#include <iostream> //for the object cout
#include <cstdlib>
#include <ctime>    //for the functions time and localtime
using namespace std;

class date {
	//Declarations for data members.  Members are private by default.
	int year;
	int month;  //in the range 1 to 12 inclusive
	int day;    //in the range 1 to 31 inclusive

	static const int length[];          //static data member

public:
	//Declarations for member functions:
	date(int m, int d, int y);          //constructor
	date();                             //defualt constructor

	void print() const;                 //const member function
	void next(int n);                   //non-const member function
	void next();
};

int main()
{
	try {
		//Output the date of Independence Day.
		const date independenceDay {7, 4, 1776};   //month, day, year
		independenceDay.print();
		cout << " is Independence Day.\n";


		//Output today's date.
		const date today;  //Call the default constructor.
		today.print();
		cout << " is today.\n";

		//Output tomorrow's date.
		date tomorrow {today}; //Call the "copy constructor".
		tomorrow.next();       //Advance one day.
		tomorrow.print();
		cout << " is tomorrow.\n";

		//Output the date that is one week from today.
		date nextWeek {today}; //Call the "copy constructor".
		nextWeek.next(7);
		nextWeek.print();
		cout << " is next week.\n";
	}
	catch (invalid_argument e) {
		cerr << e.what() << "\n";
		return EXIT_FAILURE;
	}

	return EXIT_SUCCESS;
}

const int date::length[] {
	 0,   //dummy, so that January will have subscript 1
	31,   //January
	28,   //February.  Pretend there are no leap years.
	31,   //March
	30,   //April
	31,   //May
	30,   //June
	31,   //July
	31,   //August
	30,   //September
	31,   //October
	30,   //November
	31    //December
};

//The constructor installs 3 valid values into a newborn date object,
//or it throws an exception.

date::date(int init_month, int init_day, int init_year)
	: year {init_year}, month {init_month}, day {init_day}
{
	if (month < 1 || month > 12) {
		throw invalid_argument("bad month");
	}

	if (day < 1 || day > length[month]) {
		throw invalid_argument("bad day of the month");
	}
}

date::date()    //Default constructor puts today's date into the newborn object.
{
	const time_t t {time(nullptr)};
	const tm *const p {localtime(&t)};

	year = p->tm_year + 1900;
	month = p->tm_mon + 1;
	day = p->tm_mday;
}

void date::print() const  //This member function can't change the date object.
{
	cout << month << "/" << day << "/" << year;
}

void date::next(int n)    //This member function can change the date struct.
{
	for (int i {0}; i < n; ++i) {
		next(); //Call the other next function, the one with no argument
	}
}

void date::next()   //Move this date object one day into the future.
{
	if (day < length[month]) {
		++day;
	} else {
		day = 1;             //Advance into the next month.
		if (month < 12) {
			++month;
		} else {
			month = 1;   //Advance into the next year.
			++year;
		}
	}
}