#pragma once

#include <iostream>
#include <string>

class Date;

  ///////////////////////////
 // Function declarations //
///////////////////////////

// Insert date into an output stream.
std::ostream &operator<<( std::ostream &out,
                          Date const   &date );

  //////////////////////
 // Class definition //
///////////////////////

class Date {
  public:

    // Construct the specified date.
    Date( unsigned int const year,
          unsigned int const month,
          unsigned int const day );

    // Return the year.
    unsigned int year() const;

    // Return the month.
    unsigned int month() const;

    // Return the day.
    unsigned int day() const;

    // Move to the next date and return this object.
    Date &operator++();

    // Move to the next date and return the previous value.
    Date operator++( int );

    // Move to the previous date and return this object.
    Date &operator--();

    // Move to the previous date and return the previous value.
    Date operator--( int );

    // Return a string representation of this date.
    std::string to_string() const;

  private:

    // Store the year, month and day.
    unsigned int year_;
    unsigned int month_;
    unsigned int day_;

    // Determine whether the specified year is a leap year.
    static bool is_leap_year( unsigned int const year );

    // Return the number of days in the specified month.
    static unsigned int days_in_month(
        unsigned int const year,
        unsigned int const month
    );

    // Determine whether the specified values form a valid date.
    static bool is_valid( unsigned int const year,
                          unsigned int const month,
                          unsigned int const day );
};