"""Test for issue #1016: checkpointer should not return None."""

from unittest.mock import MagicMock

import pytest
from langgraph.checkpoint.memory import InMemorySaver


class TestCheckpointerNoneFix:
    """Tests that checkpointer context managers return InMemorySaver instead of None."""

    @pytest.mark.anyio
    async def test_async_make_checkpointer_returns_in_memory_saver_when_not_configured(self):
        """make_checkpointer should return InMemorySaver when config.checkpointer is None."""
        from deerflow.runtime.checkpointer.async_provider import make_checkpointer

        mock_config = MagicMock()
        mock_config.checkpointer = None
        mock_config.database = None

        async with make_checkpointer(mock_config) as checkpointer:
            # Should return InMemorySaver, not None
            assert checkpointer is not None
            assert isinstance(checkpointer, InMemorySaver)

            # Should be able to call alist() without AttributeError
            # This is what LangGraph does and what was failing in issue #1016
            result = []
            async for item in checkpointer.alist(config={"configurable": {"thread_id": "test"}}):
                result.append(item)

            # Empty list is expected for a fresh checkpointer
            assert result == []

    def test_sync_checkpointer_context_returns_in_memory_saver_when_not_configured(self):
        """checkpointer_context should return InMemorySaver when config.checkpointer is None."""
        from deerflow.runtime.checkpointer.provider import checkpointer_context

        mock_config = MagicMock()
        mock_config.checkpointer = None

        with checkpointer_context(mock_config) as checkpointer:
            # Should return InMemorySaver, not None
            assert checkpointer is not None
            assert isinstance(checkpointer, InMemorySaver)

            # Should be able to call list() without AttributeError
            result = list(checkpointer.list(config={"configurable": {"thread_id": "test"}}))

            # Empty list is expected for a fresh checkpointer
            assert result == []