// This file Copyright 2014-2022 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0), GPLv3 (SPDX: GPL-3.0),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.

#include <mutex>

#if defined(CYASSL_IS_WOLFSSL)
#define API_HEADER(x) <wolfssl/x>
#define API_HEADER_CRYPT(x) API_HEADER(wolfcrypt/x)
#define API(x) wc_##x
#define API_VERSION_HEX LIBWOLFSSL_VERSION_HEX
#else
#define API_HEADER(x) <cyassl/x>
#define API_HEADER_CRYPT(x) API_HEADER(ctaocrypt/x)
#define API(x) x
#define API_VERSION_HEX LIBCYASSL_VERSION_HEX
#endif

#include API_HEADER(options.h)
#include API_HEADER_CRYPT(dh.h)
#include API_HEADER_CRYPT(error-crypt.h)
#include API_HEADER_CRYPT(random.h)
#include API_HEADER_CRYPT(sha.h)
#include API_HEADER(version.h)

#include "transmission.h"
#include "crypto-utils.h"
#include "log.h"
#include "platform.h"
#include "tr-assert.h"
#include "utils.h"

#define TR_CRYPTO_DH_SECRET_FALLBACK
#define TR_CRYPTO_X509_FALLBACK
#include "crypto-utils-fallback.cc"

struct tr_dh_ctx
{
    DhKey dh;
    word32 key_length;
    uint8_t* private_key;
    word32 private_key_length;
};

/***
****
***/

static char constexpr MyName[] = "tr_crypto_utils";

static void log_cyassl_error(int error_code, char const* file, int line)
{
    if (tr_logLevelIsActive(TR_LOG_ERROR))
    {
#if API_VERSION_HEX >= 0x03004000
        char const* error_message = API(GetErrorString)(error_code);
#elif API_VERSION_HEX >= 0x03000002
        char const* error_message = CTaoCryptGetErrorString(error_code);
#else
        char error_message[CYASSL_MAX_ERROR_SZ] = {};
        CTaoCryptErrorString(error_code, error_message);
#endif

        tr_logAddMessage(file, line, TR_LOG_ERROR, MyName, "CyaSSL error: %s", error_message);
    }
}

static bool check_cyassl_result(int result, char const* file, int line)
{
    bool const ret = result == 0;

    if (!ret)
    {
        log_cyassl_error(result, file, line);
    }

    return ret;
}

#define check_result(result) check_cyassl_result((result), __FILE__, __LINE__)

/***
****
***/

static RNG* get_rng(void)
{
    static RNG rng;
    static bool rng_initialized = false;

    if (!rng_initialized)
    {
        if (!check_result(API(InitRng)(&rng)))
        {
            return nullptr;
        }

        rng_initialized = true;
    }

    return &rng;
}

static std::mutex rng_mutex_;

/***
****
***/

tr_sha1_ctx_t tr_sha1_init(void)
{
    Sha* handle = tr_new(Sha, 1);

    if (check_result(API(InitSha)(handle)))
    {
        return handle;
    }

    tr_free(handle);
    return nullptr;
}

bool tr_sha1_update(tr_sha1_ctx_t raw_handle, void const* data, size_t data_length)
{
    auto* handle = static_cast<Sha*>(raw_handle);
    TR_ASSERT(handle != nullptr);

    if (data_length == 0)
    {
        return true;
    }

    TR_ASSERT(data != nullptr);

    return check_result(API(ShaUpdate)(handle, static_cast<byte const*>(data), data_length));
}

std::optional<tr_sha1_digest_t> tr_sha1_final(tr_sha1_ctx_t raw_handle)
{
    auto* handle = static_cast<Sha*>(raw_handle);
    TR_ASSERT(handle != nullptr);

    auto digest = tr_sha1_digest_t{};
    auto* const digest_as_uchar = reinterpret_cast<unsigned char*>(std::data(digest));
    auto const ok = check_result(API(ShaFinal)(handle, digest_as_uchar));
    tr_free(handle);

    return ok ? std::make_optional(digest) : std::nullopt;
}

/***
****
***/

tr_dh_ctx_t tr_dh_new(
    uint8_t const* prime_num,
    size_t prime_num_length,
    uint8_t const* generator_num,
    size_t generator_num_length)
{
    TR_ASSERT(prime_num != nullptr);
    TR_ASSERT(generator_num != nullptr);

    struct tr_dh_ctx* handle = tr_new0(struct tr_dh_ctx, 1);

    API(InitDhKey)(&handle->dh);

    if (!check_result(API(DhSetKey)(&handle->dh, prime_num, prime_num_length, generator_num, generator_num_length)))
    {
        tr_free(handle);
        return nullptr;
    }

    handle->key_length = prime_num_length;

    return handle;
}

void tr_dh_free(tr_dh_ctx_t raw_handle)
{
    auto* handle = static_cast<struct tr_dh_ctx*>(raw_handle);

    if (handle == nullptr)
    {
        return;
    }

    API(FreeDhKey)(&handle->dh);
    tr_free(handle->private_key);
    tr_free(handle);
}

bool tr_dh_make_key(tr_dh_ctx_t raw_handle, size_t /*private_key_length*/, uint8_t* public_key, size_t* public_key_length)
{
    TR_ASSERT(raw_handle != nullptr);
    TR_ASSERT(public_key != nullptr);

    auto* handle = static_cast<struct tr_dh_ctx*>(raw_handle);

    if (handle->private_key == nullptr)
    {
        handle->private_key = static_cast<uint8_t*>(tr_malloc(handle->key_length));
    }

    auto const lock = std::lock_guard(rng_mutex_);

    auto my_private_key_length = word32{};
    auto my_public_key_length = word32{};
    if (!check_result(API(DhGenerateKeyPair)(
            &handle->dh,
            get_rng(),
            handle->private_key,
            &my_private_key_length,
            public_key,
            &my_public_key_length)))
    {
        return false;
    }

    tr_dh_align_key(public_key, my_public_key_length, handle->key_length);

    handle->private_key_length = my_private_key_length;

    if (public_key_length != nullptr)
    {
        *public_key_length = handle->key_length;
    }

    return true;
}

tr_dh_secret_t tr_dh_agree(tr_dh_ctx_t raw_handle, uint8_t const* other_public_key, size_t other_public_key_length)
{
    TR_ASSERT(raw_handle != nullptr);
    TR_ASSERT(other_public_key != nullptr);

    auto* handle = static_cast<struct tr_dh_ctx*>(raw_handle);

    tr_dh_secret* ret = tr_dh_secret_new(handle->key_length);

    auto my_secret_key_length = word32{};
    if (check_result(API(DhAgree)(
            &handle->dh,
            ret->key,
            &my_secret_key_length,
            handle->private_key,
            handle->private_key_length,
            other_public_key,
            other_public_key_length)))
    {
        tr_dh_secret_align(ret, my_secret_key_length);
    }
    else
    {
        tr_dh_secret_free(ret);
        ret = nullptr;
    }

    return ret;
}

/***
****
***/

bool tr_rand_buffer(void* buffer, size_t length)
{
    if (length == 0)
    {
        return true;
    }

    TR_ASSERT(buffer != nullptr);

    auto const lock = std::lock_guard(rng_mutex_);
    return check_result(API(RNG_GenerateBlock)(get_rng(), static_cast<byte*>(buffer), length));
}