# frozen_string_literal: true

module MergeRequests
  class RefreshService < MergeRequests::BaseService
    include Gitlab::Utils::StrongMemoize
    attr_reader :push

    def execute(oldrev, newrev, ref)
      @push = Gitlab::Git::Push.new(@project, oldrev, newrev, ref)
      return true unless @push.branch_push?

      refresh_merge_requests!
    end

    private

    def refresh_merge_requests!
      # n + 1: https://gitlab.com/gitlab-org/gitlab-foss/issues/60289
      Gitlab::GitalyClient.allow_n_plus_1_calls { find_new_commits }

      # Be sure to close outstanding MRs before reloading them to avoid generating an
      # empty diff during a manual merge
      close_upon_missing_source_branch_ref
      post_merge_manually_merged
      link_forks_lfs_objects
      reload_merge_requests

      merge_requests_for_source_branch.each do |mr|
        outdate_suggestions(mr)
        abort_auto_merges(mr)
        mark_pending_todos_done(mr)
      end

      abort_ff_merge_requests_with_when_pipeline_succeeds
      cache_merge_requests_closing_issues

      merge_requests_for_source_branch.each do |mr|
        # Leave a system note if a branch was deleted/added
        if branch_added_or_removed?
          comment_mr_branch_presence_changed(mr)
        end

        notify_about_push(mr)
        mark_mr_as_draft_from_commits(mr)
        execute_mr_web_hooks(mr)
        # Run at the end of the loop to avoid any potential contention on the MR object
        refresh_pipelines_on_merge_requests(mr)
        merge_request_activity_counter.track_mr_including_ci_config(user: mr.author, merge_request: mr)
      end

      true
    end

    def branch_added_or_removed?
      strong_memoize(:branch_added_or_removed) do
        @push.branch_added? || @push.branch_removed?
      end
    end

    def close_upon_missing_source_branch_ref
      # MergeRequest#reload_diff ignores not opened MRs. This means it won't
      # create an `empty` diff for `closed` MRs without a source branch, keeping
      # the latest diff state as the last _valid_ one.
      merge_requests_for_source_branch.reject(&:source_branch_exists?).each do |mr|
        MergeRequests::CloseService
          .new(project: mr.target_project, current_user: @current_user)
          .execute(mr)
      end
    end

    # Collect open merge requests that target same branch we push into
    # and close if push to master include last commit from merge request
    # We need this to close(as merged) merge requests that were merged into
    # target branch manually
    # rubocop: disable CodeReuse/ActiveRecord
    def post_merge_manually_merged
      commit_ids = @commits.map(&:id)
      merge_requests = @project.merge_requests.opened
        .preload_project_and_latest_diff
        .preload_latest_diff_commit
        .where(target_branch: @push.branch_name).to_a
        .select(&:diff_head_commit)
        .select do |merge_request|
          commit_ids.include?(merge_request.diff_head_sha) &&
            merge_request.merge_request_diff.state != 'empty'
        end
      merge_requests = filter_merge_requests(merge_requests)

      return if merge_requests.empty?

      analyzer = Gitlab::BranchPushMergeCommitAnalyzer.new(
        @commits.reverse,
        relevant_commit_ids: merge_requests.map(&:diff_head_sha)
      )

      merge_requests.each do |merge_request|
        merge_request.merge_commit_sha = analyzer.get_merge_commit(merge_request.diff_head_sha)

        MergeRequests::PostMergeService
          .new(project: merge_request.target_project, current_user: @current_user)
          .execute(merge_request)
      end
    end
    # rubocop: enable CodeReuse/ActiveRecord

    # Link LFS objects that exists in forks but does not exists in merge requests
    # target project
    def link_forks_lfs_objects
      return unless @push.branch_updated?

      merge_requests_for_forks.find_each do |mr|
        LinkLfsObjectsService
          .new(project: mr.target_project)
          .execute(mr, oldrev: @push.oldrev, newrev: @push.newrev)
      end
    end

    # Refresh merge request diff if we push to source or target branch of merge request
    # Note: we should update merge requests from forks too
    def reload_merge_requests
      merge_requests = @project.merge_requests.opened
        .by_source_or_target_branch(@push.branch_name)
        .preload_project_and_latest_diff

      merge_requests_from_forks = merge_requests_for_forks
        .preload_project_and_latest_diff

      merge_requests_array = merge_requests.to_a + merge_requests_from_forks.to_a
      filter_merge_requests(merge_requests_array).each do |merge_request|
        skip_merge_status_trigger = true

        if branch_and_project_match?(merge_request) || @push.force_push?
          merge_request.reload_diff(current_user)
          # Clear existing merge error if the push were directed at the
          # source branch. Clearing the error when the target branch
          # changes will hide the error from the user.
          merge_request.merge_error = nil

          # Don't skip trigger since we to update the MR's merge status in real-time
          # when the push if for the MR's source branch and project.
          skip_merge_status_trigger = false
        elsif merge_request.merge_request_diff.includes_any_commits?(push_commit_ids)
          merge_request.reload_diff(current_user)
        end

        merge_request.skip_merge_status_trigger = skip_merge_status_trigger
        merge_request.mark_as_unchecked
      end

      # Upcoming method calls need the refreshed version of
      # @source_merge_requests diffs (for MergeRequest#commit_shas for instance).
      merge_requests_for_source_branch(reload: true)
    end

    def push_commit_ids
      @push_commit_ids ||= @commits.map(&:id)
    end

    def branch_and_project_match?(merge_request)
      merge_request.source_project == @project &&
        merge_request.source_branch == @push.branch_name
    end

    def outdate_suggestions(merge_request)
      outdate_service.execute(merge_request)
    end

    def outdate_service
      @outdate_service ||= Suggestions::OutdateService.new
    end

    def abort_auto_merges(merge_request)
      abort_auto_merge(merge_request, 'source branch was updated')
    end

    def abort_ff_merge_requests_with_when_pipeline_succeeds
      return unless @project.ff_merge_must_be_possible?

      merge_requests_with_auto_merge_enabled_to(@push.branch_name).each do |merge_request|
        next unless merge_request.auto_merge_strategy == AutoMergeService::STRATEGY_MERGE_WHEN_PIPELINE_SUCCEEDS
        next unless merge_request.should_be_rebased?

        abort_auto_merge_with_todo(merge_request, 'target branch was updated')
      end
    end

    def abort_auto_merge_with_todo(merge_request, reason)
      response = abort_auto_merge(merge_request, reason)
      response = ServiceResponse.new(**response)
      return unless response.success?

      todo_service.merge_request_became_unmergeable(merge_request)
    end

    def merge_requests_with_auto_merge_enabled_to(target_branch)
      @project
        .merge_requests
        .by_target_branch(target_branch)
        .with_auto_merge_enabled
    end

    def mark_pending_todos_done(merge_request)
      todo_service.merge_request_push(merge_request, @current_user)
    end

    def find_new_commits
      if @push.branch_added?
        @commits = []

        merge_request = merge_requests_for_source_branch.first
        return unless merge_request

        begin
          # Since any number of commits could have been made to the restored branch,
          # find the common root to see what has been added.
          common_ref = @project.repository.merge_base(merge_request.diff_head_sha, @push.newrev)
          # If the a commit no longer exists in this repo, gitlab_git throws
          # a Rugged::OdbError. This is fixed in https://gitlab.com/gitlab-org/gitlab_git/merge_requests/52
          @commits = @project.repository.commits_between(common_ref, @push.newrev) if common_ref
        rescue StandardError
        end
      elsif @push.branch_removed?
        # No commits for a deleted branch.
        @commits = []
      else
        @commits = @project.repository.commits_between(@push.oldrev, @push.newrev)
      end
    end

    # Add comment about branches being deleted or added to merge requests
    def comment_mr_branch_presence_changed(merge_request)
      presence = @push.branch_added? ? :add : :delete

      SystemNoteService.change_branch_presence(
        merge_request, merge_request.project, @current_user,
        :source, @push.branch_name, presence)
    end

    # Add comment about pushing new commits to merge requests and send notification emails
    #
    def notify_about_push(merge_request)
      return unless @commits.present?

      mr_commit_ids = Set.new(merge_request.commit_shas)

      new_commits, existing_commits = @commits.partition do |commit|
        mr_commit_ids.include?(commit.id)
      end

      SystemNoteService.add_commits(
        merge_request, merge_request.project,
        @current_user, new_commits,
        existing_commits, @push.oldrev
      )

      notification_service.push_to_merge_request(merge_request, @current_user, new_commits: new_commits, existing_commits: existing_commits)
    end

    def mark_mr_as_draft_from_commits(merge_request)
      return unless @commits.present?

      commit_shas = merge_request.commit_shas

      draft_commit = @commits.detect do |commit|
        commit.draft? && commit_shas.include?(commit.sha)
      end

      if draft_commit && !merge_request.draft?
        merge_request.update(title: merge_request.draft_title)
        SystemNoteService.add_merge_request_draft_from_commit(
          merge_request,
          merge_request.project,
          @current_user,
          draft_commit
        )
      end
    end

    # Call merge request webhook with update branches
    def execute_mr_web_hooks(merge_request)
      execute_hooks(merge_request, 'update', old_rev: @push.oldrev)
    end

    # If the merge requests closes any issues, save this information in the
    # `MergeRequestsClosingIssues` model (as a performance optimization).
    # rubocop: disable CodeReuse/ActiveRecord
    def cache_merge_requests_closing_issues
      @project.merge_requests.where(source_branch: @push.branch_name).each do |merge_request|
        merge_request.cache_merge_request_closes_issues!(@current_user)
      end
    end
    # rubocop: enable CodeReuse/ActiveRecord

    def filter_merge_requests(merge_requests)
      merge_requests.uniq.select(&:source_project)
    end

    def merge_requests_for_source_branch(reload: false)
      @source_merge_requests = nil if reload
      @source_merge_requests ||= merge_requests_for(@push.branch_name)
    end

    def merge_requests_for_forks
      @merge_requests_for_forks ||=
        MergeRequest
          .opened
          .from_project(project)
          .from_source_branches(@push.branch_name)
          .from_fork
    end
  end
end

MergeRequests::RefreshService.prepend_mod_with('MergeRequests::RefreshService')