/* phone3.cpp simulates the processing of a phone number
 * by the telephone company.
 *
 * Input:  phoneNumber.
 * Output: areaCode, exchange and localNumber.
 ***************************************************************/

#include <iostream.h>              // cin, cout, >>, <<
#include <string>                  // string

void CheckValidity(string aString);

int main()
{
  const string PROMPT = "\nEnter a phone number: ";
  cout << PROMPT;

  string phoneNumber;
  cin >> phoneNumber;

  CheckValidity(phoneNumber);

  if (phoneNumber[0] == '1')
    cout << '(' << phoneNumber.substr(1, 3) << ")-"
         << phoneNumber.substr(4, 3) << '-'
         << phoneNumber.substr(7, 4) << endl;
  else
     cout << phoneNumber.substr(0, 3) << '-'
          << phoneNumber.substr(3, 4) << endl;

  return 0;
}

/*** Insert the contents of Figure 4.2 here:
       the prototype for PhoneError
       the definition of CheckValidity
       #include <cstdlib> 
       the definition of PhoneError   ***/

/* CheckValidity ensures that a string is a valid phone number.
 * 
 * Receive: aString, a string
 * Return:  nothing if aString is valid
 *          (terminate the program otherwise)
 ***************************************************************/

void PhoneError(string message);

void CheckValidity(string aString)
{
   if (aString.size() != 7 && aString.size() != 11)
      PhoneError("A phone number has 7 or 11 characters");
   else
	{
      if (aString.size() == 7 && (aString[0] == '0' || aString[0] == 
'1'))
         PhoneError("A local call cannot begin with 0 or 1");
      else if (aString.size() == 11 && aString[0] != '1')
         PhoneError("A long distance call must begin with 1");
      if (aString.find_first_not_of("0123456789", 0) != NPOS)
         PhoneError("A phone number must consist of all digits");
   }
}

/* PhoneError displays an error msg and terminates the program
 * 
 * Receive: message, a string.
 * Output:  message, with phone-specific text
 * Postcondition: Program has been terminated.
 **************************************************************/

#include <stdlib.h>                     // exit()
void PhoneError(string message)
{
   cerr << "Your call cannot be completed because:\n"
        << message <<  ".\nPlease try again." << endl;
   exit(1);
}