feat(CORE-001A): add decimal unit value foundation
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Bu5hm4nn
19
app/domain/__init__.py
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19
app/domain/__init__.py
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from app.domain.units import (
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BaseCurrency,
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Money,
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PricePerWeight,
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Weight,
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WeightUnit,
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decimal_from_float,
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to_decimal,
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)
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__all__ = [
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"BaseCurrency",
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"WeightUnit",
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"Money",
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"Weight",
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"PricePerWeight",
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"to_decimal",
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"decimal_from_float",
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]
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245
app/domain/units.py
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245
app/domain/units.py
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from __future__ import annotations
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from dataclasses import dataclass
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from decimal import Decimal
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from enum import StrEnum
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class BaseCurrency(StrEnum):
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USD = "USD"
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EUR = "EUR"
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CHF = "CHF"
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class WeightUnit(StrEnum):
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GRAM = "g"
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KILOGRAM = "kg"
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OUNCE_TROY = "ozt"
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GRAMS_PER_KILOGRAM = Decimal("1000")
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GRAMS_PER_TROY_OUNCE = Decimal("31.1034768")
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DecimalLike = Decimal | int | str
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def to_decimal(value: DecimalLike) -> Decimal:
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if isinstance(value, bool):
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raise TypeError("Boolean values are not valid Decimal inputs")
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if isinstance(value, Decimal):
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amount = value
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elif isinstance(value, int):
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amount = Decimal(value)
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elif isinstance(value, str):
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amount = Decimal(value)
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else:
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raise TypeError(f"Unsupported decimal input type: {type(value)!r}")
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if not amount.is_finite():
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raise ValueError("Decimal value must be finite")
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return amount
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def decimal_from_float(value: float) -> Decimal:
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if not isinstance(value, float):
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raise TypeError(f"Expected float, got {type(value)!r}")
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amount = Decimal(str(value))
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if not amount.is_finite():
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raise ValueError("Decimal value must be finite")
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return amount
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def _coerce_currency(value: BaseCurrency | str) -> BaseCurrency:
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if isinstance(value, BaseCurrency):
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return value
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try:
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return BaseCurrency(value)
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except ValueError as exc:
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raise ValueError(f"Invalid currency: {value!r}") from exc
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def _coerce_weight_unit(value: WeightUnit | str) -> WeightUnit:
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if isinstance(value, WeightUnit):
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return value
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try:
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return WeightUnit(value)
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except ValueError as exc:
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raise ValueError(f"Invalid weight unit: {value!r}") from exc
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def weight_unit_factor(unit: WeightUnit) -> Decimal:
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if unit is WeightUnit.GRAM:
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return Decimal("1")
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if unit is WeightUnit.KILOGRAM:
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return GRAMS_PER_KILOGRAM
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if unit is WeightUnit.OUNCE_TROY:
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return GRAMS_PER_TROY_OUNCE
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raise ValueError(f"Unsupported weight unit: {unit}")
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def convert_weight(amount: Decimal, from_unit: WeightUnit, to_unit: WeightUnit) -> Decimal:
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if from_unit is to_unit:
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return amount
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grams = amount * weight_unit_factor(from_unit)
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return grams / weight_unit_factor(to_unit)
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def convert_price_per_weight(amount: Decimal, from_unit: WeightUnit, to_unit: WeightUnit) -> Decimal:
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if from_unit is to_unit:
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return amount
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return amount * weight_unit_factor(to_unit) / weight_unit_factor(from_unit)
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@dataclass(frozen=True, slots=True)
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class Money:
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amount: Decimal
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currency: BaseCurrency | str
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def __post_init__(self) -> None:
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object.__setattr__(self, "amount", to_decimal(self.amount))
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object.__setattr__(self, "currency", _coerce_currency(self.currency))
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@classmethod
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def zero(cls, currency: BaseCurrency) -> Money:
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return cls(amount=Decimal("0"), currency=currency)
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def assert_currency(self, currency: BaseCurrency) -> Money:
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if self.currency is not currency:
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raise ValueError(f"Currency mismatch: {self.currency} != {currency}")
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return self
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def __add__(self, other: object) -> Money:
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if not isinstance(other, Money):
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return NotImplemented
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if self.currency is not other.currency:
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raise ValueError(f"Currency mismatch: {self.currency} != {other.currency}")
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return Money(amount=self.amount + other.amount, currency=self.currency)
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def __sub__(self, other: object) -> Money:
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if not isinstance(other, Money):
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return NotImplemented
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if self.currency is not other.currency:
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raise ValueError(f"Currency mismatch: {self.currency} != {other.currency}")
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return Money(amount=self.amount - other.amount, currency=self.currency)
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def __mul__(self, other: object) -> Money:
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if isinstance(other, bool):
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return NotImplemented
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if isinstance(other, Decimal):
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return Money(amount=self.amount * other, currency=self.currency)
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if isinstance(other, int):
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return Money(amount=self.amount * Decimal(other), currency=self.currency)
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return NotImplemented
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def __rmul__(self, other: object) -> Money:
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return self.__mul__(other)
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def __truediv__(self, other: object) -> Money:
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if isinstance(other, bool):
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return NotImplemented
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if isinstance(other, Decimal):
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return Money(amount=self.amount / other, currency=self.currency)
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if isinstance(other, int):
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return Money(amount=self.amount / Decimal(other), currency=self.currency)
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return NotImplemented
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def __neg__(self) -> Money:
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return Money(amount=-self.amount, currency=self.currency)
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@dataclass(frozen=True, slots=True)
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class Weight:
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amount: Decimal
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unit: WeightUnit | str
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def __post_init__(self) -> None:
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object.__setattr__(self, "amount", to_decimal(self.amount))
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object.__setattr__(self, "unit", _coerce_weight_unit(self.unit))
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def to_unit(self, unit: WeightUnit) -> Weight:
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return Weight(amount=convert_weight(self.amount, self.unit, unit), unit=unit)
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def __add__(self, other: object) -> Weight:
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if not isinstance(other, Weight):
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return NotImplemented
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other_converted = other.to_unit(self.unit)
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return Weight(amount=self.amount + other_converted.amount, unit=self.unit)
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def __sub__(self, other: object) -> Weight:
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if not isinstance(other, Weight):
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return NotImplemented
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other_converted = other.to_unit(self.unit)
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return Weight(amount=self.amount - other_converted.amount, unit=self.unit)
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def __mul__(self, other: object) -> Weight | Money:
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if isinstance(other, bool):
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return NotImplemented
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if isinstance(other, Decimal):
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return Weight(amount=self.amount * other, unit=self.unit)
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if isinstance(other, int):
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return Weight(amount=self.amount * Decimal(other), unit=self.unit)
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if isinstance(other, PricePerWeight):
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adjusted_weight = self.to_unit(other.per_unit)
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return Money(amount=adjusted_weight.amount * other.amount, currency=other.currency)
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return NotImplemented
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def __rmul__(self, other: object) -> Weight:
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if isinstance(other, bool):
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return NotImplemented
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if isinstance(other, Decimal):
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return Weight(amount=self.amount * other, unit=self.unit)
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if isinstance(other, int):
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return Weight(amount=self.amount * Decimal(other), unit=self.unit)
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return NotImplemented
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def __truediv__(self, other: object) -> Weight:
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if isinstance(other, bool):
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return NotImplemented
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if isinstance(other, Decimal):
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return Weight(amount=self.amount / other, unit=self.unit)
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if isinstance(other, int):
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return Weight(amount=self.amount / Decimal(other), unit=self.unit)
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return NotImplemented
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@dataclass(frozen=True, slots=True)
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class PricePerWeight:
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amount: Decimal
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currency: BaseCurrency | str
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per_unit: WeightUnit | str
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def __post_init__(self) -> None:
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amount = to_decimal(self.amount)
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if amount < 0:
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raise ValueError("PricePerWeight amount must be non-negative")
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object.__setattr__(self, "amount", amount)
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object.__setattr__(self, "currency", _coerce_currency(self.currency))
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object.__setattr__(self, "per_unit", _coerce_weight_unit(self.per_unit))
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def to_unit(self, unit: WeightUnit) -> PricePerWeight:
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return PricePerWeight(
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amount=convert_price_per_weight(self.amount, self.per_unit, unit),
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currency=self.currency,
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per_unit=unit,
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)
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def __mul__(self, other: object) -> Money | PricePerWeight:
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if isinstance(other, bool):
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return NotImplemented
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if isinstance(other, Weight):
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adjusted_weight = other.to_unit(self.per_unit)
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return Money(amount=adjusted_weight.amount * self.amount, currency=self.currency)
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if isinstance(other, Decimal):
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return PricePerWeight(amount=self.amount * other, currency=self.currency, per_unit=self.per_unit)
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if isinstance(other, int):
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return PricePerWeight(amount=self.amount * Decimal(other), currency=self.currency, per_unit=self.per_unit)
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return NotImplemented
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def __rmul__(self, other: object) -> PricePerWeight:
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if isinstance(other, bool):
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return NotImplemented
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if isinstance(other, Decimal):
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return PricePerWeight(amount=self.amount * other, currency=self.currency, per_unit=self.per_unit)
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if isinstance(other, int):
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return PricePerWeight(amount=self.amount * Decimal(other), currency=self.currency, per_unit=self.per_unit)
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return NotImplemented
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