Simplify fiat convert and fix USD coingecko problem

freqtrade/rpc/fiat_convert.py

@@ -4,9 +4,9 @@ e.g BTC to USD
 """
 
 import logging
-import time
-from typing import Dict, List
+from typing import Dict
 
+from cachetools.ttl import TTLCache
 from pycoingecko import CoinGeckoAPI
 
 from freqtrade.constants import SUPPORTED_FIAT
@@ -15,51 +15,6 @@ from freqtrade.constants import SUPPORTED_FIAT
 logger = logging.getLogger(__name__)
 
 
-class CryptoFiat:
-    """
-    Object to describe what is the price of Crypto-currency in a FIAT
-    """
-    # Constants
-    CACHE_DURATION = 6 * 60 * 60  # 6 hours
-
-    def __init__(self, crypto_symbol: str, fiat_symbol: str, price: float) -> None:
-        """
-        Create an object that will contains the price for a crypto-currency in fiat
-        :param crypto_symbol: Crypto-currency you want to convert (e.g BTC)
-        :param fiat_symbol: FIAT currency you want to convert to (e.g USD)
-        :param price: Price in FIAT
-        """
-
-        # Public attributes
-        self.crypto_symbol = None
-        self.fiat_symbol = None
-        self.price = 0.0
-
-        # Private attributes
-        self._expiration = 0.0
-
-        self.crypto_symbol = crypto_symbol.lower()
-        self.fiat_symbol = fiat_symbol.lower()
-        self.set_price(price=price)
-
-    def set_price(self, price: float) -> None:
-        """
-        Set the price of the Crypto-currency in FIAT and set the expiration time
-        :param price: Price of the current Crypto currency in the fiat
-        :return: None
-        """
-        self.price = price
-        self._expiration = time.time() + self.CACHE_DURATION
-
-    def is_expired(self) -> bool:
-        """
-        Return if the current price is still valid or needs to be refreshed
-        :return: bool, true the price is expired and needs to be refreshed, false the price is
-         still valid
-        """
-        return self._expiration - time.time() <= 0
-
-
 class CryptoToFiatConverter:
     """
     Main class to initiate Crypto to FIAT.
@@ -84,7 +39,9 @@ class CryptoToFiatConverter:
         return CryptoToFiatConverter.__instance
 
     def __init__(self) -> None:
-        self._pairs: List[CryptoFiat] = []
+        # Timeout: 6h
+        self._pair_price: TTLCache = TTLCache(maxsize=500, ttl=6 * 60 * 60)
+
         self._load_cryptomap()
 
     def _load_cryptomap(self) -> None:
@@ -118,49 +75,31 @@ class CryptoToFiatConverter:
         """
         crypto_symbol = crypto_symbol.lower()
         fiat_symbol = fiat_symbol.lower()
+        inverse = False
 
+        if crypto_symbol == 'usd':
+            # usd corresponds to "uniswap-state-dollar" for coingecko.
+            # We'll therefore need to "swap" the currencies
+            logger.info(f"reversing Rates {crypto_symbol}, {fiat_symbol}")
+            crypto_symbol = fiat_symbol
+            fiat_symbol = 'usd'
+            inverse = True
+
+        symbol = f"{crypto_symbol}/{fiat_symbol}"
         # Check if the fiat convertion you want is supported
         if not self._is_supported_fiat(fiat=fiat_symbol):
             raise ValueError(f'The fiat {fiat_symbol} is not supported.')
 
-        # Get the pair that interest us and return the price in fiat
-        for pair in self._pairs:
-            if pair.crypto_symbol == crypto_symbol and pair.fiat_symbol == fiat_symbol:
-                # If the price is expired we refresh it, avoid to call the API all the time
-                if pair.is_expired():
-                    pair.set_price(
-                        price=self._find_price(
-                            crypto_symbol=pair.crypto_symbol,
-                            fiat_symbol=pair.fiat_symbol
-                        )
-                    )
+        price = self._pair_price.get(symbol, None)
 
-                # return the last price we have for this pair
-                return pair.price
-
-        # The pair does not exist, so we create it and return the price
-        return self._add_pair(
-            crypto_symbol=crypto_symbol,
-            fiat_symbol=fiat_symbol,
-            price=self._find_price(
+        if not price:
+            price = self._find_price(
                 crypto_symbol=crypto_symbol,
                 fiat_symbol=fiat_symbol
             )
-        )
-
-    def _add_pair(self, crypto_symbol: str, fiat_symbol: str, price: float) -> float:
-        """
-        :param crypto_symbol: Crypto-currency you want to convert (e.g BTC)
-        :param fiat_symbol: FIAT currency you want to convert to (e.g USD)
-        :return: price in FIAT
-        """
-        self._pairs.append(
-            CryptoFiat(
-                crypto_symbol=crypto_symbol,
-                fiat_symbol=fiat_symbol,
-                price=price
-            )
-        )
+            if inverse and price != 0.0:
+                price = 1 / price
+            self._pair_price[symbol] = price
 
         return price