// date.cpp
// ----------------------------------------------------------------------
// implements class Date
// Do not modify this file.
// 
// CSE 143
// Homework 2, 3
// http://www.cs.washington.edu/education/courses/143/00su/homework/
// 25 Jun 2000; Man-Hing Wong, Ken Yasuhara


#include <iostream.h>
#include <assert.h>

#include "date.h"


const int NUM_MONTHS = 12;

// standard (i.e. not leap year) number of days in each month 
const int monthLengths[NUM_MONTHS] =  {
  31, // Jan
  28, // Feb
  31, // Mar
  30, // Apr
  31, // May
  30, // Jun
  31, // Jul
  31, // Aug
  30, // Sep
  31, // Oct
  30, // Nov
  31, // Dec
};


//////////////////////////////////////////////////////////////////////
// constructors

Date::Date() 
{
  month = 0;
  day = 0;
}


Date::Date(int newMonth, int newDay, int newYear) 
{
  month = newMonth;
  day = newDay;
  year = newYear;
}


bool Date::isValid()
{
  if (month < 1 || month > NUM_MONTHS) {
    return false;
  }
        
  // month is valid, check day
  if (day < 1 || day > daysInMonth(month, year)) {
    return false;
  }
        
  // day is valid, check year
  if (year < 1) {
    return false;
  }

  // Date is valid
  return true;
}


int Date::getMonth() 
{
  return month;
}


int Date::getDay() 
{
  return day;
}


int Date::getYear() 
{
  return year;
}


int Date::compare(Date otherDay) 
{
  if (isValid()) {
    if (otherDay.isValid()) {
      // First, check year.
      if (year < otherDay.year) return 1;
      if (year > otherDay.year) return -1;

      // Year is equal, check month.
      if (month < otherDay.month) return 1;
      if (month > otherDay.month) return -1;

      // Year and month are the equal, check day.
      if (day < otherDay.day) return 1;
      if (day > otherDay.day) return -1;

      // This date and otherDay are equal
      return 0;
    }

    return -1;  // an invalid otherDay means otherDay is earlier
  }

  if (otherDay.isValid()) 
    return 1;   // invalid date is earlier than otherDay

  return 0;     // both invalid means they are equal
}


void Date::addDays(int numDays) 
{
  // just ignore if this is not a valid date 
  if (!isValid()) { 
    return;
  }

  assert (numDays >= 0);

  day += numDays;
  while(day > daysInMonth(month, year))  {
    // subtract off the number of days in this month and
    // increment the month to the next one
    day -= daysInMonth(month, year); 
    month++;                                             

    // check to for roll-over into the next year
    if (month > NUM_MONTHS) {
      assert(month == 13);  
      month = 1;
      year++;
    }
  }

  assert(0 < day && day <= daysInMonth(month, year));
}


int Date::dayDifference(Date d) 
{
  int diff = 0;                    // counter of num of days difference
  Date thisCopy(month, day, year); // get the current date

  if (!isValid() || !d.isValid()) {
    return diff;
  }

  Date earlier, later;
  
  if (d.compare(thisCopy) >= 0) {
    earlier = d;
    later = thisCopy;
  } else {
    earlier = thisCopy;
    later = d;
  }

  // loop while earlier != later
  while (earlier.month != later.month || earlier.day != later.day || 
         earlier.year != later.year) {
    earlier.addDays(1);         // increment thisCopy by 1 day
    diff++;                     // increment counter
  }

  return diff;
}


// returns the number of days in the given month of the given year,
// taking leap years into account 

int Date::daysInMonth(int m, int y) 
{
  assert(m >= 1 && m <= NUM_MONTHS);

  int days = monthLengths[m-1]; // get number of days in month m

  // check if it is a leap year
  if (year % 4 == 0 && (!(year % 100 == 0) || (year % 400 == 0))) {
    // It is a leap year, increment days if month is Feb
    if (m == 2) {
      return days + 1;
    }
  }

  return days;
}


void Date::printDate() 
{
  cout << month << "/" << day << "/" << year;
}