swap Money for MoneyAmount, fix a couple of things along the way

tests/tests_integration/test_get_rates.py

@@ -108,11 +108,10 @@ def test_get_rates_dry_run_always_returns_42_as_rates():
         # Check that all rows have the expected rate of 42, 1/42 or 1 and the correct dates
         for row in rows:
             assert row["rate"] in (
-                "42",
+                "42.00000000",
-                "0.024",
+                "0.02380952",
-                "0.02",
+                "0.00000000",
-                "0",
+                "1.00000000",
-                "1",
             ), f"Expected rate to be 42, 1/42 or 1, but got {row['rate']}"
             assert row["rate_date"] in [
                 (some_random_date + datetime.timedelta(days=i)).strftime("%Y-%m-%d")

tests/tests_unit/test_money_amount.py

@@ -3,7 +3,7 @@ from decimal import Decimal
 import pytest
 from money.currency import Currency
 
-from xexe.money_amount import DEFAULT_MAX_DECIMALS, MoneyAmount
+from xexe.money_amount import DEFAULT_MONEY_PRECISION, MoneyAmount
 
 
 def test_money_amount_simple_creation_works():
@@ -23,13 +23,13 @@ def test_money_amount_takes_integer_amounts():
 def test_money_amount_takes_decimal_amounts():
     an_amount = MoneyAmount(amount=Decimal(10.5), currency=Currency.USD)
 
-    assert an_amount.amount == Decimal(10.5).quantize(DEFAULT_MAX_DECIMALS)
+    assert an_amount.amount == Decimal(10.5).quantize(DEFAULT_MONEY_PRECISION)
 
 
 def test_money_amount_takes_proper_strings_amounts():
     an_amount = MoneyAmount(amount="10.55", currency=Currency.USD)
 
-    assert an_amount.amount == Decimal(10.55).quantize(DEFAULT_MAX_DECIMALS)
+    assert an_amount.amount == Decimal(10.55).quantize(DEFAULT_MONEY_PRECISION)
 
 
 def test_money_amount_fails_with_ugly_strings():
@@ -46,4 +46,4 @@ def test_money_amount_takes_string_for_currency():
 def test_money_amount_works_with_8_decimal_positions():
     an_amount = MoneyAmount(amount="1.12345678", currency="USD")
 
-    assert an_amount.amount == Decimal(1.12345678).quantize(DEFAULT_MAX_DECIMALS)
+    assert an_amount.amount == Decimal(1.12345678).quantize(DEFAULT_MONEY_PRECISION)

xexe/constants.py

@@ -1,6 +1,5 @@
 import pathlib
 from dataclasses import dataclass
-from decimal import Decimal
 
 from money.currency import Currency
 
@@ -8,8 +7,6 @@ from xexe.rate_fetching import MockRateFetcher, XERateFetcher
 
 DEFAULT_CURRENCIES = {Currency("EUR"), Currency("GBP"), Currency("USD")}
 
-DEFAULT_MAX_DECIMALS = Decimal("0.00000001")
-
 RATES_SOURCES = {"mock": MockRateFetcher, "xe": XERateFetcher}
 
 DWH_SCHEMA = "sync_xedotcom_currency_rates"

xexe/exchange_rates.py

@@ -3,8 +3,9 @@ from decimal import Decimal
 from numbers import Number
 from typing import Iterable, Set, Union
 
-from money.currency import Currency, CurrencyHelper
+from money.currency import Currency
-from money.money import Money
+
+from xexe.money_amount import DEFAULT_MONEY_PRECISION_POSITIONS, MoneyAmount
 
 
 class ExchangeRate:
@@ -13,13 +14,13 @@ class ExchangeRate:
         self,
         from_currency: Currency,
         to_currency: Currency,
-        rate: Union[Money, Number, str],
+        rate: Union[MoneyAmount, Number, str],
         rate_date: datetime.date,
     ) -> None:
         self.from_currency = from_currency
         self.to_currency = to_currency
-        if not isinstance(rate, Money):
+        if not isinstance(rate, MoneyAmount):
-            rate = Money(rate, to_currency)
+            rate = MoneyAmount(amount=rate, currency=to_currency)
         self.rate = rate
         self.rate_date = rate_date
 
@@ -100,7 +101,7 @@ def add_equal_rates(rates: ExchangeRates, overwrite: bool = False) -> ExchangeRa
             new_rate = ExchangeRate(
                 from_currency=currency,
                 to_currency=currency,
-                rate=Money(1, currency),
+                rate=MoneyAmount(1, currency),
                 rate_date=date,
             )
             if new_rate in rates and not overwrite:
@@ -122,7 +123,7 @@ def add_inverse_rates(rates: ExchangeRates) -> ExchangeRates:
             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}",
+            rate=f"{1 / rate.amount:.{DEFAULT_MONEY_PRECISION_POSITIONS}f}",
         )
         rates.add_rate(inverse_rate)
 

xexe/money_amount.py

@@ -3,9 +3,12 @@ from typing import Union
 
 from money.currency import Currency
 
-from xexe.constants import DEFAULT_MAX_DECIMALS
+DEFAULT_MONEY_PRECISION_POSITIONS = 8
-
+DEFAULT_MONEY_PRECISION = Decimal(
-DEFAULT_MONEY_PRECISION = DEFAULT_MAX_DECIMALS
+    "0." + ("0" * (DEFAULT_MONEY_PRECISION_POSITIONS - 1)) + "1"
+)
+# If we have X decimal positions, we want 7 zeros and 1 one
+# i.e. 0. 000 000 01
 
 
 class MoneyAmount:

xexe/rate_fetching.py

@@ -1,13 +1,12 @@
 import datetime
 import os
 from abc import ABC, abstractmethod
-from decimal import Decimal
 
-from money.currency import Currency, CurrencyHelper
+from money.currency import Currency
-from money.money import Money
 from xecd_rates_client import XecdClient
 
 from xexe.exchange_rates import ExchangeRate
+from xexe.money_amount import DEFAULT_MONEY_PRECISION_POSITIONS, MoneyAmount
 
 
 class RateFetcher(ABC):
@@ -35,7 +34,7 @@ class MockRateFetcher(RateFetcher):
         return ExchangeRate(
             from_currency=from_currency,
             to_currency=to_currency,
-            rate=Money(42, to_currency),
+            rate=MoneyAmount(42, to_currency),
             rate_date=rate_date,
         )
 
@@ -71,7 +70,7 @@ class XERateFetcher(RateFetcher):
                 "Z", "+00:00"
             )  # Funny replace is necessary because of API response format
         ).date()
-        rate = f"""{response["to"][0]["mid"]:.{CurrencyHelper.decimal_precision_for_currency(to_currency)}f}"""
+        rate = f"""{response["to"][0]["mid"]:.{DEFAULT_MONEY_PRECISION_POSITIONS}f}"""
 
         return ExchangeRate(
             from_currency=from_currency,