// 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 'dart:io';

import 'package:flutter/services.dart';
import 'package:meta/meta.dart';

import 'auth_strings.dart';
import 'error_codes.dart';

enum BiometricType { face, fingerprint, iris }

const MethodChannel _channel = MethodChannel('plugins.flutter.io/local_auth');

/// A Flutter plugin for authenticating the user identity locally.
class LocalAuthentication {
  /// Authenticates the user with biometrics available on the device.
  ///
  /// Returns a [Future] holding true, if the user successfully authenticated,
  /// false otherwise.
  ///
  /// [localizedReason] is the message to show to user while prompting them
  /// for authentication. This is typically along the lines of: 'Please scan
  /// your finger to access MyApp.'
  ///
  /// [useErrorDialogs] = true means the system will attempt to handle user
  /// fixable issues encountered while authenticating. For instance, if
  /// fingerprint reader exists on the phone but there's no fingerprint
  /// registered, the plugin will attempt to take the user to settings to add
  /// one. Anything that is not user fixable, such as no biometric sensor on
  /// device, will be returned as a [PlatformException].
  ///
  /// [stickyAuth] is used when the application goes into background for any
  /// reason while the authentication is in progress. Due to security reasons,
  /// the authentication has to be stopped at that time. If stickyAuth is set
  /// to true, authentication resumes when the app is resumed. If it is set to
  /// false (default), then as soon as app is paused a failure message is sent
  /// back to Dart and it is up to the client app to restart authentication or
  /// do something else.
  ///
  /// Construct [AndroidAuthStrings] and [IOSAuthStrings] if you want to
  /// customize messages in the dialogs.
  ///
  /// Throws an [PlatformException] if there were technical problems with local
  /// authentication (e.g. lack of relevant hardware). This might throw
  /// [PlatformException] with error code [otherOperatingSystem] on the iOS
  /// simulator.
  Future<bool> authenticateWithBiometrics({
    @required String localizedReason,
    bool useErrorDialogs = true,
    bool stickyAuth = false,
    AndroidAuthMessages androidAuthStrings = const AndroidAuthMessages(),
    IOSAuthMessages iOSAuthStrings = const IOSAuthMessages(),
  }) async {
    assert(localizedReason != null);
    final Map<String, Object> args = <String, Object>{
      'localizedReason': localizedReason,
      'useErrorDialogs': useErrorDialogs,
      'stickyAuth': stickyAuth,
    };
    if (Platform.isIOS) {
      args.addAll(iOSAuthStrings.args);
    } else if (Platform.isAndroid) {
      args.addAll(androidAuthStrings.args);
    } else {
      throw PlatformException(
          code: otherOperatingSystem,
          message: 'Local authentication does not support non-Android/iOS '
              'operating systems.',
          details: 'Your operating system is ${Platform.operatingSystem}');
    }
    // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
    // https://github.com/flutter/flutter/issues/26431
    // ignore: strong_mode_implicit_dynamic_method
    return await _channel.invokeMethod('authenticateWithBiometrics', args);
  }

  /// Returns true if device is capable of checking biometrics
  ///
  /// Returns a [Future] bool true or false:
  Future<bool> get canCheckBiometrics async =>
      // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
      // https://github.com/flutter/flutter/issues/26431
      // ignore: strong_mode_implicit_dynamic_method
      (await _channel.invokeMethod('getAvailableBiometrics')).isNotEmpty;

  /// Returns a list of enrolled biometrics
  ///
  /// Returns a [Future] List<BiometricType> with the following possibilities:
  /// - BiometricType.face
  /// - BiometricType.fingerprint
  /// - BiometricType.iris (not yet implemented)
  Future<List<BiometricType>> getAvailableBiometrics() async {
    final List<String> result =
        // TODO(amirh): remove this on when the invokeMethod update makes it to stable Flutter.
        // https://github.com/flutter/flutter/issues/26431
        // ignore: strong_mode_implicit_dynamic_method
        (await _channel.invokeMethod('getAvailableBiometrics')).cast<String>();
    final List<BiometricType> biometrics = <BiometricType>[];
    result.forEach((String value) {
      switch (value) {
        case 'face':
          biometrics.add(BiometricType.face);
          break;
        case 'fingerprint':
          biometrics.add(BiometricType.fingerprint);
          break;
        case 'iris':
          biometrics.add(BiometricType.iris);
          break;
        case 'undefined':
          break;
      }
    });
    return biometrics;
  }
}