#include <iostream>
using namespace std;

//This function is just used to determine if a character is a ASCII digit.
inline int isDigit(char cIn) {return (cIn >= '0' && cIn <='9');  }

//This function determins the seperators used in the SSN.
//  you can add to this function to allow different input formats.
inline int isSeperator(char cIn) {return (cIn=='-' ); }

//This function will parse the input for a valid SSN,
//   if the string SSN does not hold a valid SSN then
//   this function return a 0 (false) else it returns a
//   long int containing the SSN.
long validateSSN(char *SSN);


//This union is used to extract a SSN encoded into a long.
typedef union
{
    long hold;
    struct
    {
        unsigned group:8;
        unsigned area:10;
        unsigned serial:14;
    };
} SSNumber;


int main()
{
    SSNumber SSN;
    char buffer[256];
    do
    {
        cout <<"Input your SSN (###-##-####): ";
        cin.getline(buffer, 255);
        SSN.hold = validateSSN(buffer);
        if (!SSN.hold)
        {
            cout << "\nInvalid SSN!!!\n";
        }
    } while (!SSN.hold);
    cout << "You entered: ";
    cout << SSN.area << "-" << SSN.group << "-" << SSN.serial <<"." << endl;
    return 0;
}
                


long validateSSN(char *SSN)
{
    SSNumber RetSSN;
    long retVal = true;
    int SSN_Numbers[] = {0, 0, 0}; //used to hold the numbers...
    int SSN_Digits[] = {3,2,4}; //keep track of how many digits we have read.
    int i, j; //counters, i loops though the buffer, and j counts how many sections in the SSN.
    i=0; j=0;
    do
    {
        if (isDigit(SSN[i]))
        {
            do
            {
                SSN_Numbers[j] *= 10;
                SSN_Numbers[j] += SSN[i]-'0';
                i++;
            } while (--SSN_Digits[j] && isDigit(SSN[i]));
            
            //this line allows the user to enter: 123456789 w/o the '-'
            //  if it is removed then the user MUST enter the '-' char between segments.
            if ((SSN_Digits[j]==0) && isDigit(SSN[i])) { j++; }

        } else if (isSeperator(SSN[i]))
        {
            if (j<2)
            {
                j++;
                i++;
            } else
            {
                //ERROR we have too many sections!!!
                retVal = 0;
            }
        } else
        {
            //ERROR unexpected character
            retVal = 0;
        }

    } while (j<3 && SSN[i] && retVal);
    
    
    //we want to ensure that there were 3 sets of digits (thus j==2)
    //   and that retVal has not been set to zero (false).
    if(j==2 && retVal)
    {
        cout << SSN_Numbers[0] << "." << SSN_Numbers[1] << "." <<SSN_Numbers[2]<<"\n";
        RetSSN.area=SSN_Numbers[0];    //Assign the first 3 to the area code...
        RetSSN.group=SSN_Numbers[1]; //Assign the next 2 to the group code...
        RetSSN.serial=SSN_Numbers[2]; //Assign the last 4 to the serial code...
        //This if statment checks to make sure that the SSN is a valid SSN... if you are willing
        //  to accept ANY SSN then replace this with 'retVal=RetSSN.hold;'
        if (RetSSN.area == 0 || RetSSN.area >=740 || (RetSSN.group==0) || (RetSSN.serial==0))
        {
            //Invalid SSN according to http://www.usrecordsearch.com/ssn.htm
            retVal = 0;
        }else
        {
            retVal=RetSSN.hold;
        }
    }
    
    return retVal;
}