feat: internal code for automatic exchange rate fetching

app/apps/currencies/exchange_rates/providers.py

@@ -0,0 +1,140 @@
+import logging
+import time
+
+import requests
+from decimal import Decimal
+from typing import Tuple, List
+
+from django.db.models import QuerySet
+
+from apps.currencies.models import Currency
+from apps.currencies.exchange_rates.base import ExchangeRateProvider
+
+logger = logging.getLogger(__name__)
+
+
+class SynthFinanceProvider(ExchangeRateProvider):
+    """Implementation for Synth Finance API (synthfinance.com)"""
+
+    BASE_URL = "https://api.synthfinance.com/rates/live"
+    rates_inverted = False  # SynthFinance returns non-inverted rates
+
+    def __init__(self, api_key: str = None):
+        super().__init__(api_key)
+        self.session = requests.Session()
+        self.session.headers.update({"Authorization": f"Bearer {self.api_key}"})
+
+    def get_rates(
+        self, target_currencies: QuerySet, exchange_currencies: set
+    ) -> List[Tuple[Currency, Currency, Decimal]]:
+        results = []
+        currency_groups = {}
+        for currency in target_currencies:
+            if currency.exchange_currency in exchange_currencies:
+                group = currency_groups.setdefault(currency.exchange_currency.code, [])
+                group.append(currency)
+
+        for base_currency, currencies in currency_groups.items():
+            try:
+                to_currencies = ",".join(
+                    currency.code
+                    for currency in currencies
+                    if currency.code != base_currency
+                )
+                response = self.session.get(
+                    f"{self.BASE_URL}",
+                    params={"from": base_currency, "to": to_currencies},
+                )
+                response.raise_for_status()
+                data = response.json()
+                rates = data["data"]["rates"]
+
+                for currency in currencies:
+                    if currency.code == base_currency:
+                        rate = Decimal("1")
+                    else:
+                        rate = Decimal(str(rates[currency.code]))
+                    # Return the rate as is, without inversion
+                    results.append((currency.exchange_currency, currency, rate))
+
+                credits_used = data["meta"]["credits_used"]
+                credits_remaining = data["meta"]["credits_remaining"]
+                logger.info(
+                    f"Synth Finance API call: {credits_used} credits used, {credits_remaining} remaining"
+                )
+            except requests.RequestException as e:
+                logger.error(
+                    f"Error fetching rates from Synth Finance API for base {base_currency}: {e}"
+                )
+            except KeyError as e:
+                logger.error(
+                    f"Unexpected response structure from Synth Finance API for base {base_currency}: {e}"
+                )
+            except Exception as e:
+                logger.error(
+                    f"Unexpected error processing Synth Finance data for base {base_currency}: {e}"
+                )
+        return results
+
+
+class CoinGeckoProvider(ExchangeRateProvider):
+    """Implementation for CoinGecko API"""
+
+    BASE_URL = "https://api.coingecko.com/api/v3"
+    rates_inverted = True
+
+    def __init__(self, api_key: str):
+        super().__init__(api_key)
+        self.session = requests.Session()
+        self.session.headers.update({"x-cg-demo-api-key": api_key})
+
+    @classmethod
+    def requires_api_key(cls) -> bool:
+        return True
+
+    def get_rates(
+        self, target_currencies: QuerySet, exchange_currencies: set
+    ) -> List[Tuple[Currency, Currency, Decimal]]:
+        results = []
+        all_currencies = set(currency.code.lower() for currency in target_currencies)
+        all_currencies.update(currency.code.lower() for currency in exchange_currencies)
+
+        try:
+            response = self.session.get(
+                f"{self.BASE_URL}/simple/price",
+                params={
+                    "ids": ",".join(all_currencies),
+                    "vs_currencies": ",".join(all_currencies),
+                },
+            )
+            response.raise_for_status()
+            rates_data = response.json()
+
+            for target_currency in target_currencies:
+                if target_currency.exchange_currency in exchange_currencies:
+                    try:
+                        rate = Decimal(
+                            str(
+                                rates_data[target_currency.code.lower()][
+                                    target_currency.exchange_currency.code.lower()
+                                ]
+                            )
+                        )
+                        # The rate is already inverted, so we don't need to invert it again
+                        results.append(
+                            (target_currency.exchange_currency, target_currency, rate)
+                        )
+                    except KeyError:
+                        logger.error(
+                            f"Rate not found for {target_currency.code} or {target_currency.exchange_currency.code}"
+                        )
+                    except Exception as e:
+                        logger.error(
+                            f"Error calculating rate for {target_currency.code}: {e}"
+                        )
+
+            time.sleep(1)  # CoinGecko allows 10-30 calls/minute for free tier
+        except requests.RequestException as e:
+            logger.error(f"Error fetching rates from CoinGecko API: {e}")
+
+        return results