/*
 * Copyright 2012-2019 Amazon Technologies, Inc.
 *
 * Portions copyright 2006-2009 James Murty. Please see LICENSE.txt
 * for applicable license terms and NOTICE.txt for applicable notices.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *    http://aws.amazon.com/apache2.0
 *
 * This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES
 * OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and
 * limitations under the License.
 */

package com.amazonaws.util;

import com.amazonaws.logging.LogFactory;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * Utility methods for computing MD5 sums.
 */
public class Md5Utils {

    private static final int FOURTEEN = 14;
    private static final int SIXTEEN_K = 1 << FOURTEEN;

    /**
     * Computes the MD5 hash of the data in the given input stream and returns
     * it as an array of bytes. Note this method closes the given input stream
     * upon completion.
     * @param is the input stream.
     * @return MD5 hash of the data.
     */
    public static byte[] computeMD5Hash(InputStream is) throws IOException {
        BufferedInputStream bis = new BufferedInputStream(is);
        try {
            MessageDigest messageDigest = MessageDigest.getInstance("MD5");
            byte[] buffer = new byte[SIXTEEN_K];
            int bytesRead;
            while ((bytesRead = bis.read(buffer, 0, buffer.length)) != -1) {
                messageDigest.update(buffer, 0, bytesRead);
            }
            return messageDigest.digest();
        } catch (NoSuchAlgorithmException e) {
            // should never get here
            throw new IllegalStateException(e);
        } finally {
            try {
                bis.close();
            } catch (Exception e) {
                LogFactory.getLog(Md5Utils.class).debug(
                        "Unable to close input stream of hash candidate: " + e);
            }
        }
    }

    /**
     * @param is the input stream.
     * @return the MD5 in base64 for the data from the given input stream. Note
     * this method closes the given input stream upon completion.
     */
    public static String md5AsBase64(InputStream is) throws IOException {
        return Base64.encodeAsString(computeMD5Hash(is));
    }

    /**
     * Computes the MD5 hash of the given data and returns it as an array of
     * bytes.
     * @param input the input in bytes.
     * @return the MD5 hash of the data.
     */
    public static byte[] computeMD5Hash(byte[] input) {
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            return md.digest(input);
        } catch (NoSuchAlgorithmException e) {
            // should never get here
            throw new IllegalStateException(e);
        }
    }

    /**
     * @param input the input in bytes.
     * @return the MD5 in base64 for the given byte array.
     */
    public static String md5AsBase64(byte[] input) {
        return Base64.encodeAsString(computeMD5Hash(input));
    }

    /**
     * Computes the MD5 of the given file.
     * @param file the file.
     * @return the MD5 hash of the data.
     */
    public static byte[] computeMD5Hash(File file) throws IOException {
        return computeMD5Hash(new FileInputStream(file));
    }

    /**
     * @param file the file.
     * @return the MD5 in base64 for the given file.
     */
    public static String md5AsBase64(File file) throws IOException {
        return Base64.encodeAsString(computeMD5Hash(file));
    }
}