/*
 * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <AK/Array.h>
#include <AK/ByteBuffer.h>
#include <AK/Hex.h>
#include <AK/String.h>
#include <AK/StringBuilder.h>
#include <AK/StringView.h>
#include <AK/Types.h>
#include <AK/Vector.h>

namespace AK {

static u8 decode_hex_digit(char digit)
{
    if (digit >= '0' && digit <= '9')
        return digit - '0';
    if (digit >= 'a' && digit <= 'f')
        return 10 + (digit - 'a');
    if (digit >= 'A' && digit <= 'F')
        return 10 + (digit - 'A');
    return 255;
}

Optional<ByteBuffer> decode_hex(const StringView& input)
{
    if ((input.length() % 2) != 0)
        return {};

    auto output = ByteBuffer::create_zeroed(input.length() / 2);

    for (long unsigned int i = 0; i < input.length() / 2; i++) {
        auto c1 = decode_hex_digit(input[i * 2]);
        if (c1 >= 16)
            return {};

        auto c2 = decode_hex_digit(input[i * 2 + 1]);
        if (c2 >= 16)
            return {};

        output[i] = (c1 << 4) + c2;
    }

    return output;
}

String encode_hex(ReadonlyBytes input)
{
    StringBuilder output(input.size() * 2);

    for (auto ch : input)
        output.appendff("{:02x}", ch);

    return output.build();
}

}