// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/// Helpers for dealing with HTTP.
import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'dart:math' as math;

import 'package:http/http.dart' as http;
import 'package:http_retry/http_retry.dart';
import 'package:http_throttle/http_throttle.dart';
import 'package:stack_trace/stack_trace.dart';

import 'command_runner.dart';
import 'io.dart';
import 'log.dart' as log;
import 'oauth2.dart' as oauth2;
import 'package.dart';
import 'sdk.dart';
import 'utils.dart';

/// Headers and field names that should be censored in the log output.
final _CENSORED_FIELDS = const ['refresh_token', 'authorization'];

/// Headers required for pub.dartlang.org API requests.
///
/// The Accept header tells pub.dartlang.org which version of the API we're
/// expecting, so it can either serve that version or give us a 406 error if
/// it's not supported.
final PUB_API_HEADERS = const {'Accept': 'application/vnd.pub.v2+json'};

/// A unique ID to identify this particular invocation of pub.
final _sessionId = createUuid();

/// An HTTP client that transforms 40* errors and socket exceptions into more
/// user-friendly error messages.
class _PubHttpClient extends http.BaseClient {
  final _requestStopwatches = new Map<http.BaseRequest, Stopwatch>();

  http.Client _inner;

  _PubHttpClient([http.Client inner])
      : this._inner = inner == null ? new http.Client() : inner;

  Future<http.StreamedResponse> send(http.BaseRequest request) async {
    if (_shouldAddMetadata(request)) {
      request.headers["X-Pub-OS"] = Platform.operatingSystem;
      request.headers["X-Pub-Command"] = PubCommandRunner.command;
      request.headers["X-Pub-Session-ID"] = _sessionId;

      var environment = Platform.environment["PUB_ENVIRONMENT"];
      if (environment != null) {
        request.headers["X-Pub-Environment"] = environment;
      }

      var type = Zone.current[#_dependencyType];
      if (type != null) request.headers["X-Pub-Reason"] = type.toString();
    }

    _requestStopwatches[request] = new Stopwatch()..start();
    request.headers[HttpHeaders.USER_AGENT] = "Dart pub ${sdk.version}";
    _logRequest(request);

    var streamedResponse;
    try {
      streamedResponse = await _inner.send(request);
    } on SocketException catch (error, stackTraceOrNull) {
      // Work around issue 23008.
      var stackTrace = stackTraceOrNull ?? new Chain.current();

      if (error.osError == null) rethrow;

      if (error.osError.errorCode == 8 ||
          error.osError.errorCode == -2 ||
          error.osError.errorCode == -5 ||
          error.osError.errorCode == 11001 ||
          error.osError.errorCode == 11004) {
        fail('Could not resolve URL "${request.url.origin}".', error,
            stackTrace);
      } else if (error.osError.errorCode == -12276) {
        fail(
            'Unable to validate SSL certificate for '
            '"${request.url.origin}".',
            error,
            stackTrace);
      } else {
        rethrow;
      }
    }

    _logResponse(streamedResponse);

    return streamedResponse;
  }

  /// Whether extra metadata headers should be added to [request].
  bool _shouldAddMetadata(http.BaseRequest request) {
    if (runningFromTest && Platform.environment.containsKey("PUB_HOSTED_URL")) {
      if (request.url.origin != Platform.environment["PUB_HOSTED_URL"]) {
        return false;
      }
    } else {
      if (request.url.origin != "https://pub.dartlang.org") return false;
    }

    return const [
      "cache add",
      "cache repair",
      "downgrade",
      "get",
      "global activate",
      "upgrade",
    ].contains(PubCommandRunner.command);
  }

  /// Logs the fact that [request] was sent, and information about it.
  void _logRequest(http.BaseRequest request) {
    var requestLog = new StringBuffer();
    requestLog.writeln("HTTP ${request.method} ${request.url}");
    request.headers
        .forEach((name, value) => requestLog.writeln(_logField(name, value)));

    if (request.method == 'POST') {
      var contentTypeString = request.headers[HttpHeaders.CONTENT_TYPE];
      if (contentTypeString == null) contentTypeString = '';
      var contentType = ContentType.parse(contentTypeString);
      if (request is http.MultipartRequest) {
        requestLog.writeln();
        requestLog.writeln("Body fields:");
        request.fields.forEach(
            (name, value) => requestLog.writeln(_logField(name, value)));

        // TODO(nweiz): make MultipartRequest.files readable, and log them?
      } else if (request is http.Request) {
        if (contentType.value == 'application/x-www-form-urlencoded') {
          requestLog.writeln();
          requestLog.writeln("Body fields:");
          request.bodyFields.forEach(
              (name, value) => requestLog.writeln(_logField(name, value)));
        } else if (contentType.value == 'text/plain' ||
            contentType.value == 'application/json') {
          requestLog.write(request.body);
        }
      }
    }

    log.io(requestLog.toString().trim());
  }

  /// Logs the fact that [response] was received, and information about it.
  void _logResponse(http.StreamedResponse response) {
    // TODO(nweiz): Fork the response stream and log the response body. Be
    // careful not to log OAuth2 private data, though.

    var responseLog = new StringBuffer();
    var request = response.request;
    var stopwatch = _requestStopwatches.remove(request)..stop();
    responseLog.writeln("HTTP response ${response.statusCode} "
        "${response.reasonPhrase} for ${request.method} ${request.url}");
    responseLog.writeln("took ${stopwatch.elapsed}");
    response.headers
        .forEach((name, value) => responseLog.writeln(_logField(name, value)));

    log.io(responseLog.toString().trim());
  }

  /// Returns a log-formatted string for the HTTP field or header with the given
  /// [name] and [value].
  String _logField(String name, String value) {
    if (_CENSORED_FIELDS.contains(name.toLowerCase())) {
      return "$name: <censored>";
    } else {
      return "$name: $value";
    }
  }
}

/// The [_PubHttpClient] wrapped by [httpClient].
final _pubClient = new _PubHttpClient();

/// A set of all hostnames for which we've printed a message indicating that
/// we're waiting for them to come back up.
final _retriedHosts = new Set<String>();

/// Intercepts all requests and throws exceptions if the response was not
/// considered successful.
class _ThrowingClient extends http.BaseClient {
  final http.Client _inner;

  _ThrowingClient(this._inner);

  Future<http.StreamedResponse> send(http.BaseRequest request) async {
    final streamedResponse = await _inner.send(request);

    var status = streamedResponse.statusCode;
    // 401 responses should be handled by the OAuth2 client. It's very
    // unlikely that they'll be returned by non-OAuth2 requests. We also want
    // to pass along 400 responses from the token endpoint.
    var tokenRequest = streamedResponse.request.url == oauth2.tokenEndpoint;
    if (status < 400 || status == 401 || (status == 400 && tokenRequest)) {
      return streamedResponse;
    }

    if (status == 406 &&
        request.headers['Accept'] == PUB_API_HEADERS['Accept']) {
      fail("Pub ${sdk.version} is incompatible with the current version of "
          "${request.url.host}.\n"
          "Upgrade pub to the latest version and try again.");
    }

    if (status == 500 &&
        (request.url.host == "pub.dartlang.org" ||
            request.url.host == "storage.googleapis.com")) {
      fail("HTTP error 500: Internal Server Error at ${request.url}.\n"
          "This is likely a transient error. Please try again later.");
    }

    throw new PubHttpException(
        await http.Response.fromStream(streamedResponse));
  }
}

/// The HTTP client to use for all HTTP requests.
final httpClient = new ThrottleClient(
    16,
    new _ThrowingClient(new RetryClient(_pubClient,
        retries: 5,
        when: (response) =>
            const [500, 502, 503, 504].contains(response.statusCode),
        whenError: (error, stackTrace) {
          if (error is! IOException) return false;

          var chain = new Chain.forTrace(stackTrace);
          log.io("HTTP error:\n$error\n\n${chain.terse}");
          return true;
        },
        delay: (retryCount) {
          if (retryCount < 3) {
            // Retry quickly a couple times in case of a short transient error.
            //
            // Add a random delay to avoid retrying a bunch of parallel requests
            // all at the same time.
            return new Duration(milliseconds: 500) * math.pow(1.5, retryCount) +
                new Duration(milliseconds: random.nextInt(500));
          } else {
            // If the error persists, wait a long time. This works around issues
            // where an AppEngine instance will go down and need to be rebooted,
            // which takes about a minute.
            return new Duration(seconds: 30);
          }
        },
        onRetry: (request, response, retryCount) {
          log.io("Retry #${retryCount + 1} for "
              "${request.method} ${request.url}...");
          if (retryCount != 3) return;
          if (!_retriedHosts.add(request.url.host)) return;
          log.message(
              "It looks like ${request.url.host} is having some trouble.\n"
              "Pub will wait for a while before trying to connect again.");
        })));

/// The underlying HTTP client wrapped by [httpClient].
http.Client get innerHttpClient => _pubClient._inner;
set innerHttpClient(http.Client client) => _pubClient._inner = client;

/// Runs [callback] in a zone where all HTTP requests sent to `pub.dartlang.org`
/// will indicate the [type] of the relationship between the root package and
/// the package being requested.
///
/// If [type] is [DependencyType.none], no extra metadata is added.
Future<T> withDependencyType<T>(DependencyType type, Future<T> callback()) {
  if (type == DependencyType.none) return callback();
  return runZoned(callback, zoneValues: {#_dependencyType: type});
}

/// Handles a successful JSON-formatted response from pub.dartlang.org.
///
/// These responses are expected to be of the form `{"success": {"message":
/// "some message"}}`. If the format is correct, the message will be printed;
/// otherwise an error will be raised.
void handleJsonSuccess(http.Response response) {
  var parsed = parseJsonResponse(response);
  if (parsed['success'] is! Map ||
      !parsed['success'].containsKey('message') ||
      parsed['success']['message'] is! String) {
    invalidServerResponse(response);
  }
  log.message(log.green(parsed['success']['message']));
}

/// Handles an unsuccessful JSON-formatted response from pub.dartlang.org.
///
/// These responses are expected to be of the form `{"error": {"message": "some
/// message"}}`. If the format is correct, the message will be raised as an
/// error; otherwise an [invalidServerResponse] error will be raised.
void handleJsonError(http.Response response) {
  var errorMap = parseJsonResponse(response);
  if (errorMap['error'] is! Map ||
      !errorMap['error'].containsKey('message') ||
      errorMap['error']['message'] is! String) {
    invalidServerResponse(response);
  }
  fail(log.red(errorMap['error']['message']));
}

/// Parses a response body, assuming it's JSON-formatted.
///
/// Throws a user-friendly error if the response body is invalid JSON, or if
/// it's not a map.
Map parseJsonResponse(http.Response response) {
  var value;
  try {
    value = jsonDecode(response.body);
  } on FormatException {
    invalidServerResponse(response);
  }
  if (value is! Map) invalidServerResponse(response);
  return value;
}

/// Throws an error describing an invalid response from the server.
void invalidServerResponse(http.Response response) =>
    fail(log.red('Invalid server response:\n${response.body}'));

/// Exception thrown when an HTTP operation fails.
class PubHttpException implements Exception {
  final http.Response response;

  const PubHttpException(this.response);

  String toString() => 'HTTP error ${response.statusCode}: '
      '${response.reasonPhrase}';
}