module API
  class MergeRequests < Grape::API
    include PaginationParams

    before { authenticate! }

    params do
      requires :id, type: String, desc: 'The ID of a project'
    end
    resource :projects, requirements: { id: %r{[^/]+} } do
      include TimeTrackingEndpoints

      helpers do
        def handle_merge_request_errors!(errors)
          if errors[:project_access].any?
            error!(errors[:project_access], 422)
          elsif errors[:branch_conflict].any?
            error!(errors[:branch_conflict], 422)
          elsif errors[:validate_fork].any?
            error!(errors[:validate_fork], 422)
          elsif errors[:validate_branches].any?
            conflict!(errors[:validate_branches])
          end

          render_api_error!(errors, 400)
        end

        def issue_entity(project)
          if project.has_external_issue_tracker?
            Entities::ExternalIssue
          else
            Entities::IssueBasic
          end
        end

        params :optional_params do
          optional :description, type: String, desc: 'The description of the merge request'
          optional :assignee_id, type: Integer, desc: 'The ID of a user to assign the merge request'
          optional :milestone_id, type: Integer, desc: 'The ID of a milestone to assign the merge request'
          optional :labels, type: String, desc: 'Comma-separated list of label names'
          optional :remove_source_branch, type: Boolean, desc: 'Remove source branch when merging'
        end
      end

      desc 'List merge requests' do
        success Entities::MergeRequestBasic
      end
      params do
        optional :state, type: String, values: %w[opened closed merged all], default: 'all',
                         desc: 'Return opened, closed, merged, or all merge requests'
        optional :order_by, type: String, values: %w[created_at updated_at], default: 'created_at',
                            desc: 'Return merge requests ordered by `created_at` or `updated_at` fields.'
        optional :sort, type: String, values: %w[asc desc], default: 'desc',
                        desc: 'Return merge requests sorted in `asc` or `desc` order.'
        optional :iids, type: Array[Integer], desc: 'The IID array of merge requests'
        use :pagination
      end
      get ":id/merge_requests" do
        authorize! :read_merge_request, user_project

        merge_requests = user_project.merge_requests.inc_notes_with_associations
        merge_requests = filter_by_iid(merge_requests, params[:iids]) if params[:iids].present?

        merge_requests =
          case params[:state]
          when 'opened' then merge_requests.opened
          when 'closed' then merge_requests.closed
          when 'merged' then merge_requests.merged
          else merge_requests
          end

        merge_requests = merge_requests.reorder(params[:order_by] => params[:sort])
        present paginate(merge_requests), with: Entities::MergeRequestBasic, current_user: current_user, project: user_project
      end

      desc 'Create a merge request' do
        success Entities::MergeRequest
      end
      params do
        requires :title, type: String, desc: 'The title of the merge request'
        requires :source_branch, type: String, desc: 'The source branch'
        requires :target_branch, type: String, desc: 'The target branch'
        optional :target_project_id, type: Integer,
                                     desc: 'The target project of the merge request defaults to the :id of the project'
        use :optional_params
      end
      post ":id/merge_requests" do
        authorize! :create_merge_request, user_project

        mr_params = declared_params(include_missing: false)
        mr_params[:force_remove_source_branch] = mr_params.delete(:remove_source_branch) if mr_params[:remove_source_branch].present?

        merge_request = ::MergeRequests::CreateService.new(user_project, current_user, mr_params).execute

        if merge_request.valid?
          present merge_request, with: Entities::MergeRequest, current_user: current_user, project: user_project
        else
          handle_merge_request_errors! merge_request.errors
        end
      end

      desc 'Delete a merge request'
      params do
        requires :merge_request_iid, type: Integer, desc: 'The IID of a merge request'
      end
      delete ":id/merge_requests/:merge_request_iid" do
        merge_request = find_project_merge_request(params[:merge_request_iid])

        authorize!(:destroy_merge_request, merge_request)
        merge_request.destroy
      end

      params do
        requires :merge_request_iid, type: Integer, desc: 'The IID of a merge request'
      end
      desc 'Get a single merge request' do
        success Entities::MergeRequest
      end
      get ':id/merge_requests/:merge_request_iid' do
        merge_request = find_merge_request_with_access(params[:merge_request_iid])

        present merge_request, with: Entities::MergeRequest, current_user: current_user, project: user_project
      end

      desc 'Get the commits of a merge request' do
        success Entities::RepoCommit
      end
      get ':id/merge_requests/:merge_request_iid/commits' do
        merge_request = find_merge_request_with_access(params[:merge_request_iid])
        commits = ::Kaminari.paginate_array(merge_request.commits)

        present paginate(commits), with: Entities::RepoCommit
      end

      desc 'Show the merge request changes' do
        success Entities::MergeRequestChanges
      end
      get ':id/merge_requests/:merge_request_iid/changes' do
        merge_request = find_merge_request_with_access(params[:merge_request_iid])

        present merge_request, with: Entities::MergeRequestChanges, current_user: current_user
      end

      desc 'Update a merge request' do
        success Entities::MergeRequest
      end
      params do
        optional :title, type: String, allow_blank: false, desc: 'The title of the merge request'
        optional :target_branch, type: String, allow_blank: false, desc: 'The target branch'
        optional :state_event, type: String, values: %w[close reopen],
                               desc: 'Status of the merge request'
        use :optional_params
        at_least_one_of :title, :target_branch, :description, :assignee_id,
                        :milestone_id, :labels, :state_event,
                        :remove_source_branch
      end
      put ':id/merge_requests/:merge_request_iid' do
        merge_request = find_merge_request_with_access(params.delete(:merge_request_iid), :update_merge_request)

        mr_params = declared_params(include_missing: false)
        mr_params[:force_remove_source_branch] = mr_params.delete(:remove_source_branch) if mr_params[:remove_source_branch].present?

        merge_request = ::MergeRequests::UpdateService.new(user_project, current_user, mr_params).execute(merge_request)

        if merge_request.valid?
          present merge_request, with: Entities::MergeRequest, current_user: current_user, project: user_project
        else
          handle_merge_request_errors! merge_request.errors
        end
      end

      desc 'Merge a merge request' do
        success Entities::MergeRequest
      end
      params do
        optional :merge_commit_message, type: String, desc: 'Custom merge commit message'
        optional :should_remove_source_branch, type: Boolean,
                                               desc: 'When true, the source branch will be deleted if possible'
        optional :merge_when_pipeline_succeeds, type: Boolean,
                                                desc: 'When true, this merge request will be merged when the pipeline succeeds'
        optional :sha, type: String, desc: 'When present, must have the HEAD SHA of the source branch'
      end
      put ':id/merge_requests/:merge_request_iid/merge' do
        merge_request = find_project_merge_request(params[:merge_request_iid])

        # Merge request can not be merged
        # because user dont have permissions to push into target branch
        unauthorized! unless merge_request.can_be_merged_by?(current_user)

        not_allowed! unless merge_request.mergeable_state?

        render_api_error!('Branch cannot be merged', 406) unless merge_request.mergeable?

        if params[:sha] && merge_request.diff_head_sha != params[:sha]
          render_api_error!("SHA does not match HEAD of source branch: #{merge_request.diff_head_sha}", 409)
        end

        merge_params = {
          commit_message: params[:merge_commit_message],
          should_remove_source_branch: params[:should_remove_source_branch]
        }

        if params[:merge_when_pipeline_succeeds] && merge_request.head_pipeline && merge_request.head_pipeline.active?
          ::MergeRequests::MergeWhenPipelineSucceedsService
            .new(merge_request.target_project, current_user, merge_params)
            .execute(merge_request)
        else
          ::MergeRequests::MergeService
            .new(merge_request.target_project, current_user, merge_params)
            .execute(merge_request)
        end

        present merge_request, with: Entities::MergeRequest, current_user: current_user, project: user_project
      end

      desc 'Cancel merge if "Merge When Pipeline Succeeds" is enabled' do
        success Entities::MergeRequest
      end
      post ':id/merge_requests/:merge_request_iid/cancel_merge_when_pipeline_succeeds' do
        merge_request = find_project_merge_request(params[:merge_request_iid])

        unauthorized! unless merge_request.can_cancel_merge_when_pipeline_succeeds?(current_user)

        ::MergeRequest::MergeWhenPipelineSucceedsService
          .new(merge_request.target_project, current_user)
          .cancel(merge_request)
      end

      desc 'List issues that will be closed on merge' do
        success Entities::MRNote
      end
      params do
        use :pagination
      end
      get ':id/merge_requests/:merge_request_iid/closes_issues' do
        merge_request = find_merge_request_with_access(params[:merge_request_iid])
        issues = ::Kaminari.paginate_array(merge_request.closes_issues(current_user))
        present paginate(issues), with: issue_entity(user_project), current_user: current_user
      end
    end
  end
end