// speedy-functions.js
import express from "express";
import { VM, VMScript } from "vm2";
import { JSDOM } from "jsdom";
import cheerio from "cheerio";
import FileReader from "filereader";

// ────── 1. one-time constants ──────────────────────────────────────────
const PORT = +(process.env.PORT ?? 5000);
const TIMEOUT_MS = 5_000;
const HTTP_STATUS_CODES = Object.freeze({
  OK: 200,
  BAD_REQUEST: 400,
  UNAUTHORIZED: 401,
  FORBIDDEN: 403,
  NOT_FOUND: 404,
  INTERNAL_SERVER_ERROR: 500,
  BAD_GATEWAY: 502,
  SERVICE_UNAVAILABLE: 503,
  GATEWAY_TIMEOUT: 504,
});

const States = Object.freeze({
  SUCCESS: "SUCCESS",
  NOT_A_FUNCTION: "NOT_A_FUNCTION",
  SCRIPT_ERROR: "ERROR",
  TIMEOUT: "TIMEOUT",
});

// convenience helpers
const Response = (body = "", headers = {}, status = HTTP_STATUS_CODES.OK) => ({
  body,
  status,
  headers,
});
const JsonResponse = (body = {}, headers = {}, status = HTTP_STATUS_CODES.OK) =>
  Response(
    JSON.stringify(body),
    { "Content-Type": "application/json", ...headers },
    status
  );
const HtmlResponse = (body = "", headers = {}, status = HTTP_STATUS_CODES.OK) =>
  Response(body, { "Content-Type": "text/html", ...headers }, status);
const TextResponse = (body = "", headers = {}, status = HTTP_STATUS_CODES.OK) =>
  Response(body, { "Content-Type": "text/plain", ...headers }, status);

// ────── 2. one-time imports ────────────────────────────────────────────
const fetch = (await import("node-fetch")).default;

// ────── 3. tiny script cache (precompiled) ─────────────────────────────
const scriptCache = new Map(); // code-string  -> VMScript
const cachedScript = (code) => {
  if (!scriptCache.has(code)) {
    scriptCache.set(code, new VMScript(code));
  }
  return scriptCache.get(code);
};

// ────── 4. shared VM options (lightweight to clone) ────────────────────
const baseSandbox = {
  fetch,
  parseHTML: (html) => new JSDOM(html).window.document,
  JSDOM,
  cheerio,
  HTTP_STATUS_CODES,
  Response,
  JsonResponse,
  HtmlResponse,
  TextResponse,
  FileReader,
};

function createVm(logs, requestObject, env, funcName) {
  return new VM({
    timeout: TIMEOUT_MS,
    sandbox: {
      ...baseSandbox,
      console: {
        log: (...args) => (
          logs.push(args), /* bubble to host */ console.log(...args)
        ),
        error: (...args) => (logs.push(args), console.error(...args)),
      },
      requestObject,
      environment: env,
      FUNCTION_NAME: funcName,
    },
    require: { external: true },
  });
}

// ────── 5. evaluator ───────────────────────────────────────────────────
async function executeUserCode(
  code,
  requestObject,
  env = {},
  funcName = "userFunc"
) {
  const logs = [];
  const startTime = process.hrtime();
  const vm = createVm(
    logs,
    requestObject,
    JSON.parse(JSON.stringify(env)),
    funcName
  );

  try {
    const userFn = vm.run(cachedScript(code));
    if (typeof userFn !== "function") {
      return {
        status: States.NOT_A_FUNCTION,
        result: null,
        logs,
        environment: vm.sandbox.environment,
      };
    }

    const result = await Promise.resolve(
      userFn(requestObject, vm.sandbox.environment)
    );
    const endTime = process.hrtime(startTime);
    const executionTime = (endTime[0] * 1e9 + endTime[1]) / 1e6; // in milliseconds
    return {
      status: States.SUCCESS,
      result,
      logs,
      environment: vm.sandbox.environment,
      execution_time: executionTime,
    };
  } catch (err) {
    const status = /timed out/i.test(err.message)
      ? States.TIMEOUT
      : States.SCRIPT_ERROR;
    const endTime = process.hrtime(startTime);
    const executionTime = (endTime[0] * 1e9 + endTime[1]) / 1e6; // in milliseconds
    return {
      status,
      result: err.message ?? err,
      logs,
      environment: vm.sandbox.environment,
      execution_time: executionTime,
    };
  }
}

// ────── 6. API surface ────────────────────────────────────────────────
const app = express();
app.use(express.json({ limit: "50mb" }));
app.use((_, res, next) => {
  res.set({
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Headers":
      "Origin, X-Requested-With, Content-Type, Accept",
  });
  next();
});

app.post("/execute", async ({ body }, res) => {
  const { code = "", request = {}, environment = {}, name } = body;
  const payload = await executeUserCode(code, request, environment, name);
  res.json(payload);
});

app.listen(PORT, () => console.log(`⚡  server ready on :${PORT}`));