import os
from pathlib import Path

from sqlalchemy import create_engine, event
from sqlalchemy.orm import DeclarativeBase, sessionmaker

# The one database. It is SQLite, on this machine, in a file.
#
# Upstream could also point at a server database — `AIDND_DATABASE_URL` or the
# platform-conventional `DATABASE_URL`, normalised onto psycopg3, with
# pre-ping for a serverless Postgres that suspends when idle. That existed for
# a hosted deployment. M2 removed it along with the deployment: a local
# single-user storyteller has one reader, and a network database would be one
# more thing that has to be running, and one more place the story lives.
#
# `AIDND_DB_PATH` stays. It is how the Docker image puts the database on a
# volume, and how a test points at a throwaway file.
_env_db_path = os.environ.get("AIDND_DB_PATH")
DB_PATH = (
    Path(_env_db_path).resolve()
    if _env_db_path
    else Path(__file__).resolve().parent.parent / "data.db"
)

DB_PATH.parent.mkdir(parents=True, exist_ok=True)
engine = create_engine(
    f"sqlite:///{DB_PATH}",
    connect_args={"check_same_thread": False},
)


@event.listens_for(engine, "connect")
def _enable_sqlite_foreign_keys(dbapi_connection, _record):
    # SQLite ships with foreign keys OFF per connection; without this every
    # ondelete=CASCADE/SET NULL in models.py is silently ignored.
    cursor = dbapi_connection.cursor()
    cursor.execute("PRAGMA foreign_keys=ON")
    cursor.close()


SessionLocal = sessionmaker(bind=engine, autoflush=False, expire_on_commit=False)


class Base(DeclarativeBase):
    pass


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