feat: implement contact message storage and retrieval functionality

.gitignore

@@ -40,3 +40,6 @@ yarn-error.log*
 # typescript
 *.tsbuildinfo
 next-env.d.ts
+
+# dummy contact submissions (generated at runtime)
+data/contact-messages.json

src/app/api/contact/route.ts

@@ -1,6 +1,33 @@
 import { NextResponse } from "next/server";
+import { mkdir, readFile, writeFile } from "fs/promises";
+import path from "path";
 
-// Dummy endpoint sementara, ganti dengan API asli saat sudah tersedia.
+export const runtime = "nodejs";
+
+const DATA_DIR = path.join(process.cwd(), "data");
+const DATA_FILE = path.join(DATA_DIR, "contact-messages.json");
+
+interface ContactMessage {
+  id: string;
+  name: string;
+  email: string;
+  subject: string;
+  message: string;
+  created_at: string;
+}
+
+async function readMessages(): Promise<ContactMessage[]> {
+  try {
+    const raw = await readFile(DATA_FILE, "utf-8");
+    const parsed = JSON.parse(raw);
+    return Array.isArray(parsed) ? parsed : [];
+  } catch {
+    // File belum ada atau isinya rusak, mulai dari array kosong.
+    return [];
+  }
+}
+
+// Dummy endpoint sementara, data disimpan ke data/contact-messages.json.
 export async function POST(request: Request) {
   const body = await request.json();
 
@@ -11,7 +38,25 @@ export async function POST(request: Request) {
     return NextResponse.json({ status: 422, message: "Data belum lengkap", errors: Object.fromEntries(missing.map((field) => [field, [`${field} harus diisi`]])) }, { status: 422 });
   }
 
-  console.log("[contact] dummy submission:", body);
+  const entry: ContactMessage = {
+    id: crypto.randomUUID(),
+    name: String(body.name).trim(),
+    email: String(body.email).trim(),
+    subject: String(body.subject).trim(),
+    message: String(body.message).trim(),
+    created_at: new Date().toISOString(),
+  };
 
-  return NextResponse.json({ status: 200, message: "Pesan berhasil dikirim", data: body });
+  try {
+    const messages = await readMessages();
+    messages.push(entry);
+
+    await mkdir(DATA_DIR, { recursive: true });
+    await writeFile(DATA_FILE, JSON.stringify(messages, null, 2), "utf-8");
+  } catch (error) {
+    console.error("[contact] gagal menyimpan pesan:", error);
+    return NextResponse.json({ status: 500, message: "Gagal menyimpan pesan" }, { status: 500 });
+  }
+
+  return NextResponse.json({ status: 200, message: "Pesan berhasil dikirim", data: entry });
 }