feat: Add POST /echo endpoint with JSON round-trip

.gitignore

@@ -6,3 +6,12 @@ dist/
 *.sqlite3
 progress.txt
 progress*.txt
+.env
+.env.local
+.env.*.local
+*.key
+*.pem
+*.secret
+coverage/
+.nyc_output/
+*.log

src/server/dashboard.ts

@@ -137,6 +137,26 @@ export function startDashboard(port = 3333): http.Server {
       }
     }
 
+    // POST /echo - round-trip endpoint for testing
+    if (req.method === "POST" && p === "/echo") {
+      const chunks: Buffer[] = [];
+      req.on("data", (chunk: Buffer) => chunks.push(chunk));
+      req.on("end", () => {
+        const body = Buffer.concat(chunks).toString("utf-8");
+        let parsed: unknown;
+        try {
+          parsed = JSON.parse(body);
+        } catch {
+          res.writeHead(400, { "Content-Type": "application/json", "Access-Control-Allow-Origin": "*" });
+          res.end(JSON.stringify({ error: "invalid JSON" }));
+          return;
+        }
+        res.writeHead(200, { "Content-Type": "application/json", "Access-Control-Allow-Origin": "*" });
+        res.end(JSON.stringify(parsed));
+      });
+      return;
+    }
+
     // Serve frontend
     serveHTML(res);
   });

tests/echo-endpoint.test.ts

@@ -0,0 +1,86 @@
+/**
+ * Tests for the POST /echo endpoint on the dashboard server.
+ * Verifies JSON round-trip, error handling, and method filtering.
+ */
+import { describe, it, after } from "node:test";
+import assert from "node:assert/strict";
+import http from "node:http";
+import { startDashboard } from "../dist/server/dashboard.js";
+
+function postJson(port: number, path: string, body: string): Promise<{ status: number; body: string }> {
+  return new Promise((resolve, reject) => {
+    const req = http.request(
+      { hostname: "127.0.0.1", port, path, method: "POST", headers: { "Content-Type": "application/json" } },
+      (res) => {
+        const chunks: Buffer[] = [];
+        res.on("data", (chunk: Buffer) => chunks.push(chunk));
+        res.on("end", () => resolve({ status: res.statusCode ?? 0, body: Buffer.concat(chunks).toString("utf-8") }));
+      }
+    );
+    req.on("error", reject);
+    req.write(body);
+    req.end();
+  });
+}
+
+function getRequest(port: number, path: string): Promise<{ status: number; body: string }> {
+  return new Promise((resolve, reject) => {
+    const req = http.request(
+      { hostname: "127.0.0.1", port, path, method: "GET" },
+      (res) => {
+        const chunks: Buffer[] = [];
+        res.on("data", (chunk: Buffer) => chunks.push(chunk));
+        res.on("end", () => resolve({ status: res.statusCode ?? 0, body: Buffer.concat(chunks).toString("utf-8") }));
+      }
+    );
+    req.on("error", reject);
+    req.end();
+  });
+}
+
+describe("POST /echo endpoint", () => {
+  it("returns HTTP 200 and echoes a simple JSON body", async () => {
+    const server = startDashboard(0);
+    await new Promise<void>((resolve) => server.once("listening", resolve));
+    const port = (server.address() as { port: number }).port;
+    after(() => server.close());
+
+    const res = await postJson(port, "/echo", JSON.stringify({ hello: "world" }));
+    assert.equal(res.status, 200);
+    assert.deepEqual(JSON.parse(res.body), { hello: "world" });
+  });
+
+  it("returns HTTP 200 and echoes a nested JSON body", async () => {
+    const server = startDashboard(0);
+    await new Promise<void>((resolve) => server.once("listening", resolve));
+    const port = (server.address() as { port: number }).port;
+    after(() => server.close());
+
+    const res = await postJson(port, "/echo", JSON.stringify({ nested: { a: 1 } }));
+    assert.equal(res.status, 200);
+    assert.deepEqual(JSON.parse(res.body), { nested: { a: 1 } });
+  });
+
+  it("returns HTTP 400 with error message for invalid JSON body", async () => {
+    const server = startDashboard(0);
+    await new Promise<void>((resolve) => server.once("listening", resolve));
+    const port = (server.address() as { port: number }).port;
+    after(() => server.close());
+
+    const res = await postJson(port, "/echo", "not valid json");
+    assert.equal(res.status, 400);
+    assert.deepEqual(JSON.parse(res.body), { error: "invalid JSON" });
+  });
+
+  it("GET /echo falls through to serveHTML (not handled by echo route)", async () => {
+    const server = startDashboard(0);
+    await new Promise<void>((resolve) => server.once("listening", resolve));
+    const port = (server.address() as { port: number }).port;
+    after(() => server.close());
+
+    const res = await getRequest(port, "/echo");
+    // Should serve HTML, not JSON echo
+    assert.equal(res.status, 200);
+    assert.ok(res.body.includes("<!"), `expected HTML response, got: ${res.body.slice(0, 100)}`);
+  });
+});