// Lawrence Bush

// Lab Session:  1
// RCS account:  bushl

//	decode.cpp -	This is the main file for the decode workspace.
//			The program accepts three arguments (R,d,N) 
//			(Encoded Message, decode key, product of the 
//			two primes).  It then uses this information to 
//			decode N.

#include <iostream>
#include <iomanip>

using std::endl;

#include "modexp.h"


int main(long int argc, char * argv[]) {
	

	
	
	// This function tests the size of argc to make sure two parameters were 
	// passed to the function.
	// Note that the computer considers the program name as one argument,
	// therefore, we test to see if there are 3 arguments.
	if(argc != 4)  {  // arg needs to be 4 for this
		std::cerr << "Invalid command line parameters.\n"
			<<	"\nUsage:  \ndecode.exe 38 27 55\n         [ R, d, N ]\n"
			<<"\n\nIf you are running this in VC++, do the following:\n     Alt+F7\n     Click on Debug Tab (next to general)"
			<<"\n     Type parameters "
			<<"into Program Arguments text box.\n"<<endl;
		
		
		exit(0);
	}
	// This function tests the four arguments to make sure they are digits.
	for(int aaa=1;aaa<4;aaa++) {
		if (! isdigit(*(argv[aaa])) ) {
			std::cerr << "Invalid command line parameters.\nOne of your parameters is not a digit.\n"
				<<	"\nUsage:  \ndecode.exe 38 27 55\n         [ R, d, N ]\n"
			<<"\n\nIf you are running this in VC++, do the following:\n     Alt+F7\n     Click on Debug Tab (next to general)"
			<<"\n     Type parameters "
		<<"into Program Arguments text box.\n"<<endl;
				exit(0);
		}
	}
	
	// Get command-line arguments
	long int R = atol(argv[1]);
	long int d = atoi(argv[2]);
	long int N = atoi(argv[3]);

	
	//*********************************************
// Output command line arguments.
std::cout<< "R "<<R<<" d "<<d<<" N "<<N<<endl;
long int Q = modexp(R,d,N); // call modexp function on R d N

std::cout<<"Decoded Message Q = "<<Q<<endl; // output decoded message


return 0;
}