main.js

const electron = require("electron");
const url = require("url");
const path = require("path");
const Excel = require('exceljs');
require('electron-reload')(__dirname);
const {app,BrowserWindow,Menu,ipcMain, session} = electron;
const nodemailer = require('nodemailer');

let mainWindow;
let htmlPreviewWindow;
function createAddWindow(){
    htmlPreviewWindow = new BrowserWindow({
        width:600,
        height:800,
        frame:true,
        title:"HTML Preview",
        webPreferences: {
            nodeIntegration: true
        },
        parent:mainWindow,
    });
    htmlPreviewWindow.setAlwaysOnTop(true);
    // addWindow.setApplicationMenu(mainMenu);
    // load html into window
    htmlPreviewWindow.loadURL(url.format({
        pathname:path.join(__dirname,"addWindow.html"),
        protocol:"file",
        slashes:true
    }));
    
}
//Set Environment
process.env.NODE_ENV = 'development';

//listen for app to be ready

app.on('ready',function(){
    // create new window
    mainWindow = new BrowserWindow({
        frame:false,
        height:800,
        width:800,
        minHeight:800,
        minWidth:600,
        webPreferences: {
            nodeIntegration: true
        }});
    // load html into window
    mainWindow.loadURL(url.format({
        pathname:path.join(__dirname,"mainWindow.html"),
        protocol:"file",
        slashes:true
    }));
    mainWindow.maximize()
    //Quit app when closed
    mainWindow.on('closed', function(){
        app.quit();
    })

    //Build Menu from template
    const mainMenu = Menu.buildFromTemplate(mainMenuTemplate);
    //Insert menu
    Menu.setApplicationMenu(mainMenu);
    // Menu.setApplicationMenu(null);
    // mainWindow.setMenu(mainMenu)
});
//Catch item:add
ipcMain.on('send_email',function(e,item){
    var ws;
    console.log(item);
    var workbook = new Excel.Workbook();
    workbook.xlsx.readFile(item.excel_path)
    .then(function(){
        ws = workbook.getWorksheet('Sheet1');
        var cell = ws.getCell('A1').value;
        //console.log(cell);
        var rowHeader;
        ws.eachRow(function(row, rowNumber) {
            if(rowNumber==1){
                rowHeader = row.values;
                return;
            }
            if(!item.email_array[rowNumber-2]){
                var info = {'rowNumber':rowNumber,'status':2,'message':'Row not selected'};
                mainWindow.webContents.send('email_status',info);    
                return;
            }
            var HTMLText = replacePlaceholder(rowHeader,item.htmltext,row.values);
            sendEmail(item.host, item.port, item.email, item.pass, item.subject,row.values[item.emailHeader],item.text,HTMLText,rowNumber);
        })
    })
    .catch((err)=>{console.log(err)});
});

ipcMain.on("htmlpreview",function(e,item){
    console.log('HTML-----------',item);
    createAddWindow();
    setTimeout(()=>{
        htmlPreviewWindow.webContents.send('htmlpreview',item);
    },500);
});

function replaceAll(str, term, replacement) {
    return 
}
function escapeRegex(string) {
    return string.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&');
}
function replacePlaceholder(row_header,html_text,row_values){
    for(let i = 1;i<=row_header.length;i++){
        html_text = html_text.replace(new RegExp(escapeRegex("{{"+row_header[i]+"}}"), 'g'),row_values[i]);
    }
    return html_text;
}

const mainMenuTemplate = [{
    label:'File',
    submenu:[
        {   
            label: 'Open Excel',
            accelerator: process.platform == 'darwin' ? 'Command+F':'Ctrl+F',
            click(){
                mainWindow.webContents.send('openexcel');
            }
        },
        {   
            label: 'Quit',
            accelerator: process.platform == 'darwin' ? 'Command+Q':'Ctrl+Q',
            click(){
                app.quit();
            }
        },
    ]
}];

//if mac, add empty object to menu
if(process.platform === "darwin"){
    mainMenuTemplate.unshift({});
}

//add developer tools item if not in production
if(process.env.NODE_ENV !== "production"){
    mainMenuTemplate.push({
        label:'Developer Tools',
        submenu:[
            {
                label: 'Toggle DevTools',
                accelerator: process.platform == 'darwin' ? 'Command+I':'Ctrl+I',
                click(item,focusedWindow){
                    focusedWindow.toggleDevTools();
                }
            },
            {
                role:'reload'
            }
        ]
    })
}
async function sendEmail(email_host, host_port, email_id, password, subject, to_email,text,htmltext,rowNumber){
    let transport = nodemailer.createTransport({
        host: email_host,
        port: host_port,
        auth: {
           user: email_id,
           pass: password
        }
    });
    const message = { 
        from:email_id, 
        to: to_email, 
        subject: subject, 
        text: text,
        html:htmltext
    };
    return new Promise(function (resolve, reject){
        transport.sendMail(message, function(err, info){
            if (err) {
                console.log(err);
                console.log(err.code);
                var item = {'rowNumber':rowNumber,'status':0,'message':'Something gone wrong'};
                if(err.response){
                    item.response = err.response;
                }
                mainWindow.webContents.send('email_status',item);
            } else {
                info.rowNumber = rowNumber;
                info.status = '1';
                console.log(info);
                mainWindow.webContents.send('email_status',info);
            }
        });
     });
}