Fix LemFi EUR to NGN rate integration

utils/lemfi.js

@@ -0,0 +1,33 @@
+export function parseLemfiQuote(result) {
+    const quote = result?.data;
+    if (quote?.exchange_from !== "EUR" || quote?.exchange_to !== "NGN") {
+        throw new Error("LemFi did not return a EUR to NGN quote");
+    }
+
+    // Match LemFi's calculator: divide the encoded rate by the digits in its ID.
+    // Use the base rate so referral rewards and LemFi Cash do not inflate comparisons.
+    const divisor = typeof quote.ID === "string" ? Number(quote.ID.replace(/\D/g, "")) : 0;
+    const encodedRate = typeof quote.rate === "string" || typeof quote.rate === "number"
+        ? Number(quote.rate)
+        : NaN;
+    const rate = encodedRate / divisor;
+    if (!Number.isFinite(divisor) || divisor <= 0 || !Number.isFinite(rate) || rate <= 0) {
+        throw new Error("LemFi returned an invalid exchange rate");
+    }
+
+    return rate;
+}
+
+export async function fetchLemfiRate() {
+    const url = new URL("https://lemfi.com/api/exchange-quote");
+    url.search = new URLSearchParams({ from: "EUR", to: "NGN", country: "Netherlands", lang: "en" });
+    const response = await fetch(url, {
+        headers: { accept: "application/json" },
+        signal: AbortSignal.timeout(8000),
+    });
+    if (!response.ok) {
+        throw new Error(`LemFi quote request failed (${response.status})`);
+    }
+
+    return parseLemfiQuote(await response.json());
+}