/*
 * Copyright (C) 2020 Emeric Poupon
 *
 * This file is part of LMS.
 *
 * LMS is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * LMS is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with LMS.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "utils/UUID.hpp"

#include <cassert>
#include <iomanip>
#include <regex>
#include <sstream>

#include "utils/Random.hpp"
#include "utils/String.hpp"

namespace StringUtils
{
    template <>
    std::optional<UUID>
        readAs(std::string_view str)
    {
        return UUID::fromString(str);
    }
}
namespace
{
    bool stringIsUUID(std::string_view str)
    {
        static const std::regex re{ R"([0-9a-fA-F]{8}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{12})" };

        return std::regex_match(std::cbegin(str), std::cend(str), re);
    }
}

UUID::UUID(std::string_view str)
    : _value{ StringUtils::stringToLower(str) }
{
}

std::optional<UUID> UUID::fromString(std::string_view str)
{
    if (!stringIsUUID(str))
        return std::nullopt;

    return UUID{ str };
}

UUID UUID::generate()
{
    // Form is "123e4567-e89b-12d3-a456-426614174000"
    // TODO: store 128 bits and only convert to string when necessary

    std::ostringstream oss;

    auto concatRandomBytes{ [](std::ostream& os, std::size_t byteCount)
    {
        for (std::size_t i {}; i < byteCount; ++i)
            os << std::hex << std::setfill('0') << std::setw(2) << static_cast<int>(Random::getRandom<std::uint8_t>(0, 255));
    } };

    concatRandomBytes(oss, 4);
    oss << "-";
    concatRandomBytes(oss, 2);
    oss << "-";
    concatRandomBytes(oss, 2);
    oss << "-";
    concatRandomBytes(oss, 2);
    oss << "-";
    concatRandomBytes(oss, 6);

    const auto uuid{fromString(oss.str())};
    assert(uuid);
    return uuid.value();
}