package FeldmanVerifiableSecretSharing;

import ShamirSecretSharing.SecretSharing;
import org.bouncycastle.util.Arrays;
import org.factcenter.qilin.primitives.concrete.Zpstar;

import java.math.BigInteger;
import java.util.Random;

/**
 * Created by Tzlil on 1/27/2016.
 */
public class VerifiableSecretSharing extends SecretSharing {

    private final BigInteger[] commitments;
    private final BigInteger g;

    public VerifiableSecretSharing(Zpstar zpstar, int t, int n, BigInteger s, Random random) {
        super(zpstar, t, n, s, random);
        this.g = BigInteger.ONE; //ToDO zpstar.getGenerator()
        this.commitments = generateCommitments();
    }

    private BigInteger[] generateCommitments() {
        BigInteger[] coefficients = polynomial.getCoefficients();
        BigInteger[] commitments = new BigInteger[coefficients.length];
        for (int i = 0 ; i < commitments.length;i++){
            commitments[i] = zpstar.multiply(g,coefficients[i]);
        }
        return commitments;
    }

    public BigInteger verify(int i) throws Exception {
        if(i < 1 || i > n){
            throw new Exception();
        }
        BigInteger v = BigInteger.ONE;
        int power = 1;
        for (int j = 0 ; j < commitments.length ; j ++){
            v.multiply(commitments[i].pow(power));
            power *=i;
        }
        return zpstar.add(BigInteger.ONE,v);
    }


    public BigInteger getG() {
        return g;
    }

    public BigInteger[] getCommitments() {
        return Arrays.clone(commitments);
    }
}