#include <iostream>
#include <cstdlib>
#include <iomanip>
#include <string>	//whenever we use variable type 'string,' we need to #include it.
using namespace std;

struct Book {  // The blueprint for a structure containing multiple fields.
	string title;	// String variable type since the values will be words.

	string author;	// refer to above about string.
	
	double price; // Price in US dollars, we need double to show the decimal
		      // places.

	bool bestseller; // I use bool here to indicate that this is either true or
		         // false.

};

void applyDiscount(Book *p, double discountPercentage);	//declaring the function before the main function, so we can let the program know to expect it.
void print (const Book *p);				//declaring the print function for use later on.

int main()
{
	Book novel {"Holmes Is Missing", "James Patterson", 30.00, true};	//calling the structure and giving values to the variables.
	
	print(&novel);								//calling the print function from above.


	string userInput; // we use string because the input will be a word and not a numerical value.

	cout << "Would you like to use your discount code? (yes/no):\n\n";
	
	cin >> userInput;	// This is where the user inputs the code.

	if (userInput == "yes") {	//If the user's answer is equivalent to the word 'yes'
        
		applyDiscount(&novel, 30.0); // Apply a 30% discount

		cout << "Discount applied!\n"; //program will output this after applying the discount.
	
	} else if (userInput == "no") { 	//if the user, for some reason doesn't want to save money... 
		
		cout << "No discount applied.\n";	// the program output this statement.
	
	} else {
        
		cout << "Invalid input. No discount applied.\n";	//The user will get hit with an output, not an error
									//message (which would stop the program after EXIT_FAILURE
    }

    cout << "After checking discount option:\n\n";		

	print(&novel);

	return EXIT_SUCCESS;
}

void applyDiscount(Book *p, double discountPercentage)

{
	// Apply the discount to the price
	p->price *= ( 100 - discountPercentage )/ 100;
    
	// Append to the title if it's a bestseller
	if (p->bestseller) {
		p->title += " (Bestseller)";
    }
}

void print(const Book *p)   //This function cannot change the structure.
{
        cout << "Title: " << p->title << "\n"
                << "Author: " << p->author << "\n"
                << "Price: $" << fixed << setprecision(2) << p->price << "\n"
                << "Bestseller: " << (p->bestseller ? "Yes" : "No") << "\n\n";
}