Merged PR 2142: More decimals

This PR implements foundational changes in how money amounts ara managed to allow exchange rates to have up to 8 decimal positions. Before, this was limited to 0, 2 or 3 decimal positions, depending on the currency.

.gitignore

@@ -160,3 +160,6 @@ cython_debug/
 #  and can be added to the global gitignore or merged into this file.  For a more nuclear
 #  option (not recommended) you can uncomment the following to ignore the entire idea folder.
 #.idea/
+
+# to avoid test files being commited
+*.csv

CHANGELOG.md

@@ -0,0 +1,15 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [1.0.1] - 2024-06-27
+
+### Changed
+
+- Rates now have up to 8 decimal positions of precision, up from the previous 0, 2 or 3 depending on the currency.
+- Internally, `xexe` now uses an in-house `MoneyAmount` class as a replacement of `py-money`'s `Money` class.
+- The table schema when writing to Postgresql has gone from `DECIMAL(19,4)` to `DECIMAL(23,8)` to adapt accordingly.
+- `CHF` has been added to the default currencies included in the `run_xexe.sh` deployment script.

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "xexe"
-version = "1.0.0"
+version = "1.0.1"
 description = ""
 authors = ["Pablo Martin <pablo.martin@superhog.com>"]
 readme = "README.md"

tests/tests_integration/test_get_rates.py

@@ -11,8 +11,8 @@ from xexe.constants import DEFAULT_CURRENCIES
 
 def test_get_rates_for_hardcoded_case_returns_expected_output():
     """
-    Calling the CLI get-rates command to get the rates between USD, EUR and GBP
-    for 2024-01-01 to 2024-01-03 returns the expected records in a CSV.
+    Calling the CLI get-rates command to get the rates between CAD and GBP for
+    2024-06-20 returns the expected records in a CSV.
 
     ATTENTION!
 
@@ -35,11 +35,11 @@ def test_get_rates_for_hardcoded_case_returns_expected_output():
             get_rates,
             [
                 "--start-date",
-                "2024-01-01",
+                "2024-06-20",
                 "--end-date",
-                "2024-01-02",
+                "2024-06-20",
                 "--currencies",
-                "USD,GBP",
+                "CAD,EUR",
                 "--rates-source",
                 "xe",
                 "--output",
@@ -49,11 +49,30 @@ def test_get_rates_for_hardcoded_case_returns_expected_output():
 
         assert run_result.exit_code == 0
 
-        # Write code here to read output file and compare it against expected
-        # output
-        assert False
+        expected_output = [
+            ["from_currency", "to_currency", "rate", "rate_date", "exported_at"],
+            ["CAD", "EUR", "0.67884137", "2024-06-20", "2024-06-27T17:26:04"],
+            ["EUR", "CAD", "1.47309820", "2024-06-20", "2024-06-27T17:26:04"],
+            ["CAD", "CAD", "1.00000000", "2024-06-20", "2024-06-27T17:26:04"],
+            ["EUR", "EUR", "1.00000000", "2024-06-20", "2024-06-27T17:26:04"],
+        ]
+
+        with open("test_output.csv", newline="") as csvfile:
+            reader = csv.reader(csvfile)
+            output = list(reader)
+
+        headers_match = output[0] == expected_output[0]
+        assert headers_match
+
+        for i, row in enumerate(output[1:], start=1):
+            row_matches = row[:4] == expected_output[i][:4]
+            exported_at_is_valid_iso_datetime = bool(
+                datetime.datetime.fromisoformat(row[4])
+            )
+            assert row_matches and exported_at_is_valid_iso_datetime
     """
 
+    # This is for when the main test is commented out
     assert True
 
 
@@ -108,11 +127,10 @@ 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",
-                "0.024",
-                "0.02",
-                "0",
-                "1",
+                "42.00000000",
+                "0.02380952",
+                "0.00000000",
+                "1.00000000",
             ), 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_exchange_rates.py

@@ -2,7 +2,6 @@ import datetime
 from decimal import Decimal
 
 from money.currency import Currency
-from money.money import Money
 
 from xexe.exchange_rates import (
     ExchangeRate,
@@ -27,6 +26,20 @@ def test_exchange_rate_creation_works():
     assert a_rate.rate_date == datetime.date.today()
 
 
+def test_exchange_rate_can_hold_8_decimal_positions():
+    a_rate = ExchangeRate(
+        from_currency=Currency.USD,
+        to_currency=Currency.EUR,
+        rate=Decimal("1.12345678"),
+        rate_date=datetime.date.today(),
+    )
+
+    assert a_rate.from_currency.value == "USD"
+    assert a_rate.to_currency.value == "EUR"
+    assert a_rate.rate.amount == Decimal("1.12345678")
+    assert a_rate.rate_date == datetime.date.today()
+
+
 def test_descriptor_builds_properly():
 
     a_rate = ExchangeRate(
@@ -237,13 +250,13 @@ def test_add_inverse_rates_returns_expected():
     a_rate = ExchangeRate(
         from_currency=Currency.EUR,
         to_currency=Currency.USD,
-        rate=Decimal("1.25"),
+        rate=Decimal("1.12345000"),
         rate_date=datetime.date(2020, 3, 10),
     )
     inverse_rate = ExchangeRate(
         from_currency=Currency.USD,
         to_currency=Currency.EUR,
-        rate=Decimal("0.8"),
+        rate=Decimal("0.89011527"),
         rate_date=datetime.date(2020, 3, 10),
     )
 
@@ -256,7 +269,7 @@ def test_add_inverse_rates_returns_expected():
     assert len(rates) == 2
 
     assert rates.is_rate_present(inverse_rate)
-    assert rates[inverse_rate.descriptor].amount == Decimal("0.8")
+    assert rates[inverse_rate.descriptor].amount == Decimal("0.89011527")
 
 
 def test_add_inverse_rates_runs_on_empty_rates():

tests/tests_unit/test_money_amount.py

@@ -0,0 +1,49 @@
+from decimal import Decimal
+
+import pytest
+from money.currency import Currency
+
+from xexe.money_amount import DEFAULT_MONEY_PRECISION, MoneyAmount
+
+
+def test_money_amount_simple_creation_works():
+
+    an_amount = MoneyAmount(amount=10, currency=Currency.USD)
+
+    assert an_amount.amount == 10
+    assert an_amount.currency == Currency.USD
+
+
+def test_money_amount_takes_integer_amounts():
+    an_amount = MoneyAmount(amount=10, currency=Currency.USD)
+
+    assert an_amount.amount == 10
+
+
+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_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_MONEY_PRECISION)
+
+
+def test_money_amount_fails_with_ugly_strings():
+    with pytest.raises(ValueError):
+        MoneyAmount(amount="not a nuuuuumber", currency=Currency.USD)
+
+
+def test_money_amount_takes_string_for_currency():
+    an_amount = MoneyAmount(amount="10.55", currency="USD")
+
+    assert an_amount.currency == Currency.USD
+
+
+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_MONEY_PRECISION)

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.money import Money
+from money.currency import Currency
+
+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):
-            rate = Money(rate, to_currency)
+        if not isinstance(rate, MoneyAmount):
+            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

@@ -0,0 +1,45 @@
+from decimal import Decimal, InvalidOperation
+from typing import Union
+
+from money.currency import Currency
+
+DEFAULT_MONEY_PRECISION_POSITIONS = 8
+DEFAULT_MONEY_PRECISION = Decimal(
+    "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:
+    def __init__(
+        self, amount: Union[int, Decimal, str], currency: Union[str, Currency]
+    ) -> "MoneyAmount":
+        self.amount = self._parse_amount(amount)
+        self.currency = self._parse_currency(currency)
+
+    def _parse_amount(self, amount: Union[int, Decimal, str]) -> Decimal:
+        if isinstance(amount, (int, Decimal)):
+            return Decimal(amount).quantize(DEFAULT_MONEY_PRECISION)
+        elif isinstance(amount, str):
+            try:
+                return Decimal(amount).quantize(DEFAULT_MONEY_PRECISION)
+            except InvalidOperation:
+                raise ValueError(f"Invalid amount: {amount}")
+        else:
+            raise TypeError(f"Amount must be int, Decimal, or str, not {type(amount)}")
+
+    def _parse_currency(self, currency: Union[str, Currency]) -> Currency:
+        if isinstance(currency, Currency):
+            return currency
+        if isinstance(currency, str):
+            return Currency[currency]
+
+        raise TypeError(
+            f"Currency must be a Currency object or str, not {type(currency)}"
+        )
+
+    def __eq__(self, other):
+        if isinstance(other, MoneyAmount):
+            return self.amount == other.amount and self.currency == other.currency
+        return False

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.money import Money
+from money.currency import Currency
 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,

xexe/rate_writing.py

@@ -142,7 +142,7 @@ class DWHRateWriter(RateWriter):
             CREATE TABLE IF NOT EXISTS {}.{} (
                 from_currency CHAR(3) NOT NULL,
                 to_currency CHAR(3) NOT NULL,
-                rate DECIMAL(19, 4) NOT NULL,
+                rate DECIMAL(23, 8) NOT NULL,
                 rate_date_utc DATE NOT NULL,
                 exported_at_utc TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
                 PRIMARY KEY (from_currency, to_currency, rate_date_utc)