/*************************************************************************
 *                                                                       *
 *  CERT-CVC: EAC 1.11 Card Verifiable Certificate Library               * 
 *                                                                       *
 *  This software is free software; you can redistribute it and/or       *
 *  modify it under the terms of the GNU Lesser General Public           *
 *  License as published by the Free Software Foundation; either         *
 *  version 2.1 of the License, or any later version.                    *
 *                                                                       *
 *  See terms of license at gnu.org.                                     *
 *                                                                       *
 *************************************************************************/
package org.ejbca.cvc;

import java.security.PublicKey;
import java.security.interfaces.ECPublicKey;
import java.security.interfaces.RSAPublicKey;

import org.ejbca.cvc.exception.ConstructionException;

/**
 * Tiny factory for creating instances of (subclasses to) CVCPublicKey
 * 
 * @author Keijo Kurkinen, Swedish National Police Board
 * @version $Id: KeyFactory.java 18595 2014-03-13 09:19:51Z samuellb $
 */
public class KeyFactory {

    /**
     * Constructs instance from a PublicKey and a hash algorithm
     * 
     * @param pubKey
     * @param algorithmName
     * 	   @see AlgorithmUtil
     * @param authRole
     *            role of certificate holder (affects creation of PublicKeyEC
     *            instances)
     * @return
     */
    public static CVCPublicKey createInstance(PublicKey pubKey, String algorithmName, AuthorizationRole authRole)
	    throws ConstructionException {

	if (pubKey instanceof CVCPublicKey) {
	    // Object is already of the expected type
	    return (CVCPublicKey) pubKey;
	}

	// Here we can use algorithmName to the find the corresponding OID
	// which in turn identifies the type of key (RSA or EC)
	CVCPublicKey cvcPublicKey = null;
	OIDField oid = AlgorithmUtil.getOIDField(algorithmName);
	if (oid.getValue().startsWith(CVCObjectIdentifiers.id_TA_RSA)) {
	    // It's RSA
	    cvcPublicKey = new PublicKeyRSA(oid, (RSAPublicKey) pubKey);
	} else if (oid.getValue().startsWith(CVCObjectIdentifiers.id_TA_ECDSA)) {
	    // It's EC
	    cvcPublicKey = new PublicKeyEC(oid, (ECPublicKey) pubKey, authRole);
	} else {
	    throw new IllegalArgumentException("Unknown key type: " + oid);
	}
	return cvcPublicKey;
    }

    /**
     * Constructs instance from a PublicKey and a hash algorithm. This seemingly
     * redundant overloaded method is for binary (.class file) backwards
     * compatibility. It is NOT deprecated to use these argument types.
     */
    public static CVCPublicKey createInstance(PublicKey pubKey, String algorithmName, AuthorizationRoleEnum authRole)
	    throws ConstructionException {
	return createInstance(pubKey, algorithmName, (AuthorizationRole) authRole);
    }

    /**
     * Constructs instance from a GenericPublicKeyField (i e when parsing
     * DER-encoded data)
     * 
     * @param genericKey
     * @return
     */
    static CVCPublicKey createInstance(GenericPublicKeyField genericKey) throws ConstructionException {
	CVCPublicKey cvcPublicKey = null;

	try {
	    OIDField oid = (OIDField) genericKey.getOptionalSubfield(CVCTagEnum.OID);
	    if (oid.getValue().startsWith(CVCObjectIdentifiers.id_TA_RSA)) {
		copyField(CVCTagEnum.COEFFICIENT_A, CVCTagEnum.EXPONENT, genericKey);
		cvcPublicKey = new PublicKeyRSA(genericKey);
	    } else if (oid.getValue().startsWith(CVCObjectIdentifiers.id_TA_ECDSA)) {
		copyField(CVCTagEnum.EXPONENT, CVCTagEnum.COEFFICIENT_A, genericKey);
		cvcPublicKey = new PublicKeyEC(genericKey);
	    } else {
		throw new IllegalArgumentException("Unknown public key OID: " + oid.getValue());
	    }
	} catch (NoSuchFieldException e) {
	    throw new ConstructionException(e);
	}
	return cvcPublicKey;
    }

    /**
     * Special helper method that deals with the problem that two different public
     * key tags have the same value. TODO: This handling is subject for improvement!
     * 
     * @param fromTag
     * @param toTag
     * @param generic
     */
    private static void copyField(CVCTagEnum fromTag, CVCTagEnum toTag, GenericPublicKeyField generic)
	    throws ConstructionException {
	if (fromTag.getValue() != toTag.getValue()) {
	    throw new IllegalArgumentException("Tag values are not equal");
	}
	ByteField field = (ByteField) generic.getOptionalSubfield(toTag);
	if (field == null) {
	    // OK, the field hasn't been added - check if 'fromTag' is available
	    field = (ByteField) generic.getOptionalSubfield(fromTag);
	    if (field != null) {
		// Yes, copy the value and add it as 'toTag'
		generic.addSubfield(new ByteField(toTag, field.getData()));
	    }
	}
    }

}