Persist chat history

test/music_library/chats_test.exs

@@ -0,0 +1,153 @@
+defmodule MusicLibrary.ChatsTest do
+  use MusicLibrary.DataCase
+
+  alias MusicLibrary.Chats
+  alias MusicLibrary.Chats.Chat
+
+  @musicbrainz_id Ecto.UUID.generate()
+
+  defp create_chat(_context) do
+    {:ok, chat} =
+      Chats.create_chat_with_message(
+        %{entity: :record, musicbrainz_id: @musicbrainz_id},
+        %{role: "user", content: "Tell me about this album"}
+      )
+
+    %{chat: chat}
+  end
+
+  describe "list_chats/2" do
+    setup [:create_chat]
+
+    test "returns empty list when no chats exist" do
+      assert Chats.list_chats(:record, Ecto.UUID.generate()) == []
+    end
+
+    test "returns chats for entity with message count", %{chat: chat} do
+      chats = Chats.list_chats(:record, @musicbrainz_id)
+
+      assert [listed_chat] = chats
+      assert listed_chat.id == chat.id
+      assert listed_chat.message_count == 1
+    end
+
+    test "does not return chats for different entity", %{chat: _chat} do
+      assert Chats.list_chats(:artist, @musicbrainz_id) == []
+    end
+
+    test "orders by updated_at desc", %{chat: first_chat} do
+      {:ok, second_chat} =
+        Chats.create_chat_with_message(
+          %{entity: :record, musicbrainz_id: @musicbrainz_id},
+          %{role: "user", content: "Another question"}
+        )
+
+      chats = Chats.list_chats(:record, @musicbrainz_id)
+      assert [%{id: id1}, %{id: id2}] = chats
+      assert id1 == second_chat.id
+      assert id2 == first_chat.id
+    end
+  end
+
+  describe "get_chat!/1" do
+    setup [:create_chat]
+
+    test "returns chat with preloaded messages", %{chat: chat} do
+      found = Chats.get_chat!(chat.id)
+
+      assert found.id == chat.id
+      assert found.entity == :record
+      assert [message] = found.messages
+      assert message.role == "user"
+      assert message.content == "Tell me about this album"
+    end
+
+    test "raises for nonexistent chat" do
+      assert_raise Ecto.NoResultsError, fn ->
+        Chats.get_chat!(Ecto.UUID.generate())
+      end
+    end
+  end
+
+  describe "create_chat_with_message/2" do
+    test "creates chat with first message" do
+      assert {:ok, chat} =
+               Chats.create_chat_with_message(
+                 %{entity: :artist, musicbrainz_id: @musicbrainz_id},
+                 %{role: "user", content: "Who is this artist?"}
+               )
+
+      assert chat.entity == :artist
+      assert chat.musicbrainz_id == @musicbrainz_id
+      assert chat.topic == "Who is this artist?"
+      assert [message] = chat.messages
+      assert message.role == "user"
+      assert message.position == 0
+    end
+
+    test "truncates topic to 80 characters" do
+      long_message = String.duplicate("a", 200)
+
+      assert {:ok, chat} =
+               Chats.create_chat_with_message(
+                 %{entity: :record, musicbrainz_id: @musicbrainz_id},
+                 %{role: "user", content: long_message}
+               )
+
+      assert String.length(chat.topic) == 80
+    end
+
+    test "returns error for invalid chat attrs" do
+      assert {:error, _changeset} =
+               Chats.create_chat_with_message(
+                 %{},
+                 %{role: "user", content: "Hello"}
+               )
+    end
+  end
+
+  describe "add_message/2" do
+    setup [:create_chat]
+
+    test "adds message with auto-computed position", %{chat: chat} do
+      assert {:ok, message} =
+               Chats.add_message(chat, %{role: "assistant", content: "Here's what I know..."})
+
+      assert message.role == "assistant"
+      assert message.position == 1
+      assert message.chat_id == chat.id
+    end
+
+    test "increments position for each message", %{chat: chat} do
+      {:ok, _} = Chats.add_message(chat, %{role: "assistant", content: "Response 1"})
+      {:ok, msg} = Chats.add_message(chat, %{role: "user", content: "Follow up"})
+
+      assert msg.position == 2
+    end
+
+    test "touches chat updated_at", %{chat: chat} do
+      # Force a different timestamp by manually setting the original earlier
+      Repo.update_all(
+        from(c in Chat, where: c.id == ^chat.id),
+        set: [updated_at: ~U[2025-01-01 00:00:00Z]]
+      )
+
+      {:ok, _} = Chats.add_message(chat, %{role: "assistant", content: "Response"})
+
+      updated_chat = Chats.get_chat!(chat.id)
+      assert DateTime.compare(updated_chat.updated_at, ~U[2025-01-01 00:00:00Z]) == :gt
+    end
+  end
+
+  describe "delete_chat/1" do
+    setup [:create_chat]
+
+    test "deletes chat and its messages", %{chat: chat} do
+      assert {:ok, _} = Chats.delete_chat(chat)
+
+      assert_raise Ecto.NoResultsError, fn ->
+        Chats.get_chat!(chat.id)
+      end
+    end
+  end
+end