1 files changed, 82 insertions, 0 deletions
diff --git a/lib/api/issue_links.rb b/lib/api/issue_links.rb
new file mode 100644
index 00000000000..6cc5b344f47
--- /dev/null
+++ b/lib/api/issue_links.rb
@@ -0,0 +1,82 @@
+# frozen_string_literal: true
+
+module API
+  class IssueLinks < Grape::API::Instance
+    include PaginationParams
+
+    before { authenticate! }
+
+    params do
+      requires :id, type: String, desc: 'The ID of a project'
+      requires :issue_iid, type: Integer, desc: 'The internal ID of a project issue'
+    end
+    resource :projects, requirements: { id: %r{[^/]+} } do
+      desc 'Get related issues' do
+        success Entities::RelatedIssue
+      end
+      get ':id/issues/:issue_iid/links' do
+        source_issue = find_project_issue(params[:issue_iid])
+        related_issues = source_issue.related_issues(current_user)
+
+        present related_issues,
+                with: Entities::RelatedIssue,
+                current_user: current_user,
+                project: user_project
+      end
+
+      desc 'Relate issues' do
+        success Entities::IssueLink
+      end
+      params do
+        requires :target_project_id, type: String, desc: 'The ID of the target project'
+        requires :target_issue_iid, type: Integer, desc: 'The IID of the target issue'
+        optional :link_type, type: String, values: IssueLink.link_types.keys,
+          desc: 'The type of the relation'
+      end
+      # rubocop: disable CodeReuse/ActiveRecord
+      post ':id/issues/:issue_iid/links' do
+        source_issue = find_project_issue(params[:issue_iid])
+        target_issue = find_project_issue(declared_params[:target_issue_iid],
+                                          declared_params[:target_project_id])
+
+        create_params = { target_issuable: target_issue, link_type: declared_params[:link_type] }
+
+        result = ::IssueLinks::CreateService
+                   .new(source_issue, current_user, create_params)
+                   .execute
+
+        if result[:status] == :success
+          issue_link = IssueLink.find_by!(source: source_issue, target: target_issue)
+
+          present issue_link, with: Entities::IssueLink
+        else
+          render_api_error!(result[:message], result[:http_status])
+        end
+      end
+      # rubocop: enable CodeReuse/ActiveRecord
+
+      desc 'Remove issues relation' do
+        success Entities::IssueLink
+      end
+      params do
+        requires :issue_link_id, type: Integer, desc: 'The ID of an issue link'
+      end
+      delete ':id/issues/:issue_iid/links/:issue_link_id' do
+        issue_link = IssueLink.find(declared_params[:issue_link_id])
+
+        find_project_issue(params[:issue_iid])
+        find_project_issue(issue_link.target.iid.to_s, issue_link.target.project_id.to_s)
+
+        result = ::IssueLinks::DestroyService
+                   .new(issue_link, current_user)
+                   .execute
+
+        if result[:status] == :success
+          present issue_link, with: Entities::IssueLink
+        else
+          render_api_error!(result[:message], result[:http_status])
+        end
+      end
+    end
+  end
+end