milltest/Buyer.js

class Buyer {
    constructor(market) {
        this.market = market;
    }

    /**
     * Build an order preference table for particular product
     * @param product
     */
    buildOrderPrefBestPrice(product) {
        let sellers = [];

        // build up the initial list
        this.market.sellers.forEach((seller, i) => {
            if (seller.inventory.hasOwnProperty(product)) {
                const price = seller.quote(product);
                sellers.push({id: seller.id, price: price, index: i, quantity: seller.inventory[product].quantity})
            }

        });

        // sort by best price
        sellers.sort((a, b) => {
            return a.price - b.price;
        })

        return sellers;
    }


    buildOrderPrefFastFill(product) {
        let sellers = [];

        // build up the initial list
        this.market.sellers.forEach((seller, i) => {
            if (seller.inventory.hasOwnProperty(product)) {
                const price = seller.quote(product);
                sellers.push({id: seller.id, price: price, index: i, quantity: seller.inventory[product].quantity, deliveryWait:seller.deliveryWait})
            }

        });

        // sort by best price
        sellers.sort((a, b) => {
            return a.deliveryWait - b.deliveryWait;
        })

        return sellers;
    }

    buildOrderPrefMostFill(product) {
        let sellers = [];

        // build up the initial list
        this.market.sellers.forEach((seller, i) => {
            if (seller.inventory.hasOwnProperty(product)) {
                const price = seller.quote(product);
                sellers.push({id: seller.id, price: price, index: i, quantity: seller.inventory[product].quantity, deliveryWait:seller.deliveryWait})
            }

        });

        // sort by best price
        sellers.sort((a, b) => {
            return b.quantity - a.quantity;
        })

        return sellers;
    }

    /**
     * This method should get the best price for a given product
     * across all sellers
     */
    getBestPrice(product) {
        let lowestPrice = null;
        this.market.sellers.forEach(seller => {
            if (seller.inventory.hasOwnProperty(product)) {
                const price = seller.quote(product);
                if (lowestPrice === null || lowestPrice > price) lowestPrice = price;
            }

        });

        return lowestPrice || 0;
    }


    /**
     * This method should optimise price when filling an order
     * if the quantity is greater than any single seller can accomodate
     * then the next cheapest seller should be used.
     */
    fillWithBestPrices(product, quantity) {

        let total = 0;
        let wantedQuantity = quantity;
        let sellerPreference = this.buildOrderPrefBestPrice(product);

        let receipt = [];

        while (sellerPreference.length > 0 && wantedQuantity > 0) {

            let seller = sellerPreference.shift();

            let r = this.market.sellers[seller.index].sell(product, wantedQuantity);
            wantedQuantity = (wantedQuantity - r.boughtQuantity) < 0 ? 0 : (wantedQuantity - r.boughtQuantity);

            receipt.push(r);
        }

        if (receipt.length > 1) {
            total = receipt.reduce((a, cv) => {
                return (typeof a === 'number' ? a : a.cost) + cv.cost;
            });
        } else if (receipt.length === 1) total = receipt[0].cost;

        return total;
    }


    /**
     * This method should optimise for sellers with the largest inventory when filling an order
     * if the quantity is greater than any single seller can accomodate
     * then the next largest seller should be used.
     * if multiple sellers have the same amount of inventory
     * you should use the cheaper of the two.
     */
    fillWithLargestSellers(product, quantity) {
        let total = 0;
        let wantedQuantity = quantity;
        let sellerPreference = this.buildOrderPrefMostFill(product);

        let receipt = [];

        while (sellerPreference.length > 0 && wantedQuantity > 0) {

            let seller = sellerPreference.shift();

            let r = this.market.sellers[seller.index].sell(product, wantedQuantity);
            wantedQuantity = (wantedQuantity - r.boughtQuantity) < 0 ? 0 : (wantedQuantity - r.boughtQuantity);

            receipt.push(r);
        }

        if (receipt.length > 1) {
            total = receipt.reduce((a, cv) => {
                return (typeof a === 'number' ? a : a.cost) + cv.cost;
            });
        } else if (receipt.length === 1) total = receipt[0].cost;

        return total;

    }

    /**
     * This fulfils orders based on time to deliver
     * @param product
     * @param quantity
     * @returns {number}
     */
    quicklyFill(product, quantity) {
        let total = 0;
        let wantedQuantity = quantity;
        let sellerPreference = this.buildOrderPrefFastFill(product);

        let receipt = [];

        while (sellerPreference.length > 0 && wantedQuantity > 0) {

            let seller = sellerPreference.shift();

            let r = this.market.sellers[seller.index].sell(product, wantedQuantity);
            wantedQuantity = (wantedQuantity - r.boughtQuantity) < 0 ? 0 : (wantedQuantity - r.boughtQuantity);

            receipt.push(r);
        }

        if (receipt.length > 1) {
            total = receipt.reduce((a, cv) => {
                return (typeof a === 'number' ? a : a.cost) + cv.cost;
            });
        } else if (receipt.length === 1) total = receipt[0].cost;

        return total;

    }
}

module.exports = {Buyer}