milltest/Buyer.js

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

  /**
   * Build an order preference table for particular product
   * @param product
   */
  buildOrderPreference(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;
  }

  /**
   * 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 wantedQuantity = quantity;
    let sellerPreference = this.buildOrderPreference(product);

    console.log(sellerPreference);

    let reciept = [];

    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);

      reciept.push(r);

    }

    console.log(reciept);

    console.log(reciept.reduce((a, cv) => {
      return a.cost + cv.cost;
    })


    );

    throw Error("Not Implemented");

  }


  /**
   * 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) {
    throw Error("Not Implemented");
  }
}

module.exports = {Buyer}