from functools import cached_property

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

from ttfrog.path import database
from ttfrog.db.schema import metadata


class SQLDatabaseManager:
    """
    A context manager for working with sqllite database.
    """
    @cached_property
    def url(self):
        return f"sqlite:///{database()}"

    @cached_property
    def engine(self):
        return create_engine(self.url, future=True)

    @cached_property
    def DBSession(self):
        maker = sessionmaker(bind=self.engine, future=True, autoflush=True)
        return scoped_session(maker)

    @cached_property
    def tables(self):
        return dict((t.name, t) for t in metadata.sorted_tables)

    def query(self, *args, **kwargs):
        return self.DBSession.query(*args, **kwargs)

    def init_model(self, engine=None):
        metadata.create_all(bind=engine or self.engine)
        return self.DBSession

    def __getattr__(self, name: str):
        try:
            return self.tables[name]
        except KeyError:
            raise AttributeError(f"{self} does not contain the attribute '{name}'.")

    def __enter__(self):
        self.init_model(self.engine)
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        if self.DBSession:
            self.DBSession.close()


db = SQLDatabaseManager()
session = db.DBSession