// 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 'base/io.dart';
import 'base/platform.dart';
import 'doctor_validator.dart';

/// A validator that displays configured HTTP_PROXY environment variables.
///
/// if the `HTTP_PROXY` environment variable is non-empty, the contents are
/// validated along with `NO_PROXY`.
class ProxyValidator extends DoctorValidator {
  ProxyValidator({required Platform platform})
    : shouldShow = _getEnv('HTTP_PROXY', platform).isNotEmpty,
      _httpProxy = _getEnv('HTTP_PROXY', platform),
      _noProxy = _getEnv('NO_PROXY', platform),
      super('Proxy Configuration');

  final bool shouldShow;
  final String _httpProxy;
  final String _noProxy;

  /// Gets a trimmed, non-null environment variable. If the variable is not set
  /// an empty string will be returned. Checks for the lowercase version of the
  /// environment variable first, then uppercase to match Dart's HTTP implementation.
  static String _getEnv(String key, Platform platform) =>
      platform.environment[key.toLowerCase()]?.trim() ??
      platform.environment[key.toUpperCase()]?.trim() ??
      '';

  @override
  Future<ValidationResult> validateImpl() async {
    if (_httpProxy.isEmpty) {
      return ValidationResult(ValidationType.success, const <ValidationMessage>[]);
    }

    final messages = <ValidationMessage>[const ValidationMessage('HTTP_PROXY is set')];
    if (_noProxy.isEmpty) {
      messages.add(const ValidationMessage.hint('NO_PROXY is not set'));
    } else {
      messages.add(ValidationMessage('NO_PROXY is $_noProxy'));
      final Set<String> proxyHosts = _noProxy.split(',').map((String e) => e.trim()).toSet();
      final List<String> loopbackAddresses = await _getLoopbackAddresses();
      for (final host in loopbackAddresses) {
        if (proxyHosts.contains(host)) {
          messages.add(ValidationMessage('NO_PROXY contains $host'));
        } else {
          messages.add(ValidationMessage.hint('NO_PROXY does not contain $host'));
        }
      }
    }
    final bool hasIssues = messages.any((ValidationMessage msg) => msg.isHint || msg.isError);

    return ValidationResult(hasIssues ? ValidationType.partial : ValidationType.success, messages);
  }

  Future<List<String>> _getLoopbackAddresses() async {
    final List<NetworkInterface> networkInterfaces = await listNetworkInterfaces(
      includeLinkLocal: true,
      includeLoopback: true,
    );

    return <String>[
      'localhost',
      for (final NetworkInterface networkInterface in networkInterfaces)
        for (final InternetAddress internetAddress in networkInterface.addresses)
          if (internetAddress.isLoopback) internetAddress.address,
    ];
  }
}