"""Two pre-built engines so pool_starvation (phase-0-base-project-spec.md §7)
can be toggled live, with no restart: the flag picks which already-initialised
pool a request borrows a connection from, rather than resizing a pool in
place (SQLAlchemy pools aren't resizable live)."""
from sqlalchemy.ext.asyncio import async_sessionmaker

from common.db import make_engine

normal_engine = make_engine(pool_size=20, max_overflow=10)
starved_engine = make_engine(pool_size=2, max_overflow=0, pool_timeout=10)

NormalSession = async_sessionmaker(normal_engine, expire_on_commit=False)
StarvedSession = async_sessionmaker(starved_engine, expire_on_commit=False)


def session_factory(starved: bool):
    return StarvedSession() if starved else NormalSession()