package org.spongycastle.asn1.cmp;

import org.spongycastle.asn1.ASN1Encodable;
import org.spongycastle.asn1.ASN1EncodableVector;
import org.spongycastle.asn1.ASN1Object;
import org.spongycastle.asn1.ASN1OctetString;
import org.spongycastle.asn1.ASN1Primitive;
import org.spongycastle.asn1.ASN1Sequence;
import org.spongycastle.asn1.DEROctetString;
import org.spongycastle.asn1.DERSequence;
import org.spongycastle.asn1.x509.AlgorithmIdentifier;

public class Challenge
    extends ASN1Object
{
    private AlgorithmIdentifier owf;
    private ASN1OctetString witness;
    private ASN1OctetString challenge;

    private Challenge(ASN1Sequence seq)
    {
        int index = 0;

        if (seq.size() == 3)
        {
            owf = AlgorithmIdentifier.getInstance(seq.getObjectAt(index++));
        }

        witness = ASN1OctetString.getInstance(seq.getObjectAt(index++));
        challenge = ASN1OctetString.getInstance(seq.getObjectAt(index));
    }

    public static Challenge getInstance(Object o)
    {
        if (o instanceof Challenge)
        {
            return (Challenge)o;
        }

        if (o != null)
        {
            return new Challenge(ASN1Sequence.getInstance(o));
        }

        return null;
    }

    public Challenge(byte[] witness, byte[] challenge)
    {
        this(null, witness, challenge);
    }

    public Challenge(AlgorithmIdentifier owf, byte[] witness, byte[] challenge)
    {
        this.owf = owf;
        this.witness = new DEROctetString(witness);
        this.challenge = new DEROctetString(challenge);
    }

    public AlgorithmIdentifier getOwf()
    {
        return owf;
    }

    public byte[] getWitness()
    {
        return witness.getOctets();
    }

    public byte[] getChallenge()
    {
        return challenge.getOctets();
    }

    /**
     * <pre>
     * Challenge ::= SEQUENCE {
     *                 owf                 AlgorithmIdentifier  OPTIONAL,
     *
     *                 -- MUST be present in the first Challenge; MAY be omitted in
     *                 -- any subsequent Challenge in POPODecKeyChallContent (if
     *                 -- omitted, then the owf used in the immediately preceding
     *                 -- Challenge is to be used).
     *
     *                 witness             OCTET STRING,
     *                 -- the result of applying the one-way function (owf) to a
     *                 -- randomly-generated INTEGER, A.  [Note that a different
     *                 -- INTEGER MUST be used for each Challenge.]
     *                 challenge           OCTET STRING
     *                 -- the encryption (under the public key for which the cert.
     *                 -- request is being made) of Rand, where Rand is specified as
     *                 --   Rand ::= SEQUENCE {
     *                 --      int      INTEGER,
     *                 --       - the randomly-generated INTEGER A (above)
     *                 --      sender   GeneralName
     *                 --       - the sender's name (as included in PKIHeader)
     *                 --   }
     *      }
     * </pre>
     * @return a basic ASN.1 object representation.
     */
    public ASN1Primitive toASN1Primitive()
    {
        ASN1EncodableVector v = new ASN1EncodableVector();

        addOptional(v, owf);
        v.add(witness);
        v.add(challenge);

        return new DERSequence(v);
    }

    private void addOptional(ASN1EncodableVector v, ASN1Encodable obj)
    {
        if (obj != null)
        {
            v.add(obj);
        }
    }
}
