
    const tx = db.transaction(STORE, "readwrite");
    tx.objectStore(STORE).delete(id);
    tx.oncomplete = () => resolve();
    tx.onerror = () => reject(tx.error);
  });
}

export async function markQueueItemFailed(id: string): Promise<void> {
  const db = await openDb();
  return new Promise((resolve, reject) => {
    const tx = db.transaction(STORE, "readwrite");
    const store = tx.objectStore(STORE);
    const getReq = store.get(id);
    getReq.onsuccess = () => {
      const item = getReq.result as OfflineQueueItem;
      if (item) store.put({ ...item, status: "failed", retries: item.retries + 1 });
    };
    tx.oncomplete = () => resolve();
    tx.onerror = () => reject(tx.error);
  });
}
