import { createHash, createHmac, randomUUID } from "crypto";
import { getVercelOidcToken } from "@vercel/oidc";
import { QueueClient } from "@vercel/queue";

const TRIGGER_PATH = "/api/v1/internal/queue/vercel/trigger";
const BODY_LIMIT = 16 * 1024;

export async function forwardVercelQueueTrigger(topicName: unknown, message: unknown): Promise<void> {
  const url = process.env.QUEUE_WORKER_TRIGGER_URL;
  const secret = process.env.QUEUE_VERCEL_FORWARD_SECRET;
  if (!url || !secret || Buffer.byteLength(secret) < 32) {
    throw new Error("QUEUE_WORKER_TRIGGER_URL and QUEUE_VERCEL_FORWARD_SECRET are required");
  }
  if (typeof topicName !== "string" || topicName === "") {
    throw new Error("Vercel queue topic is missing");
  }
  const rawBody = JSON.stringify({ topicName, message });
  if (Buffer.byteLength(rawBody) > BODY_LIMIT) {
    throw new Error("Vercel queue trigger body is too large");
  }
  const timestamp = String(Math.floor(Date.now() / 1000));
  const nonce = randomUUID();
  const token = await getVercelOidcToken();
  const bodyHash = createHash("sha256").update(rawBody).digest("hex");
  const signature = createHmac("sha256", secret)
    .update(`POST\n${TRIGGER_PATH}\n${timestamp}\n${nonce}\n${bodyHash}`)
    .digest("hex");
  let response: { ok: boolean; status: number };
  try {
    response = await fetch(url, {
      method: "POST",
      headers: {
        Authorization: `Bearer ${token}`,
        "Content-Type": "application/json",
        "X-CS-Queue-Timestamp": timestamp,
        "X-CS-Queue-Nonce": nonce,
        "X-CS-Queue-Signature": signature
      },
      body: rawBody,
      signal: AbortSignal.timeout(10000)
    });
  } catch (error) {
    throw error instanceof Error ? error : new Error("Core worker trigger request failed");
  }
  if (!response.ok) {
    throw new Error(`Core worker trigger failed with status ${response.status}`);
  }
}

const client = new QueueClient({ region: process.env.QUEUE_VERCEL_REGION || "sin1" });

// queue/v2beta in vercel.json is the Vercel Queue trigger protocol identifier, not a CS queue version.
export default client.handleNodeCallback(async (message, metadata) => {
  await forwardVercelQueueTrigger(metadata && metadata.topicName, message);
}, { visibilityTimeoutSeconds: 300 });