/*
 * This file is part of the AzerothCore Project. See AUTHORS file for Copyright information
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Affero General Public License as published by the
 * Free Software Foundation; either version 3 of the License, or (at your
 * option) any later version.
 *
 * This program 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 Affero General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef AZEROTHCORE_HMAC_H
#define AZEROTHCORE_HMAC_H

#include "CryptoConstants.h"
#include "Define.h"
#include "Errors.h"
#include <array>
#include <openssl/hmac.h>
#include <string>
#include <string_view>

class BigNumber;

namespace Acore::Impl
{
    struct HMACImpl
    {
        typedef EVP_MD const* (*HashCreator)();

#if defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER < 0x10100000L
        static HMAC_CTX* MakeCTX()
        {
            HMAC_CTX* ctx = new HMAC_CTX();
            HMAC_CTX_init(ctx);
            return ctx;
        }

        static void DestroyCTX(HMAC_CTX* ctx)
        {
            HMAC_CTX_cleanup(ctx);
            delete ctx;
        }
#else
        static HMAC_CTX* MakeCTX() { return HMAC_CTX_new(); }
        static void DestroyCTX(HMAC_CTX* ctx) { HMAC_CTX_free(ctx); }
#endif
    };

    template <HMACImpl::HashCreator HashCreator, size_t DigestLength>
    class GenericHMAC
    {
    public:
        static constexpr size_t DIGEST_LENGTH = DigestLength;
        using Digest = std::array<uint8, DIGEST_LENGTH>;

        template <typename Container>
        static Digest GetDigestOf(Container const& seed, uint8 const* data, size_t len)
        {
            GenericHMAC hash(seed);
            hash.UpdateData(data, len);
            hash.Finalize();
            return hash.GetDigest();
        }

        template <typename Container, typename... Ts>
        static auto GetDigestOf(Container const& seed, Ts&& ... pack) -> std::enable_if_t < !(std::is_integral_v<std::decay_t<Ts>> || ...), Digest >
        {
            GenericHMAC hash(seed);
            (hash.UpdateData(std::forward<Ts>(pack)), ...);
            hash.Finalize();
            return hash.GetDigest();
        }

        GenericHMAC(uint8 const* seed, size_t len) : _ctx(HMACImpl::MakeCTX())
        {
            int result = HMAC_Init_ex(_ctx, seed, len, HashCreator(), nullptr);
            ASSERT(result == 1);
        }
        template <typename Container> GenericHMAC(Container const& container) : GenericHMAC(std::data(container), std::size(container)) {}

        ~GenericHMAC()
        {
            if (!_ctx)
            {
                return;
            }
            HMACImpl::DestroyCTX(_ctx);
            _ctx = nullptr;
        }

        void UpdateData(uint8 const* data, size_t len)
        {
            int result = HMAC_Update(_ctx, data, len);
            ASSERT(result == 1);
        }
        void UpdateData(std::string_view str) { UpdateData(reinterpret_cast<uint8 const*>(str.data()), str.size()); }
        void UpdateData(std::string const& str) { UpdateData(std::string_view(str)); } /* explicit overload to avoid using the container template */
        void UpdateData(char const* str) { UpdateData(std::string_view(str)); } /* explicit overload to avoid using the container template */
        template <typename Container>
        void UpdateData(Container const& c) { UpdateData(std::data(c), std::size(c)); }

        void Finalize()
        {
            uint32 length = 0;
            int result = HMAC_Final(_ctx, _digest.data(), &length);
            ASSERT(result == 1);
            ASSERT(length == DIGEST_LENGTH);
            HMACImpl::DestroyCTX(_ctx);
            _ctx = nullptr;
        }

        Digest const& GetDigest() const { return _digest; }
    private:
        HMAC_CTX* _ctx;
        Digest _digest = { };
    };
}

namespace Acore::Crypto
{
    using HMAC_SHA1 = Acore::Impl::GenericHMAC<EVP_sha1, Constants::SHA1_DIGEST_LENGTH_BYTES>;
    using HMAC_SHA256 = Acore::Impl::GenericHMAC<EVP_sha256, Constants::SHA256_DIGEST_LENGTH_BYTES>;
}
#endif
