'use-strict'
// Core libraries required to run firebase
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);

// To compute SHA value for transaction
// TODO : Send Confirmation mail when transactions is successful.
const sha512 = require('js-sha512');

// Libraries required to send mail.
const nodemailer = require("nodemailer");
const gmailEmail = functions.config().gmail.email; // Google environment variable.
const gmailPassword = functions.config().gmail.password; // Google environment variable.
const mailTransport = nodemailer.createTransport({
  service: 'gmail',
  auth: {
    user: gmailEmail,
    pass: gmailPassword,
  },
});

const chartjsNode = require('chartjs-node');

// Chartjs-node is used to generate Charts for the pdf
//const chartjsNode = require('chartjs-node');
// Library to create monthly report PDF file.
const pdfkit = require('pdfkit');
const genrateHashMod = require('./generateHash');
const db = admin.firestore();

// EventListener listens when a transaction starts
exports.provideHash = functions.firestore.document('TRANSACTIONS/{TRAN_ID}')
  .onCreate((snapshot, context) => {
    return genrateHashMod.handler(snapshot, context, sha512, db);
})

/*
function generateMail() {
  // Mail options
  const mailOptions = {
    from: '"Avas Abacus Co." <noreply@firebase.com>',
    to: 'rahulyupz@gmail.com',
    subject: 'Monthly Report From Abacus Team.',
    text: 'As promised we are providing you with monthly report of your child. On the basis of this report you can make informed decisions. A warmth welcome to became a part of avas team.'
    attachments: [
      {
        filename: 'Report,pdf',
        content:
      }
    ]
  };

  return mailTransport.sendMail(mailOptions)
          .then(() => console.log("Mail successfully transfered."))
          .catch((error) => console.error('There has been some error', error));
}*/

function generatePdf() {
  const reportPdf = admin.storage().bucket().file('/test/example.pdf');
  const doc = new pdfkit;
  doc.pipe(reportPdf.createWriteStream());

  doc.fontSize(20).text('Avas Abacus Co.', {
        align: 'center',
        underline: 'true'
     });
  doc.fontSize(16).text('Monthly Report (March\'19)', {
        align: 'center'
     });

  doc.moveDown();
  doc.moveDown();

  for (var i = 0; i<10; i++) {
    doc.fontSize(10).text(list[i], {
         underline: true
       });

    doc.image(admin.storage().bucket().file('/test/example.png'), {
      fit: [450, 500],
      align: 'center',
      valign: 'center'
    });

    doc.moveDown();

    doc.fontSize(10)
       .text('Total Test Taken : 30', 50, 690);
    doc.fontSize(10)
       .text('Average Score : 87.45', 50, 700);

    if( i!==9) {
      doc.addPage();
    }
  }
  doc.end();
}

var config = {
  type: 'line',
  data: {
    label: ['01', '02', '03', '04','05','06','07','08','09','10', '11', '12', '13', '14','15','16','17','18','19','20 ','21', '22', '23', '24','25','26','27','28','29', '30'],
    datasets: [{
        label: 'Scores',
        data: ['91', '82', '93', '74','85', '66', '77', '88', '79', '80', '91', '82', '93', '74', '85', '66', '77', '88', '79', '80', '91', '82', '93', '74', '85', '66', '77', '88', '79', '80',]
    }]
  },
  options: {
    title: {
      display: true,
      text: 'Report'
    },
    scales: {
      xAxes: [{
        display: true,
        scaleLabel: {
          display: true,
          labelString: 'Day'
        }
      }],
      yAxes: [{
        display: true,
        scaleLabel: {
          display: true,
          labelString: 'Score'
        }
      }]
    }
  }
}

function generateChart() {
  console.log("generateChart is called.");

  var chartnode = new chartjsNode(600, 600);
  console.log("new object created.");
` return chartnode.drawChart(config)
    .then(() => {
      console.log("return buffer.");

      return chartnode.getImageBuffer('image/png');
    })
    .then(buffer => {
      console.log("return stream.");
      Array.isArray(buffer) // => true
      return chartnode.getImageStream('image/png');
    })
    .then(streamResult => {
      console.log("return image.");
      streamResult.stream // => Stream object
      streamResult.length // => Integer length of stream
      return chartnode.writeImageToFile('image/png', admin.storage().bucket().file('/test/example.png'));
    })
    .then(() => {
      return generatePdf();
    });
}

// Https hook to be triggered monhtly.
exports.generateReport = functions.https.onRequest((req, res) => {
  console.log("generateFunction called.");
  generateChart();
});