type/centcount.py

   1 #!/usr/bin/env python3
   2
   3 import re
   4 from typing import Optional, Tuple, TypeVar
   5
   6 import math_utils
   7
   8
   9 class CentCount(object):
  10     """A class for representing monetary amounts potentially with
  11     different currencies meant to avoid floating point rounding
  12     issues by treating amount as a simple integral count of cents.
  13     """
  14
  15     def __init__(self, centcount, currency: str = 'USD', *, strict_mode=False):
  16         self.strict_mode = strict_mode
  17         if isinstance(centcount, str):
  18             ret = CentCount._parse(centcount)
  19             if ret is None:
  20                 raise Exception(f'Unable to parse money string "{centcount}"')
  21             centcount = ret[0]
  22             currency = ret[1]
  23         if isinstance(centcount, float):
  24             centcount = int(centcount * 100.0)
  25         if not isinstance(centcount, int):
  26             centcount = int(centcount)
  27         self.centcount = centcount
  28         if not currency:
  29             self.currency: Optional[str] = None
  30         else:
  31             self.currency = currency
  32
  33     def __repr__(self):
  34         a = float(self.centcount)
  35         a /= 100
  36         a = round(a, 2)
  37         s = f'{a:,.2f}'
  38         if self.currency is not None:
  39             return '%s %s' % (s, self.currency)
  40         else:
  41             return '$%s' % s
  42
  43     def __pos__(self):
  44         return CentCount(centcount=self.centcount, currency=self.currency)
  45
  46     def __neg__(self):
  47         return CentCount(centcount=-self.centcount, currency=self.currency)
  48
  49     def __add__(self, other):
  50         if isinstance(other, CentCount):
  51             if self.currency == other.currency:
  52                 return CentCount(
  53                     centcount=self.centcount + other.centcount, currency=self.currency
  54                 )
  55             else:
  56                 raise TypeError('Incompatible currencies in add expression')
  57         else:
  58             if self.strict_mode:
  59                 raise TypeError('In strict_mode only two moneys can be added')
  60             else:
  61                 return self.__add__(CentCount(other, self.currency))
  62
  63     def __sub__(self, other):
  64         if isinstance(other, CentCount):
  65             if self.currency == other.currency:
  66                 return CentCount(
  67                     centcount=self.centcount - other.centcount, currency=self.currency
  68                 )
  69             else:
  70                 raise TypeError('Incompatible currencies in add expression')
  71         else:
  72             if self.strict_mode:
  73                 raise TypeError('In strict_mode only two moneys can be added')
  74             else:
  75                 return self.__sub__(CentCount(other, self.currency))
  76
  77     def __mul__(self, other):
  78         if isinstance(other, CentCount):
  79             raise TypeError('can not multiply monetary quantities')
  80         else:
  81             return CentCount(
  82                 centcount=int(self.centcount * float(other)), currency=self.currency
  83             )
  84
  85     def __truediv__(self, other):
  86         if isinstance(other, CentCount):
  87             raise TypeError('can not divide monetary quantities')
  88         else:
  89             return CentCount(
  90                 centcount=int(float(self.centcount) / float(other)),
  91                 currency=self.currency,
  92             )
  93
  94     def __int__(self):
  95         return self.centcount.__int__()
  96
  97     def __float__(self):
  98         return self.centcount.__float__() / 100.0
  99
 100     def truncate_fractional_cents(self):
 101         x = int(self)
 102         self.centcount = int(math_utils.truncate_float(x))
 103         return self.centcount
 104
 105     def round_fractional_cents(self):
 106         x = int(self)
 107         self.centcount = int(round(x, 2))
 108         return self.centcount
 109
 110     __radd__ = __add__
 111
 112     def __rsub__(self, other):
 113         if isinstance(other, CentCount):
 114             if self.currency == other.currency:
 115                 return CentCount(
 116                     centcount=other.centcount - self.centcount, currency=self.currency
 117                 )
 118             else:
 119                 raise TypeError('Incompatible currencies in sub expression')
 120         else:
 121             if self.strict_mode:
 122                 raise TypeError('In strict_mode only two moneys can be added')
 123             else:
 124                 return CentCount(
 125                     centcount=int(other) - self.centcount, currency=self.currency
 126                 )
 127
 128     __rmul__ = __mul__
 129
 130     #
 131     # Override comparison operators to also compare currency.
 132     #
 133     def __eq__(self, other):
 134         if other is None:
 135             return False
 136         if isinstance(other, CentCount):
 137             return self.centcount == other.centcount and self.currency == other.currency
 138         if self.strict_mode:
 139             raise TypeError("In strict mode only two CentCounts can be compared")
 140         else:
 141             return self.centcount == int(other)
 142
 143     def __ne__(self, other):
 144         result = self.__eq__(other)
 145         if result is NotImplemented:
 146             return result
 147         return not result
 148
 149     def __lt__(self, other):
 150         if isinstance(other, CentCount):
 151             if self.currency == other.currency:
 152                 return self.centcount < other.centcount
 153             else:
 154                 raise TypeError('can not directly compare different currencies')
 155         else:
 156             if self.strict_mode:
 157                 raise TypeError('In strict mode, only two CentCounts can be compated')
 158             else:
 159                 return self.centcount < int(other)
 160
 161     def __gt__(self, other):
 162         if isinstance(other, CentCount):
 163             if self.currency == other.currency:
 164                 return self.centcount > other.centcount
 165             else:
 166                 raise TypeError('can not directly compare different currencies')
 167         else:
 168             if self.strict_mode:
 169                 raise TypeError('In strict mode, only two CentCounts can be compated')
 170             else:
 171                 return self.centcount > int(other)
 172
 173     def __le__(self, other):
 174         return self < other or self == other
 175
 176     def __ge__(self, other):
 177         return self > other or self == other
 178
 179     def __hash__(self):
 180         return self.__repr__
 181
 182     CENTCOUNT_RE = re.compile(r"^([+|-]?)(\d+)(\.\d+)$")
 183     CURRENCY_RE = re.compile(r"^[A-Z][A-Z][A-Z]$")
 184
 185     @classmethod
 186     def _parse(cls, s: str) -> Optional[Tuple[int, str]]:
 187         centcount = None
 188         currency = None
 189         s = s.strip()
 190         chunks = s.split(' ')
 191         try:
 192             for chunk in chunks:
 193                 if CentCount.CENTCOUNT_RE.match(chunk) is not None:
 194                     centcount = int(float(chunk) * 100.0)
 195                 elif CentCount.CURRENCY_RE.match(chunk) is not None:
 196                     currency = chunk
 197         except Exception:
 198             pass
 199         if centcount is not None and currency is not None:
 200             return (centcount, currency)
 201         elif centcount is not None:
 202             return (centcount, 'USD')
 203         return None
 204
 205     @classmethod
 206     def parse(cls, s: str) -> 'CentCount':
 207         chunks = CentCount._parse(s)
 208         if chunks is not None:
 209             return CentCount(chunks[0], chunks[1])
 210         raise Exception(f'Unable to parse money string "{s}"')