export type ErrorLike = {
  message: string;
  key?: string;
};

export type Callback = (error?: Error | null) => void;

export type CallbackWithResult<T> = (
  error?: Error | null,
  result?: T | null
) => void;

export type KeyValuePair = [string, string | null];

export type MultiCallback = (errors?: readonly (Error | null)[] | null) => void;

export type MultiGetCallback = (
  errors?: readonly (Error | null)[] | null,
  result?: readonly KeyValuePair[]
) => void;

export type MultiRequest = {
  keys: readonly string[];
  callback?: MultiGetCallback;
  keyIndex: number;
  resolve?: (result: readonly KeyValuePair[]) => void;
  reject?: (error?: ErrorLike) => void;
};

export type AsyncStorageHook = {
  getItem: (callback?: CallbackWithResult<string>) => Promise<string | null>;
  setItem: (value: string, callback?: Callback) => Promise<void>;
  mergeItem: (value: string, callback?: Callback) => Promise<void>;
  removeItem: (callback?: Callback) => Promise<void>;
};

/**
 * `AsyncStorage` is a simple, unencrypted, asynchronous, persistent, key-value
 * storage system that is global to the app.  It should be used instead of
 * LocalStorage.
 *
 * See https://react-native-async-storage.github.io/async-storage/docs/api
 */
export type AsyncStorageStatic = {
  /**
   * Fetches an item for a `key` and invokes a callback upon completion.
   *
   * See https://react-native-async-storage.github.io/async-storage/docs/api#getitem
   */
  getItem: (
    key: string,
    callback?: CallbackWithResult<string>
  ) => Promise<string | null>;

  /**
   * Sets the value for a `key` and invokes a callback upon completion.
   *
   * See https://react-native-async-storage.github.io/async-storage/docs/api#setitem
   */
  setItem: (key: string, value: string, callback?: Callback) => Promise<void>;

  /**
   * Removes an item for a `key` and invokes a callback upon completion.
   *
   * See https://react-native-async-storage.github.io/async-storage/docs/api#removeitem
   */
  removeItem: (key: string, callback?: Callback) => Promise<void>;

  /**
   * Merges an existing `key` value with an input value, assuming both values
   * are stringified JSON.
   *
   * See https://react-native-async-storage.github.io/async-storage/docs/api#mergeitem
   */
  mergeItem: (key: string, value: string, callback?: Callback) => Promise<void>;

  /**
   * Erases *all* `AsyncStorage` for all clients, libraries, etc. You probably
   * don't want to call this; use `removeItem` or `multiRemove` to clear only
   * your app's keys.
   *
   * See https://react-native-async-storage.github.io/async-storage/docs/api#clear
   */
  clear: (callback?: Callback) => Promise<void>;

  /**
   * Gets *all* keys known to your app; for all callers, libraries, etc.
   *
   * See https://react-native-async-storage.github.io/async-storage/docs/api#getallkeys
   */
  getAllKeys: (
    callback?: CallbackWithResult<readonly string[]>
  ) => Promise<readonly string[]>;

  /**
   * The following batched functions are useful for executing a lot of
   * operations at once, allowing for native optimizations and provide the
   * convenience of a single callback after all operations are complete.
   *
   * These functions return arrays of errors, potentially one for every key.
   * For key-specific errors, the Error object will have a key property to
   * indicate which key caused the error.
   */

  /**
   * Flushes any pending requests using a single batch call to get the data.
   *
   * See https://react-native-async-storage.github.io/async-storage/docs/api#flushgetrequests
   * */
  flushGetRequests: () => void;

  /**
   * This allows you to batch the fetching of items given an array of `key`
   * inputs. Your callback will be invoked with an array of corresponding
   * key-value pairs found.
   *
   * See https://react-native-async-storage.github.io/async-storage/docs/api#multiget
   */
  multiGet: (
    keys: readonly string[],
    callback?: MultiGetCallback
  ) => Promise<readonly KeyValuePair[]>;

  /**
   * Use this as a batch operation for storing multiple key-value pairs. When
   * the operation completes you'll get a single callback with any errors.
   *
   * See https://react-native-async-storage.github.io/async-storage/docs/api#multiset
   */
  multiSet: (
    keyValuePairs: ReadonlyArray<readonly [string, string]>,
    callback?: MultiCallback
  ) => Promise<void>;

  /**
   * Call this to batch the deletion of all keys in the `keys` array.
   *
   * See https://react-native-async-storage.github.io/async-storage/docs/api#multiremove
   */
  multiRemove: (
    keys: readonly string[],
    callback?: MultiCallback
  ) => Promise<void>;

  /**
   * Batch operation to merge in existing and new values for a given set of
   * keys. This assumes that the values are stringified JSON.
   *
   * See https://react-native-async-storage.github.io/async-storage/docs/api#multimerge
   */
  multiMerge: (
    keyValuePairs: [string, string][],
    callback?: MultiCallback
  ) => Promise<void>;
};