# ================================================================
# services/forecasting/app/core/database.py
# ================================================================
"""
Database configuration for forecasting service
"""

import structlog
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
from sqlalchemy import text
from typing import AsyncGenerator

from app.core.config import settings
from shared.database.base import Base, DatabaseManager

logger = structlog.get_logger()

# Create async engine
async_engine = create_async_engine(
    settings.DATABASE_URL,
    echo=settings.DEBUG,
    pool_size=10,
    max_overflow=20,
    pool_pre_ping=True,
    pool_recycle=3600
)

# Create async session factory
AsyncSessionLocal = async_sessionmaker(
    bind=async_engine,
    class_=AsyncSession,
    expire_on_commit=False
)

async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """Get database session"""
    async with AsyncSessionLocal() as session:
        try:
            yield session
        except Exception as e:
            await session.rollback()
            logger.error("Database session error", error=str(e))
            raise
        finally:
            await session.close()

async def init_database():
    """Initialize database tables"""
    try:
        async with async_engine.begin() as conn:
            # Import all models to ensure they are registered
            from app.models.forecast import ForecastBatch, Forecast
            from app.models.prediction import PredictionBatch, Prediction

            # Create all tables
            await conn.run_sync(Base.metadata.create_all)

        logger.info("Forecasting database initialized successfully")
    except Exception as e:
        logger.error("Failed to initialize forecasting database", error=str(e))
        raise

async def get_db_health() -> bool:
    """Check database health"""
    try:
        async with async_engine.begin() as conn:
            await conn.execute(text("SELECT 1"))
        return True
    except Exception as e:
        logger.error("Database health check failed", error=str(e))
        return False


async def get_connection_pool_stats() -> dict:
    """
    Get current connection pool statistics for monitoring.

    Returns:
        Dictionary with pool statistics including usage and capacity
    """
    try:
        pool = async_engine.pool

        # Get pool stats
        stats = {
            "pool_size": pool.size(),
            "checked_in_connections": pool.checkedin(),
            "checked_out_connections": pool.checkedout(),
            "overflow_connections": pool.overflow(),
            "total_connections": pool.size() + pool.overflow(),
            "max_capacity": 10 + 20,  # pool_size + max_overflow
            "usage_percentage": round(((pool.size() + pool.overflow()) / 30) * 100, 2)
        }

        # Add health status
        if stats["usage_percentage"] > 90:
            stats["status"] = "critical"
            stats["message"] = "Connection pool near capacity"
        elif stats["usage_percentage"] > 80:
            stats["status"] = "warning"
            stats["message"] = "Connection pool usage high"
        else:
            stats["status"] = "healthy"
            stats["message"] = "Connection pool healthy"

        return stats
    except Exception as e:
        logger.error("Failed to get connection pool stats", error=str(e))
        return {
            "status": "error",
            "message": f"Failed to get pool stats: {str(e)}"
        }

# Database manager instance for service_base compatibility
database_manager = DatabaseManager(
    database_url=settings.DATABASE_URL,
    service_name="forecasting-service",
    pool_size=10,
    max_overflow=20,
    echo=settings.DEBUG
)