#include <iostream>  //for cout
#include "date.h"
using namespace std; //because invalid_argument and cout belong to namespace std

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.
//this is a pointer to the object being constructed, so
//this->year is a data member belonging to the object being constructed.
//Plain old year without the this-> is an argument of the constructor.

date::date(int month, int day, int year)
{
	this->year = year;
	if (month < 1 || month > 12) {
		throw invalid_argument("bad month");
	}
	this->month = month;
	if (day < 1 || day > length[month]) {
		throw invalid_argument("bad day of the month");
	}
	this->day = day;
}

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

void date::next(int n)   //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 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;
		}
	}
}