react-native-devtools-frontend/scripts/hosted_mode/server.js

// Copyright (c) 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
const fs = require('fs');
const http = require('http');
const path = require('path');
const parseURL = require('url').parse;

const remoteDebuggingPort = parseInt(process.env.REMOTE_DEBUGGING_PORT, 10) || 9222;
const serverPort = parseInt(process.env.PORT, 10) || 8090;
const devtoolsFolder = path.resolve(path.join(__dirname, '..', '..'));

http.createServer(requestHandler).listen(serverPort);
console.log(`Started hosted mode server at http://localhost:${serverPort}\n`);
console.log('For info on using the hosted mode server, see our contributing docs:');
console.log('https://bit.ly/devtools-contribution-guide');
console.log('Tip: Look for the \'Development server options\' section\n');

function requestHandler(request, response) {
  const filePath = parseURL(request.url).pathname;
  if (filePath === '/') {
    const landingURL = `http://localhost:${remoteDebuggingPort}#custom=true`;
    sendResponse(200, `<html>Please go to <a href="${landingURL}">${landingURL}</a></html>`);
    return;
  }

  const absoluteFilePath = path.join(devtoolsFolder, filePath);
  if (!path.resolve(absoluteFilePath).startsWith(devtoolsFolder)) {
    console.log(`File requested (${absoluteFilePath}) is outside of devtools folder: ${devtoolsFolder}`);
    sendResponse(403, `403 - Access denied. File requested is outside of devtools folder: ${devtoolsFolder}`);
    return;
  }

  fs.exists(absoluteFilePath, fsExistsCallback);

  function fsExistsCallback(fileExists) {
    if (!fileExists) {
      console.log(`Cannot find file ${absoluteFilePath}`);
      sendResponse(404, '404 - File not found');
      return;
    }

    let encoding = 'utf8';
    if (absoluteFilePath.endsWith('.wasm') || absoluteFilePath.endsWith('.png') || absoluteFilePath.endsWith('.jpg')) {
      encoding = 'binary';
    }

    fs.readFile(absoluteFilePath, encoding, readFileCallback);
  }

  function readFileCallback(err, file) {
    if (err) {
      console.log(`Unable to read local file ${absoluteFilePath}:`, err);
      sendResponse(500, '500 - Internal Server Error');
      return;
    }
    sendResponse(200, file);
  }

  function sendResponse(statusCode, data) {
    const path = parseURL(request.url).pathname;

    if (path.endsWith('.rawresponse')) {
      sendRawResponse(data);
      return;
    }

    let encoding = 'utf8';
    if (path.endsWith('.js') || path.endsWith('.mjs')) {
      response.setHeader('Content-Type', 'text/javascript; charset=utf-8');
    } else if (path.endsWith('.css')) {
      response.setHeader('Content-Type', 'text/css; charset=utf-8');
    } else if (path.endsWith('.wasm')) {
      response.setHeader('Content-Type', 'application/wasm');
      encoding = 'binary';
    } else if (path.endsWith('.svg')) {
      response.setHeader('Content-Type', 'image/svg+xml; charset=utf-8');
    } else if (path.endsWith('.png')) {
      response.setHeader('Content-Type', 'image/png');
      encoding = 'binary';
    } else if (path.endsWith('.jpg')) {
      response.setHeader('Content-Type', 'image/jpg');
      encoding = 'binary';
    }

    response.writeHead(statusCode);
    response.write(data, encoding);
    response.end();
  }

  function sendRawResponse(data) {
    const lines = data.split('\n');

    let isHeader = true;
    let line = lines.shift();
    const statusCode = parseInt(line, 10);

    while ((line = lines.shift()) !== undefined) {
      if (line.trim() === '') {
        isHeader = false;
        if (request.headers['if-none-match'] && response.getHeader('ETag') === request.headers['if-none-match']) {
          response.writeHead(304);
          response.end();
          return;
        }
        response.writeHead(statusCode);
        continue;
      }

      if (isHeader) {
        const firstColon = line.indexOf(':');
        response.setHeader(line.substring(0, firstColon), line.substring(firstColon + 1).trim());
      } else {
        response.write(line);
      }
    }

    response.end();
  }
}