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

    if (json.compare(valuePos, 4, "true") == 0) {
        outValue = true;
        return true;
    }
    if (json.compare(valuePos, 5, "false") == 0) {
        outValue = false;
        return true;
    }

    return false;
}

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;
}

bool TryParseCullMode(const Containers::String& value, MaterialCullMode& outMode) {
    const Containers::String normalized = value.Trim().ToLower();
    if (normalized == "none" || normalized == "off") {
        outMode = MaterialCullMode::None;
        return true;
    }
    if (normalized == "front") {
        outMode = MaterialCullMode::Front;
        return true;
    }
    if (normalized == "back") {
        outMode = MaterialCullMode::Back;
        return true;
    }

    return false;
}

bool TryParseComparisonFunc(const Containers::String& value, MaterialComparisonFunc& outFunc) {
    const Containers::String normalized = value.Trim().ToLower();
    if (normalized == "never") {
        outFunc = MaterialComparisonFunc::Never;
        return true;
    }
    if (normalized == "less") {
        outFunc = MaterialComparisonFunc::Less;
        return true;
    }
    if (normalized == "equal") {
        outFunc = MaterialComparisonFunc::Equal;
        return true;
    }
    if (normalized == "lessequal" || normalized == "less_equal" || normalized == "lequal") {
        outFunc = MaterialComparisonFunc::LessEqual;
        return true;
    }
    if (normalized == "greater") {
        outFunc = MaterialComparisonFunc::Greater;
        return true;
    }
    if (normalized == "notequal" || normalized == "not_equal") {
        outFunc = MaterialComparisonFunc::NotEqual;
        return true;
    }
    if (normalized == "greaterequal" || normalized == "greater_equal" || normalized == "gequal") {
        outFunc = MaterialComparisonFunc::GreaterEqual;
        return true;
    }
    if (normalized == "always") {
        outFunc = MaterialComparisonFunc::Always;
        return true;
    }

    return false;
}

bool TryParseBlendFactor(const Containers::String& value, MaterialBlendFactor& outFactor) {
    const Containers::String normalized = value.Trim().ToLower();
    if (normalized == "zero") {
        outFactor = MaterialBlendFactor::Zero;
        return true;
    }
    if (normalized == "one") {
        outFactor = MaterialBlendFactor::One;
        return true;
    }
    if (normalized == "srccolor" || normalized == "src_color") {
        outFactor = MaterialBlendFactor::SrcColor;
        return true;
    }
    if (normalized == "invsrccolor" || normalized == "inv_src_color" || normalized == "one_minus_src_color") {
        outFactor = MaterialBlendFactor::InvSrcColor;
        return true;
    }
    if (normalized == "srcalpha" || normalized == "src_alpha") {
        outFactor = MaterialBlendFactor::SrcAlpha;
        return true;
    }
    if (normalized == "invsrcalpha" || normalized == "inv_src_alpha" || normalized == "one_minus_src_alpha") {
        outFactor = MaterialBlendFactor::InvSrcAlpha;
        return true;
    }
    if (normalized == "dstalpha" || normalized == "dst_alpha") {
        outFactor = MaterialBlendFactor::DstAlpha;
        return true;
    }
    if (normalized == "invdstalpha" || normalized == "inv_dst_alpha" || normalized == "one_minus_dst_alpha") {
        outFactor = MaterialBlendFactor::InvDstAlpha;
        return true;
    }
    if (normalized == "dstcolor" || normalized == "dst_color") {
        outFactor = MaterialBlendFactor::DstColor;
        return true;
    }
    if (normalized == "invdstcolor" || normalized == "inv_dst_color" || normalized == "one_minus_dst_color") {
        outFactor = MaterialBlendFactor::InvDstColor;
        return true;
    }
    if (normalized == "srcalphasat" || normalized == "src_alpha_sat") {
        outFactor = MaterialBlendFactor::SrcAlphaSat;
        return true;
    }
    if (normalized == "blendfactor" || normalized == "blend_factor") {
        outFactor = MaterialBlendFactor::BlendFactor;
        return true;
    }
    if (normalized == "invblendfactor" || normalized == "inv_blend_factor" || normalized == "one_minus_blend_factor") {
        outFactor = MaterialBlendFactor::InvBlendFactor;
        return true;
    }
    if (normalized == "src1color" || normalized == "src1_color") {
        outFactor = MaterialBlendFactor::Src1Color;
        return true;
    }
    if (normalized == "invsrc1color" || normalized == "inv_src1_color" || normalized == "one_minus_src1_color") {
        outFactor = MaterialBlendFactor::InvSrc1Color;
        return true;
    }
    if (normalized == "src1alpha" || normalized == "src1_alpha") {
        outFactor = MaterialBlendFactor::Src1Alpha;
        return true;
    }
    if (normalized == "invsrc1alpha" || normalized == "inv_src1_alpha" || normalized == "one_minus_src1_alpha") {
        outFactor = MaterialBlendFactor::InvSrc1Alpha;
        return true;
    }

    return false;
}

bool TryParseBlendOp(const Containers::String& value, MaterialBlendOp& outOp) {
    const Containers::String normalized = value.Trim().ToLower();
    if (normalized == "add") {
        outOp = MaterialBlendOp::Add;
        return true;
    }
    if (normalized == "subtract") {
        outOp = MaterialBlendOp::Subtract;
        return true;
    }
    if (normalized == "reversesubtract" || normalized == "reverse_subtract") {
        outOp = MaterialBlendOp::ReverseSubtract;
        return true;
    }
    if (normalized == "min") {
        outOp = MaterialBlendOp::Min;
        return true;
    }
    if (normalized == "max") {
        outOp = MaterialBlendOp::Max;
        return true;
    }

    return false;
}

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

    MaterialRenderState renderState = material->GetRenderState();

    Containers::String enumValue;
    if (HasKey(objectText, "cull")) {
        if (!TryParseStringValue(objectText, "cull", enumValue) ||
            !TryParseCullMode(enumValue, renderState.cullMode)) {
            return false;
        }
    }

    bool boolValue = false;
    if (HasKey(objectText, "depthTest")) {
        if (!TryParseBoolValue(objectText, "depthTest", boolValue)) {
            return false;
        }
        renderState.depthTestEnable = boolValue;
    }
    if (HasKey(objectText, "depthWrite")) {
        if (!TryParseBoolValue(objectText, "depthWrite", boolValue)) {
            return false;
        }
        renderState.depthWriteEnable = boolValue;
    }
    if (HasKey(objectText, "zWrite")) {
        if (!TryParseBoolValue(objectText, "zWrite", boolValue)) {
            return false;
        }
        renderState.depthWriteEnable = boolValue;
    }
    if (HasKey(objectText, "blend")) {
        if (!TryParseBoolValue(objectText, "blend", boolValue)) {
            return false;
        }
        renderState.blendEnable = boolValue;
    }
    if (HasKey(objectText, "blendEnable")) {
        if (!TryParseBoolValue(objectText, "blendEnable", boolValue)) {
            return false;
        }
        renderState.blendEnable = boolValue;
    }

    if (HasKey(objectText, "depthFunc")) {
        if (!TryParseStringValue(objectText, "depthFunc", enumValue) ||
            !TryParseComparisonFunc(enumValue, renderState.depthFunc)) {
            return false;
        }
    }
    if (HasKey(objectText, "zTest")) {
        if (!TryParseStringValue(objectText, "zTest", enumValue) ||
            !TryParseComparisonFunc(enumValue, renderState.depthFunc)) {
            return false;
        }
    }
    if (HasKey(objectText, "colorWriteMask")) {
        Core::int32 colorWriteMask = 0;
        if (!TryParseIntValue(objectText, "colorWriteMask", colorWriteMask) ||
            colorWriteMask < 0 || colorWriteMask > 0xF) {
            return false;
        }
        renderState.colorWriteMask = static_cast<Core::uint8>(colorWriteMask);
    }
    if (HasKey(objectText, "srcBlend")) {
        if (!TryParseStringValue(objectText, "srcBlend", enumValue) ||
            !TryParseBlendFactor(enumValue, renderState.srcBlend)) {
            return false;
        }
    }
    if (HasKey(objectText, "dstBlend")) {
        if (!TryParseStringValue(objectText, "dstBlend", enumValue) ||
            !TryParseBlendFactor(enumValue, renderState.dstBlend)) {
            return false;
        }
    }
    if (HasKey(objectText, "srcBlendAlpha")) {
        if (!TryParseStringValue(objectText, "srcBlendAlpha", enumValue) ||
            !TryParseBlendFactor(enumValue, renderState.srcBlendAlpha)) {
            return false;
        }
    }
    if (HasKey(objectText, "dstBlendAlpha")) {
        if (!TryParseStringValue(objectText, "dstBlendAlpha", enumValue) ||
            !TryParseBlendFactor(enumValue, renderState.dstBlendAlpha)) {
            return false;
        }
    }
    if (HasKey(objectText, "blendOp")) {
        if (!TryParseStringValue(objectText, "blendOp", enumValue) ||
            !TryParseBlendOp(enumValue, renderState.blendOp)) {
            return false;
        }
    }
    if (HasKey(objectText, "blendOpAlpha")) {
        if (!TryParseStringValue(objectText, "blendOpAlpha", enumValue) ||
            !TryParseBlendOp(enumValue, renderState.blendOpAlpha)) {
            return false;
        }
    }

    material->SetRenderState(renderState);
    return true;
}

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;
        }
    }

    if (HasKey(jsonText, "renderState")) {
        std::string renderStateObject;
        if (!TryExtractObject(jsonText, "renderState", renderStateObject) ||
            !TryParseRenderStateObject(renderStateObject, material)) {
            return false;
        }
    }

    return true;
}

} // namespace Resources
} // namespace XCEngine