feat: implement API handler for edge runtime with method validation and target normalization

.gitignore

@@ -5,7 +5,6 @@ node_modules
 out
 dist
 *.tgz
-api
 
 # code coverage
 coverage

api/index.ts

@@ -0,0 +1,50 @@
+import {
+	buildRelayRequest,
+	createRelayResponse,
+	normalizeTargetUrl,
+	stripRelayHeaders,
+	isAllowedTarget,
+} from "../relay-utils";
+
+export const config = { runtime: "edge" };
+
+const ALLOWED_METHODS = new Set(["GET", "POST", "PUT", "DELETE", "PATCH", "HEAD", "OPTIONS"]);
+
+export default async function handler(req: Request): Promise<Response> {
+	if (!ALLOWED_METHODS.has(req.method)) {
+		return new Response(JSON.stringify({ error: "Method not allowed" }), {
+			status: 405,
+			headers: { "content-type": "application/json" },
+		});
+	}
+
+	const target = req.headers.get("x-relay-target");
+	const relayPath = req.headers.get("x-relay-path") || "/";
+
+	const targetUrl = normalizeTargetUrl(target, relayPath);
+	if (!targetUrl) {
+		return new Response(
+			JSON.stringify({ error: "Missing x-relay-target header" }),
+			{
+				status: 400,
+				headers: { "content-type": "application/json" },
+			},
+		);
+	}
+
+	if (!isAllowedTarget(targetUrl)) {
+		return new Response(
+			JSON.stringify({ error: "Target domain not allowed" }),
+			{
+				status: 403,
+				headers: { "content-type": "application/json" },
+			},
+		);
+	}
+
+	const headers = stripRelayHeaders(new Headers(req.headers));
+	const fetchOptions = buildRelayRequest(req, headers);
+
+	const response = await fetch(targetUrl, fetchOptions);
+	return createRelayResponse(response);
+}

package.json

@@ -4,7 +4,7 @@
 	"type": "module",
 	"private": true,
 	"scripts": {
-		"build": "bun build src/index.ts --target=bun --outdir=api && mkdir -p dist && cp public/index.html dist/index.html",
+		"build": "mkdir -p dist && cp public/index.html dist/index.html",
 		"start": "bun run src/index.ts",
 		"dev": "bun --hot run src/index.ts",
 		"test": "bun test",

vercel.json

@@ -1,5 +1,12 @@
 {
 	"$schema": "https://openapi.vercel.sh/vercel.json",
 	"bunVersion": "1",
-	"installCommand": "bun install"
-}
+	"installCommand": "bun install",
+	"outputDirectory": "dist",
+	"rewrites": [
+		{
+			"source": "/api/(.*)",
+			"destination": "/api/index.ts"
+		}
+	]
+}