/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @format
 */

type ChangeEventName = 'connectionChange';

export type ConnectionType =
  // iOS & Android
  | 'none'
  | 'cellular'
  | 'unknown'
  | 'wifi'
  // Android only
  | 'bluetooth'
  | 'ethernet'
  | 'wimax';

export type EffectiveConnectionType = 'unknown' | '2g' | '3g' | '4g';

export interface ConnectionInfo {
  type: ConnectionType;
  effectiveType: EffectiveConnectionType;
}

export interface NetInfoStatic {
  /**
   * This function is deprecated. Use `getConnectionInfo` instead. Returns a promise that
   * resolves with one of the deprecated connectivity types listed above.
   */
  fetch: () => Promise<ConnectionType>;

  /**
   * Adds an event handler. Supported events:
   *
   * - `connectionChange`: Fires when the network status changes. The argument to the event
   *   handler is an object with keys:
   *   - `type`: A `DeprecatedConnectionType` (listed above)
   *   - `effectiveType`: An `EffectiveConnectionType` (listed above)
   */
  addEventListener: (
    eventName: ChangeEventName,
    listener: (result: ConnectionInfo) => void,
  ) => void;

  /**
   * Removes the listener for network status changes.
   */
  removeEventListener: (
    eventName: ChangeEventName,
    listener: (result: ConnectionInfo) => void,
  ) => void;

  /**
   * Returns a promise that resolves to an object with `type` and `effectiveType` keys
   * whose values are a `ConnectionType` and an `EffectiveConnectionType`, (described above),
   * respectively.
   */
  getConnectionInfo: () => Promise<ConnectionInfo>;

  /**
   * An object with the same methods as above but the listener receives a
   * boolean which represents the internet connectivity.
   * Use this if you are only interested with whether the device has internet
   * connectivity.
   */
  isConnected: {
    fetch: () => Promise<boolean>,

    /**
     * eventName is expected to be `change`(deprecated) or `connectionChange`
     */
    addEventListener: (
      eventName: ChangeEventName,
      listener: (result: boolean) => void,
    ) => void,

    /**
     * eventName is expected to be `change`(deprecated) or `connectionChange`
     */
    removeEventListener: (
      eventName: ChangeEventName,
      listener: (result: boolean) => void,
    ) => void,
  };

  /**
   * Detect if the current active connection is
   * metered or not. A network is classified as metered when the user is
   * sensitive to heavy data usage on that connection due to monetary
   * costs, data limitations or battery/performance issues.
   */
  isConnectionExpensive: () => Promise<boolean>;
}

declare let NetInfo: NetInfoStatic;
export default NetInfo;