Pager solution

pager-solution.js

const Hapi = require('@hapi/hapi');
const MongoClient = require('mongodb').MongoClient;
const Boom = require('@hapi/boom');

const totalAmountReducer = (userItems) => (prev, item) => {
    const itemsPrice = item.price * userItems.find(v => v.itemId === item.itemId).quantity
    return prev + itemsPrice;
};

const server = Hapi.server({
    port: 3000,
    debug: {
        request: ['*']
    }
});

const routes = [
    {
        method: 'GET',
        path: '/locations',
        handler: async (request, h) => {

            const db = server.app.db;
            const locationCollection = db.collection('locations');

            // query all locations
            const documents = await locationCollection.find({}).toArray();
            return documents;
        }
    },
    {
        method: 'GET',
        path: '/locations/{locationId}/items',
        handler: async (request, h) => {
            const locationId = parseInt(request.params.locationId);

            const { db } = server.app;
            const Items = db.collection('items');
            const Locations = db.collection('locations')

            const location = await Locations.findOne({ locationId });
            if (!location) {
                throw Boom.notFound('Location not found')
            }

            const documents = await Items.find({ locationId }).toArray();

            return documents;
        }
    },
    {
        method: 'POST',
        path: '/locations/{locationId}/order',
        handler: async (request, h) => {
            const { customerId, items } = request.payload;
            if (!customerId === undefined) throw Boom.badRequest('Missing customerId');
            if (!Array.isArray(items)) throw Boom.badRequest('Missing Item array');

            const db = server.app.db;
            /** @type {import('mongodb').Collection} */
            const Orders = db.collection('orders');
            const Items = db.collection('items');

            const itemsIds = items.map(value => value.itemId);
            const itemsObjects = await Items.find({ itemId: { $in: itemsIds } }).toArray();

            const total = itemsObjects.reduce(totalAmountReducer(items),0);

            await Orders.insertOne({ customerId, items });

            return { customerId, items, total }
        }
    },
];

const init = async () => {

    // connect to DB
    const url = 'mongodb://localhost:27017/local-grocery-store';
    const client = new MongoClient(url, { useNewUrlParser: true, useUnifiedTopology: true });
    await client.connect();

    const db = client.db();
    server.app.db = db;

    console.log("Connected successfully to mongo");

    // routes configuration
    server.route(routes);

    try {
        if (!module.parent) {
            await server.start();
        }
        else {
            await server.initialize();
        }
        return server;
    }
    catch (error) {
        console.error(error);
        process.exit(1);
    }
};

process.on('unhandledRejection', (err) => {

    console.log(err);
    process.exit(1);
});

void async function () {
    if (!module.parent) {
        await init();
    }
}();

module.exports = {
    init
}