Initial commit

app/api/rates/route.ts

@@ -0,0 +1,75 @@
+import { NextResponse } from "next/server";
+import { fetchUnifiedRates } from "@/lib/api/normalize";
+import type { RatesResponse } from "@/lib/rates";
+
+const CACHE_TTL_MS = 300_000;
+const CACHE_CONTROL_VALUE = "s-maxage=300, stale-while-revalidate=1800";
+
+let cachedRates: RatesResponse | null = null;
+let cacheTimestamp = 0;
+let inFlightRequest: Promise<RatesResponse> | null = null;
+
+export const revalidate = 300;
+
+async function getRatesWithCache(): Promise<RatesResponse> {
+  const now = Date.now();
+  const hasFreshCache = cachedRates && now - cacheTimestamp < CACHE_TTL_MS;
+
+  if (hasFreshCache && cachedRates) {
+    return cachedRates;
+  }
+
+  if (inFlightRequest) {
+    return inFlightRequest;
+  }
+
+  inFlightRequest = (async () => {
+    const freshRates = await fetchUnifiedRates();
+    cachedRates = freshRates;
+    cacheTimestamp = Date.now();
+    return freshRates;
+  })();
+
+  try {
+    return await inFlightRequest;
+  } finally {
+    inFlightRequest = null;
+  }
+}
+
+export async function GET() {
+  try {
+    const data = await getRatesWithCache();
+
+    return NextResponse.json(data, {
+      status: 200,
+      headers: {
+        "Cache-Control": CACHE_CONTROL_VALUE
+      }
+    });
+  } catch (error) {
+    if (cachedRates) {
+      return NextResponse.json(cachedRates, {
+        status: 200,
+        headers: {
+          "Cache-Control": CACHE_CONTROL_VALUE,
+          "X-Cache-Fallback": "stale-on-error"
+        }
+      });
+    }
+
+    const message =
+      error instanceof Error
+        ? error.message
+        : "Unexpected error while loading rates";
+
+    return NextResponse.json(
+      {
+        message
+      },
+      {
+        status: 500
+      }
+    );
+  }
+}