export const TENSAMIN_DB_NAME = "tensamin";
export const TENSAMIN_DB_VERSION = 1;
export type TensaminStore = "storage" | "cache" | "keys";

const stores: TensaminStore[] = ["storage", "cache", "keys"];
let databasePromise: Promise<IDBDatabase> | undefined;

export function openTensaminDatabase(
  indexedDb: IDBFactory = globalThis.indexedDB,
) {
  databasePromise ??= new Promise<IDBDatabase>((resolve, reject) => {
    const request = indexedDb.open(TENSAMIN_DB_NAME, TENSAMIN_DB_VERSION);
    request.onupgradeneeded = () => {
      for (const store of stores) {
        if (!request.result.objectStoreNames.contains(store)) {
          request.result.createObjectStore(store);
        }
      }
    };
    request.onsuccess = () => {
      request.result.onversionchange = () => request.result.close();
      resolve(request.result);
    };
    request.onerror = () => {
      databasePromise = undefined;
      reject(request.error);
    };
    request.onblocked = () => {
      databasePromise = undefined;
      reject(new Error("The Tensamin database upgrade is blocked."));
    };
  });
  return databasePromise;
}

export async function getDatabaseEntry<T>(store: TensaminStore, key: string) {
  const database = await openTensaminDatabase();
  return new Promise<T | undefined>((resolve, reject) => {
    const request = database
      .transaction(store, "readonly")
      .objectStore(store)
      .get(key);
    request.onsuccess = () => resolve(request.result as T | undefined);
    request.onerror = () => reject(request.error);
  });
}

export async function setDatabaseEntry(
  store: TensaminStore,
  key: string,
  value: unknown,
) {
  const database = await openTensaminDatabase();
  return new Promise<void>((resolve, reject) => {
    const transaction = database.transaction(store, "readwrite");
    transaction.objectStore(store).put(value, key);
    transaction.oncomplete = () => resolve();
    transaction.onerror = () => reject(transaction.error);
    transaction.onabort = () => reject(transaction.error);
  });
}

export async function deleteDatabaseEntry(store: TensaminStore, key: string) {
  const database = await openTensaminDatabase();
  return new Promise<void>((resolve, reject) => {
    const transaction = database.transaction(store, "readwrite");
    transaction.objectStore(store).delete(key);
    transaction.oncomplete = () => resolve();
    transaction.onerror = () => reject(transaction.error);
    transaction.onabort = () => reject(transaction.error);
  });
}

export async function listDatabaseEntries(
  store: TensaminStore,
  keyPrefix: string,
) {
  const database = await openTensaminDatabase();
  return new Promise<Array<[string, unknown]>>((resolve, reject) => {
    const entries: Array<[string, unknown]> = [];
    const cursor = database
      .transaction(store, "readonly")
      .objectStore(store)
      .openCursor();
    cursor.onsuccess = () => {
      const value = cursor.result;
      if (!value) {
        resolve(entries);
        return;
      }
      if (typeof value.key === "string" && value.key.startsWith(keyPrefix)) {
        entries.push([value.key, value.value]);
      }
      value.continue();
    };
    cursor.onerror = () => reject(cursor.error);
  });
}