This code requires three external modules (fs, path, and express) and sets up environment variables and file paths to interact with a file system and create a web server. It defines several functions, including deleteSession, createSession, and getSessionCapabilities, and sets up an Express router with routes for creating, deleting, and retrieving session information.

Cell 4

var fs = require('fs');
var path = require('path');
var express = require('express');
var router = express.Router();

var TOKEN_DIR = path.join(process.env.HOME || process.env.HOMEPATH || process.env.USERPROFILE, '.credentials');
var SESSIONS_PATH = path.join(TOKEN_DIR, 'sessions.txt');
var sessionId = fs.readFileSync(SESSIONS_PATH).toString().split('\n')[0];

function deleteSession() {
    if (typeof getTab() !== 'undefined') {
        return promisifyChrome('debugger.detach', {tabId: getTab()})
            .then(() => ({value: {}}))
            .catch(e => console.log(e))
    } else {
        return Promise.resolve({value: {}});
    }
}

function createSession() {
    return Promise.resolve({
        value: {
            sessionId: sessionId,
            capabilities: {}
        }
    });
}

function getSessionCapabilities(sessionId) {
    return Promise.resolve({value: {}});
}

router.post('/session', (req, res) =>
    response(res, createSession()));
router.delete('/session/:sessionId', (req, res) =>
    response(res, deleteSession()));
router.get('/session/:sessionId', (req, res) => {
    response(res, getSessionCapabilities(req.params['sessionId']));
}); //,"GetSessionCapabilities",ExecuteGetSessionCapabilities,


module.exports = {
    deleteSession,
    createSession,
    router
}

// Import required modules
const express = require('express');
const { promisify } = require('util');
const fs = require('fs');
const path = require('path');

// Initialize Express router
const router = express.Router();

// Define constants for storing session credentials
const TOKEN_DIR = path.join(
  process.env.HOME || process.env.HOMEPATH || process.env.USERPROFILE,
  '.credentials'
);
const SESSIONS_PATH = path.join(TOKEN_DIR,'sessions.txt');

/**
 * Retrieves the first session ID from the sessions file.
 * @returns {string} The first session ID.
 */
function getSessionId() {
  try {
    return fs.readFileSync(SESSIONS_PATH).toString().split('\n')[0];
  } catch (error) {
    // Handle file read error
    console.error('Error reading sessions file:', error);
    return null;
  }
}

/**
 * Deletes a session and detaches the debugger.
 * @param {number} tabId The tab ID.
 * @returns {Promise<Object>} A promise resolving to an empty object.
 */
async function deleteSession(tabId) {
  try {
    if (tabId) {
      return promisifyChrome('debugger.detach', { tabId })({ value: {} });
    } else {
      return { value: {} };
    }
  } catch (error) {
    // Handle error detaching debugger
    console.error('Error detaching debugger:', error);
    return { value: {} };
  }
}

/**
 * Creates a new session.
 * @returns {Promise<Object>} A promise resolving to a session object.
 */
async function createSession() {
  const sessionId = getSessionId();
  if (!sessionId) {
    // TODO: Handle case where session ID is not found
    return { value: {} };
  }
  return { value: { sessionId, capabilities: {} } };
}

/**
 * Retrieves session capabilities for a given session ID.
 * @param {string} sessionId The session ID.
 * @returns {Promise<Object>} A promise resolving to session capabilities.
 */
async function getSessionCapabilities(sessionId) {
  // TODO: Implement retrieving session capabilities
  return { value: {} };
}

/**
 * Responds to API requests.
 * @param {express.Response} res The response object.
 * @param {Object} resolve The result of the API request.
 */
function response(res, resolve) {
  res.status(200).json(resolve);
}

// Define API endpoints
router.post('/session', (req, res) => response(res, createSession()));
router.delete('/session/:sessionId', (req, res) =>
  response(res, deleteSession(req.params.sessionId))
);
router.get('/session/:sessionId', (req, res) =>
  response(res, getSessionCapabilities(req.params.sessionId))
);

// Export router and session management functions
module.exports = {
  deleteSession,
  createSession,
  getSessionCapabilities,
  getSessionId,
  router,
};

// Helper function to promisify Chrome API calls
function promisifyChrome(method, data) {
  // TODO: Implement promisifyChrome function
  return Promise.resolve();
}

Code Breakdown

Dependencies and Variables

• The code requires three external modules:
  • fs (File System) to interact with the file system
  • path to manipulate file paths
  • express to create a web server
• It sets up some environment variables and file paths:
  • TOKEN_DIR points to a directory containing credentials
  • SESSIONS_PATH points to a file called sessions.txt within TOKEN_DIR
  • sessionId is read from the file at SESSIONS_PATH

Functions

deleteSession

• This function detaches a debugger from a specified tab ID (if one is available)
• If a tab ID is not available, it returns an empty object
• The function uses promisifyChrome to interact with the Chrome debugger, but its implementation is not shown in this code snippet

createSession

• This function creates a new session and returns an object with sessionId and capabilities
• The sessionId is obtained from the sessions.txt file

getSessionCapabilities

• This function retrieves the capabilities for a given session ID
• It returns an empty object by default, but its implementation is incomplete in this code snippet

Express Router

• The code sets up an Express router with three routes:
  • POST /session: Creates a new session and returns the result
  • DELETE /session/:sessionId: Deletes a session (calls deleteSession)
  • GET /session/:sessionId: Retrieves the capabilities for a given session ID (calls getSessionCapabilities)

Exports

• The code exports the deleteSession, createSession, and router objects.