# -*- coding: utf-8 -*-
"""Database module, including the SQLAlchemy database object and DB-related utilities."""
from sqlalchemy.orm import relationship

from .extensions import db

# Alias common SQLAlchemy names
Column = db.Column
relationship = relationship
Model = db.Model


# From Mike Bayer's "Building the app" talk
# https://speakerdeck.com/zzzeek/building-the-app
class SurrogatePK(object):
    """A mixin that adds a surrogate integer 'primary key' column named ``id`` \
        to any declarative-mapped class.
    """

    __table_args__ = {'extend_existing': True}

    id = db.Column(db.Integer, primary_key=True)

    @classmethod
    def get_by_id(cls, record_id):
        """Get record by ID."""
        if any(
            (isinstance(record_id, (str, bytes)) and record_id.isdigit(),
             isinstance(record_id, (int, float))),
        ):
            return cls.query.get(int(record_id))


def reference_col(tablename, nullable=False, pk_name='id', **kwargs):
    """Column that adds primary key foreign key reference.

    Usage: ::

        category_id = reference_col('category')
        category = relationship('Category', backref='categories')
    """
    return db.Column(
        db.ForeignKey('{0}.{1}'.format(tablename, pk_name)),
        nullable=nullable, **kwargs)