"""Tests for subagent executor async/sync execution paths.

Covers:
- SubagentExecutor.execute() synchronous execution path
- SubagentExecutor._aexecute() asynchronous execution path
- asyncio.run() properly executes async workflow within thread pool context
- Error handling in both sync and async paths
- Async tool support (MCP tools)
- Cooperative cancellation via cancel_event

Note: Due to circular import issues in the main codebase, conftest.py mocks
deerflow.subagents.executor. This test file uses delayed import via fixture to test
the real implementation in isolation.
"""

import asyncio
import sys
import threading
from datetime import datetime
from unittest.mock import MagicMock, patch

import pytest

# Module names that need to be mocked to break circular imports
_MOCKED_MODULE_NAMES = [
    "deerflow.agents",
    "deerflow.agents.thread_state",
    "deerflow.agents.middlewares",
    "deerflow.agents.middlewares.thread_data_middleware",
    "deerflow.sandbox",
    "deerflow.sandbox.middleware",
    "deerflow.sandbox.security",
    "deerflow.models",
]


@pytest.fixture(scope="session", autouse=True)
def _setup_executor_classes():
    """Set up mocked modules and import real executor classes.

    This fixture runs once per session and yields the executor classes.
    It handles module cleanup to avoid affecting other test files.
    """
    # Save original modules
    original_modules = {name: sys.modules.get(name) for name in _MOCKED_MODULE_NAMES}
    original_executor = sys.modules.get("deerflow.subagents.executor")

    # Remove mocked executor if exists (from conftest.py)
    if "deerflow.subagents.executor" in sys.modules:
        del sys.modules["deerflow.subagents.executor"]

    # Set up mocks
    for name in _MOCKED_MODULE_NAMES:
        sys.modules[name] = MagicMock()

    # Import real classes inside fixture
    from langchain_core.messages import AIMessage, HumanMessage

    from deerflow.subagents.config import SubagentConfig
    from deerflow.subagents.executor import (
        SubagentExecutor,
        SubagentResult,
        SubagentStatus,
    )

    # Store classes in a dict to yield
    classes = {
        "AIMessage": AIMessage,
        "HumanMessage": HumanMessage,
        "SubagentConfig": SubagentConfig,
        "SubagentExecutor": SubagentExecutor,
        "SubagentResult": SubagentResult,
        "SubagentStatus": SubagentStatus,
    }

    yield classes

    # Cleanup: Restore original modules
    for name in _MOCKED_MODULE_NAMES:
        if original_modules[name] is not None:
            sys.modules[name] = original_modules[name]
        elif name in sys.modules:
            del sys.modules[name]

    # Restore executor module (conftest.py mock)
    if original_executor is not None:
        sys.modules["deerflow.subagents.executor"] = original_executor
    elif "deerflow.subagents.executor" in sys.modules:
        del sys.modules["deerflow.subagents.executor"]


# Helper classes that wrap real classes for testing
class MockHumanMessage:
    """Mock HumanMessage for testing - wraps real class from fixture."""

    def __init__(self, content, _classes=None):
        self._content = content
        self._classes = _classes

    def _get_real(self):
        return self._classes["HumanMessage"](content=self._content)


class MockAIMessage:
    """Mock AIMessage for testing - wraps real class from fixture."""

    def __init__(self, content, msg_id=None, _classes=None):
        self._content = content
        self._msg_id = msg_id
        self._classes = _classes

    def _get_real(self):
        msg = self._classes["AIMessage"](content=self._content)
        if self._msg_id:
            msg.id = self._msg_id
        return msg


async def async_iterator(items):
    """Helper to create an async iterator from a list."""
    for item in items:
        yield item


# -----------------------------------------------------------------------------
# Fixtures
# -----------------------------------------------------------------------------


@pytest.fixture
def classes(_setup_executor_classes):
    """Provide access to executor classes."""
    return _setup_executor_classes


@pytest.fixture
def base_config(classes):
    """Return a basic subagent config for testing."""
    return classes["SubagentConfig"](
        name="test-agent",
        description="Test agent",
        system_prompt="You are a test agent.",
        max_turns=10,
        timeout_seconds=60,
    )


@pytest.fixture
def mock_agent():
    """Return a properly configured mock agent with async stream."""
    agent = MagicMock()
    agent.astream = MagicMock()
    return agent


# Helper to create real message objects
class _MsgHelper:
    """Helper to create real message objects from fixture classes."""

    def __init__(self, classes):
        self.classes = classes

    def human(self, content):
        return self.classes["HumanMessage"](content=content)

    def ai(self, content, msg_id=None):
        msg = self.classes["AIMessage"](content=content)
        if msg_id:
            msg.id = msg_id
        return msg


@pytest.fixture
def msg(classes):
    """Provide message factory."""
    return _MsgHelper(classes)


# -----------------------------------------------------------------------------
# Async Execution Path Tests
# -----------------------------------------------------------------------------


class TestAsyncExecutionPath:
    """Test _aexecute() async execution path."""

    @pytest.mark.anyio
    async def test_aexecute_success(self, classes, base_config, mock_agent, msg):
        """Test successful async execution returns completed result."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        final_message = msg.ai("Task completed successfully", "msg-1")
        final_state = {
            "messages": [
                msg.human("Do something"),
                final_message,
            ]
        }
        mock_agent.astream = lambda *args, **kwargs: async_iterator([final_state])

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
            trace_id="test-trace",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = await executor._aexecute("Do something")

        assert result.status == SubagentStatus.COMPLETED
        assert result.result == "Task completed successfully"
        assert result.error is None
        assert result.started_at is not None
        assert result.completed_at is not None

    @pytest.mark.anyio
    async def test_aexecute_collects_ai_messages(self, classes, base_config, mock_agent, msg):
        """Test that AI messages are collected during streaming."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        msg1 = msg.ai("First response", "msg-1")
        msg2 = msg.ai("Second response", "msg-2")

        chunk1 = {"messages": [msg.human("Task"), msg1]}
        chunk2 = {"messages": [msg.human("Task"), msg1, msg2]}

        mock_agent.astream = lambda *args, **kwargs: async_iterator([chunk1, chunk2])

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = await executor._aexecute("Task")

        assert result.status == SubagentStatus.COMPLETED
        assert len(result.ai_messages) == 2
        assert result.ai_messages[0]["id"] == "msg-1"
        assert result.ai_messages[1]["id"] == "msg-2"

    @pytest.mark.anyio
    async def test_aexecute_handles_duplicate_messages(self, classes, base_config, mock_agent, msg):
        """Test that duplicate AI messages are not added."""
        SubagentExecutor = classes["SubagentExecutor"]

        msg1 = msg.ai("Response", "msg-1")

        # Same message appears in multiple chunks
        chunk1 = {"messages": [msg.human("Task"), msg1]}
        chunk2 = {"messages": [msg.human("Task"), msg1]}

        mock_agent.astream = lambda *args, **kwargs: async_iterator([chunk1, chunk2])

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = await executor._aexecute("Task")

        assert len(result.ai_messages) == 1

    @pytest.mark.anyio
    async def test_aexecute_handles_list_content(self, classes, base_config, mock_agent, msg):
        """Test handling of list-type content in AIMessage."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        final_message = msg.ai([{"text": "Part 1"}, {"text": "Part 2"}])
        final_state = {
            "messages": [
                msg.human("Task"),
                final_message,
            ]
        }
        mock_agent.astream = lambda *args, **kwargs: async_iterator([final_state])

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = await executor._aexecute("Task")

        assert result.status == SubagentStatus.COMPLETED
        assert "Part 1" in result.result
        assert "Part 2" in result.result

    @pytest.mark.anyio
    async def test_aexecute_handles_agent_exception(self, classes, base_config, mock_agent):
        """Test that exceptions during execution are caught and returned as FAILED."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        mock_agent.astream.side_effect = Exception("Agent error")

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = await executor._aexecute("Task")

        assert result.status == SubagentStatus.FAILED
        assert "Agent error" in result.error
        assert result.completed_at is not None

    @pytest.mark.anyio
    async def test_aexecute_no_final_state(self, classes, base_config, mock_agent):
        """Test handling when no final state is returned."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        mock_agent.astream = lambda *args, **kwargs: async_iterator([])

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = await executor._aexecute("Task")

        assert result.status == SubagentStatus.COMPLETED
        assert result.result == "No response generated"

    @pytest.mark.anyio
    async def test_aexecute_no_ai_message_in_state(self, classes, base_config, mock_agent, msg):
        """Test fallback when no AIMessage found in final state."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        final_state = {"messages": [msg.human("Task")]}
        mock_agent.astream = lambda *args, **kwargs: async_iterator([final_state])

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = await executor._aexecute("Task")

        # Should fallback to string representation of last message
        assert result.status == SubagentStatus.COMPLETED
        assert "Task" in result.result


# -----------------------------------------------------------------------------
# Sync Execution Path Tests
# -----------------------------------------------------------------------------


class TestSyncExecutionPath:
    """Test execute() synchronous execution path with asyncio.run()."""

    def test_execute_runs_async_in_event_loop(self, classes, base_config, mock_agent, msg):
        """Test that execute() runs _aexecute() in a new event loop via asyncio.run()."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        final_message = msg.ai("Sync result", "msg-1")
        final_state = {
            "messages": [
                msg.human("Task"),
                final_message,
            ]
        }
        mock_agent.astream = lambda *args, **kwargs: async_iterator([final_state])

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = executor.execute("Task")

        assert result.status == SubagentStatus.COMPLETED
        assert result.result == "Sync result"

    def test_execute_in_thread_pool_context(self, classes, base_config, msg):
        """Test that execute() works correctly when called from a thread pool.

        This simulates the real-world usage where execute() is called from
        _execution_pool in execute_async().
        """
        from concurrent.futures import ThreadPoolExecutor

        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        final_message = msg.ai("Thread pool result", "msg-1")
        final_state = {
            "messages": [
                msg.human("Task"),
                final_message,
            ]
        }

        def run_in_thread():
            mock_agent = MagicMock()
            mock_agent.astream = lambda *args, **kwargs: async_iterator([final_state])

            executor = SubagentExecutor(
                config=base_config,
                tools=[],
                thread_id="test-thread",
            )

            with patch.object(executor, "_create_agent", return_value=mock_agent):
                return executor.execute("Task")

        # Execute in thread pool (simulating _execution_pool usage)
        with ThreadPoolExecutor(max_workers=1) as pool:
            future = pool.submit(run_in_thread)
            result = future.result(timeout=5)

        assert result.status == SubagentStatus.COMPLETED
        assert result.result == "Thread pool result"

    @pytest.mark.anyio
    async def test_execute_in_running_event_loop_uses_isolated_thread(self, classes, base_config, mock_agent, msg):
        """Test that execute() uses the isolated-thread path inside a running loop."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        execution_threads = []
        final_state = {
            "messages": [
                msg.human("Task"),
                msg.ai("Async loop result", "msg-1"),
            ]
        }

        async def mock_astream(*args, **kwargs):
            execution_threads.append(threading.current_thread().name)
            yield final_state

        mock_agent.astream = mock_astream

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            with patch.object(executor, "_execute_in_isolated_loop", wraps=executor._execute_in_isolated_loop) as isolated:
                result = executor.execute("Task")

        assert isolated.call_count == 1
        assert execution_threads
        assert all(name.startswith("subagent-isolated-") for name in execution_threads)
        assert result.status == SubagentStatus.COMPLETED
        assert result.result == "Async loop result"

    def test_execute_handles_asyncio_run_failure(self, classes, base_config):
        """Test handling when asyncio.run() itself fails."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_aexecute") as mock_aexecute:
            mock_aexecute.side_effect = Exception("Asyncio run error")

            result = executor.execute("Task")

        assert result.status == SubagentStatus.FAILED
        assert "Asyncio run error" in result.error
        assert result.completed_at is not None

    def test_execute_with_result_holder(self, classes, base_config, mock_agent, msg):
        """Test execute() updates provided result_holder in real-time."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentResult = classes["SubagentResult"]
        SubagentStatus = classes["SubagentStatus"]

        msg1 = msg.ai("Step 1", "msg-1")
        chunk1 = {"messages": [msg.human("Task"), msg1]}

        mock_agent.astream = lambda *args, **kwargs: async_iterator([chunk1])

        # Pre-create result holder (as done in execute_async)
        result_holder = SubagentResult(
            task_id="predefined-id",
            trace_id="test-trace",
            status=SubagentStatus.RUNNING,
            started_at=datetime.now(),
        )

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = executor.execute("Task", result_holder=result_holder)

        # Should be the same object
        assert result is result_holder
        assert result.task_id == "predefined-id"
        assert result.status == SubagentStatus.COMPLETED


# -----------------------------------------------------------------------------
# Async Tool Support Tests (MCP Tools)
# -----------------------------------------------------------------------------


class TestAsyncToolSupport:
    """Test that async-only tools (like MCP tools) work correctly."""

    @pytest.mark.anyio
    async def test_async_tool_called_in_astream(self, classes, base_config, msg):
        """Test that async tools are properly awaited in astream.

        This verifies the fix for: async MCP tools not being executed properly
        because they were being called synchronously.
        """
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        async_tool_calls = []

        async def mock_async_tool(*args, **kwargs):
            async_tool_calls.append("called")
            await asyncio.sleep(0.01)  # Simulate async work
            return {"result": "async tool result"}

        mock_agent = MagicMock()

        # Simulate agent that calls async tools during streaming
        async def mock_astream(*args, **kwargs):
            await mock_async_tool()
            yield {
                "messages": [
                    msg.human("Task"),
                    msg.ai("Done", "msg-1"),
                ]
            }

        mock_agent.astream = mock_astream

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = await executor._aexecute("Task")

        assert len(async_tool_calls) == 1
        assert result.status == SubagentStatus.COMPLETED

    def test_sync_execute_with_async_tools(self, classes, base_config, msg):
        """Test that sync execute() properly runs async tools via asyncio.run()."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        async_tool_calls = []

        async def mock_async_tool():
            async_tool_calls.append("called")
            await asyncio.sleep(0.01)
            return {"result": "async result"}

        mock_agent = MagicMock()

        async def mock_astream(*args, **kwargs):
            await mock_async_tool()
            yield {
                "messages": [
                    msg.human("Task"),
                    msg.ai("Done", "msg-1"),
                ]
            }

        mock_agent.astream = mock_astream

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = executor.execute("Task")

        assert len(async_tool_calls) == 1
        assert result.status == SubagentStatus.COMPLETED


# -----------------------------------------------------------------------------
# Thread Safety Tests
# -----------------------------------------------------------------------------


class TestThreadSafety:
    """Test thread safety of executor operations."""

    def test_multiple_executors_in_parallel(self, classes, base_config, msg):
        """Test multiple executors running in parallel via thread pool."""
        from concurrent.futures import ThreadPoolExecutor, as_completed

        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        results = []

        def execute_task(task_id: int):
            def make_astream(*args, **kwargs):
                return async_iterator(
                    [
                        {
                            "messages": [
                                msg.human(f"Task {task_id}"),
                                msg.ai(f"Result {task_id}", f"msg-{task_id}"),
                            ]
                        }
                    ]
                )

            mock_agent = MagicMock()
            mock_agent.astream = make_astream

            executor = SubagentExecutor(
                config=base_config,
                tools=[],
                thread_id=f"thread-{task_id}",
            )

            with patch.object(executor, "_create_agent", return_value=mock_agent):
                return executor.execute(f"Task {task_id}")

        # Execute multiple tasks in parallel
        with ThreadPoolExecutor(max_workers=3) as pool:
            futures = [pool.submit(execute_task, i) for i in range(5)]
            for future in as_completed(futures):
                results.append(future.result())

        assert len(results) == 5
        for result in results:
            assert result.status == SubagentStatus.COMPLETED
            assert "Result" in result.result


# -----------------------------------------------------------------------------
# Cleanup Background Task Tests
# -----------------------------------------------------------------------------


class TestCleanupBackgroundTask:
    """Test cleanup_background_task function for race condition prevention."""

    @pytest.fixture
    def executor_module(self, _setup_executor_classes):
        """Import the executor module with real classes."""
        # Re-import to get the real module with cleanup_background_task
        import importlib

        from deerflow.subagents import executor

        return importlib.reload(executor)

    def test_cleanup_removes_terminal_completed_task(self, executor_module, classes):
        """Test that cleanup removes a COMPLETED task."""
        SubagentResult = classes["SubagentResult"]
        SubagentStatus = classes["SubagentStatus"]

        # Add a completed task
        task_id = "test-completed-task"
        result = SubagentResult(
            task_id=task_id,
            trace_id="test-trace",
            status=SubagentStatus.COMPLETED,
            result="done",
            completed_at=datetime.now(),
        )
        executor_module._background_tasks[task_id] = result

        # Cleanup should remove it
        executor_module.cleanup_background_task(task_id)

        assert task_id not in executor_module._background_tasks

    def test_cleanup_removes_terminal_failed_task(self, executor_module, classes):
        """Test that cleanup removes a FAILED task."""
        SubagentResult = classes["SubagentResult"]
        SubagentStatus = classes["SubagentStatus"]

        task_id = "test-failed-task"
        result = SubagentResult(
            task_id=task_id,
            trace_id="test-trace",
            status=SubagentStatus.FAILED,
            error="error",
            completed_at=datetime.now(),
        )
        executor_module._background_tasks[task_id] = result

        executor_module.cleanup_background_task(task_id)

        assert task_id not in executor_module._background_tasks

    def test_cleanup_removes_terminal_timed_out_task(self, executor_module, classes):
        """Test that cleanup removes a TIMED_OUT task."""
        SubagentResult = classes["SubagentResult"]
        SubagentStatus = classes["SubagentStatus"]

        task_id = "test-timedout-task"
        result = SubagentResult(
            task_id=task_id,
            trace_id="test-trace",
            status=SubagentStatus.TIMED_OUT,
            error="timeout",
            completed_at=datetime.now(),
        )
        executor_module._background_tasks[task_id] = result

        executor_module.cleanup_background_task(task_id)

        assert task_id not in executor_module._background_tasks

    def test_cleanup_skips_running_task(self, executor_module, classes):
        """Test that cleanup does NOT remove a RUNNING task.

        This prevents race conditions where task_tool calls cleanup
        while the background executor is still updating the task.
        """
        SubagentResult = classes["SubagentResult"]
        SubagentStatus = classes["SubagentStatus"]

        task_id = "test-running-task"
        result = SubagentResult(
            task_id=task_id,
            trace_id="test-trace",
            status=SubagentStatus.RUNNING,
            started_at=datetime.now(),
        )
        executor_module._background_tasks[task_id] = result

        executor_module.cleanup_background_task(task_id)

        # Should still be present because it's RUNNING
        assert task_id in executor_module._background_tasks

    def test_cleanup_skips_pending_task(self, executor_module, classes):
        """Test that cleanup does NOT remove a PENDING task."""
        SubagentResult = classes["SubagentResult"]
        SubagentStatus = classes["SubagentStatus"]

        task_id = "test-pending-task"
        result = SubagentResult(
            task_id=task_id,
            trace_id="test-trace",
            status=SubagentStatus.PENDING,
        )
        executor_module._background_tasks[task_id] = result

        executor_module.cleanup_background_task(task_id)

        assert task_id in executor_module._background_tasks

    def test_cleanup_handles_unknown_task_gracefully(self, executor_module):
        """Test that cleanup doesn't raise for unknown task IDs."""
        # Should not raise
        executor_module.cleanup_background_task("nonexistent-task")

    def test_cleanup_removes_task_with_completed_at_even_if_running(self, executor_module, classes):
        """Test that cleanup removes task if completed_at is set, even if status is RUNNING.

        This is a safety net: if completed_at is set, the task is considered done
        regardless of status.
        """
        SubagentResult = classes["SubagentResult"]
        SubagentStatus = classes["SubagentStatus"]

        task_id = "test-completed-at-task"
        result = SubagentResult(
            task_id=task_id,
            trace_id="test-trace",
            status=SubagentStatus.RUNNING,  # Status not terminal
            completed_at=datetime.now(),  # But completed_at is set
        )
        executor_module._background_tasks[task_id] = result

        executor_module.cleanup_background_task(task_id)

        # Should be removed because completed_at is set
        assert task_id not in executor_module._background_tasks


# -----------------------------------------------------------------------------
# Cooperative Cancellation Tests
# -----------------------------------------------------------------------------


class TestCooperativeCancellation:
    """Test cooperative cancellation via cancel_event."""

    @pytest.fixture
    def executor_module(self, _setup_executor_classes):
        """Import the executor module with real classes."""
        import importlib

        from deerflow.subagents import executor

        return importlib.reload(executor)

    @pytest.mark.anyio
    async def test_aexecute_cancelled_before_streaming(self, classes, base_config, mock_agent, msg):
        """Test that _aexecute returns CANCELLED when cancel_event is set before streaming."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentResult = classes["SubagentResult"]
        SubagentStatus = classes["SubagentStatus"]

        # The agent should never be called
        call_count = 0

        async def mock_astream(*args, **kwargs):
            nonlocal call_count
            call_count += 1
            yield {"messages": [msg.human("Task"), msg.ai("Done", "msg-1")]}

        mock_agent.astream = mock_astream

        # Pre-create result holder with cancel_event already set
        result_holder = SubagentResult(
            task_id="cancel-before",
            trace_id="test-trace",
            status=SubagentStatus.RUNNING,
            started_at=datetime.now(),
        )
        result_holder.cancel_event.set()

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = await executor._aexecute("Task", result_holder=result_holder)

        assert result.status == SubagentStatus.CANCELLED
        assert result.error == "Cancelled by user"
        assert result.completed_at is not None
        assert call_count == 0  # astream was never entered

    @pytest.mark.anyio
    async def test_aexecute_cancelled_mid_stream(self, classes, base_config, msg):
        """Test that _aexecute returns CANCELLED when cancel_event is set during streaming."""
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentResult = classes["SubagentResult"]
        SubagentStatus = classes["SubagentStatus"]

        cancel_event = threading.Event()

        async def mock_astream(*args, **kwargs):
            yield {"messages": [msg.human("Task"), msg.ai("Partial", "msg-1")]}
            # Simulate cancellation during streaming
            cancel_event.set()
            yield {"messages": [msg.human("Task"), msg.ai("Should not appear", "msg-2")]}

        mock_agent = MagicMock()
        mock_agent.astream = mock_astream

        result_holder = SubagentResult(
            task_id="cancel-mid",
            trace_id="test-trace",
            status=SubagentStatus.RUNNING,
            started_at=datetime.now(),
        )
        result_holder.cancel_event = cancel_event

        executor = SubagentExecutor(
            config=base_config,
            tools=[],
            thread_id="test-thread",
        )

        with patch.object(executor, "_create_agent", return_value=mock_agent):
            result = await executor._aexecute("Task", result_holder=result_holder)

        assert result.status == SubagentStatus.CANCELLED
        assert result.error == "Cancelled by user"
        assert result.completed_at is not None

    def test_request_cancel_sets_event(self, executor_module, classes):
        """Test that request_cancel_background_task sets the cancel_event."""
        SubagentResult = classes["SubagentResult"]
        SubagentStatus = classes["SubagentStatus"]

        task_id = "test-cancel-event"
        result = SubagentResult(
            task_id=task_id,
            trace_id="test-trace",
            status=SubagentStatus.RUNNING,
            started_at=datetime.now(),
        )
        executor_module._background_tasks[task_id] = result

        assert not result.cancel_event.is_set()

        executor_module.request_cancel_background_task(task_id)

        assert result.cancel_event.is_set()

    def test_request_cancel_nonexistent_task_is_noop(self, executor_module):
        """Test that requesting cancellation on a nonexistent task does not raise."""
        executor_module.request_cancel_background_task("nonexistent-task")

    def test_timeout_does_not_overwrite_cancelled(self, executor_module, classes, base_config, msg):
        """Test that the real timeout handler does not overwrite CANCELLED status.

        This exercises the actual execute_async → run_task → FuturesTimeoutError
        code path in executor.py.  We make execute() block so the timeout fires
        deterministically, pre-set the task to CANCELLED, and verify the RUNNING
        guard preserves it.  Uses threading.Event for synchronisation instead of
        wall-clock sleeps.
        """
        SubagentExecutor = classes["SubagentExecutor"]
        SubagentStatus = classes["SubagentStatus"]

        short_config = classes["SubagentConfig"](
            name="test-agent",
            description="Test agent",
            system_prompt="You are a test agent.",
            max_turns=10,
            timeout_seconds=0.05,  # 50ms – just enough for the future to time out
        )

        # Synchronisation primitives
        execute_entered = threading.Event()  # signals that execute() has started
        execute_release = threading.Event()  # lets execute() return
        run_task_done = threading.Event()  # signals that run_task() has finished

        # A blocking execute() replacement so we control the timing exactly
        def blocking_execute(task, result_holder=None):
            # Cooperative cancellation: honour cancel_event like real _aexecute
            if result_holder and result_holder.cancel_event.is_set():
                result_holder.status = SubagentStatus.CANCELLED
                result_holder.error = "Cancelled by user"
                result_holder.completed_at = datetime.now()
                execute_entered.set()
                return result_holder
            execute_entered.set()
            execute_release.wait(timeout=5)
            # Return a minimal completed result (will be ignored because timeout fires first)
            from deerflow.subagents.executor import SubagentResult as _R

            return _R(task_id="x", trace_id="t", status=SubagentStatus.COMPLETED, result="late")

        executor = SubagentExecutor(
            config=short_config,
            tools=[],
            thread_id="test-thread",
            trace_id="test-trace",
        )

        # Wrap _scheduler_pool.submit so we know when run_task finishes
        original_scheduler_submit = executor_module._scheduler_pool.submit

        def tracked_submit(fn, *args, **kwargs):
            def wrapper():
                try:
                    fn(*args, **kwargs)
                finally:
                    run_task_done.set()

            return original_scheduler_submit(wrapper)

        with patch.object(executor, "execute", blocking_execute), patch.object(executor_module._scheduler_pool, "submit", tracked_submit):
            task_id = executor.execute_async("Task")

            # Wait until execute() is entered (i.e. it's running in _execution_pool)
            assert execute_entered.wait(timeout=3), "execute() was never called"

            # Set CANCELLED on the result before the timeout handler runs.
            # The 50ms timeout will fire while execute() is blocked.
            with executor_module._background_tasks_lock:
                executor_module._background_tasks[task_id].status = SubagentStatus.CANCELLED
                executor_module._background_tasks[task_id].error = "Cancelled by user"
                executor_module._background_tasks[task_id].completed_at = datetime.now()

            # Wait for run_task to finish — the FuturesTimeoutError handler has
            # now executed and (should have) left CANCELLED intact.
            assert run_task_done.wait(timeout=5), "run_task() did not finish"

            # Only NOW release the blocked execute() so the thread pool worker
            # can be reclaimed.  This MUST come after run_task_done to avoid a
            # race where execute() returns before the timeout fires.
            execute_release.set()

        result = executor_module._background_tasks.get(task_id)
        assert result is not None
        # The RUNNING guard in the FuturesTimeoutError handler must have
        # preserved CANCELLED instead of overwriting with TIMED_OUT.
        assert result.status.value == SubagentStatus.CANCELLED.value
        assert result.error == "Cancelled by user"
        assert result.completed_at is not None

    def test_cleanup_removes_cancelled_task(self, executor_module, classes):
        """Test that cleanup removes a CANCELLED task (terminal state)."""
        SubagentResult = classes["SubagentResult"]
        SubagentStatus = classes["SubagentStatus"]

        task_id = "test-cancelled-cleanup"
        result = SubagentResult(
            task_id=task_id,
            trace_id="test-trace",
            status=SubagentStatus.CANCELLED,
            error="Cancelled by user",
            completed_at=datetime.now(),
        )
        executor_module._background_tasks[task_id] = result

        executor_module.cleanup_background_task(task_id)

        assert task_id not in executor_module._background_tasks