/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License 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 org.apache.atlas.utils;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class SHA256Utils {
    private static final ThreadLocal<MessageDigest> DIGESTER_FACTORY = ThreadLocal.withInitial(() -> {
        try {
            return MessageDigest.getInstance("SHA-256");
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
    });

    private SHA256Utils() {
        // to block instanations
    }

    /**
     * Create a thread local SHA256 digester.
     */

    public static MessageDigest getDigester() {
        MessageDigest digester = DIGESTER_FACTORY.get();

        digester.reset();

        return digester;
    }

    public static String toString(byte[] hash) {
        try {
            StringBuilder hexString = new StringBuilder();

            for (int i = 0; i < hash.length; i++) {
                String hex = Integer.toHexString(0xff & hash[i]);

                if (hex.length() == 1) {
                    hexString.append('0');
                }

                hexString.append(hex);
            }

            return hexString.toString();
        } catch (Exception ex) {
            throw new RuntimeException(ex);
        }
    }
}
