const express = require("express");
const bodyParser = require("body-parser");
const { VM } = require("vm2");
const { JSDOM } = require("jsdom");
const cheerio = require("cheerio");

const app = express();
const port = 5000;

app.use(bodyParser.json());

app.use((req, res, next) => {
  res.header("Access-Control-Allow-Origin", "*");
  res.header(
    "Access-Control-Allow-Headers",
    "Origin, X-Requested-With, Content-Type, Accept"
  );
  next();
});

const TIMEOUT_MS = 5000; // Set timeout to 5000 milliseconds (5 seconds)

async function executeUserCode(
  code,
  requestObject,
  environment = {},
  name,
  timeout = TIMEOUT_MS
) {
  const logs = [];

  const States = {
    SUCCESS: "SUCCESS",
    NOT_A_FUNCTION: "NOT_A_FUNCTION",
    SCRIPT_ERROR: "ERROR",
    TIMEOUT: "TIMEOUT",
  };

  const HTTP_STATUS_CODES = {
    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 Response = (
    body = "",
    headers = {},
    status = HTTP_STATUS_CODES.OK
  ) => ({
    body,
    status,
    headers,
  });

  const JsonResponse = (
    body = {},
    headers = {},
    status = HTTP_STATUS_CODES.OK
  ) => ({
    status,
    body: JSON.stringify(body),
    headers: {
      "Content-Type": "application/json",
      ...headers,
    },
  });

  const HtmlResponse = (
    body = "",
    headers = {},
    status = HTTP_STATUS_CODES.OK
  ) => ({
    status,
    body,
    headers: {
      "Content-Type": "text/html",
      ...headers,
    },
  });

  const TextResponse = (
    body = "",
    headers = {},
    status = HTTP_STATUS_CODES.OK
  ) => ({
    status,
    body,
    headers: {
      "Content-Type": "text/plain",
      ...headers,
    },
  });

  const Result = (status, result, environment) => {
    console.log(`Status: ${status}`);
    console.log(`Result: ${JSON.stringify(result, null, 2)}`);
    console.log(`Logs: ${JSON.stringify(logs, null, 2)}`);
    console.log(`Environment (post): ${JSON.stringify(environment, null, 2)}`);
    console.log(`\n`);

    return {
      status,
      result,
      logs,
      environment,
    };
  };

  //Set Function name as environment variable
  const FUNCTION_NAME = name;

  // Dynamically import node-fetch
  const fetch = await import("node-fetch").then((module) => module.default);

  const vm = new VM({
    timeout,
    sandbox: {
      fetch,
      parseHTML: async (html) => {
        const dom = new JSDOM(html);
        return dom.window.document;
      },
      console: {
        log: (...args) => {
          logs.push(args);
          console.log(...args);
        },
        error: (...args) => {
          logs.push(args);
          console.error(...args);
        },
      },
      requestObject,
      environment,
      JSDOM,
      cheerio,
      HTTP_STATUS_CODES,
      Response,
      JsonResponse,
      HtmlResponse,
      TextResponse,
      FUNCTION_NAME,
    },
    require: {
      external: true,
    },
  });

  try {
    // If the user code is a function that needs to be invoked
    const userFunction = vm.run(code);
    if (typeof userFunction === "function") {
      console.log(`Function: ${code}`);
      let requestObjectString = JSON.stringify(requestObject, null, 2);
      console.log(`Request: ${requestObjectString}`);
      console.log(
        `Environment (pre): ${JSON.stringify(environment, null, 2)})`
      );

      // Call the user function with request object
      let result = await userFunction(requestObject);

      return Result(States.SUCCESS, result, environment);
    } else {
      return Result(States.NOT_A_FUNCTION, null, environment);
    }
  } catch (err) {
    if (err.message === "Script execution timed out.") {
      return Result(States.TIMEOUT, null, environment);
    } else {
      return Result(States.SCRIPT_ERROR, err.message || err, environment);
    }
  }
}

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

  const timeout = req.query.timeout || TIMEOUT_MS;

  const result = await executeUserCode(
    code,
    request,
    environment,
    timeout,
    name
  );
  res.send(result);
});

app.listen(port, () => {
  console.log(`Server listening on port: ${port}`);
});