// Copyright 2019 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 'dart:convert';
import 'dart:io';

import 'package:cocoon_service/src/service/github_status_service.dart';
import 'package:cocoon_service/src/service/luci_build_service.dart';
import 'package:crypto/crypto.dart';
import 'package:github/github.dart';
import 'package:github/hooks.dart';
import 'package:meta/meta.dart';

import '../datastore/cocoon_config.dart';

import '../request_handling/body.dart';
import '../request_handling/exceptions.dart';
import '../request_handling/request_handler.dart';
import '../service/buildbucket.dart';

/// List of repos that require CQ+1 label.
const Set<String> kNeedsCQLabelList = <String>{'flutter/flutter'};

/// List of repos that require check for golden triage.
const Set<String> kNeedsCheckGoldenTriage = <String>{'flutter/flutter'};

/// List of repos that require check for labels and tests.
const Set<String> kNeedsCheckLabelsAndTests = <String>{
  'flutter/flutter',
  'flutter/engine'
};

final RegExp kEngineTestRegExp = RegExp(r'tests?\.(dart|java|mm|m|cc)$');

@immutable
class GithubWebhook extends RequestHandler<Body> {
  GithubWebhook(Config config, this.buildBucketClient, this.luciBuildService,
      this.githubStatusService,
      {HttpClient skiaClient})
      : assert(buildBucketClient != null),
        skiaClient = skiaClient ?? HttpClient(),
        super(config: config);

  /// A client for querying and scheduling LUCI Builds.
  final BuildBucketClient buildBucketClient;

  /// An Http Client for querying the Skia Gold API.
  final HttpClient skiaClient;

  /// Github status service to update the state of the build
  /// in the Github UI.
  final GithubStatusService githubStatusService;

  /// LUCI service class to communicate with buildBucket service.
  final LuciBuildService luciBuildService;

  @override
  Future<Body> post() async {
    final String gitHubEvent = request.headers.value('X-GitHub-Event');
    if (gitHubEvent == null ||
        request.headers.value('X-Hub-Signature') == null) {
      throw const BadRequestException('Missing required headers.');
    }

    final List<int> requestBytes = await request.expand((_) => _).toList();
    final String hmacSignature = request.headers.value('X-Hub-Signature');
    if (!await _validateRequest(hmacSignature, requestBytes)) {
      throw const Forbidden();
    }

    try {
      final String stringRequest = utf8.decode(requestBytes);
      switch (gitHubEvent) {
        case 'pull_request':
          await _handlePullRequest(stringRequest);
          break;
      }

      return Body.empty;
    } on FormatException {
      throw const BadRequestException('Could not process input data.');
    } on InternalServerError {
      rethrow;
    }
  }

  Future<void> _handlePullRequest(
    String rawRequest,
  ) async {
    final PullRequestEvent pullRequestEvent =
        await _getPullRequestEvent(rawRequest);
    if (pullRequestEvent == null) {
      throw const BadRequestException('Expected pull request event.');
    }
    final String eventAction = pullRequestEvent.action;
    final PullRequest pr = pullRequestEvent.pullRequest;

    // See the API reference:
    // https://developer.github.com/v3/activity/events/types/#pullrequestevent
    // which unfortunately is a bit light on explanations.
    switch (eventAction) {
      case 'closed':
        // On a successful merge, check for gold.
        // If it was closed without merging, cancel any outstanding tryjobs.
        // We'll leave unfinished jobs if it was merged since we care about those
        // results.
        if (pr.merged) {
          await _checkForGoldenTriage(pullRequestEvent);
        } else {
          await luciBuildService.cancelBuilds(
            pullRequestEvent.repository.slug(),
            pr.number,
            pr.head.sha,
            'Pull request closed',
          );
        }
        break;
      case 'edited':
        // Editing a PR should not trigger new jobs, but may update whether
        // it has tests.
        await _checkForLabelsAndTests(pullRequestEvent);
        break;
      case 'opened':
      case 'ready_for_review':
      case 'reopened':
        // These cases should trigger LUCI jobs.
        await _checkForLabelsAndTests(pullRequestEvent);
        await _scheduleIfMergeable(pullRequestEvent);
        break;
      case 'labeled':
        // This should only trigger a LUCI job for flutter/flutter right now,
        // since it is in the needsCQLabelList.
        if (kNeedsCQLabelList.contains(pr.base.repo.fullName.toLowerCase())) {
          await _scheduleIfMergeable(pullRequestEvent);
        }
        break;
      case 'synchronize':
        // This indicates the PR has new commits. We need to cancel old jobs
        // and schedule new ones.
        await _scheduleIfMergeable(pullRequestEvent);
        break;
      case 'unlabeled':
        // Cancel the jobs if someone removed the label on a repo that needs
        // them.
        if (!kNeedsCQLabelList.contains(pr.base.repo.fullName.toLowerCase())) {
          break;
        }
        if (!await _checkForCqLabel(pr.labels)) {
          await luciBuildService.cancelBuilds(
            pullRequestEvent.repository.slug(),
            pr.number,
            pr.head.sha,
            'Tryjobs canceled (label removed)',
          );
        }
        break;
      // Ignore the rest of the events.
      case 'assigned':
      case 'locked':
      case 'review_request_removed':
      case 'review_requested':
      case 'unassigned':
      case 'unlocked':
        break;
    }
  }

  /// This method assumes that jobs should be cancelled if they are already
  /// runnning. [githubStatusService] is used to update the status of a build
  /// in the GitHub UI. When the build is triggered the status is set to "pending"
  /// without a details link. Once the test starts running then the state is set
  /// to "pending" with a details link pointing to the build in LUCI infrastructure.
  Future<void> _scheduleIfMergeable(
    PullRequestEvent pullRequestEvent,
  ) async {
    // The mergeable flag may be null. False indicates there's a merge conflict,
    // null indicates unknown. Err on the side of allowing the job to run.
    final PullRequest pr = pullRequestEvent.pullRequest;
    // For flutter/flutter tests need to be optimized before enforcing CQ.
    if (kNeedsCQLabelList.contains(pr.base.repo.fullName.toLowerCase())) {
      if (!await _checkForCqLabel(pr.labels)) {
        return;
      }
    }

    // Always cancel running builds so we don't ever schedule duplicates.
    await luciBuildService.cancelBuilds(
      pullRequestEvent.repository.slug(),
      pr.number,
      pr.head.sha,
      'Newer commit available',
    );
    await luciBuildService.scheduleBuilds(
      slug: pullRequestEvent.repository.slug(),
      prNumber: pr.number,
      commitSha: pr.head.sha,
    );
    await githubStatusService.setBuildsPendingStatus(
        pr.number, pr.head.sha, pr.head.repo.slug());
  }

  /// Checks the issue in the given repository for `config.cqLabelName`.
  Future<bool> _checkForCqLabel(List<IssueLabel> labels) async {
    final String cqLabelName = config.cqLabelName;
    return labels.any((IssueLabel label) => label.name == cqLabelName);
  }

  Future<bool> _isIgnoredForGold(String eventAction, PullRequest pr) async {
    bool ignored = false;
    String rawResponse;
    try {
      final HttpClientRequest request = await skiaClient
          .getUrl(Uri.parse('https://flutter-gold.skia.org/json/ignores'));
      final HttpClientResponse response = await request.close();
      rawResponse = await utf8.decodeStream(response);
      final List<dynamic> ignores = jsonDecode(rawResponse) as List<dynamic>;
      for (Map<String, dynamic> ignore
          in ignores.cast<Map<String, dynamic>>()) {
        if ((ignore['note'] as String).isNotEmpty &&
            pr.number.toString() == ignore['note'].split('/').last) {
          ignored = true;
          break;
        }
      }
    } on IOException catch (e) {
      log.error('Request to Flutter Gold for ignores failed for PR '
          '#${pr.number} on action: $eventAction.\n'
          'error: $e');
    } on FormatException catch (_) {
      log.error('Format Exception from Flutter Gold ignore request.\n'
          'rawResponse: $rawResponse');
      rethrow;
    }
    return ignored;
  }

  Future<void> _checkForGoldenTriage(PullRequestEvent pullRequestEvent) async {
    final PullRequest pr = pullRequestEvent.pullRequest;
    final String eventAction = pullRequestEvent.action;
    final RepositorySlug slug = pullRequestEvent.repository.slug();
    if (kNeedsCheckGoldenTriage.contains(pr.base.repo.fullName.toLowerCase()) &&
        await _isIgnoredForGold(eventAction, pr)) {
      final GitHub gitHubClient =
          await config.createGitHubClient(slug.owner, slug.name);
      try {
        await _pingForTriage(gitHubClient, pr);
      } finally {
        gitHubClient.dispose();
      }
    }
  }

  Future<void> _pingForTriage(GitHub gitHubClient, PullRequest pr) async {
    final String body = config.goldenTriageMessage;
    final RepositorySlug slug = pr.base.repo.slug();
    await gitHubClient.issues.createComment(slug, pr.number, body);
  }

  Future<void> _checkForLabelsAndTests(
      PullRequestEvent pullRequestEvent) async {
    final PullRequest pr = pullRequestEvent.pullRequest;
    final String eventAction = pullRequestEvent.action;
    final RepositorySlug slug = pullRequestEvent.repository.slug();
    final String repo = pr.base.repo.fullName.toLowerCase();
    if (kNeedsCheckLabelsAndTests.contains(repo)) {
      final GitHub gitHubClient =
          await config.createGitHubClient(slug.owner, slug.name);
      try {
        await _checkBaseRef(gitHubClient, pr);
        if (repo == 'flutter/flutter') {
          await _applyFrameworkRepoLabels(gitHubClient, eventAction, pr);
        } else if (repo == 'flutter/engine') {
          await _applyEngineRepoLabels(gitHubClient, eventAction, pr);
        }
      } finally {
        gitHubClient.dispose();
      }
    }
  }

  Future<void> _applyFrameworkRepoLabels(
      GitHub gitHubClient, String eventAction, PullRequest pr) async {
    if (pr.user.login == 'engine-flutter-autoroll') {
      return;
    }
    final RepositorySlug slug = pr.base.repo.slug();
    final Stream<PullRequestFile> files =
        gitHubClient.pullRequests.listFiles(slug, pr.number);
    final Set<String> labels = <String>{};
    bool hasTests = false;
    bool needsTests = false;
    bool isGoldenChange = false;

    await for (PullRequestFile file in files) {
      if (file.filename.endsWith('pubspec.yaml')) {
        // These get updated by a script, and are updated en masse.
        labels.add('team');
        continue;
      }
      if (file.filename.endsWith('.dart')) {
        needsTests = true;
      }
      if (file.filename.endsWith('_test.dart')) {
        hasTests = true;
      }

      if (file.filename.startsWith('dev/')) {
        labels.add('team');
      }
      if (file.filename.startsWith('packages/flutter_tools/') ||
          file.filename.startsWith('packages/fuchsia_remote_debug_protocol')) {
        labels.add('tool');
      }
      if (file.filename == 'bin/internal/engine.version') {
        labels.add('engine');
      }
      if (await _isIgnoredForGold(eventAction, pr)) {
        isGoldenChange = true;
        labels.add('will affect goldens');
        labels.add('severe: API break');
        labels.add('a: tests');
      }

      if (file.filename.startsWith('packages/flutter/') ||
          file.filename.startsWith('packages/flutter_test/') ||
          file.filename.startsWith('packages/flutter_driver/')) {
        labels.add('framework');
      }
      if (file.filename.contains('material')) {
        labels.add('f: material design');
      }
      if (file.filename.contains('cupertino')) {
        labels.add('f: cupertino');
      }

      if (file.filename.startsWith('packages/flutter_localizations')) {
        labels.add('a: internationalization');
      }

      if (file.filename.startsWith('packages/flutter_test') ||
          file.filename.startsWith('packages/flutter_driver')) {
        labels.add('a: tests');
      }

      if (file.filename.contains('semantics') ||
          file.filename.contains('accessibilty')) {
        labels.add('a: accessibility');
      }

      if (file.filename.startsWith('examples/')) {
        labels.add('d: examples');
        labels.add('team');
        if (file.filename.startsWith('examples/flutter_gallery')) {
          labels.add('team: gallery');
        }
      }
    }

    if (pr.draft) {
      labels.add('work in progress; do not review');
    }

    if (labels.isNotEmpty) {
      await gitHubClient.issues
          .addLabelsToIssue(slug, pr.number, labels.toList());
    }

    if (!hasTests && needsTests && !pr.draft) {
      final String body = config.missingTestsPullRequestMessage;
      if (!await _alreadyCommented(gitHubClient, pr, slug, body)) {
        await gitHubClient.issues.createComment(slug, pr.number, body);
      }
    }

    if (isGoldenChange) {
      final String body = config.goldenBreakingChangeMessage;
      if (!await _alreadyCommented(gitHubClient, pr, slug, body)) {
        await gitHubClient.issues.createComment(slug, pr.number, body);
      }
    }
  }

  Future<void> _applyEngineRepoLabels(
      GitHub gitHubClient, String eventAction, PullRequest pr) async {
    if (pr.user.login == 'skia-flutter-autoroll') {
      return;
    }
    final RepositorySlug slug = pr.base.repo.slug();
    final Stream<PullRequestFile> files =
        gitHubClient.pullRequests.listFiles(slug, pr.number);
    final Set<String> labels = <String>{};
    bool hasTests = false;
    bool needsTests = false;

    await for (PullRequestFile file in files) {
      final String filename = file.filename.toLowerCase();
      if (filename.endsWith('.dart') ||
          filename.endsWith('.mm') ||
          filename.endsWith('.m') ||
          filename.endsWith('.java') ||
          filename.endsWith('.cc')) {
        needsTests = true;
      }

      if (kEngineTestRegExp.hasMatch(filename)) {
        hasTests = true;
      }

      if (filename.startsWith('shell/platform/darwin/ios')) {
        labels.add('platform-ios');
      }

      if (filename.startsWith('shell/platform/android')) {
        labels.add('platform-android');
      }
    }

    if (labels.isNotEmpty) {
      await gitHubClient.issues
          .addLabelsToIssue(slug, pr.number, labels.toList());
    }

    if (!hasTests && needsTests && !pr.draft) {
      final String body = config.missingTestsPullRequestMessage;
      if (!await _alreadyCommented(gitHubClient, pr, slug, body)) {
        await gitHubClient.issues.createComment(slug, pr.number, body);
      }
    }
  }

  Future<void> _checkBaseRef(
    GitHub gitHubClient,
    PullRequest pr,
  ) async {
    if (pr.base.ref != 'master') {
      final String body = await _getWrongBaseComment(pr.base.ref);
      final RepositorySlug slug = pr.base.repo.slug();
      if (!await _alreadyCommented(gitHubClient, pr, slug, body)) {
        await gitHubClient.pullRequests.edit(
          slug,
          pr.number,
          base: 'master',
        );
        await gitHubClient.issues.createComment(slug, pr.number, body);
      }
    }
  }

  Future<bool> _alreadyCommented(
    GitHub gitHubClient,
    PullRequest pr,
    RepositorySlug slug,
    String message,
  ) async {
    final Stream<IssueComment> comments =
        gitHubClient.issues.listCommentsByIssue(slug, pr.number);
    await for (IssueComment comment in comments) {
      if (comment.body.contains(message)) {
        return true;
      }
    }
    return false;
  }

  Future<String> _getWrongBaseComment(String base) async {
    final String messageTemplate = config.nonMasterPullRequestMessage;
    return messageTemplate.replaceAll('{{branch}}', base);
  }

  Future<bool> _validateRequest(
    String signature,
    List<int> requestBody,
  ) async {
    final String rawKey = await config.webhookKey;
    final List<int> key = utf8.encode(rawKey);
    final Hmac hmac = Hmac(sha1, key);
    final Digest digest = hmac.convert(requestBody);
    final String bodySignature = 'sha1=$digest';
    return bodySignature == signature;
  }

  Future<PullRequestEvent> _getPullRequestEvent(String request) async {
    if (request == null) {
      return null;
    }
    try {
      return PullRequestEvent.fromJson(
          json.decode(request) as Map<String, dynamic>);
    } on FormatException {
      return null;
    }
  }
}