/*
 * 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
 *
 *      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.apache.activemq.openwire.utils;

import org.apache.activemq.openwire.buffer.Buffer;

/**
 * Used to convert to hex from byte arrays and back.
 */
public final class HexSupport {

    private static final String[] HEX_TABLE = new String[]{
        "00", "01", "02", "03", "04", "05", "06", "07", "08", "09", "0a", "0b", "0c", "0d", "0e", "0f",
        "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "1a", "1b", "1c", "1d", "1e", "1f",
        "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "2a", "2b", "2c", "2d", "2e", "2f",
        "30", "31", "32", "33", "34", "35", "36", "37", "38", "39", "3a", "3b", "3c", "3d", "3e", "3f",
        "40", "41", "42", "43", "44", "45", "46", "47", "48", "49", "4a", "4b", "4c", "4d", "4e", "4f",
        "50", "51", "52", "53", "54", "55", "56", "57", "58", "59", "5a", "5b", "5c", "5d", "5e", "5f",
        "60", "61", "62", "63", "64", "65", "66", "67", "68", "69", "6a", "6b", "6c", "6d", "6e", "6f",
        "70", "71", "72", "73", "74", "75", "76", "77", "78", "79", "7a", "7b", "7c", "7d", "7e", "7f",
        "80", "81", "82", "83", "84", "85", "86", "87", "88", "89", "8a", "8b", "8c", "8d", "8e", "8f",
        "90", "91", "92", "93", "94", "95", "96", "97", "98", "99", "9a", "9b", "9c", "9d", "9e", "9f",
        "a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9", "aa", "ab", "ac", "ad", "ae", "af",
        "b0", "b1", "b2", "b3", "b4", "b5", "b6", "b7", "b8", "b9", "ba", "bb", "bc", "bd", "be", "bf",
        "c0", "c1", "c2", "c3", "c4", "c5", "c6", "c7", "c8", "c9", "ca", "cb", "cc", "cd", "ce", "cf",
        "d0", "d1", "d2", "d3", "d4", "d5", "d6", "d7", "d8", "d9", "da", "db", "dc", "dd", "de", "df",
        "e0", "e1", "e2", "e3", "e4", "e5", "e6", "e7", "e8", "e9", "ea", "eb", "ec", "ed", "ee", "ef",
        "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7", "f8", "f9", "fa", "fb", "fc", "fd", "fe", "ff",
    };

    private static final int[] INT_OFFSETS = new int[]{
        24,16,8,0
    };

    private HexSupport() {
    }

    /**
     * Create a buffer from a previously encoded HEX String.
     *
     * @param hex
     *      the encoded string value of a buffer.
     *
     * @return a new Buffer instance with the decoded value.
     */
    public static Buffer toBufferFromHex(String hex) {
        byte rc[] = new byte[hex.length() / 2];

        for (int i = 0; i < rc.length; i++) {
            String h = hex.substring(i * 2, i * 2 + 2);
            int x = Integer.parseInt(h, 16);
            rc[i] = (byte) x;
        }

        return new Buffer(rc);
    }

    /**
     * Return a new String instance that represents the input buffer
     * encoded in Hexadecimal form.
     *
     * @param buffer
     *      The Buffer to encode.
     *
     * @return the contents of the Buffer encoded as Hexadecimal String.
     */
    public static String toHexFromBuffer(Buffer buffer) {
        byte[] data = buffer.data;
        StringBuffer rc = new StringBuffer(buffer.length * 2);
        int end = buffer.offset + buffer.length;

        for (int i = buffer.offset; i < end; i++) {
            rc.append(HEX_TABLE[0xFF & data[i]]);
        }

        return rc.toString();
    }

    /**
     * Convert an Integer value into a string in Hexadecimal form.
     *
     * @param value
     *      The integer value to convert.
     * @param trim
     *      True if the leading 0's should be trimmed off.
     *
     * @return a new String with the input value encoded as Hexadecimal.
     */
    public static String toHexFromInt(int value, boolean trim) {
        StringBuffer rc = new StringBuffer(INT_OFFSETS.length*2);

        for (int i = 0; i < INT_OFFSETS.length; i++) {
            int b = 0xFF & (value>>INT_OFFSETS[i]);
            if( !(trim && b == 0) ) {
                rc.append(HEX_TABLE[b]);
                trim=false;
            }
        }

        return rc.toString();
    }
}