Feature/improve exchange rate service for specific date (#1785)

* Calculate exchange rate indirectly via base currency

* Update changelog

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 
 - Improved the usability of the _FIRE_ calculator
+- Improved the exchange rate service for a specific date used in activities with a manual currency
 - Upgraded `ngx-device-detector` from version `3.0.0` to `5.0.1`
 
 ## 1.244.0 - 2023-03-09

apps/api/src/services/exchange-rate-data.service.ts

@@ -183,8 +183,29 @@ export class ExchangeRateDataService {
       if (marketData?.marketPrice) {
         factor = marketData?.marketPrice;
       } else {
-        // TODO: Get from data provider service or calculate indirectly via base currency
-        // and market data
+        // Calculate indirectly via base currency
+        try {
+          const [
+            { marketPrice: marketPriceBaseCurrencyFromCurrency },
+            { marketPrice: marketPriceBaseCurrencyToCurrency }
+          ] = await Promise.all([
+            this.marketDataService.get({
+              dataSource,
+              date: aDate,
+              symbol: `${this.baseCurrency}${aFromCurrency}`
+            }),
+            this.marketDataService.get({
+              dataSource,
+              date: aDate,
+              symbol: `${this.baseCurrency}${aToCurrency}`
+            })
+          ]);
+
+          // Calculate the opposite direction
+          factor =
+            (1 / marketPriceBaseCurrencyFromCurrency) *
+            marketPriceBaseCurrencyToCurrency;
+        } catch {}
       }
     }