// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:async';

import 'package:meta/meta.dart' show required, visibleForTesting;

import 'method_channel_url_launcher.dart';

/// The interface that implementations of url_launcher must implement.
///
/// Platform implementations should extend this class rather than implement it as `url_launcher`
/// does not consider newly added methods to be breaking changes. Extending this class
/// (using `extends`) ensures that the subclass will get the default implementation, while
/// platform implementations that `implements` this interface will be broken by newly added
/// [UrlLauncherPlatform] methods.
abstract class UrlLauncherPlatform {
  /// Only mock implementations should set this to true.
  ///
  /// Mockito mocks are implementing this class with `implements` which is forbidden for anything
  /// other than mocks (see class docs). This property provides a backdoor for mockito mocks to
  /// skip the verification that the class isn't implemented with `implements`.
  @visibleForTesting
  bool get isMock => false;

  /// The default instance of [UrlLauncherPlatform] to use.
  ///
  /// Platform-specific plugins should override this with their own
  /// platform-specific class that extends [UrlLauncherPlatform] when they
  /// register themselves.
  ///
  /// Defaults to [MethodChannelUrlLauncher].
  static UrlLauncherPlatform _instance = MethodChannelUrlLauncher();

  static UrlLauncherPlatform get instance => _instance;

  // TODO(amirh): Extract common platform interface logic.
  // https://github.com/flutter/flutter/issues/43368
  static set instance(UrlLauncherPlatform instance) {
    if (!instance.isMock) {
      try {
        instance._verifyProvidesDefaultImplementations();
      } on NoSuchMethodError catch (_) {
        throw AssertionError(
            'Platform interfaces must not be implemented with `implements`');
      }
    }
    _instance = instance;
  }

  /// Returns `true` if this platform is able to launch [url].
  Future<bool> canLaunch(String url) {
    throw UnimplementedError('canLaunch() has not been implemented.');
  }

  /// Returns `true` if the given [url] was successfully launched.
  ///
  /// For documentation on the other arguments, see the `launch` documentation
  /// in `package:url_launcher/url_launcher.dart`.
  Future<bool> launch(
    String url, {
    @required bool useSafariVC,
    @required bool useWebView,
    @required bool enableJavaScript,
    @required bool enableDomStorage,
    @required bool universalLinksOnly,
    @required Map<String, String> headers,
  }) {
    throw UnimplementedError('launch() has not been implemented.');
  }

  /// Closes the WebView, if one was opened earlier by [launch].
  Future<void> closeWebView() {
    throw UnimplementedError('closeWebView() has not been implemented.');
  }

  // This method makes sure that UrlLauncher isn't implemented with `implements`.
  //
  // See class doc for more details on why implementing this class is forbidden.
  //
  // This private method is called by the instance setter, which fails if the class is
  // implemented with `implements`.
  void _verifyProvidesDefaultImplementations() {}
}