#include <iostream>
#include <cstdlib>
#include <ctime> // for the functions time and localtime
using namespace std;

class date {
    // Declarations for data members:
    int year;
    int month;  // in the range 1 to 12 inclusive
    int day;    // in the range 1 to 31 inclusive

    static const int length[13]; // Static data member for month lengths

public:
    // Constructor declarations
    date(int m, int d, int y); // Existing constructor
    date(); // New constructor that initializes to today's date
    
    // Member function declarations
    void print() const;  // Print function
    void next(int n);    // Advance n days
    void next();         // Advance one day
    int dayOfYear() const; // New function to return day of the year
    
    // Friend function declaration
    friend int distance(const date& d1, const date& d2);
};

const int date::length[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

// Constructor initializing date with given values
date::date(int m, int d, int y) {
    year = y;
    if (m < 1 || m > 12) {
        throw invalid_argument("bad month");
    }
    month = m;
    if (d < 1 || d > length[month]) {
        throw invalid_argument("bad day of the month");
    }
    day = d;
}

// New constructor initializing date to today's date
date::date() {
    time_t now = time(nullptr);
    tm *p = localtime(&now);
    year = p->tm_year + 1900;
    month = p->tm_mon + 1;
    day = p->tm_mday;
}

// Print function
void date::print() const {
    cout << month << "/" << day << "/" << year;
}

// Function to move date forward by n days
void date::next(int n) {
    for (int i = 0; i < n; ++i) {
        next();
    }
}

// Function to move date forward by one day
void date::next() {
    if (day < length[month]) {
        ++day;
    } else {
        day = 1;
        if (month < 12) {
            ++month;
        } else {
            month = 1;
            ++year;
        }
    }
}

// Function to calculate day of the year
int date::dayOfYear() const {
    int dayOfYear = day;
    for (int i = 1; i < month; ++i) {
        dayOfYear += length[i];
    }
    return dayOfYear;
}

// Friend function to compute distance between two dates
int distance(const date& d1, const date& d2) {
    int yearDiff = d1.year - d2.year;
    int dayDiff = d1.dayOfYear() - d2.dayOfYear();

    // Adjust for leap years
    for (int i = min(d1.year, d2.year); i < max(d1.year, d2.year); ++i) {
        if (i % 4 == 0 && (i % 100 != 0 || i % 400 == 0)) {
            yearDiff++;  // Add an extra day for each leap year
        }
    }
    
    return yearDiff * 365 + dayDiff;
}

// Main function for testing
int main() {
    try {
        const date independenceDay(7, 4, 1776);
        independenceDay.print();
        cout << " is Independence Day.\n";

        // Get today's date
        const date t;
        t.print();
        cout << " is today.\n";

        // Calculate day of the year for Christmas
        const date xmas(12, 25, 2025);
        cout << "Christmas is on day " << xmas.dayOfYear() << " of the year.\n";

        // Compute distance between dates
        const date summer(6, 20, 2025);
        int dist = distance(summer, t);
        cout << "Only " << dist << " days till summer.\n";
    } catch (invalid_argument& e) {
        cerr << e.what() << "\n";
        return EXIT_FAILURE;
    }
    return EXIT_SUCCESS;
}