module API
  class MergeRequests < Grape::API
    include PaginationParams

    DEPRECATION_MESSAGE = 'This endpoint is deprecated and will be removed in GitLab 9.0.'.freeze

    before { authenticate! }

    params do
      requires :id, type: String, desc: 'The ID of a project'
    end
    resource :projects do
      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

        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::MergeRequest
      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 :iid, type: Array[Integer], desc: 'The IID of the 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[:iid]) if params[:iid].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::MergeRequest, 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_id, type: Integer, desc: 'The ID of a merge request'
      end
      delete ":id/merge_requests/:merge_request_id" do
        merge_request = user_project.merge_requests.find_by(id: params[:merge_request_id])

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

      # Routing "merge_request/:merge_request_id/..." is DEPRECATED and WILL BE REMOVED in version 9.0
      # Use "merge_requests/:merge_request_id/..." instead.
      #
      params do
        requires :merge_request_id, type: Integer, desc: 'The ID of a merge request'
      end
      { ":id/merge_request/:merge_request_id" => :deprecated, ":id/merge_requests/:merge_request_id" => :ok }.each do |path, status|
        desc 'Get a single merge request' do
          if status == :deprecated
            detail DEPRECATION_MESSAGE
          end
          success Entities::MergeRequest
        end
        get path do
          merge_request = user_project.merge_requests.find(params[:merge_request_id])
          authorize! :read_merge_request, merge_request
          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 "#{path}/commits" do
          merge_request = user_project.merge_requests.find(params[:merge_request_id])
          authorize! :read_merge_request, merge_request
          present merge_request.commits, with: Entities::RepoCommit
        end

        desc 'Show the merge request changes' do
          success Entities::MergeRequestChanges
        end
        get "#{path}/changes" do
          merge_request = user_project.merge_requests.find(params[:merge_request_id])
          authorize! :read_merge_request, merge_request
          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 merge],
                                 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 path do
          merge_request = user_project.merge_requests.find(params.delete(:merge_request_id))
          authorize! :update_merge_request, 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_build_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 "#{path}/merge" do
          merge_request = user_project.merge_requests.find(params[:merge_request_id])

          # 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_build_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 "#{path}/cancel_merge_when_build_succeeds" do
          merge_request = user_project.merge_requests.find(params[:merge_request_id])

          unauthorized! unless merge_request.can_cancel_merge_when_build_succeeds?(current_user)

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

        desc 'Get the comments of a merge request' do
          detail 'Duplicate. DEPRECATED and WILL BE REMOVED in 9.0'
          success Entities::MRNote
        end
        params do
          use :pagination
        end
        get "#{path}/comments" do
          merge_request = user_project.merge_requests.find(params[:merge_request_id])

          authorize! :read_merge_request, merge_request

          present paginate(merge_request.notes.fresh), with: Entities::MRNote
        end

        desc 'Post a comment to a merge request' do
          detail 'Duplicate. DEPRECATED and WILL BE REMOVED in 9.0'
          success Entities::MRNote
        end
        params do
          requires :note, type: String, desc: 'The text of the comment'
        end
        post "#{path}/comments" do
          merge_request = user_project.merge_requests.find(params[:merge_request_id])
          authorize! :create_note, merge_request

          opts = {
            note: params[:note],
            noteable_type: 'MergeRequest',
            noteable_id: merge_request.id
          }

          note = ::Notes::CreateService.new(user_project, current_user, opts).execute

          if note.save
            present note, with: Entities::MRNote
          else
            render_api_error!("Failed to save note #{note.errors.messages}", 400)
          end
        end

        desc 'List issues that will be closed on merge' do
          success Entities::MRNote
        end
        params do
          use :pagination
        end
        get "#{path}/closes_issues" do
          merge_request = user_project.merge_requests.find(params[:merge_request_id])
          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
end