1 files changed, 91 insertions, 0 deletions
diff --git a/lib/gitlab/github_import/importer/pull_request_importer.rb b/lib/gitlab/github_import/importer/pull_request_importer.rb
new file mode 100644
index 00000000000..49d859f9624
--- /dev/null
+++ b/lib/gitlab/github_import/importer/pull_request_importer.rb
@@ -0,0 +1,91 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module GithubImport
+    module Importer
+      class PullRequestImporter
+        attr_reader :pull_request, :project, :client, :user_finder,
+                    :milestone_finder, :issuable_finder
+
+        # pull_request - An instance of
+        #                `Gitlab::GithubImport::Representation::PullRequest`.
+        # project - An instance of `Project`
+        # client - An instance of `Gitlab::GithubImport::Client`
+        def initialize(pull_request, project, client)
+          @pull_request = pull_request
+          @project = project
+          @client = client
+          @user_finder = UserFinder.new(project, client)
+          @milestone_finder = MilestoneFinder.new(project)
+          @issuable_finder =
+            GithubImport::IssuableFinder.new(project, pull_request)
+        end
+
+        def execute
+          if (mr_id = create_merge_request)
+            issuable_finder.cache_database_id(mr_id)
+          end
+        end
+
+        # Creates the merge request and returns its ID.
+        #
+        # This method will return `nil` if the merge request could not be
+        # created.
+        def create_merge_request
+          author_id, author_found = user_finder.author_id_for(pull_request)
+
+          description = MarkdownText
+            .format(pull_request.description, pull_request.author, author_found)
+
+          # This work must be wrapped in a transaction as otherwise we can leave
+          # behind incomplete data in the event of an error. This can then lead
+          # to duplicate key errors when jobs are retried.
+          MergeRequest.transaction do
+            attributes = {
+              iid: pull_request.iid,
+              title: pull_request.truncated_title,
+              description: description,
+              source_project_id: project.id,
+              target_project_id: project.id,
+              source_branch: pull_request.formatted_source_branch,
+              target_branch: pull_request.target_branch,
+              state: pull_request.state,
+              milestone_id: milestone_finder.id_for(pull_request),
+              author_id: author_id,
+              assignee_id: user_finder.assignee_id_for(pull_request),
+              created_at: pull_request.created_at,
+              updated_at: pull_request.updated_at
+            }
+
+            # When creating merge requests there are a lot of hooks that may
+            # run, for many different reasons. Many of these hooks (e.g. the
+            # ones used for rendering Markdown) are completely unnecessary and
+            # may even lead to transaction timeouts.
+            #
+            # To ensure importing pull requests has a minimal impact and can
+            # complete in a reasonable time we bypass all the hooks by inserting
+            # the row and then retrieving it. We then only perform the
+            # additional work that is strictly necessary.
+            merge_request_id = GithubImport
+              .insert_and_return_id(attributes, project.merge_requests)
+
+            merge_request = project.merge_requests.find(merge_request_id)
+
+            # These fields are set so we can create the correct merge request
+            # diffs.
+            merge_request.source_branch_sha = pull_request.source_branch_sha
+            merge_request.target_branch_sha = pull_request.target_branch_sha
+
+            merge_request.keep_around_commit
+            merge_request.merge_request_diffs.create
+
+            merge_request.id
+          end
+        rescue ActiveRecord::InvalidForeignKey
+          # It's possible the project has been deleted since scheduling this
+          # job. In this case we'll just skip creating the merge request.
+        end
+      end
+    end
+  end
+end