import os
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
from sqlalchemy.orm import DeclarativeBase


def _to_asyncpg(url: str) -> str:
    if url.startswith("postgresql://"):
        return url.replace("postgresql://", "postgresql+asyncpg://", 1)
    return url


# Runtime connection — the scoped `kds` DB role, used for every request via
# get_db(). Only has SELECT/INSERT/UPDATE/DELETE on kds_tickets,
# kds_course_bumps and the specific kitchen_settings columns KDS needs (see
# deploy_kds grants) — it cannot read the rest of kitchen_db.
DATABASE_URL = _to_asyncpg(os.getenv(
    "DATABASE_URL",
    "postgresql://kitchen:kitchen_secret@localhost:5432/kitchen_gp"
))

# Migration connection — the privileged `kitchen` DB role. Used ONLY at
# startup to create KDS's own tables and ALTER kitchen_settings (adding KDS
# columns). Never used for request handling. Falls back to DATABASE_URL for
# local/dev convenience, but production must set this separately once the
# `kds` role is scoped down (see port log E17/task: KDS DB role split).
MIGRATION_DATABASE_URL = _to_asyncpg(
    os.getenv("MIGRATION_DATABASE_URL") or os.getenv(
        "DATABASE_URL", "postgresql://kitchen:kitchen_secret@localhost:5432/kitchen_gp"
    )
)

# `engine` stays the name existing migration files (`from database import
# engine`) already import — no changes needed there. It's bound to the
# privileged connection.
engine = create_async_engine(MIGRATION_DATABASE_URL, echo=False)

runtime_engine = create_async_engine(
    DATABASE_URL,
    echo=False,
    pool_size=10,      # Default is 5
    max_overflow=20,   # Default is 10 - allows burst to 30 connections
    pool_pre_ping=True  # Verify connections are alive before use
)

AsyncSessionLocal = async_sessionmaker(
    runtime_engine,
    class_=AsyncSession,
    expire_on_commit=False
)


class Base(DeclarativeBase):
    pass


async def get_db():
    async with AsyncSessionLocal() as session:
        try:
            yield session
        finally:
            await session.close()