main.js

const {app, BrowserWindow, ipcMain, dialog, shell} = require('electron')
const path = require('path')
const url = require('url')
const fs = require('fs')
const per = require('./persistance')

let win

const createWindow = function() {

    win = new BrowserWindow({width: 1024, height: 768})

    win.loadURL(url.format({
      pathname: path.join(__dirname, 'src/index.html'),
      protocol: 'file:',
      slashes: true
    }))

    win.on('closed', () => {
	win = null
    })

    console.log("BrowserWindow created")
}

app.on('ready', function(){

    const uri = url.format({
        pathname: path.join(__dirname, 'data.db'),
        protocol: 'nedb:',
        slashes: true
    })

    per.init(uri, function(err){
	if(err){
	    console.log("Error initializing persistance..")
	    console.log(err)
	    console.log("Terminating the main process")
	    app.quit()
	}else{
	    console.log("creating BrowserWindow")
	    createWindow()
	}
    })
})

app.on('window-all-closed', () => {
    app.quit()
})

const addCourse = function(event, arg){
    per.saveCourse(arg, function(err, id){
	if(err){
	    console.log("Failed to save course")
	    console.log(err)
	}
	event.sender.send('add-course', id)
    })
}

const getCourse = function(event, arg){
    per.getCourse({_id:arg}, function(err, doc){
	if (err){
	    console.log("Failed to get course")
	    console.log(err)
	}
	event.sender.send('get-course', doc)
    })
}

const getCourses = function(event, arg){
    per.getCourses({}, function(err, docs){
	if (err){
	    console.log("Failed to get course")
	    console.log(err)
	}
	event.sender.send('get-courses', docs)
    })
}

const getStudents = function(event, arg){
    per.getStudents({courseID:arg}, function(err, docs){
	if (err){
	    console.log("Failed to get students for courseID : ", arg)
	    console.log(err)
	}
	event.sender.send('get-students', docs)
    })
}

const addStudent = function(event, arg){
    per.saveStudent(arg, function(err, id){
	if(err){
	    console.log("Failed to save student")
	    console.log(err)
	}
	event.sender.send('add-student', id)
    })
}

const addTxn = function(event, arg){
    per.saveTxn(arg, function(err, id){
	if(err){
	    console.log("Failed to save transaction")
	    console.log(err)
	}
	event.sender.send('add-txn', id)
    })
}

const getTxns = function(event, arg){
    per.getTxns({_id:arg}, function(err, docs){
	if (err){
	    console.log("Failed to get transactions for studentID : ", arg)
	    console.log(err)
	}
	event.sender.send('get-txns', docs)
    })
}

const getCourseSummary = function(event, arg){
    per.getCourseSummary({_id:arg}, function(err, docs){
	if (err){
	    console.log("Failed to get transaction summary for course : ", arg)
	    console.log(err)
	}
	event.sender.send('get-course-summary', docs)
    })
}

const showSaveDialog = function(dialogOptions,cb){
    dialog.showSaveDialog(dialogOptions, function(filePath){
	if(filePath) cb(filePath)
    })
}

const writeToFile = function(filePath, data, cb){
    fs.writeFile(filePath, data, function (error) {
	if (error) throw error
	cb()
    })
}

const generatePDF = function(win, options, cb){
    const wind = BrowserWindow.fromWebContents(win)
    wind.webContents.printToPDF(options, cb)
}

const printPDF = function(event) {
    const dialogOptions = {
	title: "Where to save PDF",
	filters: [{name : 'pdf', extensions: ['pdf']}]
    }
    showSaveDialog(dialogOptions,function(filePath){
	generatePDF(event.sender, {}, function (error, data) {
    	    if (error) throw error
	    writeToFile(filePath, data, function(){
		shell.openExternal('file://' + filePath)
	    })
	})
    })
}	

ipcMain.on('add-course', addCourse)
ipcMain.on('get-course', getCourse)
ipcMain.on('get-courses', getCourses)
ipcMain.on('get-students', getStudents)
ipcMain.on('add-student', addStudent)
ipcMain.on('add-txn', addTxn)
ipcMain.on('get-txns', getTxns)
ipcMain.on('get-course-summary', getCourseSummary)
ipcMain.on('print-to-pdf', printPDF)