app.js

var express = require('express');
const cache = require('memory-cache');
const bodyParser = require('body-parser');
const cors = require('cors');
const axios = require('axios');

const app = express();

app.use(bodyParser.json());
app.use(bodyParser.urlencoded({
    extended: false
}));

app.use(cors());
app.options('*', cors());

app.get('/', (req, res) => res.status(200).send('Arkesel Rocks!!'));

app.post('/ussd', ((req, res) => {
    const {
        sessionID,
        userID,
        newSession,
        msisdn,
        userData,
        network,
    } = req.body;

    if (newSession) {
        const message = "Welcome to Arkesel Voting Portal. Please vote for your favourite service from Arkesel" +
            "\n1. SMS" +
            "\n2. Voice" +
            "\n3. Email" +
            "\n4. USSD" +
            "\n5. Payments";
        const continueSession = true;

        // Keep track of the USSD state of the user and their session
        const currentState = {
            sessionID,
            msisdn,
            userData,
            network,
            newSession,
            message,
            level: 1,
            page: 1,
        };

        let userResponseTracker = cache.get(sessionID);

        !userResponseTracker
            ? userResponseTracker = [{ ...currentState }]
            : userResponseTracker.push({ ...currentState });

        cache.put(sessionID, userResponseTracker);

        res.setHeader('Content-Type', 'application/json');
        return res.status(200).json({
            userID,
            sessionID,
            message,
            continueSession,
            msisdn
        });
    }

    const userResponseTracker = cache.get(sessionID);

    if (!userResponseTracker) {
        res.setHeader('Content-Type', 'application/json');
        return res.status(200).json({
            userID,
            sessionID,
            message: 'Error! Please dial code again!',
            continueSession: false,
            msisdn
        });
    }

    const lastResponse = userResponseTracker[userResponseTracker.length - 1];

    let message = "Bad Option";
    let continueSession = false;

    if (lastResponse.level === 1) {
        if (["2", "3", "4", "5"].includes(userData)) {
            message = "Thank you for voting!";
            continueSession = false;
        } else if (userData === '1') {
            message = "For SMS which of the features do you like best?" +
                "\n1. From File" +
                "\n2. Quick SMS" +
                "\n\n #. Next Page";

            continueSession = true;

            const currentState = {
                sessionID,
                userID,
                level: 2,
                msisdn,
                message,
                userData,
                network,
                newSession,
                page: 1,
            };

            userResponseTracker.push({ ...currentState });
            cache.put(sessionID, userResponseTracker);
        }
    } else if (lastResponse.level === 2) {
        if (lastResponse.page === 1 && userData === '#') {
            message = "For SMS which of the features do you like best?" +
                "\n3. Bulk SMS" +
                "\n\n*. Go Back" +
                "\n#. Next Page";

            continueSession = true;

            const currentState = {
                sessionID,
                userID,
                level: 2,
                msisdn,
                message,
                userData,
                network,
                newSession,
                page: 2
            };

            userResponseTracker.push({ ...currentState });
            cache.put(sessionID, userResponseTracker);

        } else if (lastResponse.page === 2 && userData === '#') {
            // Useful Resources
            message = "For SMS which of the features do you like best?" +
                "\n4. SMS To Contacts" +
                "\n5. Enter your amount to vote with" +
                "\n\n*. Go Back";

            continueSession = true;

            const currentState = {
                sessionID,
                userID,
                level: 2,
                msisdn,
                message,
                userData,
                network,
                newSession,
                page: 3,
            };

            userResponseTracker.push({ ...currentState });
            cache.put(sessionID, userResponseTracker);
        } else if (lastResponse.page === 3 && userData === '*') {
            message = "For SMS which of the features do you like best?" +
                "\n3. Bulk SMS" +
                "\n\n*. Go Back" +
                "\n#. Next Page";

            continueSession = true;

            const currentState = {
                sessionID,
                userID,
                level: 2,
                msisdn,
                message,
                userData,
                network,
                newSession,
                page: 2
            };

            userResponseTracker.push({ ...currentState });
            cache.put(sessionID, userResponseTracker);
        } else if (lastResponse.page === 2 && userData === '*') {
            message = "For SMS which of the features do you like best?" +
                "\n1. From File" +
                "\n2. Quick SMS" +
                "\n\n #. Next Page";

            continueSession = true;

            const currentState = {
                sessionID,
                userID,
                level: 2,
                msisdn,
                message,
                userData,
                network,
                newSession,
                page: 1,
            };

            userResponseTracker.push({ ...currentState });
            cache.put(sessionID, userResponseTracker);
        } else if (["1", "2", "3", "4"].includes(userData)) {
            message = "Thank you for voting!";
            continueSession = false;
        } else if (userData === "5") {
            message = "Enter your amount to pay below: ";
            continueSession = true;

            const currentState = {
                sessionID,
                userID,
                level: 3,
                msisdn,
                message,
                userData,
                network,
                newSession,
                page: 1,
            };

            userResponseTracker.push({ ...currentState });
            cache.put(sessionID, userResponseTracker);
        } else {
            message = "Bad choice!";
            continueSession = false;
        }
    } else if (lastResponse.level === 3) {
        if (!isNaN(userData) && parseFloat(userData) > 0) {
            const uniqueRef = `${Date.now() + (Math.random() * 100)}`;
            const paymentRequest = {
                account_number: msisdn,
                merchant_reference: uniqueRef,
                channel: "mobile-money",
                provider: network.toLowerCase(),
                transaction_type: "debit",
                amount: userData,
                purpose: "voting payment",
                service_name: "arkesel voting",
                currency: "GHS",
            };
            const apiKey = 'xxxxxxxxxxxxxxxxxxxxxxxx=';
            const url = 'https://payment.arkesel.com/api/v1/payment/charge/initiate';

            axios({
                method: 'post',
                url,
                data: { ...paymentRequest },
                headers: {
                    'api-key': apiKey,
                }
            }).then(res => res.data).then(data => {
                console.log({ data }, 'Initiate payment');
                // Save into DB
                // If it was successful then send message
                message = `Kindly enter your pin for the approval of GHS ${userData} debiting of your Mobile money account. We are charging you for voting. Dial *170# to visit approvals if one doesn't pop up!`;
                continueSession = false;
            });

            message = `Kindly enter your pin for the approval of GHS ${userData} debiting of your Mobile money account. We are charging you for voting. Dial *170# to visit approvals if one doesn't pop up!`;
            continueSession = false;

            res.setHeader('Content-Type', 'application/json');
            return res.status(200).json({
                userID,
                sessionID,
                message,
                continueSession,
                msisdn
            });

        } else {
            message = "You entered an invalid amount: ";
            continueSession = true;

            const currentState = {
                sessionID,
                userID,
                level: 3,
                msisdn,
                message,
                userData,
                network,
                newSession,
                page: 1,
            };

            userResponseTracker.push({ ...currentState });
            cache.put(sessionID, userResponseTracker);
        }
    }

    res.setHeader('Content-Type', 'application/json');
    return res.status(200).json({
        userID,
        sessionID,
        message,
        continueSession,
        msisdn
    });
}));

// Callback URL for payment
app.get('/payments/arkesel/callback', ((req, res) => {
    console.log({ query: res.query }, 'Callback for Arkesel payment');
    // Verify the payment...

    res.setHeader('Content-Type', 'application/json');
    return res.status(200).json({
        status: 'success',
        message: 'arkesel payment callback called'
    });
}));

// Verify payment
app.get('/payments/verify', ((req, res) => {
    const apiKey = 'XXXXXXXXXXXXXXXXXXXXXXX=';
    const transRef = 'T634E3e8cac8175';
    const url = `https://payment.arkesel.com/api/v1/verify/transaction/${transRef}`;

    axios({
        method: 'get',
        url,
        headers: {
            'api-key': apiKey,
        }
    }).then(res => res.data).then(data => {
        console.log({ data }, 'Verify payment');
        // Update payment status in DB
    });
    res.setHeader('Content-Type', 'application/json');
    return res.status(200).json({
        status: 'success',
        message: 'payment verification called'
    });
}));

app.listen(8000, function () {
    console.log('Arkesel USSD app listening on 8000!');
});