'use strict';

// dependencies
const express = require('express');
const bodyParser = require('body-parser');
const path = require('path');
const fs = require('fs');
const puppeteer = require('puppeteer'); // the package to generate pdf
const EventEmitter = require('events');
const opn = require('opn');

const app = express();
const emitter = new EventEmitter();

// generates a unique invoice number
let today = new Date();
let dd = today.getDate();
let mm = today.getMonth() + 1;
let invoicenum = '';
let yyyy = today.getFullYear();

if (dd < 10) {
    dd = '0' + dd;
}

if (mm < 10) {
    mm = '0' + mm;
}

today = dd + '.' + mm + '.' + yyyy;
invoicenum = dd + mm + yyyy + Math.floor(Math.random() * 1000) + 1;

// events
emitter.on('toPdf', () => {
    opn('http://localhost:3000/generate');
});

emitter.on('generatePdf', async () => {
    const url = 'http://localhost:3000/create';
    const browser = await puppeteer.launch();
    const page = await browser.newPage();
    await page.goto(url, {waitUntil: 'networkidle2'});
    await page.pdf({path: `invoice_${invoicenum}.pdf`, format: 'A4'});

    await browser.close();
    console.log('The invoice has been generated.');
    await opn(`http://localhost:3000/invoice_${invoicenum}.pdf`);
});

app.use(express.static(__dirname));
app.use(bodyParser.urlencoded({ extended: true }));

// routing
app.get('/', (req, res) => {
    res.sendFile(path.join(__dirname + '/index.html'));
});

app.post('/create', (req, res) => {
    let parsedHtml = req.body.data;

    fs.writeFile('invoice.html', parsedHtml, (err) => {
        if (err) {
            console.log('An error occured.');
            return;
        } else {
            console.log('The new HTML file was successfully created.');
        }
    });
});

app.get('/create', (req, res) => {
    res.sendFile(path.join(__dirname + '/invoice.html'));

    emitter.emit('toPdf');
});

app.get('/generate', (req, res) => {
    emitter.emit('generatePdf');
});

// listening on port
app.listen(3000, () => {
    console.log('Server is running on port 3000...');
});