import asyncio
from typing import List, Optional
import logging

logger = logging.getLogger('app')


class AgentPool:
    """Assistant instance pool manager."""

    def __init__(self, pool_size: int = 5):
        """
        Initialize the assistant instance pool.

        Args:
            pool_size: Number of instances in the pool, defaults to 5
        """
        self.pool_size = pool_size
        self.pool: asyncio.Queue = asyncio.Queue(maxsize=pool_size)
        self.semaphore = asyncio.Semaphore(pool_size)
        self.agents = []  # Keep references to all created instances

    async def initialize(self, agent_factory):
        """
        Initialize the instance pool using the assistant factory function.

        Args:
            agent_factory: Factory function for creating assistant instances
        """
        logger.info(f"Initializing assistant instance pool, size: {self.pool_size}")

        for i in range(self.pool_size):
            try:
                agent = agent_factory()
                await self.pool.put(agent)
                self.agents.append(agent)
                logger.info(f"Assistant instance {i+1}/{self.pool_size} created successfully")
            except Exception as e:
                logger.error(f"Failed to create assistant instance {i+1}: {e}")
                raise

        logger.info("Assistant instance pool initialization completed")

    async def get_agent(self, timeout: Optional[float] = 30.0):
        """
        Get an available assistant instance.

        Args:
            timeout: Timeout in seconds, defaults to 30

        Returns:
            Assistant instance

        Raises:
            asyncio.TimeoutError: Raised when acquisition times out
        """
        try:
            # Use the semaphore to control concurrency
            await asyncio.wait_for(self.semaphore.acquire(), timeout=timeout)
            # Get an instance from the pool
            agent = await asyncio.wait_for(self.pool.get(), timeout=timeout)
            logger.debug(f"Successfully acquired assistant instance, remaining pool size: {self.pool.qsize()}")
            return agent
        except asyncio.TimeoutError:
            logger.error(f"Timed out while acquiring assistant instance ({timeout}s)")
            raise

    async def release_agent(self, agent):
        """
        Return an assistant instance to the pool.

        Args:
            agent: Assistant instance to release
        """
        try:
            await self.pool.put(agent)
            self.semaphore.release()
            logger.debug(f"Released assistant instance, current pool size: {self.pool.qsize()}")
        except Exception as e:
            logger.error(f"Failed to release assistant instance: {e}")
            # Release the semaphore even if putting back fails
            self.semaphore.release()

    def get_pool_stats(self) -> dict:
        """
        Get pool status statistics.

        Returns:
            Dictionary containing pool status information
        """
        return {
            "pool_size": self.pool_size,
            "available_agents": self.pool.qsize(),
            "total_agents": len(self.agents),
            "in_use_agents": len(self.agents) - self.pool.qsize()
        }

    async def shutdown(self):
        """Shut down the instance pool and clean up resources."""
        logger.info("Shutting down assistant instance pool...")

        # Clear the queue
        while not self.pool.empty():
            try:
                agent = self.pool.get_nowait()
                # Call cleanup if the instance provides it
                if hasattr(agent, 'cleanup'):
                    await agent.cleanup()
            except asyncio.QueueEmpty:
                break

        logger.info("Assistant instance pool has been shut down")


# Global instance pool singleton
_global_agent_pool: Optional[AgentPool] = None


def get_agent_pool() -> Optional[AgentPool]:
    """Get the global assistant instance pool."""
    return _global_agent_pool


def set_agent_pool(pool: AgentPool):
    """Set the global assistant instance pool."""
    global _global_agent_pool
    _global_agent_pool = pool


async def init_global_agent_pool(pool_size: int = 5, agent_factory=None):
    """
    Initialize the global assistant instance pool.

    Args:
        pool_size: Pool size
        agent_factory: Instance factory function
    """
    global _global_agent_pool

    if _global_agent_pool is not None:
        logger.warning("Global assistant instance pool already exists, skipping initialization")
        return

    if agent_factory is None:
        raise ValueError("The agent_factory argument is required")

    _global_agent_pool = AgentPool(pool_size=pool_size)
    await _global_agent_pool.initialize(agent_factory)
    logger.info("Global assistant instance pool initialization completed")


async def get_agent_from_pool(timeout: Optional[float] = 30.0):
    """
    Get an assistant instance from the global pool.

    Args:
        timeout: Acquisition timeout in seconds

    Returns:
        Assistant instance
    """
    if _global_agent_pool is None:
        raise RuntimeError("Global assistant instance pool has not been initialized")

    return await _global_agent_pool.get_agent(timeout)


async def release_agent_to_pool(agent):
    """
    Release an assistant instance back to the global pool.

    Args:
        agent: Assistant instance to release
    """
    if _global_agent_pool is None:
        raise RuntimeError("Global assistant instance pool has not been initialized")

    await _global_agent_pool.release_agent(agent)