/**
 * @file       paramgen.cpp
 *
 * @brief      Parameter generation utility for Zerocoin.
 *
 * @author     Ian Miers, Christina Garman and Matthew Green
 * @date       June 2013
 *
 * @copyright  Copyright 2013 Ian Miers, Christina Garman and Matthew Green
 * @license    This project is released under the MIT license.
 **/

using namespace std;

#include <string>
#include <iostream>
#include <fstream>
#include <curses.h>
#include <exception>
#include "Zerocoin.h"
#include "bitcoin_bignum/bignum.h"
#include "bitcoin_bignum/serialize.h"
#include "Params.h"
#include "Coin.h"
#include "CoinSpend.h"
#include "ParamGeneration.h"
#include "Accumulator.h"

#define DEFAULT_MODULUS_SIZE    3072
#define MIN_MODULUS_SIZE        1026

using namespace libzerocoin;

void
PrintWarning()
{
    cout << "Zerocoin parameter generation utility" << endl;
    cout << "-------------------------------------" << endl << endl;
    cout << "This utility generates an l-bit modulus N as the product of" << endl;
    cout << "two safe primes p, q. The values p and q are not stored." << endl;
    cout << "Call this program with no arguments to see usage options." << endl;
    cout << endl;
    cout << "SECURITY WARNING: ZEROCOIN PARAMETERS MUST BE GENERATED BY" << endl;
    cout << "A TRUSTED PARTY WHO DOES NOT STORE THE FACTORS. WHILE WE MAKE" << endl;
    cout << "A BEST EFFORT TO DESTROY THIS INFORMATION WE DO NOT TAKE" << endl;
    cout << "SPECIAL PRECAUTIONS TO ENSURE THAT THEY ARE DESTROYED." << endl;
    cout << endl;
    cout << "USE THIS UTILITY AT YOUR OWN RISK" << endl << endl;
}

void usage()
{
    printf("Usage:\n");
	printf(" -b <numbits>\n");
    printf(" -o <output file>\n");
    
	exit (8);
}

int main(int argc, char **argv)
{
    static Bignum resultModulus(0);
    uint32_t numBits = DEFAULT_MODULUS_SIZE;
    ofstream outfile;
    char* outfileName;
    bool writeToFile = false;
    
	while ((argc > 1) && (argv[1][0] == '-'))
	{
		switch (argv[1][1])
		{
			case 'b':
                numBits = atoi(argv[2]);
                ++argv;
                --argc;
				break;
                
            case 'o':
                outfileName = argv[2];
                writeToFile = true;
                break;
                
            case 'h':
                usage();
                break;
                
			default:
				printf("Wrong Argument: %s\n", argv[1]);
				usage();
                break;
		}
        
		++argv;
		--argc;
	}
    
    if (numBits < MIN_MODULUS_SIZE) {
        cout << "Modulus is below minimum length (" << MIN_MODULUS_SIZE << ") bits" << endl;
        return(0);
    }
    
    PrintWarning();
    
    cout << "Modulus size set to " << numBits << " bits." << endl;
    cout << "Generating parameters. This may take a few minutes..." << endl;
    
    // Generate two safe primes "p" and "q"
    Bignum *p, *q;
    p = new Bignum(0);
    q = new Bignum(0);
    *p = Bignum::generatePrime(numBits / 2, true);
    *q = Bignum::generatePrime(numBits / 2, true);
    
    // Multiply to compute N
    resultModulus = (*p) * (*q);
    
    // Wipe out the factors
    delete p;
    delete q;
    
    // Convert to a hexidecimal string
    std::string resultHex = resultModulus.ToString(16);
    
    cout << endl << "N = " << endl << resultHex << endl;
    
    if (writeToFile) {
        try {
            outfile.open (outfileName);
            outfile << resultHex;
            outfile.close();
            cout << endl << "Result has been written to file '" << outfileName << "'." << endl;
        } catch (std::runtime_error &e) {
            cout << "Unable to write to file:" << e.what() << endl;
        }
    }
}