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

int date::length() const
{
	static const int a[] = {
		 0,   //dummy
		31,   //january
		29,   //february
		31,   //march
		30,   //april
		31,   //may
		30,   //june
		31,   //july
		31,   //august
		30,   //september
		31,   //october
		30,   //november
		31    //december
	};

	return a[month];
}

void date::install(int m, int d, int y)
{
	year = y;

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

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

date::date()   //Initialize to the current date.
{
	const time_t t = time(0);

	if (t == static_cast<time_t>(-1)) {
		cerr << "time failed\n";
		exit(EXIT_FAILURE);
	}

	const tm *const s = localtime(&t);
	install(s->tm_mon + 1, s->tm_mday, s->tm_year + 1900);
}

date& date::operator++()
{
	if (++day > length()) {
		day = 1;
		if (++month > december) {
			month = january;
			++year;
		}
	}

	return *this;
}

date& date::operator--()
{
	if (--day < 1) {
		if (--month < january) {
			month = december;
			--year;
		}
		day = length();
	}

	return *this;
}