Untitled

interface ISaleOffer {
  price: number;
  amount: number;
}

function calculateOrder(amount: number, salesBook?: ISaleOffer[] | null): any {
  const isSalesBookArray = Array.isArray(salesBook);

  if (amount < 0 || !isSalesBookArray) {
    return {
      amount: 0,
      price: 0,
    };
  }

  const salesBookCloned = [...salesBook];
  const salesBookSorted = salesBookCloned.sort((a, b) => a.price - b.price);

  const totalAmount = salesBookSorted.reduce((prev, curr) => (prev += curr.amount), 0);
  const amountSold = totalAmount >= amount ? amount : totalAmount;

  let remaining = amountSold;
  let items: ISaleOffer[] = [];

  for (let i = 0; i < salesBookSorted.length; i++) {
    const currentOffer = salesBookSorted[i];
    if (remaining - currentOffer.amount > 0) {
      remaining -= currentOffer.amount;
      items.push(currentOffer);
    } else {
      currentOffer.amount = remaining;
      items.push(currentOffer);
      break;
    }
  }

  const price = items.reduce((prev, curr) => prev + curr.amount * curr.price, 0);

  return {
    amount: amountSold,
    price: Math.round(price * 100) / 100,
  };
}

export { calculateOrder, ISaleOffer };