// Copyright (c) 2017-2020 The Khronos Group Inc.
// Copyright (c) 2017-2019 Valve Corporation
// Copyright (c) 2017-2019 LunarG, Inc.
//
// SPDX-License-Identifier: Apache-2.0
//
// Licensed 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.
//
// Author: Mark Young <marky@lunarg.com>
// Author: Dave Houlton <daveh@lunarg.com>
//

#pragma once

#include "xr_dependencies.h"
#include <string>
#include <stdlib.h>

// OpenXR paths and registry key locations
#define OPENXR_RELATIVE_PATH "openxr/"
#define OPENXR_IMPLICIT_API_LAYER_RELATIVE_PATH "/api_layers/implicit.d"
#define OPENXR_EXPLICIT_API_LAYER_RELATIVE_PATH "/api_layers/explicit.d"
#ifdef XR_OS_WINDOWS
#define OPENXR_REGISTRY_LOCATION "SOFTWARE\\Khronos\\OpenXR\\"
#define OPENXR_IMPLICIT_API_LAYER_REGISTRY_LOCATION "\\ApiLayers\\Implicit"
#define OPENXR_EXPLICIT_API_LAYER_REGISTRY_LOCATION "\\ApiLayers\\Explicit"
#endif

// OpenXR Loader environment variables of interest
#define OPENXR_RUNTIME_JSON_ENV_VAR "XR_RUNTIME_JSON"
#define OPENXR_API_LAYER_PATH_ENV_VAR "XR_API_LAYER_PATH"

// This is a CMake generated file with #defines for any functions/includes
// that it found present and build-time configuration.
// If you don't have this file, on non-Windows you'll need to define
// one of HAVE_SECURE_GETENV or HAVE___SECURE_GETENV depending on which
// of secure_getenv or __secure_getenv are present
#ifdef OPENXR_HAVE_COMMON_CONFIG
#include "common_config.h"
#endif  // OPENXR_HAVE_COMMON_CONFIG

// Environment variables
#if defined(XR_OS_LINUX) || defined(XR_OS_APPLE)

#include <unistd.h>
#include <fcntl.h>
#include <iostream>

namespace detail {

static inline char* ImplGetEnv(const char* name) { return getenv(name); }

static inline int ImplSetEnv(const char* name, const char* value, int overwrite) { return setenv(name, value, overwrite); }

static inline char* ImplGetSecureEnv(const char* name) {
#ifdef HAVE_SECURE_GETENV
    return secure_getenv(name);
#elif defined(HAVE___SECURE_GETENV)
    return __secure_getenv(name);
#else
#pragma message(                                                    \
    "Warning:  Falling back to non-secure getenv for environmental" \
    "lookups!  Consider updating to a different libc.")

    return ImplGetEnv(name);
#endif
}
}  // namespace detail

#endif  // defined(XR_OS_LINUX) || defined(XR_OS_APPLE)
#if defined(XR_OS_LINUX)

static inline std::string PlatformUtilsGetEnv(const char* name) {
    auto str = detail::ImplGetEnv(name);
    if (str == nullptr) {
        return {};
    }
    return str;
}

static inline std::string PlatformUtilsGetSecureEnv(const char* name) {
    auto str = detail::ImplGetSecureEnv(name);
    if (str == nullptr) {
        return {};
    }
    return str;
}

static inline bool PlatformUtilsGetEnvSet(const char* name) { return detail::ImplGetEnv(name) != nullptr; }

static inline bool PlatformUtilsSetEnv(const char* name, const char* value) {
    const int shouldOverwrite = 1;
    int result = detail::ImplSetEnv(name, value, shouldOverwrite);
    return (result == 0);
}

#elif defined(XR_OS_APPLE)

static inline std::string PlatformUtilsGetEnv(const char* name) {
    auto str = detail::ImplGetEnv(name);
    if (str == nullptr) {
        return {};
    }
    return str;
}

static inline std::string PlatformUtilsGetSecureEnv(const char* name) {
    auto str = detail::ImplGetSecureEnv(name);
    if (str == nullptr) {
        return {};
    }
    return str;
}

static inline bool PlatformUtilsGetEnvSet(const char* name) { return detail::ImplGetEnv(name) != nullptr; }

static inline bool PlatformUtilsSetEnv(const char* name, const char* value) {
    const int shouldOverwrite = 1;
    int result = detail::ImplSetEnv(name, value, shouldOverwrite);
    return (result == 0);
}

// Prefix for the Apple global runtime JSON file name
static const std::string rt_dir_prefix = "/usr/local/share/openxr/";
static const std::string rt_filename = "/active_runtime.json";

static inline bool PlatformGetGlobalRuntimeFileName(uint16_t major_version, std::string& file_name) {
    file_name = rt_dir_prefix;
    file_name += std::to_string(major_version);
    file_name += rt_filename;
    return true;
}

#elif defined(XR_OS_WINDOWS)

#if !defined(NDEBUG)
inline void LogError(const std::string& error) { OutputDebugStringA(error.c_str()); }
#else
#define LogError(x)
#endif

inline std::wstring utf8_to_wide(const std::string& utf8Text) {
    if (utf8Text.empty()) {
        return {};
    }

    std::wstring wideText;
    const int wideLength = ::MultiByteToWideChar(CP_UTF8, 0, utf8Text.data(), (int)utf8Text.size(), nullptr, 0);
    if (wideLength == 0) {
        LogError("utf8_to_wide get size error: " + std::to_string(::GetLastError()));
        return {};
    }

    // MultiByteToWideChar returns number of chars of the input buffer, regardless of null terminitor
    wideText.resize(wideLength, 0);
    wchar_t* wideString = const_cast<wchar_t*>(wideText.data());  // mutable data() only exists in c++17
    const int length = ::MultiByteToWideChar(CP_UTF8, 0, utf8Text.data(), (int)utf8Text.size(), wideString, wideLength);
    if (length != wideLength) {
        LogError("utf8_to_wide convert string error: " + std::to_string(::GetLastError()));
        return {};
    }

    return wideText;
}

inline std::string wide_to_utf8(const std::wstring& wideText) {
    if (wideText.empty()) {
        return {};
    }

    std::string narrowText;
    int narrowLength = ::WideCharToMultiByte(CP_UTF8, 0, wideText.data(), (int)wideText.size(), nullptr, 0, nullptr, nullptr);
    if (narrowLength == 0) {
        LogError("wide_to_utf8 get size error: " + std::to_string(::GetLastError()));
        return {};
    }

    // WideCharToMultiByte returns number of chars of the input buffer, regardless of null terminitor
    narrowText.resize(narrowLength, 0);
    char* narrowString = const_cast<char*>(narrowText.data());  // mutable data() only exists in c++17
    const int length =
        ::WideCharToMultiByte(CP_UTF8, 0, wideText.data(), (int)wideText.size(), narrowString, narrowLength, nullptr, nullptr);
    if (length != narrowLength) {
        LogError("wide_to_utf8 convert string error: " + std::to_string(::GetLastError()));
        return {};
    }

    return narrowText;
}

// Returns true if the current process has an integrity level > SECURITY_MANDATORY_MEDIUM_RID.
static inline bool IsHighIntegrityLevel() {
    // Execute this check once and save the value as a static bool.
    static bool isHighIntegrityLevel = ([] {
        HANDLE processToken;
        if (OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY | TOKEN_QUERY_SOURCE, &processToken)) {
            // Maximum possible size of SID_AND_ATTRIBUTES is maximum size of a SID + size of attributes DWORD.
            uint8_t mandatoryLabelBuffer[SECURITY_MAX_SID_SIZE + sizeof(DWORD)]{};
            DWORD bufferSize;
            if (GetTokenInformation(processToken, TokenIntegrityLevel, mandatoryLabelBuffer, sizeof(mandatoryLabelBuffer),
                                    &bufferSize) != 0) {
                const auto mandatoryLabel = reinterpret_cast<const TOKEN_MANDATORY_LABEL*>(mandatoryLabelBuffer);
                if (mandatoryLabel->Label.Sid != 0) {
                    const DWORD subAuthorityCount = *GetSidSubAuthorityCount(mandatoryLabel->Label.Sid);
                    const DWORD integrityLevel = *GetSidSubAuthority(mandatoryLabel->Label.Sid, subAuthorityCount - 1);
                    CloseHandle(processToken);
                    return integrityLevel > SECURITY_MANDATORY_MEDIUM_RID;
                }
            }

            CloseHandle(processToken);
        }

        return false;
    })();

    return isHighIntegrityLevel;
}

// Returns true if the given environment variable exists.
// The name is a case-sensitive UTF8 string.
static inline bool PlatformUtilsGetEnvSet(const char* name) {
    const std::wstring wname = utf8_to_wide(name);
    const DWORD valSize = ::GetEnvironmentVariableW(wname.c_str(), nullptr, 0);
    // GetEnvironmentVariable returns 0 when environment variable does not exist or there is an error.
    return 0 != valSize;
}

// Returns the environment variable value for the given name.
// Returns an empty string if the environment variable doesn't exist or if it exists but is empty.
// Use PlatformUtilsGetEnvSet to tell if it exists.
// The name is a case-sensitive UTF8 string.
static inline std::string PlatformUtilsGetEnv(const char* name) {
    const std::wstring wname = utf8_to_wide(name);
    const DWORD valSize = ::GetEnvironmentVariableW(wname.c_str(), nullptr, 0);
    // GetEnvironmentVariable returns 0 when environment variable does not exist or there is an error.
    // The size includes the null-terminator, so a size of 1 is means the variable was explicitly set to empty.
    if (valSize == 0 || valSize == 1) {
        return {};
    }

    // GetEnvironmentVariable returns size including null terminator for "query size" call.
    std::wstring wValue(valSize, 0);
    wchar_t* wValueData = &wValue[0];

    // GetEnvironmentVariable returns string length, excluding null terminator for "get value"
    // call if there was enough capacity. Else it returns the required capacity (including null terminator).
    const DWORD length = ::GetEnvironmentVariableW(wname.c_str(), wValueData, (DWORD)wValue.size());
    if ((length == 0) || (length >= wValue.size())) {  // If error or the variable increased length between calls...
        LogError("GetEnvironmentVariable get value error: " + std::to_string(::GetLastError()));
        return {};
    }

    wValue.resize(length);  // Strip the null terminator.

    return wide_to_utf8(wValue);
}

// Acts the same as PlatformUtilsGetEnv except returns an empty string if IsHighIntegrityLevel.
static inline std::string PlatformUtilsGetSecureEnv(const char* name) {
    // Do not allow high integrity processes to act on data that can be controlled by medium integrity processes.
    if (IsHighIntegrityLevel()) {
        return {};
    }

    // No secure version for Windows so the above integrity check is needed.
    return PlatformUtilsGetEnv(name);
}

// Sets an environment variable via UTF8 strings.
// The name is case-sensitive.
// Overwrites the variable if it already exists.
// Returns true if it could be set.
static inline bool PlatformUtilsSetEnv(const char* name, const char* value) {
    const std::wstring wname = utf8_to_wide(name);
    const std::wstring wvalue = utf8_to_wide(value);
    BOOL result = ::SetEnvironmentVariableW(wname.c_str(), wvalue.c_str());
    return (result != 0);
}

#elif defined(XR_OS_ANDROID)

static inline bool PlatformUtilsGetEnvSet(const char* /* name */) {
    // Stub func
    return false;
}

static inline std::string PlatformUtilsGetEnv(const char* /* name */) {
    // Stub func
    return {};
}

static inline std::string PlatformUtilsGetSecureEnv(const char* /* name */) {
    // Stub func
    return {};
}

static inline bool PlatformUtilsSetEnv(const char* /* name */, const char* /* value */) {
    // Stub func
    return false;
}

#include <sys/stat.h>

// Intended to be only used as a fallback on Android, with a more open, "native" technique used in most cases
static inline bool PlatformGetGlobalRuntimeFileName(uint16_t major_version, std::string& file_name) {
    // Prefix for the runtime JSON file name
    static const char* rt_dir_prefixes[] = {"/oem", "/vendor"};
    static const std::string rt_filename = "/active_runtime.json";
    static const std::string subdir = "/etc/openxr/";
    for (const auto prefix : rt_dir_prefixes) {
        auto path = prefix + subdir + std::to_string(major_version) + rt_filename;
        struct stat buf;
        if (0 == stat(path.c_str(), &buf)) {
            file_name = path;
            return true;
        }
    }
    return false;
}
#else  // Not Linux, Apple, nor Windows

static inline bool PlatformUtilsGetEnvSet(const char* /* name */) {
    // Stub func
    return false;
}

static inline std::string PlatformUtilsGetEnv(const char* /* name */) {
    // Stub func
    return {};
}

static inline std::string PlatformUtilsGetSecureEnv(const char* /* name */) {
    // Stub func
    return {};
}

static inline bool PlatformUtilsSetEnv(const char* /* name */, const char* /* value */) {
    // Stub func
    return false;
}

static inline bool PlatformGetGlobalRuntimeFileName(uint16_t /* major_version */, std::string const& /* file_name */) {
    // Stub func
    return false;
}

#endif
