import sqlalchemy.orm
from sqlalchemy.dialects.postgresql import UUID


@sqlalchemy.orm.as_declarative()
class Base:
    """
    Standard base class to define a table in a postgresql database

    Default Columns:
        -> id
            - Defines a UUID generated via postgresql's in-built "uuid_generate_v4" function,
            requires the "uuid-ossp" to be installed to the given database. The extension can be installed via
            "CREATE EXTENSION IF NOT EXISTS "uuid-ossp";"
            - May never be null
        -> creation
            - Defines the creation date in ISO 8601 format based on the sqlalchemy DateTime class and generated by the
            database using func.now()
            - May never be null
        -> Modification
            - Defines a ISO 8601 timestamp that is updated anytime the data in a column is modified for a given row
            - Can be null

    Usage:
        This class, "Base", must be inherited by subclasses to define tables within a database. A subclass must define
        a single string with a variable name of "__tablename__" which defines the actual table name within the database.

        -> Example Implementation
            >>> class SomeTable(Base):
            >>>     __tablename__ = "Some Table"
            >>>     data = sqlalchemy.Column(sqlalchemy.String)
    """

    __table__: sqlalchemy.Table

    # This ID column expects the extension "uuid-ossp" to be installed on the postgres DB
    # Can be done via "CREATE EXTENSION IF NOT EXISTS "uuid-ossp";"
    id = sqlalchemy.Column(
        UUID,
        default=sqlalchemy.text("uuid_generate_v4()"),
        primary_key=True,
    )

    creation: sqlalchemy.Column = sqlalchemy.Column(
        sqlalchemy.DateTime(timezone=True),
        key="creation",
        name="creation",
        index=True,
        quote=True,
        unique=False,
        default=None,
        nullable=False,
        primary_key=False,
        autoincrement=False,
        server_default=sqlalchemy.func.now(),
    )

    modification: sqlalchemy.Column = sqlalchemy.Column(
        sqlalchemy.DateTime(timezone=True),
        key="Modification",
        name="modification",
        index=True,
        quote=True,
        unique=False,
        default=None,
        nullable=True,
        onupdate=sqlalchemy.func.now(),
        primary_key=False,
        autoincrement=False
    )