app/core/database.py

"""
Database connection pooling and optimization module
"""

import logging
import os
from contextlib import asynccontextmanager
from collections.abc import AsyncGenerator

import redis
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.pool import QueuePool

logger = logging.getLogger(__name__)

# Database configuration
DATABASE_URL = os.getenv("DATABASE_URL", "postgresql+asyncpg://postgres:password@database:5432/zenith")
REDIS_URL = os.getenv("REDIS_URL", "redis://cache-service:6379")

# Connection pool configuration
POOL_SIZE = int(os.getenv("DB_POOL_SIZE", "20"))
MAX_OVERFLOW = int(os.getenv("DB_MAX_OVERFLOW", "30"))
POOL_TIMEOUT = int(os.getenv("DB_POOL_TIMEOUT", "30"))
POOL_RECYCLE = int(os.getenv("DB_POOL_RECYCLE", "3600"))

# Create optimized async engine with connection pooling
engine = create_async_engine(
    DATABASE_URL,
    poolclass=QueuePool,
    pool_size=POOL_SIZE,
    max_overflow=MAX_OVERFLOW,
    pool_timeout=POOL_TIMEOUT,
    pool_recycle=POOL_RECYCLE,
    echo=os.getenv("DB_ECHO", "false").lower() == "true",
    pool_pre_ping=True,
    server_side_cursors=True,
)

# Create session factory
AsyncSessionLocal = sessionmaker(
    bind=engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autoflush=False,
    autocommit=False,
)


@asynccontextmanager
async def get_db_session() -> AsyncGenerator[AsyncSession, None]:
    """Async context manager for database sessions"""
    async with AsyncSessionLocal() as session:
        try:
            yield session
        except Exception as e:
            logger.error(f"Database session error: {e}")
            await session.rollback()
            raise
        finally:
            await session.close()


# Redis connection for caching
redis_client = redis.from_url(REDIS_URL, decode_responses=True)


async def get_redis():
    """Get Redis connection"""
    return redis_client


class DatabaseManager:
    """Enhanced database manager with connection pooling"""

    def __init__(self):
        self.engine = engine
        self.redis = redis_client

    async def health_check(self) -> dict:
        """Check database and cache health"""
        try:
            # Database health
            async with get_db_session() as session:
                await session.execute("SELECT 1")
                db_status = "healthy"
        except Exception as e:
            db_status = f"unhealthy: {e}"

        # Redis health
        try:
            await self.redis.ping()
            redis_status = "healthy"
        except Exception as e:
            redis_status = f"unhealthy: {e}"

        return {
            "database": db_status,
            "redis": redis_status,
            "pool_size": POOL_SIZE,
            "active_connections": self.engine.pool.size() if hasattr(self.engine.pool, "size") else "unknown",
        }

    def get_pool_stats(self) -> dict:
        """Get connection pool statistics"""
        if hasattr(self.engine.pool, "size"):
            return {
                "size": self.engine.pool.size(),
                "checked_in": self.engine.pool.checkedin(),
                "checked_out": self.engine.pool.checkedout(),
                "overflow": self.engine.pool.overflow(),
                "invalid": self.engine.pool.invalid(),
            }
        return {"status": "pool stats not available"}


# Global database manager instance
db_manager = DatabaseManager()