// Copyright 2014 The Flutter 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 'base/io.dart';
import 'base/platform.dart';
import 'doctor_validator.dart';
import 'features.dart';

// Overridable environment variables
const String kEnvPubHostedUrl = 'PUB_HOSTED_URL';
const String kEnvCloudUrl = 'FLUTTER_STORAGE_BASE_URL';
const String kDoctorHostTimeout = 'FLUTTER_DOCTOR_HOST_TIMEOUT';

/// Common Flutter HTTP hosts.
const String kPubDevHttpHost = 'https://pub.dev/';
const String kgCloudHttpHost = 'https://cloud.google.com/';

/// Android specific required HTTP hosts.
const List<String> androidRequiredHttpHosts = <String>[
  'https://maven.google.com/',
];

/// MacOS specific required HTTP hosts.
const List<String> macOSRequiredHttpHosts = <String>[
  'https://cocoapods.org/',
];

// Validator that checks all provided hosts are reachable and responsive
class HttpHostValidator extends DoctorValidator {
  HttpHostValidator(
      {required Platform platform,
        required FeatureFlags featureFlags,
        required HttpClient httpClient})
      : _platform = platform,
        _featureFlags = featureFlags,
        _httpClient = httpClient,
        super('HTTP Host Availability');

  final Platform _platform;
  final FeatureFlags _featureFlags;
  final HttpClient _httpClient;

  @override
  String get slowWarning =>
      'HTTP Host availability check is taking a long time...';

  List<String> get _requiredHosts => <String>[
    if (_featureFlags.isMacOSEnabled) ...macOSRequiredHttpHosts,
    if (_featureFlags.isAndroidEnabled) ...androidRequiredHttpHosts,
    _platform.environment[kEnvPubHostedUrl] ?? kPubDevHttpHost,
    _platform.environment[kEnvCloudUrl] ?? kgCloudHttpHost,
  ];

  /// Make a head request to the HTTP host. HTTP Host is available if no exception happened
  Future<_HostValidationResult> _checkHostAvailability(String host) async {
    try {
      final int timeout =
      int.parse(_platform.environment[kDoctorHostTimeout] ?? '10');
      final HttpClientRequest req = await _httpClient.headUrl(Uri.parse(host));
      await req.close().timeout(Duration(seconds: timeout));
      // HTTP Host is available if no exception happened
      return _HostValidationResult.success(host);
    } on TimeoutException {
      return _HostValidationResult.fail(
          host, 'Failed to connect to $host in seconds');
    } on SocketException catch (e) {
      return _HostValidationResult.fail(
          host, 'An error occurred while checking the HTTP host: ${e.message}');
    } on HttpException catch (e) {
      return _HostValidationResult.fail(host,
          'An error occurred while checking the HTTP host: ${e.toString()}');
    } on OSError catch (e) {
      return _HostValidationResult.fail(
          host, 'An error occurred while checking the HTTP host: ${e.message}');
    }
  }

  @override
  Future<ValidationResult> validate() async {
    final List<ValidationMessage> messages = <ValidationMessage>[];
    final Iterable<Future<_HostValidationResult>> availabilityResultFutures =
    _requiredHosts.map(_checkHostAvailability);

    final List<_HostValidationResult> availabilityResults =
    (await Future.wait(availabilityResultFutures)).toList();

    if (availabilityResults
        .every((_HostValidationResult result) => result.available)) {
      return ValidationResult(
          ValidationType.installed,
          messages
            ..add(const ValidationMessage(
                'All required HTTP hosts are available')));
    }

    availabilityResults
        .removeWhere((_HostValidationResult result) => result.available);

    for (final _HostValidationResult result in availabilityResults) {
      messages.add(ValidationMessage.error(
          'HTTP host ${result.host} is not reachable. Reason: ${result.failResultInfo}'));
    }

    return ValidationResult(
        availabilityResults.length == _requiredHosts.length
            ? ValidationType.notAvailable
            : ValidationType.partial,
        messages);
  }
}

class _HostValidationResult {
  _HostValidationResult.success(this.host)
      : failResultInfo = '',
        available = true;

  _HostValidationResult.fail(this.host, this.failResultInfo)
      : available = false;

  final String failResultInfo;
  final String host;
  final bool available;
}