feat: first cut at adding loan tvl endpoint

api/tvl_loans.js

@@ -0,0 +1,59 @@
+import { createInterBtcApi } from "@interlay/interbtc-api";
+import { getCoingeckoId, getCoingeckoQueryUrl, getUsdMonetaryAmount } from "./currency-utils";
+
+const tvlLoans = async (request, response) => {
+    if (request.method === 'GET') {
+        const interbtcApi = await createInterBtcApi(
+            process.env.REACT_APP_PARACHAIN_URL,
+            process.env.REACT_APP_BITCOIN_NETWORK,
+            undefined,
+            3
+        );
+
+        const loanAssets = await interbtcApi.loans.getLoanAssets();
+        const liquidityAmounts = Object.values(loanAssets).map((loanAsset) => loanAsset.totalLiquidity);
+
+        // dedupe ids
+        const coingeckoIds = new Set(
+            liquidityAmounts.map((monetaryAmount) => monetaryAmount.currency)
+        );
+        // base: usd, get price for all coingeckoIds
+        const queryUrl = getCoingeckoQueryUrl("usd", Array.from(coingeckoIds));
+        // return format: { <coingeckoId> : { <vs_id>: <price_as_number> }, ... }
+        // eg. {"bitcoin":{"usd":36478},"interlay":{"usd":0.0240072}}
+        const cgResponse = await fetch(queryUrl, { headers: { "accept": "application/json" } });
+        const cgData = await cgResponse.json();
+
+        const amounts = liquidityAmounts.map((monetaryAmount) => {
+                const atomicAmount = monetaryAmount.toString(true);
+                const amount = monetaryAmount.toString();
+
+                const cgId = getCoingeckoId(monetaryAmount.currency);
+                const usdPrice = (cgId != undefined && cgData[cgId] != undefined && cgData[cgId]["usd"] != undefined) 
+                    ? cgData[cgId]["usd"]
+                    : undefined;
+
+                const monetaryAmountUsd = usdPrice ? getUsdMonetaryAmount(monetaryAmount, usdPrice) : undefined;
+                const amountUsd = monetaryAmountUsd?.toString();
+                return {
+                    currency: monetaryAmount.currency,
+                    coingeckoId: cgId,
+                    atomicAmount,
+                    amount,
+                    amountUsd
+                }
+            });
+
+        return response.status(200)
+            .setHeader("content-type", "application/json")
+            .setHeader("cache-control", "public, maxage=0, s-maxage=300")
+            .json(amounts);
+    } else {
+        return response.status(400).send('Bad Request');
+    }
+}
+
+export default async function (request, response) {
+    return tvlLoans(request, response);
+}
+

vercel.json

@@ -15,6 +15,10 @@
     "api/tvl_dex.js": {
       "memory": 256,
       "maxDuration": 30
+    },
+    "api/tvl_loans.js": {
+      "memory": 256,
+      "maxDuration": 30
     }
 },
   "rewrites": [
@@ -41,6 +45,10 @@
     {
       "source": "/tvl_dex",
       "destination": "/api/tvl_dex.js"
+    },
+    {
+      "source": "/tvl_loans",
+      "destination": "/api/tvl_loans.js"
     }
   ],
   "headers": [