/*
Copyright 2007 All Rights Reserved Paul Picazo (kinda)
but he used a webpage to tell him what the Luhn method was
and he also used his knowledge of programming from various courses
and he also used a few google searches to see what the names of
functions he was looking for were called. And to troubleshoot
the itoa() not working when he compiled it on G++ on linux.
References were not including because the information is so
general that he could not figure out which of the many pages
that contain the information he used initially.
*/
#include <iostream>
#include <sstream>
#include <string>
using namespace std;           

//takes in a string of numbers (with or without spaces)
//returns true if it is a valid 16 digit credit card number
//returns false if it has non numerical characters (after removing spaces)
//returns false if it is not 16 digits in length (after removing spaces)
//returns false if the number fails the luhn test, bad CC number
bool checkCC(string input);

//takes in int and returns string
string itos(int x); 

//removes the spaces from a given string
//returns the input string without spaces
string removeSpaces(string input);

int main()
{
  string userInput;
  printf("Enter Credit Card Number:");
  getline(cin, userInput);
  if(checkCC(userInput))
  {
    printf("Credit Card: %s  is good.\n", userInput.c_str());
  }
  else
  {
    printf("Credit Card: %s  is bad.\n", userInput.c_str());
  }

  return 0;
}

bool checkCC(string input)
{
  bool retVal = false;

  string temp = removeSpaces(input);

  if(temp.length() == 16)
  {
    retVal = true;
    for(int i = 0; i < 16; i++)
    {
      if(temp[i] > '9' || temp[i] < '0')
      {
        retVal = false;
      }
    }
    if(retVal == true)
    {
      for(int i = 14; i >= 0; i = i - 2)
      {
        char tempcharstar[3];
        tempcharstar[0] = temp[i];
        tempcharstar[1] = '\0';

        int tdigit =  atoi(tempcharstar);
        string tempdigit = "";

        tempdigit = itos(tdigit * 2);
        temp.replace(i,1,tempdigit);
      }
      int sum = 0;
      for(int i = 0; i < temp.length(); i++)
      {
        char tempcharstar[2];
        tempcharstar[0] = temp[i];
        tempcharstar[1] = '\0';

        int tdigit =  atoi(tempcharstar);
        sum += tdigit;
      }
      if(sum % 10 == 0)
      {
        retVal = true;
      }
      else
      {
        retVal = false;
      }
    }
    else
    {
      //it is still gonna be false, no need to set it to false
    }
  }
  else
  {
    retVal = false;
  }

  return retVal;
}

string itos(int x)
{
	ostringstream retVal;
	retVal << x;
	return retVal.str();
}

string removeSpaces(string input)
{
  string temp = "";
  int ws = 0;
  int start = 0;
  while((ws = input.find(" ",start)) >= 0)
  {
    temp += input.substr(start, ws - start);
    start = ws + 1;
  }
  if(start + 1 < input.length())
    temp += input.substr(start, input.length() - start);

  return temp;
}