Merge pull request #631 from peterslany/peter/loans-get-lend-token-ex…

…change-rates

feat(loans): add method to get lendtoken exchange rates

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@interlay/interbtc-api",
-  "version": "2.2.1",
+  "version": "2.2.2",
   "description": "JavaScript library to interact with interBTC",
   "main": "build/src/index.js",
   "typings": "build/src/index.d.ts",

src/parachain/loans.ts

@@ -91,6 +91,12 @@ export interface LoansAPI {
      */
     getLendTokens(): Promise<Array<LendToken>>;
 
+    /**
+     * @return Exchange rates for underlying currency -> lend token.
+     * Representing amount of lend token equal to 1 of underlying currency.
+     */
+    getLendTokenExchangeRates(): Promise<TickerToData<Big>>;
+
     /**
      * Get accrued subsidy rewards amounts for the account.
      *
@@ -306,6 +312,21 @@ export class DefaultLoansAPI implements LoansAPI {
         );
     }
 
+    async getLendTokenExchangeRates(): Promise<TickerToData<Big>> {
+        const exchangeRateEntries = await this.api.query.loans.exchangeRate.entries();
+        const underlyingCurrencies = await Promise.all(
+            exchangeRateEntries.map(([key]) => currencyIdToMonetaryCurrency(this.api, storageKeyToNthInner(key)))
+        );
+
+        return exchangeRateEntries.reduce((exchangeRates, [, rate], index) => {
+            const underlyingCurrencyTicker = underlyingCurrencies[index].ticker;
+            return {
+                ...exchangeRates,
+                [underlyingCurrencyTicker]: decodeFixedPointType(rate),
+            };
+        }, {});
+    }
+
     async getBorrowerAccountIds(): Promise<Array<AccountId>> {
         const accountBorrows = await this.api.query.loans.accountBorrows.entries();
         return [