MobileGL/MobileGL/ConfigLoader.cpp

// MobileGL - MobileGL/ConfigLoader.cpp
// Copyright (c) 2025-2026 MobileGL-Dev
// Licensed under the GNU Lesser General Public License v3.0:
//   https://www.gnu.org/licenses/gpl-3.0.txt
//   https://www.gnu.org/licenses/lgpl-3.0.txt
// SPDX-License-Identifier: LGPL-3.0-only
// End of Source File Header

#include "Config.h"

#ifndef _WIN32
extern char** environ;
#endif

namespace MobileGL::MG_ConfigLoader {
    static UniquePtr<UnorderedMap<String, String>> acceptedEnvVariablesMap;

    static Bool IsAcceptedPrefix(const String& key) {
        return (key.compare(0, 6, "LIBGL_") == 0 || key.compare(0, 9, "MOBILEGL_") == 0);
    }

    inline void InitializeAcceptedEnvVariables() {
        if (!acceptedEnvVariablesMap) {
            acceptedEnvVariablesMap = MakeUnique<UnorderedMap<String, String>>();
        } else {
            acceptedEnvVariablesMap->clear();
        }

        char** envPtr = nullptr;

#ifdef _WIN32
        envPtr = _environ;
#else // POSIX
        envPtr = ::environ;
#endif

        if (envPtr == nullptr) return;

        for (char** env = envPtr; *env != nullptr; ++env) {
            String entry(*env);
            SizeT pos = entry.find('=');
            if (pos != String::npos) {
                String key = entry.substr(0, pos);
                String value = entry.substr(pos + 1);

                if (IsAcceptedPrefix(key)) {
                    (*acceptedEnvVariablesMap)[key] = value;
                    MGLOG_D("Config: Accepted env variable: %s=%s", key.c_str(), value.c_str());
                }
            }
        }
    }

    inline void QueryEnvVariable(const String& key, String& outValue, const String& defaultValue) {
        auto it = acceptedEnvVariablesMap->find(key);
        if (it != acceptedEnvVariablesMap->end()) {
            outValue = it->second;
        } else {
            outValue = defaultValue;
        }
    }

    inline void InitBackendType() {
        String backendTypeStr;
        QueryEnvVariable("MOBILEGL_BACKEND_TYPE", backendTypeStr, "DirectGLES");
#define ENTRY(backendType)                                                                                             \
    if (backendTypeStr == #backendType) {                                                                              \
        MG_Config::ActiveBackendType = BackendType::backendType;                                                       \
        MGLOG_I("Config: Active backend type set to " #backendType);                                                   \
        return;                                                                                                        \
    }
        ENTRY(DirectGLES)
        ENTRY(DirectVulkan)
        ENTRY(Unknown)
        MG_Config::ActiveBackendType = BackendType::Unknown;
#undef ENTRY
    }

    void Init() {
        MGLOG_D("Loading configuration from environment variables...");
        InitializeAcceptedEnvVariables();

        InitBackendType();

        // Destroy the map since we won't need it anymore
        acceptedEnvVariablesMap.reset();
    }
} // namespace MobileGL::MG_ConfigLoader