#ifndef SALESITEM_H

#define SALESITEM_H

#include <iostream>

#include <string>

class Sales_item

{

public:

 Sales_item(const std::string &book):isbn(book),units_sold(0),revenue(0.0){}

 Sales_item(std::istream &is){ is >> *this;}

 friend std::istream& operator>>(std::istream &,Sales_item &);

 friend std::ostream& operator<<(std::ostream &,const Sales_item &);

public:

 Sales_item & operator+=(const Sales_item&);

public:

 double avg_price() const;

 bool same_isbn(const Sales_item &rhs)const

 {

  return isbn == rhs.isbn;

 }

 Sales_item():units_sold(0),revenue(0.0){}

public:

 std::string isbn;

 unsigned units_sold;

 double revenue;

};

using std::istream;

using std::ostream;

Sales_item operator+(const Sales_item &,const Sales_item &);

inline bool operator==(const Sales_item &lhs,const Sales_item &rhs)

{

 return lhs.units_sold == rhs.units_sold && lhs.revenue == rhs.revenue && lhs.same_isbn(rhs);

}

inline bool operator!=(const Sales_item &lhs,const Sales_item &rhs)

{

 return !(lhs == rhs);

}

inline Sales_item & Sales_item::operator +=(const Sales_item &rhs)

{

 units_sold += rhs.units_sold;

 revenue += rhs.revenue;

 return *this;

}

inline Sales_item operator+(const Sales_item &lhs,const Sales_item &rhs)

{

 Sales_item ret(lhs);

 ret += rhs;

 return ret;

}

inline istream& operator>>(istream &in,Sales_item &s)

{

 double price;

 in >> s.isbn >> s.units_sold >> price;

 if(in)

  s.revenue = s.units_sold * price;

 else

  s = Sales_item();

 return in;

}

inline ostream& operator<<(ostream &out,const Sales_item &s)

{

 out << s.isbn << "\t" <<s.units_sold << "\t" << s.revenue << "\t" << s.avg_price();

 return out;

}

inline double Sales_item::avg_price() const

{

 if(units_sold)

  return revenue/units_sold;

 else

  return 0;

}

#endif