/*
 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * questions.
 */

package sun.security.provider;

import sun.security.util.HexDumpEncoder;

import java.util.Arrays;
import java.util.Locale;

public abstract class AbstractHashDrbg extends AbstractDrbg {

    private static final long serialVersionUID = 9L;

    protected int outLen;
    protected int seedLen;

    private static int alg2strength(String algorithm) {
        switch (algorithm.toUpperCase(Locale.ROOT)) {
            case "SHA-1":
                return 128;
            case "SHA-224":
            case "SHA-512/224":
                return 192;
            case "SHA-256":
            case "SHA-512/256":
            case "SHA-384":
            case "SHA-512":
                return 256;
            default:
                throw new IllegalArgumentException(algorithm +
                        " not supported in Hash_DBRG");
        }
    }

    protected void chooseAlgorithmAndStrength() {
        if (requestedAlgorithm != null) {
            algorithm = requestedAlgorithm.toUpperCase(Locale.ROOT);
            int supportedStrength = alg2strength(algorithm);
            if (requestedStrength >= 0) {
                int tryStrength = getStandardStrength(requestedStrength);
                if (tryStrength > supportedStrength) {
                    throw new IllegalArgumentException(
                            algorithm + " does not support strength " + requestedStrength);
                }
                this.strength = tryStrength;
            } else {
                this.strength = defaultStrength > supportedStrength?
                        supportedStrength: defaultStrength;
            }
        } else {
            int tryStrength =
                    requestedStrength<0? defaultStrength: requestedStrength;
            tryStrength = getStandardStrength(tryStrength);
            // The default algorithm which is enough for all strengths.
            // Also described in comments of the "drbg" security property.
            algorithm = "SHA-256";
            this.strength = tryStrength;
        }
        switch (algorithm.toUpperCase(Locale.ROOT)) {
            case "SHA-1":
                this.seedLen = 440/8;
                this.outLen = 160/8;
                break;
            case "SHA-224":
            case "SHA-512/224":
                this.seedLen = 440/8;
                this.outLen = 224/8;
                break;
            case "SHA-256":
            case "SHA-512/256":
                this.seedLen = 440/8;
                this.outLen = 256/8;
                break;
            case "SHA-384":
                this.seedLen = 888/8;
                this.outLen = 384/8;
                break;
            case "SHA-512":
                this.seedLen = 888/8;
                this.outLen = 512/8;
                break;
            default:
                throw new IllegalArgumentException(algorithm +
                        " not supported in Hash_DBRG");
        }
        this.minLength = this.strength/8;
    }

    @Override
    public void instantiateAlgorithm(byte[] entropy) {
        byte[] seed = Arrays.copyOf(entropy, entropy.length + nonce.length +
                (ps == null? 0: ps.length));
        System.arraycopy(nonce, 0, seed, entropy.length, nonce.length);
        if (ps != null) {
            System.arraycopy(ps, 0, seed, entropy.length + nonce.length,
                    ps.length);
        }
        hashReseedInternal(seed);
    }

    @Override
    protected void reseedAlgorithm(
            byte[] ei,
            byte[] additionalInput) {
        if (debug != null) {
            debug.println("reseedAlgorithm");
            debug.println(new HexDumpEncoder().encodeBuffer(ei));
            if (additionalInput != null) {
                debug.println(new HexDumpEncoder().encodeBuffer(additionalInput));
            }
        }
        if (additionalInput != null) {
            ei = Arrays.copyOf(ei, ei.length + additionalInput.length);
            System.arraycopy(additionalInput, 0, ei,
                    ei.length - additionalInput.length, additionalInput.length);
        }
        hashReseedInternal(ei);
    }

    protected abstract void hashReseedInternal(byte[] seed);
}