#include <iostream>
#include <cstdlib>
#include "date.h"
using namespace std;

const int date::length[] {
	 0,   //dummy
	31,   //January
	29,   //February: assume that every year is leap
	31,   //March
	30,   //April
	31,   //May
	30,   //June
	31,   //July
	31,   //August
	30,   //September
	31,   //October
	30,   //November
	31    //December
};

void date::install(int m, int d, int y)   //called by each constructor
{
	year = y;

	if (m < 1 || m > 12) {
		cerr << "bad month " << m << "/" << d << "/" << y << "\n";
		exit(EXIT_FAILURE);
	}
	month = m;

	if (d < 1 || d > length[month]) {
		cerr << "bad day " << m << "/" << d << "/" << y << "\n";
		exit(EXIT_FAILURE);
	}
	day = d;
}

date::date()                         //Initialize to today's date.
{
	const time_t t {time(0)};
	const tm *const s {localtime(&t)};
	install(s->tm_mon + 1, s->tm_mday, s->tm_year + 1900);
}

date& date::operator++()
{
	if (++day > length[month]) {
		day = 1;
		if (++month > 12) {
			month = 1;
			++year;
		}
	}

	return *this;
}

date& date::operator--()
{
	if (--day < 1) {
		if (--month < 1) {
			month = 12;
			--year;
		}
		day = length[month];
	}

	return *this;
}