import os

from sqlalchemy import create_engine
from sqlalchemy.engine import URL
from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker


def build_database_url() -> URL | str:
    """Prefer DATABASE_URL; otherwise build a safely escaped URL from parts.

    Passwords are passed as URL components (not string interpolation), so
    characters like '@', ':', '/', '#' and '%' cannot corrupt the hostname.
    """
    database_url = os.environ.get("DATABASE_URL")
    if database_url:
        return database_url
    return URL.create(
        "postgresql+psycopg",
        username=os.environ.get("POSTGRES_USER", "time_track"),
        password=os.environ.get("POSTGRES_PASSWORD", ""),
        host=os.environ.get("POSTGRES_HOST", "localhost"),
        port=int(os.environ.get("POSTGRES_PORT", "5432")),
        database=os.environ.get("POSTGRES_DB", "time_track"),
    )


engine = create_engine(build_database_url(), pool_pre_ping=True)
SessionLocal = sessionmaker(bind=engine, autocommit=False, autoflush=False)


class Base(DeclarativeBase):
    pass


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