Add username filter to admin invitations index

app/controllers/admin/invitations_controller.rb

@@ -1,12 +1,28 @@
 class Admin::InvitationsController < Admin::BaseController
+  before_action :set_current_section
+
   def index
-    @current_section = :invitations
-    @pagy, @invitations_used = pagy(Invitation.used.order('used_at desc'))
+    @username = params[:username].presence
+    accepted_scope = Invitation.used.order('used_at desc')
+    unused_scope = Invitation.unused
+
+    if @username
+      accepted_scope = accepted_scope.joins(:user).where(users: { cn: @username })
+      unused_scope = unused_scope.joins(:user).where(users: { cn: @username })
+    end
+
+    @pagy, @invitations_used = pagy(accepted_scope)
 
     @stats = {
-      available: Invitation.unused.count,
-      accepted: @invitations_used.length,
-      users_with_referrals: Invitation.used.distinct.count(:user_id)
+      available: unused_scope.count,
+      accepted: accepted_scope.count,
+      users_with_referrals: accepted_scope.distinct.count(:user_id)
     }
   end
+
+  private
+
+    def set_current_section
+      @current_section = :invitations
+    end
 end