Implement Workflow::Step::BranchPackageStep model

Co-authored-by: Daniel Donisa <daniel.donisa@suse.com>
Co-authored-by: Eduardo Navarro <enavarro@suse.com>
Co-authored-by: Saray Cabrera Padrón <scabrerapadron@suse.de>

src/api/app/models/workflow/step/branch_package_step.rb

@@ -2,11 +2,131 @@ class Workflow
   module Step
     class BranchPackageStep
       include ActiveModel::Model
-      # TODO: Placeholder to be able to test the Workflow model. The code for this class will be added in another PR.
-      def initialize(step_instructions:, scm_extractor_payload:); end
+
+      attr_reader :errors
+
+      validates :source_project, :source_package, presence: true
+
+      def initialize(step_instructions:, scm_extractor_payload:)
+        @step_instructions = step_instructions.with_indifferent_access
+        @scm_extractor_payload = scm_extractor_payload.with_indifferent_access
+        @errors = []
+      end
 
       def allowed_event_and_action?
-        true
+        new_pull_request?
+      end
+
+      def call
+        return unless new_pull_request?
+
+        branched_package = branch
+        return if @errors.any?
+
+        add_branch_request_file(package: branched_package)
+
+        branched_package
+      end
+
+      private
+
+      def source_project
+        @step_instructions['source_project']
+      end
+
+      def source_package
+        @step_instructions['source_package'] || ''
+      end
+
+      def target_package
+        return @step_instructions['target_package'] if @step_instructions['target_package'].present?
+
+        source_package
+      end
+
+      def target_project
+        source_project + ":PR-#{@scm_extractor_payload[:pr_number]}"
+      end
+
+      def remote_source?
+        return true if Project.find_remote_project(source_project)
+
+        false
+      end
+
+      def check_source_access
+        return if remote_source?
+
+        options = { use_source: false, follow_project_links: true, follow_multibuild: true }
+        src_package = Package.get_by_project_and_name(source_project, source_package, options)
+
+        raise Pundit::NotAuthorizedError unless PackagePolicy.new(User.session, src_package).create_branch?
+      end
+
+      def branch
+        check_source_access
+
+        BranchPackage.new({ project: source_project, package: source_package,
+                            target_project: target_project,
+                            target_package: target_package }).branch
+
+        Event::BranchCommand.create(project: source_project, package: source_package,
+                                    targetproject: target_project,
+                                    targetpackage: target_package,
+                                    user: User.session.login)
+
+        Package.find_by_project_and_name(target_project, target_package)
+      rescue BranchPackage::DoubleBranchPackageError
+        @errors << 'You have already branched this package'
+        nil
+      rescue CreateProjectNoPermission
+        @errors << 'Sorry, you are not authorized to create this Project.'
+        nil
+      rescue ArgumentError, Package::UnknownObjectError, Project::UnknownObjectError, APIError, ActiveRecord::RecordInvalid => e
+        @errors << "Failed to branch: #{e.message}"
+        nil
+      end
+
+      def github_pull_request?
+        @scm_extractor_payload[:scm] == 'github' && @scm_extractor_payload[:event] == 'pull_request'
+      end
+
+      def gitlab_merge_request?
+        @scm_extractor_payload[:scm] == 'gitlab' && @scm_extractor_payload[:event] == 'Merge Request Hook'
+      end
+
+      def new_pull_request?
+        (github_pull_request? && @scm_extractor_payload[:action] == 'opened') ||
+          (gitlab_merge_request? && @scm_extractor_payload[:action] == 'open')
+      end
+
+      def add_branch_request_file(package:)
+        branch_request_file = case @scm_extractor_payload[:scm]
+                              when 'github'
+                                branch_request_file_github
+                              when 'gitlab'
+                                branch_request_file_gitlab
+                              end
+
+        package.save_file({ file: branch_request_file, filename: '_branch_request' })
+      end
+
+      def branch_request_file_github
+        {
+          action: @scm_extractor_payload[:action],
+          pull_request: {
+            head: {
+              repo: { full_name: @scm_extractor_payload[:repository_full_name] },
+              sha: @scm_extractor_payload[:commit_sha]
+            }
+          }
+        }.to_json
+      end
+
+      def branch_request_file_gitlab
+        { object_kind: @scm_extractor_payload[:object_kind],
+          project: { http_url: @scm_extractor_payload[:http_url] },
+          object_attributes: { source: { default_branch: @scm_extractor_payload[:commit_sha] } } }.to_json
       end
     end
   end