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/*
 * Copyright 2018 NEM
 *
 * 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://www.apache.org/licenses/LICENSE-2.0
 *
 * 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 io.nem.core.utils;

import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Hex;

/**
 * Static class that contains utility functions for converting hex strings to and from bytes.
 */
public class HexEncoder {

    /**
     * Converts a hex string to a byte array.
     *
     * @param hexString The input hex string.
     * @return The output byte array.
     */
    public static byte[] getBytes(final String hexString) {
        try {
            return getBytesInternal(hexString);
        } catch (final DecoderException e) {
            throw new IllegalArgumentException(e);
        }
    }

    /**
     * Tries to convert a hex string to a byte array.
     *
     * @param hexString The input hex string.
     * @return The output byte array or null if the input string is malformed.
     */
    public static byte[] tryGetBytes(final String hexString) {
        try {
            return getBytesInternal(hexString);
        } catch (final DecoderException e) {
            return null;
        }
    }

    private static byte[] getBytesInternal(final String hexString) throws DecoderException {
        final Hex codec = new Hex();
        final String paddedHexString = 0 == hexString.length() % 2 ? hexString : "0" + hexString;
        final byte[] encodedBytes = StringEncoder.getBytes(paddedHexString);
        return codec.decode(encodedBytes);
    }

    /**
     * Converts a byte array to a hex string.
     *
     * @param bytes The input byte array.
     * @return The output hex string.
     */
    public static String getString(final byte[] bytes) {
        final Hex codec = new Hex();
        final byte[] decodedBytes = codec.encode(bytes);
        return StringEncoder.getString(decodedBytes);
    }
}