server.js

'use strict'

const express = require('express');
const { v4: uuidv4 } = require('uuid');
const app = express()
app.use(express.json());
const data = require('./books.json');


app.get('/books'        , function (req, res) {readBooks(req, res);})
app.post('/books'       , function (req, res) {createBook(req, res);})
app.put('/books/:id'    , function (req, res) {updateBook(req, res);})
app.delete('/books/:id'  , function (req, res) {deleteBook(req, res);})


function deleteBook(req, res) {
    const bookToDelete = data.find(book => book.id === req.params.id);
    if (typeof bookToDelete === 'undefined') {
        res.status(404);
        res.send('No such book');
        return;
    }
    data.splice(data.indexOf(bookToDelete), 1);
    res.send('OK')    
}


function isInvalid(req) {
    if (typeof req.body == "undefined" ||
        typeof req.body.title == "undefined" ||
        typeof req.body.author == "undefined") {
        return true;
    } else {
        return false;
    }
}


function updateBook(req, res) {
    if (isInvalid(req)) {
        res.status(400).send('invalid request');
        return;
    }
    const bookToUpdate = data.find(book => book.id === req.params.id);
    if (typeof bookToUpdate === 'undefined') {
        res.status(404);
        res.send('No such book');
        return;
    }
    bookToUpdate.title = req.body.title;
    bookToUpdate.author = req.body.author;
    res.send('OK');
}



function createBook(req, res) {
    if (isInvalid(req)) {
        res.status(400)
            .send('invalid request');
        return;
    }
    const id = uuidv4()
    let newBook = {
        id: id, 
        title: req.body.title,
        author: req.body.author
    }
    data.push(newBook);
    res.status(201).send(id);
}


function readBooks(req, res) {
    res.setHeader("Content-Type", "application/json")
    res.send(data);
}



app.listen(3000);