// 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 'package:cocoon_service/ci_yaml.dart';
import 'package:collection/collection.dart';
import 'package:github/github.dart';
import 'package:meta/meta.dart';
import 'package:yaml/yaml.dart';

import '../../protos.dart' as pb;
import '../foundation/utils.dart';
import '../request_handling/api_request_handler.dart';
import '../request_handling/body.dart';
import '../service/bigquery.dart';
import '../service/config.dart';
import '../service/github_service.dart';
import 'flaky_handler_utils.dart';

/// A handler that queries build statistics from luci and file issues and pull
/// requests for tests that have high flaky ratios.
///
/// The query parameter kThresholdKey is required for this handler to use it as
/// the standard when compares the flaky ratios.
@immutable
class FileFlakyIssueAndPR extends ApiRequestHandler<Body> {
  const FileFlakyIssueAndPR({
    required super.config,
    required super.authenticationProvider,
  });

  static const String kThresholdKey = 'threshold';

  @override
  Future<Body> get() async {
    final RepositorySlug slug = Config.flutterSlug;
    final GithubService gitHub = config.createGithubServiceWithToken(await config.githubOAuthToken);
    final BigqueryService bigquery = await config.createBigQueryService();
    final List<BuilderStatistic> builderStatisticList = await bigquery.listBuilderStatistic(kBigQueryProjectId);
    final YamlMap? ci = loadYaml(await gitHub.getFileContent(slug, kCiYamlPath)) as YamlMap?;
    final pb.SchedulerConfig unCheckedSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(ci);
    final CiYaml ciYaml = CiYaml(
      slug: slug,
      branch: Config.defaultBranch(slug),
      config: unCheckedSchedulerConfig,
    );
    final String testOwnerContent = await gitHub.getFileContent(slug, kTestOwnerPath);
    final Map<String?, Issue> nameToExistingIssue = await getExistingIssues(gitHub, slug);
    final Map<String?, PullRequest> nameToExistingPR = await getExistingPRs(gitHub, slug);
    for (final BuilderStatistic statistic in builderStatisticList) {
      // Skip if ignore_flakiness is specified.
      if (getIgnoreFlakiness(statistic.name, ciYaml)) {
        continue;
      }
      if (statistic.flakyRate < _threshold) {
        continue;
      }
      final BuilderType type = getTypeForBuilder(statistic.name, ci!);
      await _fileIssueAndPR(
        gitHub,
        slug,
        builderDetail: BuilderDetail(
            statistic: statistic,
            existingIssue: nameToExistingIssue[statistic.name],
            existingPullRequest: nameToExistingPR[statistic.name],
            isMarkedFlaky: _getIsMarkedFlaky(statistic.name, ci),
            type: type,
            ownership: getTestOwnership(statistic.name, type, testOwnerContent)),
      );
    }
    return Body.forJson(const <String, dynamic>{
      'Status': 'success',
    });
  }

  double get _threshold => double.parse(request!.uri.queryParameters[kThresholdKey]!);

  Future<void> _fileIssueAndPR(
    GithubService gitHub,
    RepositorySlug slug, {
    required BuilderDetail builderDetail,
  }) async {
    Issue? issue = builderDetail.existingIssue;

    if (_shouldNotFileIssueAndPR(builderDetail, issue)) {
      return;
    }
    issue = await fileFlakyIssue(builderDetail: builderDetail, gitHub: gitHub, slug: slug, threshold: _threshold);

    if (builderDetail.type == BuilderType.shard ||
        builderDetail.type == BuilderType.unknown ||
        builderDetail.existingPullRequest != null) {
      return;
    }
    final String modifiedContent = _marksBuildFlakyInContent(
        await gitHub.getFileContent(
          slug,
          kCiYamlPath,
        ),
        builderDetail.statistic.name,
        issue.htmlUrl);
    final GitReference masterRef = await gitHub.getReference(slug, kMasterRefs);
    final PullRequestBuilder prBuilder =
        PullRequestBuilder(statistic: builderDetail.statistic, ownership: builderDetail.ownership, issue: issue);
    final PullRequest pullRequest = await gitHub.createPullRequest(slug,
        title: prBuilder.pullRequestTitle,
        body: prBuilder.pullRequestBody,
        commitMessage: prBuilder.pullRequestTitle,
        baseRef: masterRef,
        entries: <CreateGitTreeEntry>[
          CreateGitTreeEntry(
            kCiYamlPath,
            kModifyMode,
            kModifyType,
            content: modifiedContent,
          )
        ]);
    await gitHub.assignReviewer(slug, reviewer: prBuilder.pullRequestReviewer, pullRequestNumber: pullRequest.number);
  }

  bool _shouldNotFileIssueAndPR(BuilderDetail builderDetail, Issue? issue) {
    // Don't create a new issue or deflake PR using prod builds statuses if the builder has been marked as flaky.
    // If the builder is `bringup: true`, but still hit flakes, a new bug will be filed in `/api/check_flaky_builders`
    // based on staging builds statuses.
    if (builderDetail.isMarkedFlaky) {
      return true;
    }

    // Don't create a new issue or deflake PR if there is an open issue or a recent closed
    // issue within kGracePeriodForClosedFlake days. It takes time for the flaky ratio to go
    // down after the fix is merged.
    if (issue != null &&
        (issue.state != 'closed' ||
            DateTime.now().difference(issue.closedAt!) <= const Duration(days: kGracePeriodForClosedFlake))) {
      return true;
    }

    return false;
  }

  bool _getIsMarkedFlaky(String builderName, YamlMap ci) {
    final YamlList targets = ci[kCiYamlTargetsKey] as YamlList;
    final YamlMap? target = targets.firstWhere(
      (dynamic element) => element[kCiYamlTargetNameKey] == builderName,
      orElse: () => null,
    ) as YamlMap?;
    return target != null && target[kCiYamlTargetIsFlakyKey] == true;
  }

  @visibleForTesting
  static bool getIgnoreFlakiness(String builderName, CiYaml ciYaml) {
    final Target? target =
        ciYaml.postsubmitTargets.singleWhereOrNull((Target target) => target.value.name == builderName);
    return target == null ? false : target.getIgnoreFlakiness();
  }

  String _marksBuildFlakyInContent(String content, String builder, String issueUrl) {
    final List<String> lines = content.split('\n');
    final int builderLineNumber = lines.indexWhere((String line) => line.contains('name: $builder'));
    // Takes care the case if is kCiYamlTargetIsFlakyKey is already defined to false
    int nextLine = builderLineNumber + 1;
    while (nextLine < lines.length && !lines[nextLine].contains('name:')) {
      if (lines[nextLine].contains('$kCiYamlTargetIsFlakyKey:')) {
        lines[nextLine] = lines[nextLine].replaceFirst('false', 'true # Flaky $issueUrl');
        return lines.join('\n');
      }
      nextLine += 1;
    }
    lines.insert(builderLineNumber + 1, '    $kCiYamlTargetIsFlakyKey: true # Flaky $issueUrl');
    return lines.join('\n');
  }

  Future<RepositorySlug> getSlugFor(GitHub client, String repository) async {
    return RepositorySlug((await client.users.getCurrentUser()).login!, repository);
  }
}