//-------------------------------------------------------------
// Example to illustrate user-defined functions
//-------------------------------------------------------------

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

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

int DaysInMonth (int monthnum)
{
    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:    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;
    }
}

void DisplayFirstLine (int startdayofweek) 
 {
   int i;
   cout << endl;
   for (i = 0; i < startdayofweek; i++)
       cout << "    ";
   for(i = 1 ; i <= 7 - startdayofweek; i++)
      cout << setw(4) << i;
 }

void DisplayFullWeek (int startdateofweek)
 {
   int i;
   cout << endl;
   for (i = startdateofweek; i <= (startdateofweek + 6); i++)
       cout << setw(4) << i;
 } 

void DisplayLastWeek (int startdateofweek, int numdaysinmonth)
{
   int i;
   cout << endl;
   for (i = startdateofweek; i <= numdaysinmonth; i++)
       cout << setw(4) << i;
}

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

int main ( )
{

// --- Variables

    int monthnum,          // month number (1 - 12) entered by user
        numdays,           // number of days in month
        startdayofweek,    //
        begdateofnextweek, //
        begdayofmonth;   // 

// --- Get month number from user

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

// --- 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;
    }

cout << "Enter beginning day:";
cin >> begdayofmonth;

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

// --- Display output sentence 

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

   DisplayFirstLine(begdayofmonth);
   begdateofnextweek = 8 - begdayofmonth;
   DisplayFullWeek (begdateofnextweek);
   begdateofnextweek +=7;
   DisplayFullWeek (begdateofnextweek);
   begdateofnextweek +=7;
   DisplayFullWeek (begdateofnextweek);
   begdateofnextweek +=7;

   if (numdays - begdateofnextweek >=7)
   {
     DisplayFullWeek (begdateofnextweek);
     begdateofnextweek +=7;
   }
   DisplayLastWeek (begdateofnextweek, numdays);  
   cout << "\n\n";   

   return 0;
}