more methods and tests

xexe/exchange_rates.py

@@ -3,7 +3,7 @@ from decimal import Decimal
 from numbers import Number
 from typing import Iterable, Set, Union
 
-from money.currency import Currency
+from money.currency import Currency, CurrencyHelper
 from money.money import Money
 
 
@@ -13,7 +13,7 @@ class ExchangeRate:
         self,
         from_currency: Currency,
         to_currency: Currency,
-        rate: Union[Money, Number],
+        rate: Union[Money, Number, str],
         rate_date: datetime.date,
     ) -> None:
         self.from_currency = from_currency
@@ -66,26 +66,64 @@ class ExchangeRates:
         self._rate_index[new_rate.descriptor] = new_rate
 
     def __iter__(self):
-        return iter(self._rate_index.values())
+        return iter(list(self._rate_index.values()))
 
     def __len__(self):
         return len(self._rate_index)
 
+    def __contains__(self, rate) -> bool:
+        if not isinstance(rate, ExchangeRate):
+            raise TypeError("ExchangeRates can only hold Rates.")
 
-def add_equal_rates(rates: ExchangeRates) -> ExchangeRates:
+        if rate.descriptor in self._rate_index:
+            return True
+
+        return False
+
+    def is_rate_present(self, rate: ExchangeRate) -> bool:
+        if rate.descriptor in self._rate_index:
+            return True
+
+        return False
+
+    def __getitem__(self, rate_descriptor) -> ExchangeRate:
+        return self._rate_index[rate_descriptor]
+
+
+def add_equal_rates(rates: ExchangeRates, overwrite: bool = False) -> ExchangeRates:
 
     present_currencies = rates.present_currencies
     present_dates = rates.present_dates
 
     for date in present_dates:
         for currency in present_currencies:
-            rates.add_rate(
-                ExchangeRate(
-                    from_currency=currency,
-                    to_currency=currency,
-                    rate=Money(1, currency),
-                    rate_date=date,
-                )
+            new_rate = ExchangeRate(
+                from_currency=currency,
+                to_currency=currency,
+                rate=Money(1, currency),
+                rate_date=date,
             )
+            if new_rate in rates and not overwrite:
+                continue
+            rates.add_rate(new_rate)
+
+    return rates
+
+
+def add_inverse_rates(rates: ExchangeRates) -> ExchangeRates:
+
+    # Hey, I haven't thought properly what happens here if the inverse rate is
+    # *already* present in the rates set. It's probably going to be fucky. I
+    # would advise only running this against sets where you don't have inverse
+    # rates already present.
+
+    for rate in rates:
+        inverse_rate = ExchangeRate(
+            from_currency=rate.to_currency,
+            to_currency=rate.from_currency,
+            rate_date=rate.rate_date,
+            rate=f"{1 / rate.amount:.{CurrencyHelper.decimal_precision_for_currency(rate.from_currency)}f}",
+        )
+        rates.add_rate(inverse_rate)
 
     return rates