server.js

const express = require('express');
const app = express();
const mysql = require('mysql');
const session = require('express-session');
const bcrypt = require('bcrypt');
const bodyParser = require('body-parser');
const crypto = require('crypto');
const Web3 = require('web3');
const BigNumber = require('bignumber.js');
const fs = require('fs');
// const io = require('socket.io')(app);

// Secret ID for session
const secret_id = process.env.secret;

// Salt for hashing
const saltRounds = 10;

// IP and port
const IP = 'localhost';
const port = process.env.PORT || 8080;

// View engine
// app.set('views', path.join(__dirname, 'views'));
// app.set('view engine', 'ejs');

// Body-parser Middleware
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({
    extended: true
}));

// Express session Middleware
// app.use(session({
//     secret: secret_id,
//     saveUninitialized: true,
//     resave: true
// }));

// MySQL Connection
const connection = mysql.createConnection({
    host: IP,
    user: process.env.database_user,
    password: process.env.database_password,
    database: 'authentifi'
});

connection.connect(function(err) {
    if (!err) {
        console.log('Connected to MySql!\n');
    } else {
        console.log('Not connected to MySql.\n');
    }
});

// Web3 connection
const web3 = new Web3(new Web3.providers.HttpProvider('http://localhost:7545'));
console.log(`Talking with a geth server ${web3.version.api} \n`);

const abiArray = [
	{
		"constant": false,
		"inputs": [
			{
				"name": "_code",
				"type": "string"
			},
			{
				"name": "_hashedEmailRetailer",
				"type": "string"
			}
		],
		"name": "addRetailerToCode",
		"outputs": [
			{
				"name": "",
				"type": "uint256"
			}
		],
		"payable": true,
		"stateMutability": "payable",
		"type": "function"
	},
	{
		"constant": false,
		"inputs": [
			{
				"name": "_code",
				"type": "string"
			},
			{
				"name": "_oldCustomer",
				"type": "string"
			},
			{
				"name": "_newCustomer",
				"type": "string"
			}
		],
		"name": "changeOwner",
		"outputs": [
			{
				"name": "",
				"type": "bool"
			}
		],
		"payable": true,
		"stateMutability": "payable",
		"type": "function"
	},
	{
		"constant": false,
		"inputs": [
			{
				"name": "_code",
				"type": "string"
			},
			{
				"name": "_brand",
				"type": "string"
			},
			{
				"name": "_model",
				"type": "string"
			},
			{
				"name": "_status",
				"type": "uint256"
			},
			{
				"name": "_description",
				"type": "string"
			},
			{
				"name": "_manufactuerName",
				"type": "string"
			},
			{
				"name": "_manufactuerLocation",
				"type": "string"
			},
			{
				"name": "_manufactuerTimestamp",
				"type": "string"
			}
		],
		"name": "createCode",
		"outputs": [
			{
				"name": "",
				"type": "uint256"
			}
		],
		"payable": true,
		"stateMutability": "payable",
		"type": "function"
	},
	{
		"constant": false,
		"inputs": [
			{
				"name": "_hashedEmail",
				"type": "string"
			},
			{
				"name": "_name",
				"type": "string"
			},
			{
				"name": "_phone",
				"type": "string"
			}
		],
		"name": "createCustomer",
		"outputs": [
			{
				"name": "",
				"type": "bool"
			}
		],
		"payable": true,
		"stateMutability": "payable",
		"type": "function"
	},
	{
		"constant": false,
		"inputs": [],
		"name": "createOwner",
		"outputs": [],
		"payable": false,
		"stateMutability": "nonpayable",
		"type": "function"
	},
	{
		"constant": false,
		"inputs": [
			{
				"name": "_hashedEmail",
				"type": "string"
			},
			{
				"name": "_retailerName",
				"type": "string"
			},
			{
				"name": "_retailerLocation",
				"type": "string"
			}
		],
		"name": "createRetailer",
		"outputs": [
			{
				"name": "",
				"type": "uint256"
			}
		],
		"payable": true,
		"stateMutability": "payable",
		"type": "function"
	},
	{
		"constant": false,
		"inputs": [
			{
				"name": "_code",
				"type": "string"
			},
			{
				"name": "_retailer",
				"type": "string"
			},
			{
				"name": "_customer",
				"type": "string"
			}
		],
		"name": "initialOwner",
		"outputs": [
			{
				"name": "",
				"type": "bool"
			}
		],
		"payable": true,
		"stateMutability": "payable",
		"type": "function"
	},
	{
		"constant": false,
		"inputs": [
			{
				"name": "_code",
				"type": "string"
			},
			{
				"name": "_customer",
				"type": "string"
			}
		],
		"name": "reportStolen",
		"outputs": [
			{
				"name": "",
				"type": "bool"
			}
		],
		"payable": true,
		"stateMutability": "payable",
		"type": "function"
	},
	{
		"constant": true,
		"inputs": [
			{
				"name": "_customer",
				"type": "string"
			}
		],
		"name": "getCodes",
		"outputs": [
			{
				"name": "",
				"type": "string[]"
			}
		],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	},
	{
		"constant": true,
		"inputs": [
			{
				"name": "_code",
				"type": "string"
			}
		],
		"name": "getCustomerDetails",
		"outputs": [
			{
				"name": "",
				"type": "string"
			},
			{
				"name": "",
				"type": "string"
			}
		],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	},
	{
		"constant": true,
		"inputs": [
			{
				"name": "_code",
				"type": "string"
			}
		],
		"name": "getNotOwnedCodeDetails",
		"outputs": [
			{
				"name": "",
				"type": "string"
			},
			{
				"name": "",
				"type": "string"
			},
			{
				"name": "",
				"type": "uint256"
			},
			{
				"name": "",
				"type": "string"
			},
			{
				"name": "",
				"type": "string"
			},
			{
				"name": "",
				"type": "string"
			},
			{
				"name": "",
				"type": "string"
			}
		],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	},
	{
		"constant": true,
		"inputs": [
			{
				"name": "_code",
				"type": "string"
			}
		],
		"name": "getOwnedCodeDetails",
		"outputs": [
			{
				"name": "",
				"type": "string"
			},
			{
				"name": "",
				"type": "string"
			}
		],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	},
	{
		"constant": true,
		"inputs": [
			{
				"name": "_code",
				"type": "string"
			}
		],
		"name": "getretailerDetails",
		"outputs": [
			{
				"name": "",
				"type": "string"
			},
			{
				"name": "",
				"type": "string"
			}
		],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	},
	{
		"constant": true,
		"inputs": [],
		"name": "whoIsOwner",
		"outputs": [
			{
				"name": "",
				"type": "address"
			}
		],
		"payable": false,
		"stateMutability": "view",
		"type": "function"
	}
];

const address = '';

const contract = web3.eth.contract(abiArray);

const contractInstance = contract.at(address);
web3.eth.defaultAccount = web3.eth.coinbase;

// This function generates a QR code
function generateQRCode() {
    return crypto.randomBytes(20).toString('hex');
}

// Hash password using bcrypt
function hashBcrypt(password) {
    return bcrypt.hashSync(password, saltRounds);
}

// Hash email using md5
function hashMD5(email) {
    return crypto.createHash('md5').update(email).digest('hex');
}

// Routes for webpages
app.use(express.static(__dirname + '/views'));
app.use(express.static(__dirname + '/views/davidshimjs-qrcodejs-04f46c6'));

// Manufacturer generates a QR Code here
app.get('/createCodes', (req, res) => {
    res.sendFile('views/createCodes.html', { root: __dirname });
});

// Creating a new retailer
app.get('/createRetailer', (req, res) => {
    res.sendFile('views/createRetailer.html', { root: __dirname });
});

// Main website which has 2 routers - manufacturer & retailer
app.get('/', (req, res) => {
    res.sendFile('views/index.html', { root: __dirname });
});


/**
 * Description: Adds a user to the database and to the blockchain
 * Request:     POST /signUp
 * Send:        JSON object which contains name, email, password, phone
 * Receive:     200 if successful, 400 otherwise
 */
app.post('/signUp', (req, res) => {
    console.log('Request to /signUp\n');
    let name = req.body.name;
    let email = req.body.email;
    let password = req.body.password;
    let phone = req.body.phone;
    let hashedPassword = hashBcrypt(password);
    console.log(`Email: ${email} \n`);
    // Adding the user in MySQL
    connection.query('SELECT * FROM USER WHERE Email = ? LIMIT 1', [email], (error, results) => {
        if (error) {
            callback(error);
            return res.status(400);
        }
        if (results.length) {
            return res.status(400).send('Email already exists!');
        }
        connection.query('INSERT INTO USER VALUES (?,?,?,?)', [name, email, hashedPassword, phone], (error, results) => {
            if (error) {
                callback(error);
                return res.status(400);
            }
            res.status(200).send('Signup successful!');
            // Adding user to the Blockchain
            hashedEmail = hashMD5(email);
            let ok = createCustomer(hashedEmail, name, phone);
            if (ok) {
                console.log(`User ${hashedEmail} successfully added to Blockchain!\n`);
            } else {
                console.log('ERROR! User could not be added to Blockchain.\n');
            }
        });
    });
});

// Add the user in Blockchain
function createCustomer(hashedEmail, name, phone) {
    return contractInstance.createCustomer(hashedEmail, name, phone, { from: web3.eth.accounts[0], gas: 3000000 });
}


/**
 * Description: Login the user to the app
 * Request:     POST /login
 * Send:        JSON object which contains email, password
 * Receive:     200 if successful, 400 otherwise
 */
app.post('/login', (req, res) => {
    console.log('Request to /login\n');
    let email = req.body.email;
    let password = req.body.password;
    console.log(`Email: ${email} \n`);
    connection.query('SELECT * FROM USER WHERE Email = ? LIMIT 1', [email], (error, results) => {
        if (error) {
            callback(error);
            return res.status(400);
        }
        if (results.length) {
            connection.query('SELECT Password FROM USER WHERE Email = (?)', [email], (error, results) => {
                if (error) {
                    callback(error);
                    return res.status(400);
                }
                let pass = results[0].Password;
                if (bcrypt.compareSync(password, pass)) {
                    console.log(`Login successful with ${email} \n`);
                    return res.status(200).send('Login successful!');
                }
                return res.status(400).send('Login failed.');
            });
        }
        console.log('Email does not exist!\n');
        return res.status(400).send('Email does not exist!');
    });
});


/**
 * Description: Adds a retailer to the database and to the blockchain
 * Request:     POST /retailerSignUp
 * Send:        JSON object which contains name, email, password, location
 * Receive:     200 if successful, 400 otherwise
 */
app.post('/retailerSignup', (req, res) => {
    console.log('Request to /retailerSignup\n');
    let retailerEmail = req.body.email;
    let retailerName = req.body.name;
    let retailerLocation = req.body.location;
    let retailerPassword = req.body.password;
    let retailerHashedPassword = hashBcrypt(retailerPassword);
    let retailerHashedEmail = hashMD5(retailerEmail);
    console.log(`retailerEmail: ${retailerEmail}, hashedEmail: ${retailerHashedEmail} \n`);
    // Adding the retailer in MySQL
    connection.query('SELECT * FROM RETAILER WHERE retailerEmail = ? LIMIT 1', [retailerEmail], (error, results) => {
        if (error) {
            callback(error);
            return res.status(400).send('Some SQL Error');
        }
        if (results.length) {
            return res.status(400).send('Email already exists!');
        }
        connection.query('INSERT INTO RETAILER VALUES (?,?,?,?)', [retailerName, retailerEmail, retailerLocation,
                                                                    retailerHashedPassword], (error, results) => {
            if (error) {
                callback(error);
                return res.status(400).send('Some SQL Error');
            }
            // Adding retailer to Blockchain
            let ok = createRetailer(retailerHashedEmail, retailerName, retailerLocation);
            if (ok) {
                console.log(`Retailer ${retailerHashedEmail} successfully added to Blockchain!\n`);
                return res.status(200).send('Retailer successfully added');
            }
            console.log('ERROR! Retailer could not be added to Blockchain.\n');
            return res.status(400).send('Adding Retailer Unsuccessful');
        });
    });
});

// Add retailer to Blockchain
function createRetailer(retailerHashedEmail, retailerName, retailerLocation) {
    return contractInstance.createRetailer(retailerHashedEmail, retailerName, retailerLocation,
                                        { from: web3.eth.accounts[0], gas: 3000000 });
}


/**
 * Description: Login the retailer to the app
 * Request:     POST /retailerLogin
 * Send:        JSON object which contains email, password
 * Receive:     200 if successful, 400 otherwise
 */
app.post('/retailerLogin', (req, res) => {
    console.log('Request to /retailerLogin\n');
    let retailerEmail = req.body.email;
    let retailerPassword = req.body.password;
    console.log(`Email: ${retailerEmail} \n`);
    connection.query('SELECT retailerHashedPassword FROM RETAILER WHERE retailerEmail = ?', [retailerEmail], (error, results) => {
        if (error) {
            callback(error);
            return res.status(400);
        }
        let pass = results[0].retailerHashedPassword ;
        if (bcrypt.compareSync(retailerPassword, pass)){
            console.log(`${retailerEmail} has successfully logged in\n`);
            return res.status(200).send('Retailer login successful!');
        }
        console.log(`${retailerEmail} COULD NOT login\n`);
        return res.status(400).send('Retailer login failed.');
    })
});


/**
 * Description: Get reatiler details
 * Request:     GET /retailerDetails
 * Send:
 * Receive:     JSON object of retailer details if successful, 400 otherwise
 */
app.get('/retailerDetails', (req, res) => {
    connection.query('Select * from RETAILER', (error, results) => {
        if(error) {
            callback(error);
            return res.status(400).send('ERROR');
        }
        console.log(`Retailer details are:\n ${results} \n`);
        return res.status(400).send(JSON.parse(JSON.stringify(results)));
    })
});


/**
 * Description: Add retailer to code
 * Request:     POST /addRetailerToCode
 * Send:        JSON object which contains code, email
 * Receive:     200 if successful, 400 otherwise
 */
app.post('/addRetailerToCode', (req, res) => {
    console.log('Request to /addRetailerToCode\n');
    let code = req.body.code;
    let retailerEmail = req.body.email;
    let hashedEmail = hashMD5(retailerEmail);
    console.log(`retailerEmail: ${retailerEmail}, hashed email: ${hashedEmail} \n`);
    let ok = contractInstance.addRetailerToCode(code, hashedEmail);
    if(!ok) {
        return res.status(400).send('Error');
    }
    console.log(`Successfully added ${hashedEmail} to code ${code} \n`);
    return res.status(200).send('Success');
});


/**
 * Description: Lists all the assets owned by the user
 * Request:     POST /myAssets
 * Send:        JSON object which contains email
 * Receive:     JSON array of objects which contain brand, model, description, status, manufacturerName,manufacturerLocation,
 *                                                  manufacturerTimestamp, retailerName, retailerLocation, retailerTimestamp
 */
app.post('/myAssets', (req, res) => {
    console.log('Request to /myAssets\n');
    let myAssetsArray = [];
    let email = req.body.email;
    let hashedEmail = hashMD5(email);
    let arrayOfCodes = contractInstance.getCodes(hashedEmail);
    console.log(`Email ${email}`);
    console.log(`Customer has these product codes: ${arrayOfCodes} \n`);
    for (code in arrayOfCodes) {
        let ownedCodeDetails = contractInstance.getOwnedCodeDetails(arrayOfCodes[code]);
        let notOwnedCodeDetails = contractInstance.getNotOwnedCodeDetails(arrayOfCodes[code]);
        myAssetsArray.push({
            'code': arrayOfCodes[code], 'brand': notOwnedCodeDetails[0],
            'model': notOwnedCodeDetails[1], 'description': notOwnedCodeDetails[2],
            'status': notOwnedCodeDetails[3], 'manufacturerName': notOwnedCodeDetails[4],
            'manufacturerLocation': notOwnedCodeDetails[5], 'manufacturerTimestamp': notOwnedCodeDetails[6],
            'retailerName': ownedCodeDetails[0], 'retailerLocation': ownedCodeDetails[1],
            'retailerTimestamp': ownedCodeDetails[2]
        });
    }
    res.status(200).send(JSON.parse(JSON.stringify(myAssetsArray)));
});


/**
 * Description: Lists all the assets owned by the user
 * Request:     POST /stolen
 * Send:        JSON object which contains code, email
 * Receive:     200 if product status was changed, 400 otherwise.
 */
app.post('/stolen', (req, res) => {
    console.log('Request to /stolen\n');
    let code = req.body.code;
    let email = req.body.email;
    let hashedEmail = hashMD5(email);
    console.log(`Email: ${email} \n`);
    let ok = contractInstance.reportStolen(code, hashedEmail);
    if (!ok) {
        console.log(`ERROR! Code: ${code} status could not be changed.\n`);
        return res.status(400).send('ERROR! Product status could not be changed.');
    }
    console.log(`Product code ${code} successfully changed!\n`);
    res.status(200).send('Product status successfully changed!');
});


// This array keeps track of all the QR Codes in use
const QRCodes = [];

/**
 * Description: Sell a product from myAssets (aka your inventory)
 * Request:     POST /sell
 * Send:        JSON object which contains code, sellerEmail
 * Receive:     List of QR Codes owned by the seller if successful, 400 otherwise
 */
app.post('/sell', (req, res) => {
    console.log('Request to /sell\n');
    let code = req.body.code;
    let sellerEmail = req.body.email;
    console.log(`Email ${sellerEmail} \n`);
    hashedSellerEmail = hashMD5(sellerEmail);
    let currentTime = Date.now();         // Date.now() gets the current time in milliseconds
    let QRCode = generateQRCode();
    let QRCodeObj = {
        'QRCode': QRCode, 'currentTime': currentTime, 'sellerEmail': sellerEmail, 'buyerEmail': '',
        'code': code, 'confirm': '0', 'retailer': '0'
    };
    QRCodes.push(QRCodeObj);
    console.log(`Session created ${(JSON.stringify(QRCode))} \n`);
    res.status(200).send(JSON.parse(JSON.stringify(QRCode)));
});


/**
 * Description: Buy a product
 * Request:     POST /buy
 * Send:        JSON object which contains QRCode, email
 * Receive:     200 if successful, 400 otherwise
 */
app.post('/buy', (req, res) => {
    console.log('Request to /buy\n');
    let QRCode = req.body.QRCode;
    let buyerEmail = req.body.email;
    let currentTime = Date.now();         // Date.now() gets the current time in milliseconds
    console.log(`Email: ${buyerEmail} \n`);
    for (let i = 0; i < QRCodes.length; i++) {
        if (QRCode === QRCodes[i]['QRCode']) {
            let timeElapsed = Math.floor((currentTime - QRCodes[i]['currentTime']) / 1000);
            // QR Codes are valid only for 600 secs
            if (timeElapsed <= 600) {
                QRCodes[i]['buyerEmail'] = buyerEmail;
                console.log(`QRCode matches, Session updated ${(JSON.stringify(QRCode))} \n`);
                return res.status(200).send('Validated!');
            }
            console.log('Time out error\n');
            return res.status(400).send('Timed out!');
        }
    }
    console.log('Could not find QRCode\n');
    return res.status(400).send('Could not find QRCode');
});


/**
 * Description: Get product details
 * Request:     POST /getProductDetails
 * Send:        JSON object which contains code
 * Receive:     JSON object whcih contains brand, model, description, status, manufacturerName, manufacturerLocation,
 *                                         manufacturerTimestamp, retailerName, retailerLocation, retailerTimestamp
 */
app.post('/getProductDetails', (req, res) => {
    console.log('Request to /getProductDetails\n');
    let code = req.body.code;
    let QRCode = req.body.QRCode;
    let currentTime = Date.now();         // Date.now() gets the current time in milliseconds
    for (let i = 0; i < QRCodes.length; i++) {
        if (QRCode === QRCodes[i]['QRCode']) {
            let timeElapsed = Math.floor((currentTime - QRCodes[i]['currentTime']) / 1000);
            // QR Codes are valid only for 600 secs
            if (timeElapsed <= 600) {
                let ownedCodeDetails = contractInstance.getOwnedCodeDetails(code);
                let notOwnedCodeDetails = contractInstance.getNotOwnedCodeDetails(code);
                if (!ownedCodeDetails || !notOwnedCodeDetails) {
                    return res.status(400).send('Could not retrieve product details.');
                }
                let productDetails = {
                    'brand': notOwnedCodeDetails[0], 'model': notOwnedCodeDetails[1], 'description': notOwnedCodeDetails[2],
                    'status': notOwnedCodeDetails[3], 'manufacturerName': notOwnedCodeDetails[4],
                    'manufacturerLocation': notOwnedCodeDetails[5], 'manufacturerTimestamp': notOwnedCodeDetails[6],
                    'retailerName': ownedCodeDetails[0], 'retailerLocation': ownedCodeDetails[1],
                    'retailerTimestamp': ownedCodeDetails[2]
                };
                console.log('QRCode matched\n');
                return res.status(200).send(JSON.parse(JSON.stringify(productDetails)));
            }
            console.log('Time out error\n');
            return res.status(400).send('Timed out!');
        }
    }
});


/**
 * Description: Seller confirms deal and gets registered as new owner on the Blockchain
 * Request:     POST /sellerConfirm
 * Send:        JSON object which contains email, QRCode, retailer
 * Receive:     200 if successful, 400 otherwise
 */
app.post('/sellerConfirm', (req, res) => {
    console.log('Request to /sellerConfirm\n');
    let sellerEmail = req.body.email;
    let QRCode = req.body.QRCode;
    let retailer = req.body.retailer;
    console.log(`Email: ${sellerEmail} \n`);
    let currentTime = Date.now();         // Date.now() gets the current time in milliseconds
    let sellerHashedEmail = hashMD5(sellerEmail);
    for (let i = 0; i < QRCodes.length; i++) {
        if (QRCode === QRCodes[i]['QRCode']) {
            let timeElapsed = Math.floor((currentTime - QRCodes[i]['currentTime']) / 1000);
            // QR Codes are valid only for 600 secs
            if (timeElapsed <= 600) {
                QRCodes[i]['confirm'] = '1';
                if(retailer === '1') {
                    QRCodes[i]['retailer'] = '1';
                }
                console.log('Success in sellerConfirm\n');
                return res.status(200).send('Seller confirmed!');
            }
            console.log('Time out error\n');
            return res.status(400).send('Timed out!');
        }
    }
    console.log('Could not find QRCodes\n');
    return res.status(400).send('Could not find QRCodes');
});


/**
 * Description: Buyer confirms deal
 * Request:     POST /buyerConfirm
 * Send:        JSON object which contains email, QRCode
 * Receive:     200 if successful, 400 otherwise
 */
app.post('/buyerConfirm', (req, res) => {
    console.log('Request made to /buyerConfirm\n');
    let buyerEmail = req.body.email;
    let QRCode = req.body.QRCode;
    let currentTime = Date.now();         // Date.now() gets the current time in milliseconds
    console.log(`Email: ${buyerEmail} and QRCode: ${QRCode} \n`);
    for (let i = 0; i < QRCodes.length; i++) {
        if (QRCode === QRCodes[i]['QRCode']) {
            let timeElapsed = Math.floor((currentTime - QRCodes[i]['currentTime']) / 1000);
            // QR Codes are valid only for 600 secs
            if (timeElapsed <= 600) {
                if(QRCodes[i]['confirm'] === '1'){
                    let hashedSellerEmail = hashMD5(QRCodes[i]['sellerEmail']);
                    let hashedBuyerEmail = hashMD5(QRCodes[i]['buyerEmail']);
                    let code = QRCodes[i]['code'];
                    var ok;
                    if(QRCodes[i]['retailer'] === '1'){
                        console.log('Performing transaction for retailer\n');
                        ok = contractInstance.initialOwner(code, hashedSellerEmail, hashedBuyerEmail,
                                                        { from: web3.eth.accounts[0], gas: 3000000 });
                    } else {
                        console.log('Performing transaction for customer\n');
                        ok = contractInstance.changeOwner(code, hashedSellerEmail, hashedBuyerEmail,
                                                        { from: web3.eth.accounts[0], gas: 3000000 });
                    }
                    if (!ok) {
                        return res.status(400).send('Error');
                    }
                    console.log('Success in buyerConfirm, transaction is done!\n');
                    return res.status(200).send('Ok');
                }
                console.log('Buyer has not confirmed\n');
            }
            return res.status(400).send('Timed out!');
        }
    }
    console.log('Product not found\n')
    return res.status(400).send('Product not found');
});

// Function that creates an initial owner for a product
function initialOwner(code, retailerHashedEmail, customerHashedEmail) {
    return contractInstance.initialOwner(code, retailerHashedEmail, customerHashedEmail,
                                        { from: web3.eth.accounts[0], gas: 3000000 });
}

// Function that creates transfers ownership of a product
function changeOwner(code, oldOwnerHashedEmail, newOwnerHashedEmail) {
    return contractInstance.changeOwner(code, oldOwnerHashedEmail, newOwnerHashedEmail,
                                        { from: web3.eth.accounts[0], gas: 3000000 });
}


/**
 * Description: Gives product details if the scannee is not the owner of the product
 * Request:     POST /scan
 * Send:        JSON object which contains code
 * Receive:     JSON object which has productDetails
 */
app.post('/scan', (req, res) => {
    console.log('Request made to /scan\n');
    let code = req.body.code;
    let productDetails = contractInstance.getNotOwnedCodeDetails(code);
    let productDetailsObj = {
        'name': productDetails[0], 'model': productDetails[1], 'status': productDetails[2],
        'description': productDetails[3], 'manufacturerName': productDetails[4],
        'manufacturerLocation': productDetails[5], 'manufacturerTimestamp': productDetails[6]
    };
    console.log(`Code ${code} \n`);
    res.status(200).send(JSON.stringify(productDetailsObj));
});


/**
 * Description: Generates QR codes for the manufacturers
 * Request:     POST /QRCodeForManufacturer
 * Send:        JSON object which contains brand, model, status, description, manufacturerName, manufacturerLocation
 * Receive:     200 if QR code was generated, 400 otherwise.
 */
app.post('/QRCodeForManufacturer', (req, res) => {
    console.log('Request to /QRCodeForManufacturer\n');
    let brand = req.body.brand;
    let model = req.body.model;
    let status = 0;
    let description = req.body.description;
    let manufacturerName = req.body.manufacturerName;
    let manufacturerLocation = req.body.manufacturerLocation;
    let manufacturerTimestamp = new Date();         // Date() gives current timestamp
    manufacturerTimestamp = manufacturerTimestamp.toISOString().slice(0, 10);
    let salt = crypto.randomBytes(20).toString('hex');
    let code = hashMD5(brand + model + status + description + manufacturerName + manufacturerLocation + salt);
    let ok = contractInstance.createCode(code, brand, model, status, description, manufacturerName, manufacturerLocation,
                                        manufacturerTimestamp, { from: web3.eth.accounts[0], gas: 3000000 });
    console.log(`Brand: ${brand} \n`);
    if (!ok) {
        return res.status(400).send('ERROR! QR Code for manufacturer could not be generated.');
    }
    console.log(`The QR Code generated is: ${code} \n`);
    let QRcode = code + '\n' + brand + '\n' + model + '\n' + description + '\n' + manufacturerName + '\n' + manufacturerLocation;
    fs.writeFile('views/davidshimjs-qrcodejs-04f46c6/code.txt', QRcode, (err, QRcode) => {
        if (err) {
            console.log(err);
        }
        console.log('Successfully written QR code to file!\n');
    });
    res.sendFile('views/davidshimjs-qrcodejs-04f46c6/index.html', { root: __dirname });
});


/**
 * Description: Gives all the customer details
 * Request:     GET /getCustomerDetails
 * Send:        JSON object which contains email
 * Receive:     JSON object which contains name, phone
 */
app.get('/getCustomerDetails', (req, res) => {
    console.log('Request to /getCustomerDetails\n');
    let email = req.body.email;
    let hashedEmail = hash(email);
    let customerDetails = contractInstance.getCustomerDetails(hashedEmail);
    console.log(`Email: ${email} \n`);
    let customerDetailsObj = {
        'name': customerDetails[0], 'phone': customerDetails[1]
    };
    res.status(200).send(JSON.parse(JSON.stringify(customerDetailsObj)));
});

// Server start
app.listen(port, (req, res) => {
    console.log(`Listening to port ${port}...\n`);
});