react_tutorial_server.js

react_tutorial_server.js

const Http = require('http');
const Url = require('url');
const Path = require('path');
const Fs   = require('fs');

const COMMENTS_FILE = 'comments.json';

const server = Http.createServer(function requestListener(inComingMessage, serverResponse) {
  console.log(inComingMessage.method, inComingMessage.url, `at ${new Date()}`);
  console.log(inComingMessage.headers);

  function errorHandler(err, { side = 'client' } = {}) {
    console.error(err);
    const headerStatus = {
      clientError: { code: 404, name: 'NotFound' },
      serverError: { code: 500, name: 'Internal Server Error' },
    };

    const header = {
      ContentType: 'application/json',
    };

    if (side === 'client') {
      serverResponse.writeHead(headerStatus.clientError.code, headerStatus.clientError.name, header);
    } else {
      serverResponse.writeHead(headerStatus.serverError.code, headerStatus.serverError.name, header);
    }
    serverResponse.end();
  }

  function sendComments() {
    const header = {
      'ContentType': 'application/json',
      'Access-Control-Allow-Origin': 'http://localhost:63342',
      'Cache-Control': 'no-cache',
    };
    serverResponse.writeHead('200', 'OK', header);

    const filePath = Path.join(__dirname, COMMENTS_FILE);
    Fs.readFile(filePath, 'utf-8', (err, data) => {
      if (err) {
        errorHandler(err, { side: 'server' });
      } else {
        serverResponse.write(data);
        serverResponse.end();
      }
    });
  }

  function getCommentsHandler() {
    sendComments();
  }

  function postCommentsHandler() {
    inComingMessage.setEncoding('utf8');
    inComingMessage.on('data', (requestBody) => {
      const filePath = Path.join(__dirname, COMMENTS_FILE);
      Fs.readFile(filePath, (err, existingComments) => {
        if (err) {
          console.error(err);
          process.exit(1);
        }
        const comments   = JSON.parse(existingComments);
        const newComment = JSON.parse(requestBody);

        comments.push(newComment);

        /*
          nodeではreadのcallback中にwriteを書いていいらしい。

          fs.readFile(thePath, () => {
            fs.writeFile(thePath, () => {
            }
          })
        */
        const writeStream = Fs.createWriteStream(filePath);
        writeStream.write(JSON.stringify(comments));
        writeStream.end();

        sendComments();
      });
    });
  }

  (function router() {
    const requestPathName = Url.parse(inComingMessage.url).pathname;
    const requestMethod = inComingMessage.method;

    if (requestPathName === '/api/comments') {
      switch (requestMethod) {
        case 'GET':
          getCommentsHandler();
          break;
        case 'POST':
          postCommentsHandler();
          break;
        default:
          errorHandler(new Error(`requestMethod: ${requestMethod},  not allowed`));
      }
    } else {
      errorHandler(new Error(`requestPathName: ${requestPathName}, not implemented`));
    }
  })();
});

server.listen(3000, function logger() {
  console.log('start server at localhost:3000');
});