"""Database connection and session management

Supports MySQL database with connection pooling.
All tables use 'tr_' prefix to avoid conflicts in shared database.
"""
from contextlib import contextmanager
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, Session
from app.core.config import get_settings

settings = get_settings()

# Create engine with MySQL connection pooling
# Pool settings are configurable via environment variables
engine = create_engine(
    settings.DATABASE_URL,
    pool_size=settings.DB_POOL_SIZE,
    max_overflow=settings.DB_MAX_OVERFLOW,
    pool_timeout=settings.DB_POOL_TIMEOUT,
    pool_pre_ping=True,  # Verify connection before using
    pool_recycle=settings.DB_POOL_RECYCLE,
    echo=settings.DEBUG,
)

# Create session factory
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

# Base class for models
Base = declarative_base()


def get_db():
    """FastAPI dependency to get database session"""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


@contextmanager
def get_db_context() -> Session:
    """Context manager for short-lived database sessions.

    Use this for operations that need a database session but should
    not hold onto it for the entire request/connection lifecycle.

    Example:
        with get_db_context() as db:
            result = db.query(Model).filter(...).first()
    """
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()