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

const int date_length[] = {
	 0,   //dummy element so that January will have subscript 1
	31,   //January
	28,   //February
	31,   //March
	30,   //April
	31,   //May
	30,   //June
	31,   //July
	31,   //August
	30,   //September
	31,   //October
	30,   //November
	31   //December
};

date::date(int initial_month, int initial_day, int initial_year)
{
	if (initial_month < january || initial_month > december) {
		cerr << "bad month " << initial_month << "/" << initial_day
			<< "/" << initial_year << "\n";
		exit(EXIT_FAILURE);
	}

	if (initial_day < 1 || initial_day > date_length[initial_month]) {
		cerr << "bad day " << initial_month << "/" << initial_day
			<< "/" << initial_year << "\n";
		exit(EXIT_FAILURE);
	}

	year = initial_year;
	month = initial_month;
	day = initial_day;
}

date::date(int initial_day)
{
	div_t divide = div(initial_day, 365);
	if (divide.rem < 0) {
		divide.rem += 365;
		--divide.quot;
	}

	year = divide.quot;
	day = divide.rem;
	month = 1;

	while (day > date_length[month]) {
		day -= date_length[month];
		if (++month > 12) {
			month = 1;
			++year;
		}
	}
}

date::date()
{
	const time_t t = time(0);
	const tm *const p = localtime(&t);

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

void date::next(int count)
{
	day += count;

	while (day < 1) {
		if (--month < 1) {
			month = 12;
			--year;
		}
		day += date_length[month];
	}

	while (day > date_length[month]) {
		day -= date_length[month];
		if (++month > 12) {
			month = 1;
			++year;
		}
	}
}

int date::julian() const
{
	int j = day;

	for (int m = 1; m < month; ++m) {
		j += date_length[m];
	}

	return j;
}

ostream& operator<<(ostream& ost, const date &d)
{
	return ost << d.month << "/" << d.day << "/" << d.year;
}

istream& operator>>(istream& ist, date& d)
{
	int month;    //uninitialized variable
	ist >> month;
	if (!ist) {   //if (ist.operator!()) {
		return ist;
	}

	char c;   //uninitialized variable
	ist >> c;
	if (!ist) {
		return ist;
	}
	if (c != '/') {
		ist.setstate(ios_base::failbit);
		return ist;
	}

	int day;   //uninitialized variable
	ist >> day;
	if (!ist) {
		return ist;
	}

	ist >> c;
	if (!ist) {
		return ist;
	}
	if (c != '/') {
		ist.clear(ios_base::failbit);
		return ist;
	}

	int year;   //uninitialized variable
	ist >> year;
	if (!ist) {
		return ist;
	}

	//Put no values into d until we've verified that all three are valid.

	if (month < date::january || month > date::december) {
		cerr << "bad month " << month << "\n";
		ist.setstate(ios_base::failbit);
		return ist;
	}

	if (day < 1 || day > date_length[month]) {
		cerr << "bad day " << day << " of month " << month << "\n";
		ist.setstate(ios_base::failbit);
		return ist;
	}

	d.year = year;
	d.month = month;
	d.day = day;

	return ist;
}