/**
 * Assignment #3, Program 2
 * Program to calculate day number in a year
 * Author: Mark Allen Weiss
 * SSN: 000-00-0000
 * Course: COP-2210 Section 8
 * Date: October 7, 1998
 *
 * CERTIFICATION OF SOLE AUTHORSHIP
 * I certify that this work is solely my own and
 * that none if it is the work of any other person.
 * I further certify that I have not provided any
 * assistance to other students enrolled in COP-2210 that
 * would render their CERTIFICATION OF SOLE AUTHORSHIP
 * invalid. I understand that violations of this pledge
 * may result in severe sanctions.
 *
 *
 *
 * -----------------------------------
 *   (Mark Allen Weiss)       <--- Put your name here, and sign above
 */

#include <iostream.h>
#include "apstring.h"

  // Program constants
const int JANUARY = 1;
const int FEBRUARY = 2;
const int MARCH = 3;
const int APRIL = 4;
const int MAY = 5;
const int JUNE = 6;
const int JULY = 7;
const int AUGUST = 8;
const int SEPTEMBER = 9;
const int OCTOBER = 10; 
const int NOVEMBER = 11;
const int DECEMBER = 12;

  // Function declarations
void display_instructions( );
int get_input( apstring message );
int compute_day_number( int month, int day, int year );
void print_answer( int day_number );
int days_to_add( int month, int which_month, int days_in_month );
bool is_leap_year( int year );

int main( )
{
      // Inputs
    int month;
    int day;
    int year;

      // Outputs
    int day_number;

      // Read values
    display_instructions( );
    month = get_input( "month" );
    day = get_input( "day" );
    year = get_input( "year" );

      // Compute answers
    day_number = compute_day_number( month, day, year );

      // Print the answers
    print_answer( day_number );

    return 0;
}

/**
 * Print instructions.
 */
void display_instructions( )
{
    cout << "This program will compute the day number (1 to 366)" << endl;
    cout << "in a year for a date, given three parameters:" << endl;
    cout << "\t1. The month (1-12)" << endl;
    cout << "\t2. The day of the month (1-31)" << endl;
    cout << "\t3. The year (1600-)" << endl;
    cout << "Dates are not checked for validity." << endl;
}

/**
 * Print answers.
 */
void print_answer( int day_number )
{
    cout << endl;
    cout << "The entered day is day number " << day_number << endl;
}

/**
 * Read an input; message is used to give a prompt.
 */
int get_input( apstring message )
{
    int value_read;

    cout << "Please enter the " << message << ": ";
    cin >> value_read;

    return value_read;
}

/**
 * Return the number of days to add to the running total.
 * If month is past which_month, return days_in_month; otherwise
 * return 0.
 */
int days_to_add( int month, int which_month, int days_in_month )
{
    if( month > which_month )
        return days_in_month;
    else
        return 0;
}

/**
 * Compute day number.
 */
int compute_day_number( int month, int day, int year )
{
    int total_days = day;

    total_days += days_to_add( month, JANUARY, 31 );
    if( is_leap_year( year ) )
        total_days += days_to_add( month, FEBRUARY, 29 );
    else
        total_days += days_to_add( month, FEBRUARY, 28 );
    total_days += days_to_add( month, MARCH, 31 );
    total_days += days_to_add( month, APRIL, 30 );
    total_days += days_to_add( month, MAY, 31 );
    total_days += days_to_add( month, JUNE, 30 );
    total_days += days_to_add( month, JULY, 31 );
    total_days += days_to_add( month, AUGUST, 31 );
    total_days += days_to_add( month, SEPTEMBER, 30 );
    total_days += days_to_add( month, OCTOBER, 31 );
    total_days += days_to_add( month, NOVEMBER, 30 );
    total_days += days_to_add( month, DECEMBER, 31 );

    return total_days;
}

/**
 * Returns true if and only if a leap year.
 * Leap year if: divisible by 4, but not by 100, unless divisible by 400.
 */
bool is_leap_year( int year )
{
    return ( year % 400 == 0 ) || ( year % 4 == 0 && year % 100 != 0 );
}