# -*- coding: utf-8 -*-
"""Database module, including the SQLAlchemy database object and DB-related utilities."""
from .compat import basestring
from .extensions import db
from sqlalchemy.types import Integer, TypeDecorator
from decimal import Decimal

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


class CRUDMixin(object):
    """Mixin that adds convenience methods for CRUD (create, read, update, delete) operations."""

    @classmethod
    def create(cls, **kwargs):
        """Create a new record and save it the database."""
        instance = cls(**kwargs)
        return instance.save()

    def update(self, commit=True, **kwargs):
        """Update specific fields of a record."""
        for attr, value in kwargs.items():
            setattr(self, attr, value)
        return commit and self.save() or self

    def save(self, commit=True):
        """Save the record."""
        db.session.add(self)
        if commit:
            db.session.commit()
        return self

    def delete(self, commit=True):
        """Remove the record from the database."""
        db.session.delete(self)
        return commit and db.session.commit()


class Model(CRUDMixin, db.Model):
    """Base model class that includes CRUD convenience methods."""

    __abstract__ = True


class PkModel(Model):
    """Base model class that includes CRUD convenience methods, plus adds a 'primary key' column named ``id``."""

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

    @classmethod
    def get_by_id(cls, record_id):
        """Get record by ID."""
        if any(
            (
                isinstance(record_id, basestring) and record_id.isdigit(),
                isinstance(record_id, (int, float)),
            )
        ):
            return cls.query.get(int(record_id))
        return None


def reference_col(
    tablename, nullable=False, pk_name="id", foreign_key_kwargs=None, column_kwargs=None
):
    """Column that adds primary key foreign key reference.

    Usage: ::

        category_id = reference_col('category')
        category = relationship('Category', backref='categories')
    """
    foreign_key_kwargs = foreign_key_kwargs or {}
    column_kwargs = column_kwargs or {}

    return Column(
        db.ForeignKey(f"{tablename}.{pk_name}", **foreign_key_kwargs),
        nullable=nullable,
        **column_kwargs,
    )


class SqliteDecimal(TypeDecorator):
    # This TypeDecorator use Sqlalchemy Integer as impl. It converts Decimals
    # from Python to Integers which is later stored in Sqlite database.
    # code by zhukailei via https://stackoverflow.com/a/52526847
    impl = Integer

    def __init__(self, scale):
        # It takes a 'scale' parameter, which specifies the number of digits
        # to the right of the decimal point of the number in the column.
        TypeDecorator.__init__(self)
        self.scale = scale
        self.multiplier_int = 10 ** self.scale

    def process_bind_param(self, value, dialect):
        # e.g. value = Column(SqliteDecimal(2)) means a value such as
        # Decimal('12.34') will be converted to 1234 in Sqlite
        if value is not None:
            value = int(Decimal(value) * self.multiplier_int)
        return value

    def process_result_value(self, value, dialect):
        # e.g. Integer 1234 in Sqlite will be converted to Decimal('12.34'),
        # when query takes place.
        if value is not None:
            value = Decimal(value) / self.multiplier_int
        return value
