manyi/apilib/quantity.py

# -*- coding: utf-8 -*-
#!/usr/bin/env python

from functools import total_ordering

from bson.decimal128 import Decimal128

from apilib.numerics import force_decimal, UnitBase, quantize


@total_ordering
class Quantity(UnitBase):
    """
    主要用来记录消费的数额
    """

    def __init__(self, amount, places='0.0001'):

        if isinstance(amount, Quantity):
            self._amount = amount.amount

        self._amount = quantize(force_decimal(amount), places=places)

    @property
    def amount(self):
        return self._amount

    @property
    def mongo_amount(self):
        return Decimal128(self._amount)

    def _format(self, string):
        # type:(str)->str
        return string.format(type=self.__class__.__name__)

    def __str__(self):
        return u'{amount}'.format(amount=self._amount)

    def __repr__(self):
        return '{type} {amount}'.format(type=self.__class__.__name__, amount=self._amount)

    def __eq__(self, other):
        if isinstance(other, Quantity):
            return self._amount == other._amount
        else:
            raise TypeError(self._format('{type} can only be compared(__eq__) with another {type}'))

    def __lt__(self, other):
        if isinstance(other, Quantity):
            return self._amount < other._amount
        else:
            raise TypeError(self._format('{type} can only be compared(__lt__) with another {type}'))

    def __mul__(self, other):
        if isinstance(other, Quantity):
            raise TypeError(self._format('{type} cannot be multiplied by {type}'))
        else:
            return self.__class__(self.amount * other)

    def __div__(self, other):
        if isinstance(other, Quantity):
            raise TypeError(self._format('{type} cannot be divided by {type}'))
        else:
            return self.__class__(self.amount / other)

    def __add__(self, other):
        if isinstance(other, Quantity):
            return self.__class__(self._amount + other._amount)
        else:
            raise TypeError(self._format('{type} cannot be added to {type}'))

    def __sub__(self, other):
        if isinstance(other, Quantity):
            return self.__class__(self._amount - other._amount)
        else:
            raise TypeError(self._format('{type} cannot be subtracted to {type}'))

    def __float__(self):
        return float(self.amount)