Merge pull request #2 from suranyami/feat/multi-arch-docker-and-backend-proxy

feat: proxy backend API through Next.js using runtime BACKEND_URL

frontend/src/app/api/[...path]/route.ts

@@ -0,0 +1,83 @@
+/**
+ * Catch-all proxy route — forwards /api/* requests from the browser to the
+ * backend server. BACKEND_URL is a plain server-side env var (not NEXT_PUBLIC_),
+ * so it is read at request time from the runtime environment, never baked into
+ * the client bundle or the build manifest.
+ *
+ * Set BACKEND_URL in docker-compose `environment:` (e.g. http://backend:8000)
+ * to use Docker internal networking. Defaults to http://localhost:8000 for
+ * local development where both services run on the same host.
+ */
+
+import { NextRequest, NextResponse } from "next/server";
+
+// Hop-by-hop headers that must not be forwarded to the backend.
+const HOP_BY_HOP = new Set([
+  "connection",
+  "keep-alive",
+  "proxy-authenticate",
+  "proxy-authorization",
+  "te",
+  "trailers",
+  "transfer-encoding",
+  "upgrade",
+  "host",
+]);
+
+async function proxy(req: NextRequest, path: string[]): Promise<NextResponse> {
+  const backendUrl = process.env.BACKEND_URL ?? "http://localhost:8000";
+  const targetUrl = new URL(`/api/${path.join("/")}`, backendUrl);
+  targetUrl.search = req.nextUrl.search;
+
+  // Forward relevant request headers (strip hop-by-hop)
+  const forwardHeaders = new Headers();
+  req.headers.forEach((value, key) => {
+    if (!HOP_BY_HOP.has(key.toLowerCase())) {
+      forwardHeaders.set(key, value);
+    }
+  });
+
+  const isBodyless = req.method === "GET" || req.method === "HEAD";
+  const upstream = await fetch(targetUrl.toString(), {
+    method: req.method,
+    headers: forwardHeaders,
+    body: isBodyless ? undefined : req.body,
+    // Required for streaming request bodies in Node.js fetch
+    // @ts-ignore
+    duplex: "half",
+  });
+
+  // Forward response headers (strip hop-by-hop)
+  const responseHeaders = new Headers();
+  upstream.headers.forEach((value, key) => {
+    if (!HOP_BY_HOP.has(key.toLowerCase())) {
+      responseHeaders.set(key, value);
+    }
+  });
+
+  // 304 responses must have no body
+  if (upstream.status === 304) {
+    return new NextResponse(null, { status: 304, headers: responseHeaders });
+  }
+
+  return new NextResponse(upstream.body, {
+    status: upstream.status,
+    headers: responseHeaders,
+  });
+}
+
+export async function GET(req: NextRequest, { params }: { params: Promise<{ path: string[] }> }) {
+  return proxy(req, (await params).path);
+}
+
+export async function POST(req: NextRequest, { params }: { params: Promise<{ path: string[] }> }) {
+  return proxy(req, (await params).path);
+}
+
+export async function PUT(req: NextRequest, { params }: { params: Promise<{ path: string[] }> }) {
+  return proxy(req, (await params).path);
+}
+
+export async function DELETE(req: NextRequest, { params }: { params: Promise<{ path: string[] }> }) {
+  return proxy(req, (await params).path);
+}