testing new features

cashflow_model/currency.py

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+from dataclasses import dataclass
+
+CURRENCY_SYMBOLS = {
+    "RUB": "₽",
+    "USD": "$",
+    "EUR": "€",
+    "GBP": "£",
+    "CNY": "¥",
+    "JPY": "¥",
+    "KZT": "₸",
+    "UAH": "₴",
+}
+
+
+@dataclass
+class ExchangeRate:
+    from_currency: str = "USD"
+    to_currency: str = "RUB"
+    rate: float = 80.0
+
+    def to_dict(self) -> dict:
+        return {
+            "from_currency": self.from_currency,
+            "to_currency": self.to_currency,
+            "rate": self.rate,
+        }
+
+    @classmethod
+    def from_dict(cls, data: dict) -> "ExchangeRate":
+        return cls(
+            from_currency=data.get("from_currency", "USD"),
+            to_currency=data.get("to_currency", "RUB"),
+            rate=data.get("rate", 80.0),
+        )
+
+
+DEFAULT_RATES: list[ExchangeRate] = [
+    ExchangeRate(from_currency="USD", to_currency="RUB", rate=80.0),
+]
+
+
+class CurrencyError(Exception):
+    pass
+
+
+class CurrencyConverter:
+    def __init__(self, rates: list[ExchangeRate] | None = None):
+        self._rates: dict[tuple[str, str], float] = {}
+        if rates:
+            for r in rates:
+                self.set_rate(r.from_currency, r.to_currency, r.rate)
+
+    def set_rate(self, from_currency: str, to_currency: str, rate: float) -> None:
+        if rate <= 0:
+            raise CurrencyError(f"Rate must be positive: {rate}")
+        self._rates[(from_currency, to_currency)] = rate
+        inverse = 1.0 / rate
+        self._rates[(to_currency, from_currency)] = inverse
+
+    def get_rate(self, from_currency: str, to_currency: str) -> float:
+        if from_currency == to_currency:
+            return 1.0
+        try:
+            return self._rates[(from_currency, to_currency)]
+        except KeyError:
+            raise CurrencyError(f"No exchange rate: {from_currency} → {to_currency}")
+
+    def convert(self, amount: float, from_currency: str, to_currency: str) -> float:
+        if from_currency == to_currency:
+            return amount
+        rate = self.get_rate(from_currency, to_currency)
+        return round(amount * rate, 2)
+
+    def get_symbol(self, currency: str) -> str:
+        return CURRENCY_SYMBOLS.get(currency, currency)
+
+    @classmethod
+    def with_defaults(cls) -> "CurrencyConverter":
+        return cls(DEFAULT_RATES)