from collections.abc import Generator

from sqlalchemy import create_engine
from sqlalchemy.orm import Session, sessionmaker

from app.core.config import get_settings

from .base import Base


settings = get_settings()

engine = create_engine(settings.database_url, pool_pre_ping=True, pool_recycle=3600)
SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, expire_on_commit=False)

legacy_engine = (
    create_engine(settings.legacy_database_url, pool_pre_ping=True, pool_recycle=3600)
    if settings.legacy_database_url
    else None
)
LegacySessionLocal = (
    sessionmaker(bind=legacy_engine, autoflush=False, autocommit=False, expire_on_commit=False)
    if legacy_engine
    else None
)

__all__ = [
    "Base",
    "LegacySessionLocal",
    "SessionLocal",
    "engine",
    "get_db",
    "get_legacy_db",
    "legacy_engine",
]


def get_db() -> Generator[Session, None, None]:
    """Yield an application database session for FastAPI dependencies."""

    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


def get_legacy_db() -> Generator[Session, None, None]:
    """Yield a legacy database session when the legacy connection is configured."""

    if LegacySessionLocal is None:
        raise RuntimeError("LEGACY_DATABASE_URL is not configured")
    db = LegacySessionLocal()
    try:
        yield db
    finally:
        db.close()