"""Company fixed FX rates used for CNY-equivalent management summaries."""
from __future__ import annotations

from decimal import ROUND_HALF_UP, Decimal

# Units of each supported currency per CNY. These are company policy rates,
# not a live market feed; display callers must keep the native breakdown too.
FIXED_CURRENCY_PER_CNY: dict[str, Decimal] = {
    "CNY": Decimal("1.000"),
    "JPY": Decimal("20.000"),
    "SGD": Decimal("0.190"),
    "USD": Decimal("0.140"),
}
SUPPORTED_FIXED_CURRENCIES = tuple(FIXED_CURRENCY_PER_CNY)


def to_cny(amount: Decimal, currency: str) -> Decimal:
    rate = FIXED_CURRENCY_PER_CNY.get(currency.upper())
    if rate is None:
        raise ValueError(f"Unsupported fixed-FX currency: {currency}")
    return (amount / rate).quantize(Decimal("0.01"), rounding=ROUND_HALF_UP)