Add coinmarketcap historical lookup maximum months

Author: peachbits

src/config.ts

@@ -20,6 +20,7 @@ const {
   COIN_GECKO_API_KEY = '',
   COIN_MARKET_CAP_API_KEY = '',
   COIN_MARKET_CAP_HISTORICAL_API_KEY = '',
+  COIN_MARKET_CAP_HISTORICAL_MAX_MONTHS = 60,
   SLACK_WEBHOOK_URL = '',
   OPEN_EXCHANGE_RATES_API_KEY = '',
   DEFAULT_FIAT = 'iso:USD'
@@ -39,7 +40,8 @@ const providerDefaults = {
   },
   coinMarketCapHistorical: {
     uri: 'https://pro-api.coinmarketcap.com',
-    apiKey: COIN_MARKET_CAP_HISTORICAL_API_KEY
+    apiKey: COIN_MARKET_CAP_HISTORICAL_API_KEY,
+    maxHistoricalMonths: Number(COIN_MARKET_CAP_HISTORICAL_MAX_MONTHS)
   },
   openExchangeRates: {
     uri: 'https://openexchangerates.org',
@@ -146,7 +148,8 @@ export const asConfig = asObject({
       coinMarketCapHistorical: asMaybe(
         asObject({
           uri: asString,
-          apiKey: asString
+          apiKey: asString,
+          maxHistoricalMonths: asOptional(asNumber, 60)
         }),
         providerDefaults.coinMarketCapHistorical
       ),

src/v3/providers/coinmarketcap/coinmarketcap.ts

@@ -253,6 +253,14 @@ const getHistoricalRates = async (
   rightNow: Date
 ): Promise<NumberMap> => {
   const out: NumberMap = {}
+
+  const { maxHistoricalMonths } = config.providers.coinMarketCapHistorical
+  const oldestAllowed = new Date(Date.now())
+  oldestAllowed.setMonth(oldestAllowed.getMonth() - maxHistoricalMonths)
+  if (new Date(date) < oldestAllowed) {
+    return out
+  }
+
   const days = daysBetween(new Date(date), rightNow)
 
   // If we're querying a date more than 3 months in the past, use