"""
See the Database class docstring for details on this module
"""

import sqlalchemy.orm
import sqlalchemy.ext.asyncio

from .base import Base


class Database:
    """
    A class that is a composition of several other classes useful for accessing and manipulating a Postgresql database
    asynchronously.

    Usage:
        asyncdb must first be initialized with a given postgresql connection url like so:
            >>> db = asyncdb("postgresql://localhost:5432/postgres")
        After asyncdb has been initialized two important objects that are composed into asyncdb become available:
            -> async_engine
                - Relevant for handling the creation and deletion of many tables at once, for example:
                    >>> async with self.async_engine.begin() as conn:
                    >>>     await conn.run_sync(self.Base.metadata.drop_all)
                    >>>     await conn.run_sync(self.Base.metadata.create_all)
                - See the sqlalchemy documentation for futher details at
                https://docs.sqlalchemy.org/en/14/orm/extensions/asyncio.html#sqlalchemy.ext.asyncio.AsyncEngine
            -> async_session
                - Relevant for properly manipulating rows and columns within the database, for example:
                    >>> from sqlalchemy import orm as sqlalchemy_orm
                    >>> from sqlalchemy import future as sqlalchemy_future
                    >>>
                    >>> async with db.async_session() as session:
                    >>> async with session.begin():
                    >>>     session.add_all(
                    >>>         [
                    >>>             A(bs=[B(), B()], data="a1"),
                    >>>             A(bs=[B()], data="a2"),
                    >>>             A(bs=[B(), B()], data="a3"),
                    >>>         ]
                    >>>     )
                    >>>
                    >>> stmt = sqlalchemy_future.select(A).options(sqlalchemy_orm.selectinload(A.bs))
                    >>>
                    >>> result = await session.execute(stmt)
                    >>> await session.commit()
                - See the sqlalchemy documentation for further details at
                https://docs.sqlalchemy.org/en/14/orm/extensions/asyncio.html#sqlalchemy.ext.asyncio.AsyncConnection
    """

    Base = Base

    def __init__(
            self,
            db_url: str,
            async_session_expire_on_commit: bool = False,
            **engine_kwargs
    ):
        """
        Constructor for the class

        Args:
            db_url: A string defining a standard postgresql url, for instance: postgresql://localhost:5432/postgres
            async_session_expire_on_commit: A boolean for determining if the given connection via a async
                context manager should close after the session.commit() function is called.
            **engine_kwargs: Arguments that can be passed to sqlalchemy's create_async_engine function
        """
        self.connection_url = db_url
        self.async_engine = sqlalchemy.ext.asyncio.create_async_engine(
            self.connection_url,
            **engine_kwargs
        )
        self.async_session = sqlalchemy.orm.sessionmaker(
            self.async_engine,
            expire_on_commit=async_session_expire_on_commit,
            class_=sqlalchemy.ext.asyncio.AsyncSession
        )

    @property
    def connection_url(self) -> str:
        """
        Getter for self.connection_url

        Returns:
            The postgresql connection string
        """
        return self._connection_url

    @connection_url.setter
    def connection_url(self, url: str):
        """
        Converts a given typical postgresql string to our asynchronous driver used with sqlalchemy

        Args:
            url: The given normal postgresql URL

        Returns:
            Nothing, setter for self.connection_url in the constructor
        """
        self._connection_url = f"postgresql+asyncpg://{url.split('://')[-1]}"