//------------------------------------------------------------
//      Name: Kieara Mowery
//      Due : Wednesday, October 12th, 2008
//      Date: Sunday, October 9th, 2008
//      Purpose: To display a monthly calendar starting on the
//               dates given, which includes the year and leap
//               year.
//-------------------------------------------------------------

#include <iostream>
#include <iomanip>
using namespace std;

bool LeapYear(int year)
{
        int rem;        // the integer to establish the int year
        bool leapyr;
        rem = year % 4;

    if ( rem != 0 ) 
        if (year == 1700 || year == 1800 || year == 1900 || year == 2100)

          leapyr = false;
       else
          leapyr = true;
       else
          leapyr = false;

     return leapyr;
   
}


//-------------------------------------------------------------
// DaysInMonth determines the number of days of the month
// Note: This includes leap year
//-------------------------------------------------------------
// Accepts:  number (1 - 12) representing month
// Returns:  number of days in that month
//-------------------------------------------------------------


int DaysInMonth (int monthnum, int year)
{
    int numdays;  // temp variable for days in month

    switch (monthnum)
    {
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:   numdays = 31;  break;
        case 2:  
        {
           if(LeapYear(year) == true)
             numdays = 29;
           else
             numdays = 28;
        }
        break;
        case 4:
        case 6:
        case 9:
        case 11:   numdays = 30;  break;
    }

    return numdays;
}

//-------------------------------------------------------------
// DisplayMonthName displays the month name to standard output
//-------------------------------------------------------------
// Accepts:  number (1 - 12) representing month
// Returns:  nothing
//-------------------------------------------------------------

void DisplayMonthName (int monthnum)
{
    switch (monthnum)
    {
        case 1:  cout << " January";  break;
        case 2:  cout << "February";  break;
        case 3:  cout << "March";  break;
        case 4:  cout << "April";  break;
        case 5:  cout << "May";  break;
        case 6:  cout << "June";  break;
        case 7:  cout << "July";  break;
        case 8:  cout << "August";  break;
        case 9:  cout << "September";  break;
        case 10:  cout << "October";  break;
        case 11:  cout << "November";  break;
        case 12:  cout << "December";  break;
    }
}

    int CalculateDayofWeek ( int month, int day, int year)
    {
        int codes;      // code for the month
        int total;      // total overall
        int digits;     // digits of months
        int dayofweek;  // the day of the week starts
        int monthcode;  // code of the month
        int c;          // to eastablish the leap year
        switch (monthcode)
        {
            case 1: monthcode = 6; break;
            case 2: monthcode = 2; break;
            case 3: monthcode = 2; break;
            case 4: monthcode = 5; break;
            case 5: monthcode = 0; break;
            case 6: monthcode = 3; break;
            case 7: monthcode = 5; break;
            case 8: monthcode = 1; break;
            case 9: monthcode = 4; break;
            case 10: monthcode = 6; break;
            case 11: monthcode = 2; break;
            case 12: monthcode = 4; break;
        }

    digits = year % 100;
    total = digits + digits / 4;
    codes = total + monthcode + day;

    if ( LeapYear(year) == true )
       if ( month == 1 || month == 2 )
        codes = codes - 1;
   
    c = year % 100;
   
    if ( c == 17 || c == 21 )
       codes = codes + 5;
    if ( c == 18 || c == 22 )
       codes = codes + 3;
    if ( c == 19 )
       codes = codes + 1;

    dayofweek = codes % 7;         

    return dayofweek;   
}

    void DisplayTitleAndHeadings(int month)
    {
    cout << "\n\n";
    cout << "                       ";
    cout << "\n      Sun      Mon      Tues      Wed     Thurs     Fri      Sat";
    
    }

    void DisplayFirstLine(int startdayofweek)
    {
        int i;  // to establish the start day of week
        cout << endl;
        for (i = 0; i < startdayofweek; i++)
             cout << setw(9) << " ";
        for (i = 1; i <= ( 7 - startdayofweek); i++)
            {
                cout << setw(9) << i;

             }
    }
   
    void DisplayFullWeek(int startdateofweek)
    {
        int i;  // to establish the start date of week
        cout << endl;
        for ( i = startdateofweek; i <= startdateofweek + 6; i++ )
            {
                cout << setw(9) << i;
             }           
    }
   

    void DisplayLastWeek(int startdateofweek, int numdaysinmonth)
    {
        int i;
        cout << endl;
        for ( i = startdateofweek; i <= numdaysinmonth; i++ )
            {
                cout << setw(9) << i;
//                cout << "    ";


             }
    }


//----------------------------------------------------------
//  Main Function
//-------------------------------------------------------------

int main ( )
{
    int begdateofnextweek;      // the begin date of the following week


// --- Variables

    int monthnum,       // month number (1 - 12) entered by user
        year,           // the year
        numdays,        // number of days in month
        begdayofmonth;  // begin day of month

//--- Get Year from user

    cout << "\nEnter the year: ";
    cin >> year;

// --- Get month number from user

    cout << "\nEnter a month number (1-12): ";
    cin >> monthnum;

// --- Get Begin Day of Month
   
    begdayofmonth = CalculateDayofWeek ( monthnum, 1, year );
    numdays = DaysInMonth ( monthnum, year);

// --- Validate month number

    while (monthnum < 1 || monthnum > 12)
    {
       cout << "\n\n!!! Month number must be in range 1 - 12 !!!";
       cout << "\n\nPlease re-enter month number: ";
       cin >> monthnum;
    }
// --- Validate year number
    while ( year < 1000 || year > 36000 )
    {
        cout << " \n\n!!! The year must be in range 1000 - 36000 !!!";
        cout << " \n\nPlease re-enter month number: ";
        cin >> year;
     }

// --- Get number of days in month
 
    numdays = DaysInMonth(monthnum, year);

// --- Display output sentence

    cout << "\n\n";
    DisplayMonthName (monthnum);
    cout << " has " << numdays << " days.\n\n";
    cout << endl;

// --- Display Title Headings
    cout << "                           ";
    DisplayMonthName (monthnum);
    cout  << "  " << year;

   
    DisplayTitleAndHeadings(monthnum);
    DisplayFirstLine(begdayofmonth);   
    begdateofnextweek = 8 - begdayofmonth;
    DisplayFullWeek(begdateofnextweek);
    begdateofnextweek += 7;
    DisplayFullWeek(begdateofnextweek);
    begdateofnextweek += 7;
    DisplayFullWeek(begdateofnextweek);
    begdateofnextweek += 7;
    // DisplayFullWeek(begdateofnextweek);
    // begdateofnextweek += 7;   
   
    if ( numdays - begdateofnextweek >= 7)
    {
       DisplayFullWeek(begdateofnextweek);
       begdateofnextweek += 7;
    }
   
    DisplayLastWeek(begdateofnextweek, numdays);

    cout << endl;
    cout << endl;
    return 0;

}