package org.minicastle.asn1.x9;

import java.math.BigInteger;

import org.minicastle.asn1.ASN1OctetString;
import org.minicastle.asn1.DEREncodable;
import org.minicastle.asn1.DERObject;
import org.minicastle.asn1.DEROctetString;
import org.minicastle.math.ec.ECFieldElement;

/**
 * class for processing an FieldElement as a DER object.
 */
public class X9FieldElement
    implements DEREncodable
{
    private ECFieldElement  f;

    public X9FieldElement(
        ECFieldElement  f)
    {
        this.f = f;
    }

    public X9FieldElement(
        boolean          fP,
        BigInteger       q,
        ASN1OctetString  s)
    {
        if (fP)
        {
            this.f = new ECFieldElement.Fp(q, new BigInteger(1, s.getOctets()));
        }
        else
        {
            throw new RuntimeException("not implemented");
        }
    }

    public ECFieldElement getValue()
    {
        return f;
    }

    /**
     * Produce an object suitable for an ASN1OutputStream.
     * <pre>
     *  FieldElement ::= OCTET STRING
     * </pre>
     * <p>
     * <ol>
     * <li> if <i>q</i> is an odd prime then the field element is
     * processed as an Integer and converted to an octet string
     * according to x 9.62 4.3.1.</li>
     * <li> if <i>q</i> is 2<sup>m</sup> then the bit string
     * contained in the field element is converted into an octet
     * string with the same ordering padded at the front if necessary.
     * </li>
     * </ol>
     */
    public DERObject getDERObject()
    {
        return new DEROctetString(f.toBigInteger().toByteArray());
    }
}