Add User.add_alias/2 and User.alias_users/1

Ref: emit-move

lib/pleroma/user.ex

@@ -2270,6 +2270,25 @@ def change_email(user, email) do
     |> update_and_set_cache()
   end
 
+  def alias_users(user) do
+    user.also_known_as
+    |> Enum.map(&User.get_cached_by_ap_id/1)
+    |> Enum.filter(fn user -> user != nil end)
+  end
+
+  def add_alias(user, new_alias_user) do
+    current_aliases = user.also_known_as || []
+    new_alias_ap_id = new_alias_user.ap_id
+
+    if new_alias_ap_id in current_aliases do
+      {:ok, user}
+    else
+      user
+      |> cast(%{also_known_as: current_aliases ++ [new_alias_ap_id]}, [:also_known_as])
+      |> update_and_set_cache()
+    end
+  end
+
   # Internal function; public one is `deactivate/2`
   defp set_activation_status(user, status) do
     user

test/pleroma/user_test.exs

@@ -2498,4 +2498,56 @@ defp object_id_from_created_activity(user) do
     %{object: %{data: %{"id" => object_id}}} = Activity.get_by_id_with_object(id)
     object_id
   end
+
+  describe "add_alias/2" do
+    test "should add alias for another user" do
+      user = insert(:user)
+      user2 = insert(:user)
+
+      assert {:ok, user_updated} = user |> User.add_alias(user2)
+
+      assert user_updated.also_known_as |> length() == 1
+      assert user2.ap_id in user_updated.also_known_as
+    end
+
+    test "should add multiple aliases" do
+      user = insert(:user)
+      user2 = insert(:user)
+      user3 = insert(:user)
+
+      assert {:ok, user} = user |> User.add_alias(user2)
+      assert {:ok, user_updated} = user |> User.add_alias(user3)
+
+      assert user_updated.also_known_as |> length() == 2
+      assert user2.ap_id in user_updated.also_known_as
+      assert user3.ap_id in user_updated.also_known_as
+    end
+
+    test "should not add duplicate aliases" do
+      user = insert(:user)
+      user2 = insert(:user)
+
+      assert {:ok, user} = user |> User.add_alias(user2)
+
+      assert {:ok, user_updated} = user |> User.add_alias(user2)
+
+      assert user_updated.also_known_as |> length() == 1
+      assert user2.ap_id in user_updated.also_known_as
+    end
+  end
+
+  describe "alias_users/1" do
+    test "should get aliases for a user" do
+      user = insert(:user)
+      user2 = insert(:user, also_known_as: [user.ap_id])
+
+      aliases = user2 |> User.alias_users()
+
+      assert aliases |> length() == 1
+
+      alias_user = aliases |> Enum.at(0)
+
+      assert alias_user.ap_id == user.ap_id
+    end
+  end
 end