XCEngine/engine/src/Resources/Material/MaterialLoader.cpp

#include <XCEngine/Resources/Material/MaterialLoader.h>
#include <XCEngine/Core/Asset/ResourceManager.h>
#include <XCEngine/Core/Asset/ResourceTypes.h>
#include <XCEngine/Resources/Shader/ShaderLoader.h>

#include <cctype>
#include <cstdlib>
#include <string>

namespace XCEngine {
namespace Resources {

namespace {

std::string ToStdString(const Containers::Array<Core::uint8>& data) {
    return std::string(reinterpret_cast<const char*>(data.Data()), data.Size());
}

size_t SkipWhitespace(const std::string& text, size_t pos) {
    while (pos < text.size() && std::isspace(static_cast<unsigned char>(text[pos])) != 0) {
        ++pos;
    }
    return pos;
}

bool HasKey(const std::string& json, const char* key) {
    const std::string token = std::string("\"") + key + "\"";
    return json.find(token) != std::string::npos;
}

bool FindValueStart(const std::string& json, const char* key, size_t& valuePos) {
    const std::string token = std::string("\"") + key + "\"";
    const size_t keyPos = json.find(token);
    if (keyPos == std::string::npos) {
        return false;
    }

    const size_t colonPos = json.find(':', keyPos + token.length());
    if (colonPos == std::string::npos) {
        return false;
    }

    valuePos = SkipWhitespace(json, colonPos + 1);
    return valuePos < json.size();
}

bool ParseQuotedString(const std::string& text, size_t quotePos, Containers::String& outValue, size_t* nextPos = nullptr) {
    if (quotePos >= text.size() || text[quotePos] != '"') {
        return false;
    }

    std::string parsed;
    ++quotePos;

    while (quotePos < text.size()) {
        const char ch = text[quotePos];
        if (ch == '\\') {
            if (quotePos + 1 >= text.size()) {
                return false;
            }

            parsed.push_back(text[quotePos + 1]);
            quotePos += 2;
            continue;
        }

        if (ch == '"') {
            outValue = parsed.c_str();
            if (nextPos != nullptr) {
                *nextPos = quotePos + 1;
            }
            return true;
        }

        parsed.push_back(ch);
        ++quotePos;
    }

    return false;
}

bool TryParseStringValue(const std::string& json, const char* key, Containers::String& outValue) {
    size_t valuePos = 0;
    if (!FindValueStart(json, key, valuePos)) {
        return false;
    }

    return ParseQuotedString(json, valuePos, outValue);
}

bool TryParseIntValue(const std::string& json, const char* key, Core::int32& outValue) {
    size_t valuePos = 0;
    if (!FindValueStart(json, key, valuePos)) {
        return false;
    }

    if (valuePos >= json.size() ||
        (json[valuePos] != '-' && std::isdigit(static_cast<unsigned char>(json[valuePos])) == 0)) {
        return false;
    }

    char* endPtr = nullptr;
    const long parsed = std::strtol(json.c_str() + valuePos, &endPtr, 10);
    if (endPtr == json.c_str() + valuePos) {
        return false;
    }

    outValue = static_cast<Core::int32>(parsed);
    return true;
}

bool TryExtractObject(const std::string& json, const char* key, std::string& outObject) {
    size_t valuePos = 0;
    if (!FindValueStart(json, key, valuePos) || valuePos >= json.size() || json[valuePos] != '{') {
        return false;
    }

    bool inString = false;
    bool escaped = false;
    int depth = 0;

    for (size_t pos = valuePos; pos < json.size(); ++pos) {
        const char ch = json[pos];
        if (escaped) {
            escaped = false;
            continue;
        }

        if (ch == '\\') {
            escaped = true;
            continue;
        }

        if (ch == '"') {
            inString = !inString;
            continue;
        }

        if (inString) {
            continue;
        }

        if (ch == '{') {
            ++depth;
        } else if (ch == '}') {
            --depth;
            if (depth == 0) {
                outObject = json.substr(valuePos, pos - valuePos + 1);
                return true;
            }
        }
    }

    return false;
}

bool TryParseRenderQueueName(const Containers::String& queueName, Core::int32& outQueue) {
    const Containers::String normalized = queueName.ToLower();
    if (normalized == "background") {
        outQueue = static_cast<Core::int32>(MaterialRenderQueue::Background);
        return true;
    }
    if (normalized == "geometry" || normalized == "opaque") {
        outQueue = static_cast<Core::int32>(MaterialRenderQueue::Geometry);
        return true;
    }
    if (normalized == "alphatest" || normalized == "alpha_test") {
        outQueue = static_cast<Core::int32>(MaterialRenderQueue::AlphaTest);
        return true;
    }
    if (normalized == "transparent") {
        outQueue = static_cast<Core::int32>(MaterialRenderQueue::Transparent);
        return true;
    }
    if (normalized == "overlay") {
        outQueue = static_cast<Core::int32>(MaterialRenderQueue::Overlay);
        return true;
    }

    return false;
}

bool TryParseTagMap(const std::string& objectText, Material* material) {
    if (material == nullptr || objectText.empty() || objectText.front() != '{' || objectText.back() != '}') {
        return false;
    }

    size_t pos = 1;
    while (pos < objectText.size()) {
        pos = SkipWhitespace(objectText, pos);
        if (pos >= objectText.size()) {
            return false;
        }

        if (objectText[pos] == '}') {
            return true;
        }

        Containers::String key;
        if (!ParseQuotedString(objectText, pos, key, &pos)) {
            return false;
        }

        pos = SkipWhitespace(objectText, pos);
        if (pos >= objectText.size() || objectText[pos] != ':') {
            return false;
        }

        pos = SkipWhitespace(objectText, pos + 1);
        Containers::String value;
        if (!ParseQuotedString(objectText, pos, value, &pos)) {
            return false;
        }

        material->SetTag(key, value);

        pos = SkipWhitespace(objectText, pos);
        if (pos >= objectText.size()) {
            return false;
        }

        if (objectText[pos] == ',') {
            ++pos;
            continue;
        }

        if (objectText[pos] == '}') {
            return true;
        }

        return false;
    }

    return false;
}

ResourceHandle<Shader> LoadShaderHandle(const Containers::String& shaderPath) {
    ResourceHandle<Shader> shader = ResourceManager::Get().Load<Shader>(shaderPath);
    if (shader.IsValid()) {
        return shader;
    }

    ShaderLoader shaderLoader;
    LoadResult shaderResult = shaderLoader.Load(shaderPath);
    if (!shaderResult || shaderResult.resource == nullptr) {
        return ResourceHandle<Shader>();
    }

    return ResourceHandle<Shader>(static_cast<Shader*>(shaderResult.resource));
}

} // namespace

MaterialLoader::MaterialLoader() = default;

MaterialLoader::~MaterialLoader() = default;

Containers::Array<Containers::String> MaterialLoader::GetSupportedExtensions() const {
    Containers::Array<Containers::String> extensions;
    extensions.PushBack("mat");
    extensions.PushBack("material");
    extensions.PushBack("json");
    return extensions;
}

bool MaterialLoader::CanLoad(const Containers::String& path) const {
    Containers::String ext = GetExtension(path);
    return ext == "mat" || ext == "material" || ext == "json";
}

LoadResult MaterialLoader::Load(const Containers::String& path, const ImportSettings* settings) {
    (void)settings;

    Containers::Array<Core::uint8> data = ReadFileData(path);
    if (data.Empty()) {
        return LoadResult("Failed to read material file: " + path);
    }

    Material* material = new Material();
    material->m_path = path;
    material->m_name = path;
    material->m_guid = ResourceGUID::Generate(path);

    if (!ParseMaterialData(data, material)) {
        delete material;
        return LoadResult("Failed to parse material file: " + path);
    }

    material->m_isValid = true;
    material->RecalculateMemorySize();
    return LoadResult(material);
}

ImportSettings* MaterialLoader::GetDefaultSettings() const {
    return nullptr;
}

bool MaterialLoader::ParseMaterialData(const Containers::Array<Core::uint8>& data, Material* material) {
    if (material == nullptr) {
        return false;
    }

    const std::string jsonText = ToStdString(data);

    Containers::String shaderPath;
    if (HasKey(jsonText, "shader")) {
        if (!TryParseStringValue(jsonText, "shader", shaderPath)) {
            return false;
        }

        const ResourceHandle<Shader> shaderHandle = LoadShaderHandle(shaderPath);
        if (shaderHandle.IsValid()) {
            material->SetShader(shaderHandle);
        }
    }

    Containers::String shaderPass;
    if (HasKey(jsonText, "shaderPass")) {
        if (!TryParseStringValue(jsonText, "shaderPass", shaderPass)) {
            return false;
        }
        material->SetShaderPass(shaderPass);
    } else if (HasKey(jsonText, "pass")) {
        if (!TryParseStringValue(jsonText, "pass", shaderPass)) {
            return false;
        }
        material->SetShaderPass(shaderPass);
    }

    if (HasKey(jsonText, "renderQueue")) {
        Core::int32 renderQueue = 0;
        if (TryParseIntValue(jsonText, "renderQueue", renderQueue)) {
            material->SetRenderQueue(renderQueue);
        } else {
            Containers::String renderQueueName;
            if (!TryParseStringValue(jsonText, "renderQueue", renderQueueName) ||
                !TryParseRenderQueueName(renderQueueName, renderQueue)) {
                return false;
            }

            material->SetRenderQueue(renderQueue);
        }
    }

    if (HasKey(jsonText, "tags")) {
        std::string tagObject;
        if (!TryExtractObject(jsonText, "tags", tagObject) || !TryParseTagMap(tagObject, material)) {
            return false;
        }
    }

    return true;
}

} // namespace Resources
} // namespace XCEngine