"""
Unit tests for simplified threading implementation.

These tests verify that the simplified implementation:
1. Uses only essential locks
2. Accepts reasonable trade-offs
3. Maintains thread safety where necessary
4. Performs better than complex locking
"""

import asyncio
import time
from unittest.mock import Mock

import pytest

from async_cassandra.exceptions import ConnectionError
from async_cassandra.session import AsyncCassandraSession


@pytest.mark.asyncio
class TestSimplifiedThreading:
    """Test simplified threading and locking implementation."""

    async def test_no_operation_lock_overhead(self):
        """
        Test that operations don't have unnecessary lock overhead.

        What this tests:
        ---------------
        1. No locks on individual query operations
        2. Concurrent queries execute without contention
        3. Performance scales with concurrency
        4. 100 operations complete quickly

        Why this matters:
        ----------------
        Previous implementations had per-operation locks that
        caused contention under high concurrency. The simplified
        implementation removes these locks, accepting that:
        - Some edge cases during shutdown might be racy
        - Performance is more important than perfect consistency

        This test proves the performance benefit is real.
        """
        # Create session
        mock_session = Mock()
        mock_response_future = Mock()
        mock_response_future.has_more_pages = False
        mock_response_future.add_callbacks = Mock()
        mock_response_future.timeout = None
        mock_session.execute_async = Mock(return_value=mock_response_future)

        async_session = AsyncCassandraSession(mock_session)

        # Measure time for multiple concurrent operations
        start_time = time.perf_counter()

        # Run many concurrent queries
        tasks = []
        for i in range(100):
            task = asyncio.create_task(async_session.execute(f"SELECT {i}"))
            tasks.append(task)

        # Trigger callbacks
        await asyncio.sleep(0)  # Let tasks start

        # Trigger all callbacks
        for call in mock_response_future.add_callbacks.call_args_list:
            callback = call[1]["callback"]
            callback([f"row{i}" for i in range(10)])

        # Wait for all to complete
        await asyncio.gather(*tasks)

        duration = time.perf_counter() - start_time

        # With simplified implementation, 100 concurrent ops should be very fast
        # No operation locks means no contention
        assert duration < 0.5  # Should complete in well under 500ms
        assert mock_session.execute_async.call_count == 100

    async def test_simple_close_behavior(self):
        """
        Test simplified close behavior without complex state tracking.

        What this tests:
        ---------------
        1. Close is simple and predictable
        2. Fixed 5-second delay for driver cleanup
        3. Subsequent operations fail immediately
        4. No complex state machine

        Why this matters:
        ----------------
        The simplified implementation uses a simple approach:
        - Set closed flag
        - Wait 5 seconds for driver threads
        - Shutdown underlying session

        This avoids complex tracking of in-flight operations
        and accepts that some operations might fail during
        the shutdown window.
        """
        # Create session
        mock_session = Mock()
        mock_session.shutdown = Mock()
        async_session = AsyncCassandraSession(mock_session)

        # Close should be simple and fast
        start_time = time.perf_counter()
        await async_session.close()
        close_duration = time.perf_counter() - start_time

        # Close includes a 5-second delay to let driver threads finish
        assert 5.0 <= close_duration < 6.0
        assert async_session.is_closed

        # Subsequent operations should fail immediately (no complex checks)
        with pytest.raises(ConnectionError):
            await async_session.execute("SELECT 1")

    async def test_acceptable_race_condition(self):
        """
        Test that we accept reasonable race conditions for simplicity.

        What this tests:
        ---------------
        1. Operations during close might succeed or fail
        2. No guarantees about in-flight operations
        3. Various error outcomes are acceptable
        4. System remains stable regardless

        Why this matters:
        ----------------
        The simplified implementation makes a trade-off:
        - Remove complex operation tracking
        - Accept that close() might interrupt operations
        - Gain significant performance improvement

        This test verifies that the race conditions are
        indeed "reasonable" - they don't crash or corrupt
        state, they just return errors sometimes.
        """
        # Create session
        mock_session = Mock()
        mock_response_future = Mock()
        mock_response_future.has_more_pages = False
        mock_response_future.add_callbacks = Mock()
        mock_response_future.timeout = None
        mock_session.execute_async = Mock(return_value=mock_response_future)
        mock_session.shutdown = Mock()

        async_session = AsyncCassandraSession(mock_session)

        results = []

        async def execute_query():
            """Try to execute during close."""
            try:
                # Start the execute
                task = asyncio.create_task(async_session.execute("SELECT 1"))
                # Give it a moment to start
                await asyncio.sleep(0)

                # Trigger callback if it was registered
                if mock_response_future.add_callbacks.called:
                    args = mock_response_future.add_callbacks.call_args
                    callback = args[1]["callback"]
                    callback(["row1"])

                await task
                results.append("success")
            except ConnectionError:
                results.append("closed")
            except Exception as e:
                # With simplified implementation, we might get driver errors
                # if close happens during execution - this is acceptable
                results.append(f"error: {type(e).__name__}")

        async def close_session():
            """Close after a tiny delay."""
            await asyncio.sleep(0.001)
            await async_session.close()

        # Run concurrently
        await asyncio.gather(execute_query(), close_session(), return_exceptions=True)

        # With simplified implementation, we accept that the result
        # might be success, closed, or a driver error
        assert len(results) == 1
        # Any of these outcomes is acceptable
        assert results[0] in ["success", "closed"] or results[0].startswith("error:")

    async def test_no_complex_state_tracking(self):
        """
        Test that we don't have complex state tracking.

        What this tests:
        ---------------
        1. No _active_operations counter
        2. No _operation_lock for tracking
        3. No _close_event for coordination
        4. Only simple _closed flag and _close_lock

        Why this matters:
        ----------------
        Complex state tracking was removed because:
        - It added overhead to every operation
        - Lock contention hurt performance
        - Perfect tracking wasn't needed for correctness

        This test ensures we maintain the simplified
        design and don't accidentally reintroduce
        complex state management.
        """
        # Create session
        mock_session = Mock()
        async_session = AsyncCassandraSession(mock_session)

        # Check that we don't have complex state attributes
        # These should not exist in simplified implementation
        assert not hasattr(async_session, "_active_operations")
        assert not hasattr(async_session, "_operation_lock")
        assert not hasattr(async_session, "_close_event")

        # Should only have simple state
        assert hasattr(async_session, "_closed")
        assert hasattr(async_session, "_close_lock")  # Single lock for close

    async def test_result_handler_simplified(self):
        """
        Test that result handlers are simplified.

        What this tests:
        ---------------
        1. Handler has minimal state (just lock and rows)
        2. No complex initialization tracking
        3. No result ready events
        4. Thread lock is still necessary for callbacks

        Why this matters:
        ----------------
        AsyncResultHandler bridges driver callbacks to async:
        - Must be thread-safe (callbacks from driver threads)
        - But doesn't need complex state tracking
        - Just needs to safely accumulate results

        The simplified version keeps only what's essential.
        """
        from async_cassandra.result import AsyncResultHandler

        mock_future = Mock()
        mock_future.has_more_pages = False
        mock_future.add_callbacks = Mock()
        mock_future.timeout = None

        handler = AsyncResultHandler(mock_future)

        # Should have minimal state tracking
        assert hasattr(handler, "_lock")  # Thread lock is necessary
        assert hasattr(handler, "rows")

        # Should not have complex state tracking
        assert not hasattr(handler, "_future_initialized")
        assert not hasattr(handler, "_result_ready")

    async def test_streaming_simplified(self):
        """
        Test that streaming result set is simplified.

        What this tests:
        ---------------
        1. Streaming has thread lock for safety
        2. No complex callback tracking
        3. No active callback counters
        4. Minimal state management

        Why this matters:
        ----------------
        Streaming involves multiple callbacks as pages
        are fetched. The simplified implementation:
        - Keeps thread safety (essential)
        - Removes callback counting (not essential)
        - Accepts that close() might interrupt streaming

        This maintains functionality while improving performance.
        """
        from async_cassandra.streaming import AsyncStreamingResultSet, StreamConfig

        mock_future = Mock()
        mock_future.has_more_pages = True
        mock_future.add_callbacks = Mock()

        stream = AsyncStreamingResultSet(mock_future, StreamConfig())

        # Should have thread lock (necessary for callbacks)
        assert hasattr(stream, "_lock")

        # Should not have complex callback tracking
        assert not hasattr(stream, "_active_callbacks")

    async def test_idempotent_close(self):
        """
        Test that close is idempotent with simple implementation.

        What this tests:
        ---------------
        1. Multiple close() calls are safe
        2. Only shuts down once
        3. No errors on repeated close
        4. Simple flag-based implementation

        Why this matters:
        ----------------
        Users might call close() multiple times:
        - In finally blocks
        - In error handlers
        - In cleanup code

        The simple implementation uses a flag to ensure
        shutdown only happens once, without complex locking.
        """
        # Create session
        mock_session = Mock()
        mock_session.shutdown = Mock()
        async_session = AsyncCassandraSession(mock_session)

        # Multiple closes should work without complex locking
        await async_session.close()
        await async_session.close()
        await async_session.close()

        # Should only shutdown once
        assert mock_session.shutdown.call_count == 1

    async def test_no_operation_counting(self):
        """
        Test that we don't count active operations.

        What this tests:
        ---------------
        1. No tracking of in-flight operations
        2. Close doesn't wait for operations
        3. Fixed 5-second delay regardless
        4. Operations might fail during close

        Why this matters:
        ----------------
        Operation counting was removed because:
        - It required locks on every operation
        - Caused contention under load
        - Waiting for operations could hang

        The 5-second delay gives driver threads time
        to finish naturally, without complex tracking.
        """
        # Create session
        mock_session = Mock()
        mock_response_future = Mock()
        mock_response_future.has_more_pages = False
        mock_response_future.add_callbacks = Mock()
        mock_response_future.timeout = None

        # Make execute_async slow to simulate long operation
        async def slow_execute(*args, **kwargs):
            await asyncio.sleep(0.1)
            return mock_response_future

        mock_session.execute_async = Mock(side_effect=lambda *a, **k: mock_response_future)
        mock_session.shutdown = Mock()

        async_session = AsyncCassandraSession(mock_session)

        # Start a query
        query_task = asyncio.create_task(async_session.execute("SELECT 1"))
        await asyncio.sleep(0.01)  # Let it start

        # Close should not wait for operations
        start_time = time.perf_counter()
        await async_session.close()
        close_duration = time.perf_counter() - start_time

        # Close includes a 5-second delay to let driver threads finish
        assert 5.0 <= close_duration < 6.0

        # Query might fail or succeed - both are acceptable
        try:
            # Trigger callback if query is still running
            if mock_response_future.add_callbacks.called:
                callback = mock_response_future.add_callbacks.call_args[1]["callback"]
                callback(["row"])
            await query_task
        except Exception:
            # Error is acceptable if close interrupted it
            pass

    @pytest.mark.benchmark
    async def test_performance_improvement(self):
        """
        Benchmark to show performance improvement with simplified locking.

        What this tests:
        ---------------
        1. Throughput with many concurrent operations
        2. No lock contention slowing things down
        3. >5000 operations per second achievable
        4. Linear scaling with concurrency

        Why this matters:
        ----------------
        This benchmark proves the value of simplification:
        - Complex locking: ~1000 ops/second
        - Simplified: >5000 ops/second

        The 5x improvement justifies accepting some
        edge case race conditions during shutdown.
        Real applications care more about throughput
        than perfect shutdown semantics.
        """
        # This test demonstrates that simplified locking improves performance

        # Create session
        mock_session = Mock()
        mock_response_future = Mock()
        mock_response_future.has_more_pages = False
        mock_response_future.add_callbacks = Mock()
        mock_response_future.timeout = None
        mock_session.execute_async = Mock(return_value=mock_response_future)

        async_session = AsyncCassandraSession(mock_session)

        # Measure throughput
        iterations = 1000
        start_time = time.perf_counter()

        tasks = []
        for i in range(iterations):
            task = asyncio.create_task(async_session.execute(f"SELECT {i}"))
            tasks.append(task)

        # Trigger all callbacks immediately
        await asyncio.sleep(0)
        for call in mock_response_future.add_callbacks.call_args_list:
            callback = call[1]["callback"]
            callback(["row"])

        await asyncio.gather(*tasks)

        duration = time.perf_counter() - start_time
        ops_per_second = iterations / duration

        # With simplified locking, should handle >5000 ops/second
        assert ops_per_second > 5000
        print(f"Performance: {ops_per_second:.0f} ops/second")
