#include <iostream> //for the object cout
#include <cstdlib>
#include <chrono>   //for class system_clock
#include <ctime>    //for the function localtime and structure tm
#include "date.h"   //The implementation file always includes the header file.
using namespace std;

const int date::length[] {     //definition of static data member
         0,   //dummy, so that January will have subscript 1
        31,   //January
        28,   //February.  We'll do leap years later in the course.
        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 outputs an error message and terminates the program.

date::date(int init_month, int init_day, int init_year)
{
        year = init_year;

        if (init_month < 1 || init_month > 12) {
                cerr << "Bad month " << init_month << "\n";
                exit(EXIT_FAILURE);
        }
        month = init_month;

        if (init_day < 1 || init_day > length[month]) {
                cerr << "Bad month " << init_month << " and day " << init_day
                        << "\n";
                exit(EXIT_FAILURE);
        }
        day = init_day;
}

date::date()
{
        const auto now {chrono::system_clock::now()};
        const time_t t {chrono::system_clock::to_time_t(now)};
        const tm *const p {localtime(&t)};

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

int date::monthsInYear()
{
	return size(length) - 1;   //number of months in a year
}

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 object.
{
        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;
                }
        }
}

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

void date::prev()                     //Move this date object one day into the past.
{
        if (day > 1) {
                --day;
        } else {
                if (month > 1) {      //Move back to previous month.
                        --month;
                } else {
                        month = 12;   //Move back to previous year.
                        --year;
                }
                day = length[month];  //Now that in correct new month, assign day to length of month because it is the last day of the new month.
        }
}