1 files changed, 106 insertions, 0 deletions
diff --git a/app/models/ci/external_pull_request.rb b/app/models/ci/external_pull_request.rb
new file mode 100644
index 00000000000..bd37aa9f85a
--- /dev/null
+++ b/app/models/ci/external_pull_request.rb
@@ -0,0 +1,106 @@
+# frozen_string_literal: true
+
+# This model stores pull requests coming from external providers, such as
+# GitHub, when GitLab project is set as CI/CD only and remote mirror.
+#
+# When setting up a remote mirror with GitHub we subscribe to push and
+# pull_request webhook events. When a pull request is opened on GitHub,
+# a webhook is sent out, we create or update the status of the pull
+# request locally.
+#
+# When the mirror is updated and changes are pushed to branches we check
+# if there are open pull requests for the source and target branch.
+# If so, we create pipelines for external pull requests.
+module Ci
+  class ExternalPullRequest < Ci::ApplicationRecord
+    include Gitlab::Utils::StrongMemoize
+    include ShaAttribute
+    include EachBatch
+
+    belongs_to :project
+
+    sha_attribute :source_sha
+    sha_attribute :target_sha
+
+    validates :source_branch, presence: true
+    validates :target_branch, presence: true
+    validates :source_sha, presence: true
+    validates :target_sha, presence: true
+    validates :source_repository, presence: true
+    validates :target_repository, presence: true
+    validates :status, presence: true
+
+    enum status: {
+      open: 1,
+      closed: 2
+    }
+
+    # We currently don't support pull requests from fork, so
+    # we are going to return an error to the webhook
+    validate :not_from_fork
+
+    scope :by_source_branch, ->(branch) { where(source_branch: branch) }
+    scope :by_source_repository, ->(repository) { where(source_repository: repository) }
+
+    # Needed to override Ci::ApplicationRecord as this does not have ci_ table prefix
+    self.table_name = 'external_pull_requests'
+
+    def self.create_or_update_from_params(params)
+      find_params = params.slice(:project_id, :source_branch, :target_branch)
+
+      safe_find_or_initialize_and_update(find: find_params, update: params) do |pull_request|
+        yield(pull_request) if block_given?
+      end
+    end
+
+    def actual_branch_head?
+      actual_source_branch_sha == source_sha
+    end
+
+    def from_fork?
+      source_repository != target_repository
+    end
+
+    def source_ref
+      Gitlab::Git::BRANCH_REF_PREFIX + source_branch
+    end
+
+    def predefined_variables
+      Gitlab::Ci::Variables::Collection.new.tap do |variables|
+        variables.append(key: 'CI_EXTERNAL_PULL_REQUEST_IID', value: pull_request_iid.to_s)
+        variables.append(key: 'CI_EXTERNAL_PULL_REQUEST_SOURCE_REPOSITORY', value: source_repository)
+        variables.append(key: 'CI_EXTERNAL_PULL_REQUEST_TARGET_REPOSITORY', value: target_repository)
+        variables.append(key: 'CI_EXTERNAL_PULL_REQUEST_SOURCE_BRANCH_SHA', value: source_sha)
+        variables.append(key: 'CI_EXTERNAL_PULL_REQUEST_TARGET_BRANCH_SHA', value: target_sha)
+        variables.append(key: 'CI_EXTERNAL_PULL_REQUEST_SOURCE_BRANCH_NAME', value: source_branch)
+        variables.append(key: 'CI_EXTERNAL_PULL_REQUEST_TARGET_BRANCH_NAME', value: target_branch)
+      end
+    end
+
+    def modified_paths
+      project.repository.diff_stats(target_sha, source_sha).paths
+    end
+
+    private
+
+    def actual_source_branch_sha
+      project.commit(source_ref)&.sha
+    end
+
+    def not_from_fork
+      return unless from_fork?
+
+      errors.add(:base, _('Pull requests from fork are not supported'))
+    end
+
+    def self.safe_find_or_initialize_and_update(find:, update:)
+      safe_ensure_unique(retries: 1) do
+        model = find_or_initialize_by(find)
+
+        yield(model) if model.update(update) && block_given?
+
+        model
+      end
+    end
+  end
+end