/*
 * Zed Attack Proxy (ZAP) and its related class files.
 *
 * ZAP is an HTTP/HTTPS proxy for assessing web application security.
 *
 * Copyright 2018 The ZAP Development Team
 *
 * 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 org.zaproxy.addon.encoder.processors.predefined;

public class HexStringDecoder extends DefaultEncodeDecodeProcessor {

    private static final HexStringDecoder INSTANCE = new HexStringDecoder();

    @Override
    protected String processInternal(String value) {
        return decodeHexString(value);
    }

    protected static String decodeHexString(String value) {
        String decodedText = "";
        String chunk;

        if (value != null && value.length() > 0) {
            final int numBytes = value.length() / 2;

            final byte[] rawToByte = new byte[numBytes];
            int offset = 0;
            for (int i = 0; i < numBytes; i++) {
                chunk = value.substring(offset, offset + 2);
                offset += 2;
                rawToByte[i] = (byte) (Integer.parseInt(chunk, 16) & 0x000000FF);
            }
            decodedText = new String(rawToByte);
        }
        return decodedText;
    }

    static String hexDecode(String value) {
        return decodeHexString(value);
    }

    public static HexStringDecoder getSingleton() {
        return INSTANCE;
    }
}
