// Copyright 2022 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 'package:auto_submit/model/auto_submit_query_result.dart' as auto;
import 'package:auto_submit/service/config.dart';
import 'package:auto_submit/service/github_service.dart';
import 'package:auto_submit/validations/required_check_runs.dart';
import 'package:auto_submit/validations/validation.dart';
import 'package:github/github.dart' as github;
import 'package:retry/retry.dart';

import '../exception/retryable_exception.dart';
import '../service/log.dart';

class Revert extends Validation {
  Revert({
    required super.config,
    RetryOptions? retryOptions,
  }) : retryOptions = retryOptions ?? Config.requiredChecksRetryOptions;

  static const Set<String> allowedReviewers = <String>{ORG_MEMBER, ORG_OWNER};
  final RetryOptions retryOptions;

  @override
  Future<ValidationResult> validate(auto.QueryResult result, github.PullRequest messagePullRequest) async {
    final auto.PullRequest pullRequest = result.repository!.pullRequest!;
    final String authorAssociation = pullRequest.authorAssociation!;
    final String? author = pullRequest.author!.login;
    final auto.Commit commit = pullRequest.commits!.nodes!.single.commit!;
    final String? sha = commit.oid;

    if (!isValidAuthor(author, authorAssociation)) {
      final String message = 'The author $author does not have permissions to make this request.';
      log.info(message);
      return ValidationResult(false, Action.REMOVE_LABEL, message);
    }

    final bool? canMerge = messagePullRequest.mergeable;
    if (canMerge == null || !canMerge) {
      const String message =
          'This pull request cannot be merged due to conflicts. Please resolve conflicts and re-add the revert label.';
      log.info(message);
      return ValidationResult(false, Action.REMOVE_LABEL, message);
    }

    final String? pullRequestBody = messagePullRequest.body;
    final String? revertLink = extractLinkFromText(pullRequestBody);
    if (revertLink == null) {
      const String message =
          'A reverts link could not be found or was formatted incorrectly. Format is \'Reverts owner/repo#id\'';
      log.info(message);
      return ValidationResult(false, Action.REMOVE_LABEL, message);
    }

    final github.RepositorySlug repositorySlug = _getSlugFromLink(revertLink);
    final GithubService githubService = await config.createGithubService(repositorySlug);

    final bool requiredChecksCompleted = await waitForRequiredChecks(
      githubService: githubService,
      slug: repositorySlug,
      sha: sha!,
      checkNames: requiredCheckRunsMapping[repositorySlug.name]!,
    );

    if (!requiredChecksCompleted) {
      return ValidationResult(
        false,
        Action.IGNORE_TEMPORARILY,
        'Some of the required checks did not complete in time.',
      );
    }

    final int pullRequestId = _getPullRequestNumberFromLink(revertLink);
    final github.PullRequest requestToRevert = await githubService.getPullRequest(repositorySlug, pullRequestId);

    final bool requestsMatch =
        await githubService.comparePullRequests(repositorySlug, requestToRevert, messagePullRequest);

    if (requestsMatch) {
      return ValidationResult(
        true,
        Action.IGNORE_FAILURE,
        'Revert request has been verified and will be queued for merge.',
      );
    }

    return ValidationResult(
      false,
      Action.REMOVE_LABEL,
      'Validation of the revert request has failed. Verify the files in the revert request are the same as the original PR and resubmit the revert request.',
    );
  }

  /// Only a team member and code owner can submit a revert request without a review.
  bool isValidAuthor(String? author, String authorAssociation) {
    return config.rollerAccounts.contains(author) || allowedReviewers.contains(authorAssociation);
  }

  /// The full text here is 'Reverts flutter/cocoon#XXXXX' as output by github
  /// the link must be in the form github.com/flutter/repo/pull/id
  String? extractLinkFromText(String? bodyText) {
    if (bodyText == null) {
      return null;
    }
    final RegExp regExp = RegExp(r'[Rr]everts[\s]+([-\.a-zA-Z_]+/[-\.a-zA-Z_]+#[0-9]+)', multiLine: true);
    final Iterable<RegExpMatch> matches = regExp.allMatches(bodyText);

    if (matches.isNotEmpty && matches.length == 1) {
      return matches.elementAt(0).group(1);
    } else if (matches.isNotEmpty && matches.length != 1) {
      log.warning('Detected more than 1 revert link. Cannot process more than one link.');
    }
    return null;
  }

  /// Split a reverts link on the '#' then the '/' to get the parts of the repo
  /// slug. It is assumed that the link has the format flutter/repo#id.
  github.RepositorySlug _getSlugFromLink(String link) {
    final List<String> linkSplit = link.split('#');
    final List<String> slugSplit = linkSplit.elementAt(0).split('/');
    return github.RepositorySlug(slugSplit.elementAt(0), slugSplit.elementAt(1));
  }

  /// Split a reverts link on the '#' to get the id part of the link.
  /// It is assumed that the link has the format flutter/repo#id.
  int _getPullRequestNumberFromLink(String link) {
    final List<String> linkSplit = link.split('#');
    return int.parse(linkSplit.elementAt(1));
  }

  /// Wait for the required checks to complete, and if repository has no checks
  /// true is returned.
  Future<bool> waitForRequiredChecks({
    required GithubService githubService,
    required github.RepositorySlug slug,
    required String sha,
    required List<String> checkNames,
  }) async {
    final List<github.CheckRun> targetCheckRuns = [];
    for (var element in checkNames) {
      targetCheckRuns.addAll(
        await githubService.getCheckRunsFiltered(
          slug: slug,
          ref: sha,
          checkName: element,
        ),
      );
    }

    bool checksCompleted = true;

    try {
      for (github.CheckRun checkRun in targetCheckRuns) {
        await retryOptions.retry(
          () async {
            await _verifyCheckRunCompleted(
              slug,
              githubService,
              checkRun,
            );
          },
          retryIf: (Exception e) => e is RetryableException,
        );
      }
    } catch (e) {
      log.warning('Required check has not completed in time. ${e.toString()}');
      checksCompleted = false;
    }

    return checksCompleted;
  }
}

/// Function signature that will be executed with retries.
typedef RetryHandler = Function();

/// Simple function to wait on completed checkRuns with retries.
Future<void> _verifyCheckRunCompleted(
  github.RepositorySlug slug,
  GithubService githubService,
  github.CheckRun targetCheckRun,
) async {
  final List<github.CheckRun> checkRuns = await githubService.getCheckRunsFiltered(
    slug: slug,
    ref: targetCheckRun.headSha!,
    checkName: targetCheckRun.name,
  );

  if (checkRuns.first.name != targetCheckRun.name || checkRuns.first.conclusion != github.CheckRunConclusion.success) {
    throw RetryableException('${targetCheckRun.name} has not yet completed.');
  }
}