package org.apidesign.api.security;

import java.nio.ByteBuffer;

import java.util.ServiceLoader;

import org.apidesign.spi.security.Digestor;

/** Simplified version of a Digest class that allows to compute a fingerprint

 * for buffer of data.

 *

 * @author Jaroslav Tulach <jaroslav.tulach@apidesign.org>

 */

// BEGIN: day.end.bridges.Digest

public final class Digest {

    private final DigestImpl<?> impl;

    /** Factory method is better than constructor */

    private Digest(DigestImpl<?> impl) {

        this.impl = impl;

    }

    /** Factory method to create digest for an algorithm.

     */

    public static Digest getInstance(String algorithm) {

        for (Digestor<?> digestor : ServiceLoader.load(Digestor.class)) {

            DigestImpl<?> impl = DigestImpl.create(

                digestor, algorithm

            );

            if (impl != null) {

                return new Digest(impl);

            }

        }

        throw new IllegalArgumentException(algorithm);

    }

    //

    // these methods are kept the same as in original MessageDigest,

    // but for simplicity choose just some from the original API

    //

    public byte[] digest(ByteBuffer bb) {

        return impl.digest(bb);

    }

}

// END: day.end.bridges.Digest