// File Name: calv2.cpp
// Author: Xiannong Meng
// Assignment: solution for homework
// Date: Apr. 27, 1997
// Problem: this program reads an integer representing a year from keyboard
//          and prints the calendar for that year in a three-column format.
// Note: Since this program is a translation from a C program, it is not
//       in a perfect C++ format.

#include <iostream.h>
#include "calv2.h"          // header file for calendar

// Name: Calendar
// Intent: constructor which initializes certain values
// Precondition: none
// Postcondition: a calendar object with initial values created
Calendar::Calendar()
{
    // since C++ does not allow initialization like this in class
    // header file, so we do it here.
    int days[] = {31, 28, 31, 30, 31, 30,
		      31, 31, 30, 31, 30, 31};

    int daysLp[] = {31, 29, 31, 30, 31, 30,
		      31, 31, 30, 31, 30, 31};
    int i;

    for (i = 0; i < NumMon; i ++)
     {
	 daysInMonth[i] = days[i];
	 daysLpMonth[i] = daysLp[i];
     }
}

// Name: PrintCalendar
// Intent: take the parameter specifying the year to print, and print the
//         calendar. This should be the only public interface function
// Precondition: A calendar object has been created, a year has been input
//               from keyboard.
// Postcondition: A calendar is printed on screen in a three-column format
void Calendar::PrintCalendar(int year)
{
   // figure out and store days in array
   // each month can have upto 6 weeks
   int daysPerMon[NumMon][WkPerMon][DAYINWK];  
   int day;

   InitDays(daysPerMon);
   day = CalcFirstDay(year);

   // the next section calculates the values of days in each slot
   for (int i = 0; i < 12; i ++)
   {
       if (IsLeapYear(year) == false)
	   CalcMonth(day, daysInMonth[i], daysPerMon[i]);
       else
	   CalcMonth(day, daysLpMonth[i], daysPerMon[i]);
   }

   // then prints it
   cout << "                                  " << year << endl;
   PrintYear(daysPerMon);
}

// Name: InitDays
// Intent: initialize days to have the value of -1. When the calendar is
// printed, if it has a value of 0, a space will be printed, otherwise print
// its value. 
// Precondition: calendar object has been created
// Postcondition: calendary initialized
void Calendar::InitDays(int a[NumMon][WkPerMon][DAYINWK])
{
    for (int i = 0; i < NumMon; i ++)
	for (int j = 0; j < WkPerMon; j ++)
	    for (int k = 0; k < DAYINWK; k ++)
		a[i][j][k] = -1;
}

// Name: CalcMonth
// Intent: calcualte values in each day of each month
// Precondition: days have been intialized
// Postcondition: calendary is ready for print
void Calendar::CalcMonth(int &whichDay, 
               int dayInMonth, int daysValue[WkPerMon][DAYINWK])
{
  int leadDay = whichDay % DAYINWK;
  int day = 1;
  int i;
  int printDay, printWk;

  for (i = 0; i < leadDay; i ++)
      daysValue[0][i] = 0;
  for (i = day; i <= dayInMonth; i ++)
  {
      printDay = (day + leadDay - 1) % DAYINWK;
      printWk  = (day + leadDay - 1) / DAYINWK;
      daysValue[printWk][printDay] = day;
      day ++;
      whichDay ++;
  }
}

// Name: PrintYear
// Intent: After the values in each day have been filled, print the calendar
// Precondition: day values have been filled (calculated)
// Postcondition: calendary is printed
void Calendar::PrintYear(int days[NumMon][WkPerMon][DAYINWK])
{

    // print one quarter at a time
    PrintQuarter(Jan, Mar, days);
    PrintQuarter(Apr, Jun, days);
    PrintQuarter(Jul, Sep, days);
    PrintQuarter(Oct, Dec, days);
}


// Name: PrintQuarter
// Intent: print one quarter across the line (3 months)
// Precondition: day values have been calculated
// Postcondition: one quarter is printed
void Calendar::PrintQuarter(Month a, Month b, int days[NumMon][WkPerMon][DAYINWK])
{

    cout << "          ";
    PrintMonthHead(a);
    cout << "                      ";
    PrintMonthHead(Month((int)a + 1));
    cout << "                      ";
    PrintMonthHead(Month((int)a + 2));
    cout << endl;
    PrintWkHead();
    cout << "    ";
    PrintWkHead();
    cout << "    ";
    PrintWkHead();
    cout << endl;

    PrintMonth(a, b, days);
}

// Name: PrintMonth
// Intent: Print three month across the line, i.e. first week of the first
// month, first week of the second month, first week of the third month, then
// second week of the first month, second week of the second moenth, etc.
// Precondition: The headers of the months and weeks have been printed
// Postcondition: three months across the line have been printed
void Calendar::PrintMonth(Month a, Month b, int days[NumMon][WkPerMon][DAYINWK])
{
    int j, k;
    Month i;
    for (j = 0; j < WkPerMon; j ++)
    {
	 for (i = a; i <= b; i = Month((int)i + 1))
	 {
	     for (k = 0; k < DAYINWK; k ++)
	     {
		 if (days[i][j][k] <= 0)
		     cout << "   ";
		 else if (days[i][j][k] > 0)
		     cout << setw(3) << days[i][j][k];
	     }
	     if (i < b)
		 cout << "    ";
	 }
	 cout << endl;
     }
}

// Name: PrintMonthHead
// Intent: Print the month header
// Precondition: none
// Postcondition: the name of a month is printed
void Calendar::PrintMonthHead(int month)
{
    switch (month+1)
    {
    case 1 : cout << "Jan";
             break;
    case 2 : cout << "Feb";
             break;
    case 3 : cout << "Mar";
             break;
    case 4 : cout << "Apr";
             break;
    case 5 : cout << "May";
             break;
    case 6 : cout << "Jun";
             break;
    case 7 : cout << "Jul";
             break;
    case 8 : cout << "Aug";
             break;
    case 9 : cout << "Sep";
             break;
    case 10 : cout << "Oct";
             break;
    case 11 : cout << "Nov";
             break;
    case 12 : cout << "Dec";
    }
}


// Name: PrintWkHead
// Intent: Print the week header
// Precondition: none
// Postcondition: the names of seven weekdays are printed
void Calendar::PrintWkHead()
{
    cout << "  S  M Tu  W Th  F  S";
}

// Name: CalcFirstDay
// Intent:
// given the year and the first day in 1753 was a Monday
// figure out which day falls on this year's first day
// Precondition: the year is given
// Postcondition: first day value is calculated
int Calendar::CalcFirstDay(int thisYear)
{
    // calculated how many days since 1753 (BASEYEAR)
    int days = 1;

    for (int year = BASEYEAR; year < thisYear; year ++)
    {
	if (IsLeapYear(year) == true)
	    days = (days + 366) % DAYINWK;
	else
	    days = (days + 365) % DAYINWK;
    }
    return days;
}

// Name: IsLeapYear
// Intent: decide whether or not this is a leap year
// Precondition: an integer value of year has been typed in
// Postcondition: a true or false is returned
bool Calendar::IsLeapYear(int y)
{
    return (((y % 4 == 0) && (y % 100) != 0) || (y % 400 == 0));
}