15.30.cpp

/*
 * Exercise 15.30: Write your own version of the Basket class and use it to
 * compute prices for the same transactions as you used in the previous
 * exercises.
 *
 * By Faisal Saadatmand
 */

#include <iostream>
#include <memory>
#include <set>
#include <string>
#include <utility>

class Quote {
	friend double print_total(std::ostream &, const Quote &, std::size_t);
	public:
		Quote() = default;
		Quote(const std::string &book, double sales_price) :
			bookNo(book), price(sales_price) {}
		std::string isbn() const { return bookNo; }
		virtual Quote* clone() const & { return new Quote(*this); }
		virtual Quote* clone() const && { return new Quote(std::move(*this)); }
		virtual double net_price(std::size_t n) const { return n * price; }
		virtual ~Quote() {};
	private:
		std::string bookNo;
	protected:
		double price = 0.0;
};

double print_total(std::ostream &os, const Quote &item, std::size_t n)
{
	double ret = item.net_price(n);
	os << "ISBN: " << item.isbn() 
	   << " # sold: " << n << " total due: " << ret << std::endl;
	return ret;
}

class Disc_quote : public Quote {
	public:
		Disc_quote() = default;
		Disc_quote(const std::string &book, double price,
				std::size_t qty, double disc) :
				   Quote(book, price), quantity(qty), discount(disc) {}
		double net_price(std::size_t) const = 0; // pure virtual function
	protected:
		std::size_t quantity = 0;
		double discount = 0.0;
};

class Bulk_quote : public Disc_quote {
	public:
		// default constructor is synthesized
		using Disc_quote::Disc_quote; // inherit constructors
		double net_price(std::size_t) const override;
		Bulk_quote *clone() const & override { return new Bulk_quote(*this); }
		Bulk_quote *clone() const && override
						{ return new Bulk_quote(std::move(*this)); }
};

double
Bulk_quote::net_price(std::size_t cnt) const
{
	if (cnt >= quantity)
		return cnt * (1 - discount) * price;
	return cnt * price;
}
class Basket {
	public:
		void add_item(const Quote &sale)
		{ items.insert(std::shared_ptr<Quote>(sale.clone())); }
		void add_item(const Quote &&sale)
		{ items.insert(std::shared_ptr<Quote>(std::move(sale).clone())); }
		double total_receipt(std::ostream &) const;
	private:
		static bool compare(const std::shared_ptr<Quote> &lhs,
							const std::shared_ptr<Quote> &rhs)
		{ return lhs->isbn() < rhs->isbn(); }
		std::multiset<std::shared_ptr<Quote>, decltype(compare) *>
			items{compare};
};

double
Basket::total_receipt(std::ostream &os) const
{
	double sum = 0;
	for (auto iter = items.begin(); iter != items.end();
			iter = items.upper_bound(*iter))
		sum += print_total(os, **iter, items.count(*iter));
	os << "Total Sale: " << sum << '\n';
	return sum;
}

int main()
{
	Basket bsk;
	bsk.add_item({"1-111-11111-1", 25});
	bsk.add_item(Bulk_quote("2-222-22222-2", 25, 2, .5));
	bsk.add_item(Bulk_quote("2-222-22222-2", 25, 2, .5));
	bsk.total_receipt(std::cout);
	return 0;
}