#include "pywrkgame/rendering/GlobalIllumination.h"
#include <algorithm>
#include <sstream>

namespace pywrkgame {
namespace rendering {

GlobalIllumination::GlobalIllumination() = default;

GlobalIllumination::~GlobalIllumination() {
    if (initialized) {
        Shutdown();
    }
}

bool GlobalIllumination::Initialize(GraphicsDevice* dev) {
    if (initialized || !dev) {
        return false;
    }

    device = dev;
    initialized = true;
    enabled = false;
    currentTechnique = GITechnique::None;

    return true;
}

void GlobalIllumination::Shutdown() {
    if (!initialized) return;

    // Clean up all GI resources
    CleanupScreenSpaceGI();
    CleanupLightProbes();
    CleanupVoxelGI();

    device = nullptr;
    initialized = false;
    enabled = false;
}

// Technique Selection
void GlobalIllumination::SetTechnique(GITechnique technique) {
    if (!initialized) return;

    if (currentTechnique == technique) return;

    // Clean up previous technique
    switch (currentTechnique) {
        case GITechnique::ScreenSpace:
            CleanupScreenSpaceGI();
            break;
        case GITechnique::LightProbes:
            CleanupLightProbes();
            break;
        case GITechnique::VoxelBased:
            CleanupVoxelGI();
            break;
        default:
            break;
    }

    currentTechnique = technique;

    // Initialize new technique
    switch (currentTechnique) {
        case GITechnique::ScreenSpace:
            InitializeScreenSpaceGI();
            break;
        case GITechnique::LightProbes:
            InitializeLightProbes();
            break;
        case GITechnique::VoxelBased:
            InitializeVoxelGI();
            break;
        default:
            break;
    }
}

// Screen-Space GI
bool GlobalIllumination::SetupScreenSpaceGI(const SSGIConfig& config) {
    if (!initialized) return false;

    ssgiConfig = config;

    if (currentTechnique != GITechnique::ScreenSpace) {
        SetTechnique(GITechnique::ScreenSpace);
    }

    return true;
}

void GlobalIllumination::RenderScreenSpaceGI() {
    if (!initialized || !enabled || currentTechnique != GITechnique::ScreenSpace) {
        return;
    }

    // Render screen-space global illumination
    // This would involve:
    // 1. Trace rays in screen space
    // 2. Sample scene color and normals
    // 3. Accumulate indirect lighting
    // 4. Apply temporal filtering if enabled
    
    // Placeholder implementation
    if (device && ssgiShader.IsValid()) {
        // Bind SSGI shader and render
    }
}

bool GlobalIllumination::InitializeScreenSpaceGI() {
    if (!device) return false;

    // Create SSGI texture for storing indirect lighting
    TextureDesc ssgiDesc{};
    ssgiDesc.width = 1920;  // Should match render target resolution
    ssgiDesc.height = 1080;
    ssgiDesc.format = TextureFormat::RGBA16F;
    ssgiDesc.isRenderTarget = true;

    ssgiTexture = device->CreateTexture(ssgiDesc);
    if (!ssgiTexture.IsValid()) {
        return false;
    }

    // Create SSGI shader
    std::stringstream ss;
    ss << "#version 450\n";
    ss << "layout(location = 0) in vec2 texCoord;\n";
    ss << "layout(location = 0) out vec4 outColor;\n";
    ss << "layout(binding = 0) uniform sampler2D sceneColor;\n";
    ss << "layout(binding = 1) uniform sampler2D sceneNormal;\n";
    ss << "layout(binding = 2) uniform sampler2D sceneDepth;\n";
    ss << "void main() {\n";
    ss << "    // Screen-space ray tracing for indirect lighting\n";
    ss << "    vec3 color = texture(sceneColor, texCoord).rgb;\n";
    ss << "    vec3 normal = texture(sceneNormal, texCoord).rgb;\n";
    ss << "    float depth = texture(sceneDepth, texCoord).r;\n";
    ss << "    // Simplified GI calculation\n";
    ss << "    vec3 gi = color * 0.1;\n";
    ss << "    outColor = vec4(gi, 1.0);\n";
    ss << "}\n";

    ShaderDesc shaderDesc{};
    shaderDesc.stage = ShaderStage::Fragment;
    shaderDesc.source = ss.str();
    shaderDesc.isSpirV = false;

    ssgiShader = device->CreateShader(shaderDesc);
    if (!ssgiShader.IsValid()) {
        device->DestroyTexture(ssgiTexture);
        ssgiTexture = TextureHandle{};
        return false;
    }

    return true;
}

void GlobalIllumination::CleanupScreenSpaceGI() {
    if (device) {
        if (ssgiTexture.IsValid()) {
            device->DestroyTexture(ssgiTexture);
            ssgiTexture = TextureHandle{};
        }
        if (ssgiShader.IsValid()) {
            device->DestroyShader(ssgiShader);
            ssgiShader = ShaderHandle{};
        }
    }
}

// Light Probes
uint32_t GlobalIllumination::CreateLightProbe(const LightProbe& probe) {
    if (!initialized) return 0;

    uint32_t probeId = nextProbeId++;
    lightProbes.push_back(probe);
    probeIds.push_back(probeId);

    return probeId;
}

void GlobalIllumination::DestroyLightProbe(uint32_t probeId) {
    if (!initialized || probeId == 0) return;

    auto it = std::find(probeIds.begin(), probeIds.end(), probeId);
    if (it != probeIds.end()) {
        size_t index = std::distance(probeIds.begin(), it);
        probeIds.erase(it);
        lightProbes.erase(lightProbes.begin() + index);
    }
}

void GlobalIllumination::UpdateLightProbe(uint32_t probeId, const LightProbe& probe) {
    if (!initialized || probeId == 0) return;

    auto it = std::find(probeIds.begin(), probeIds.end(), probeId);
    if (it != probeIds.end()) {
        size_t index = std::distance(probeIds.begin(), it);
        lightProbes[index] = probe;
    }
}

const LightProbe* GlobalIllumination::GetLightProbe(uint32_t probeId) const {
    if (!initialized || probeId == 0) return nullptr;

    auto it = std::find(probeIds.begin(), probeIds.end(), probeId);
    if (it != probeIds.end()) {
        size_t index = std::distance(probeIds.begin(), it);
        return &lightProbes[index];
    }

    return nullptr;
}

void GlobalIllumination::RenderLightProbes() {
    if (!initialized || !enabled || currentTechnique != GITechnique::LightProbes) {
        return;
    }

    // Render light probe-based indirect lighting
    // This would involve:
    // 1. Find nearest light probes for each fragment
    // 2. Interpolate between probes
    // 3. Sample irradiance and reflection maps
    // 4. Apply indirect lighting

    // Placeholder implementation
    for (const auto& probe : lightProbes) {
        if (probe.irradianceMap.IsValid()) {
            // Use probe for indirect lighting
        }
    }
}

bool GlobalIllumination::InitializeLightProbes() {
    // Light probes don't require special initialization
    // They are created on-demand
    return true;
}

void GlobalIllumination::CleanupLightProbes() {
    lightProbes.clear();
    probeIds.clear();
    nextProbeId = 1;
}

// Voxel-Based GI
bool GlobalIllumination::SetupVoxelGI(const VoxelGridConfig& config) {
    if (!initialized) return false;

    voxelConfig = config;

    if (currentTechnique != GITechnique::VoxelBased) {
        SetTechnique(GITechnique::VoxelBased);
    }

    return true;
}

void GlobalIllumination::VoxelizeScene() {
    if (!initialized || !enabled || currentTechnique != GITechnique::VoxelBased) {
        return;
    }

    // Voxelize the scene
    // This would involve:
    // 1. Render scene from 3 orthogonal directions
    // 2. Write to 3D voxel texture
    // 3. Generate mip levels for cone tracing

    // Placeholder implementation
    if (device && voxelizeShader.IsValid()) {
        // Bind voxelization shader and render
    }
}

void GlobalIllumination::RenderVoxelGI() {
    if (!initialized || !enabled || currentTechnique != GITechnique::VoxelBased) {
        return;
    }

    // Render voxel-based global illumination using cone tracing
    // This would involve:
    // 1. For each fragment, trace cones through voxel grid
    // 2. Accumulate indirect lighting from voxels
    // 3. Apply to final image

    // Placeholder implementation
    if (device && voxelConeTracingShader.IsValid()) {
        // Bind cone tracing shader and render
    }
}

bool GlobalIllumination::InitializeVoxelGI() {
    if (!device) return false;

    // Create 3D voxel texture
    TextureDesc voxelDesc{};
    voxelDesc.width = voxelConfig.resolution;
    voxelDesc.height = voxelConfig.resolution;
    voxelDesc.depth = voxelConfig.resolution;
    voxelDesc.mipLevels = voxelConfig.mipLevels;
    voxelDesc.format = TextureFormat::RGBA8;

    voxelTexture = device->CreateTexture(voxelDesc);
    if (!voxelTexture.IsValid()) {
        return false;
    }

    // Create voxelization shader
    std::stringstream voxelizeSS;
    voxelizeSS << "#version 450\n";
    voxelizeSS << "layout(location = 0) in vec3 position;\n";
    voxelizeSS << "layout(location = 1) in vec3 normal;\n";
    voxelizeSS << "layout(location = 2) in vec2 texCoord;\n";
    voxelizeSS << "void main() {\n";
    voxelizeSS << "    // Voxelize geometry\n";
    voxelizeSS << "    gl_Position = vec4(position, 1.0);\n";
    voxelizeSS << "}\n";

    ShaderDesc voxelizeDesc{};
    voxelizeDesc.stage = ShaderStage::Vertex;
    voxelizeDesc.source = voxelizeSS.str();
    voxelizeDesc.isSpirV = false;

    voxelizeShader = device->CreateShader(voxelizeDesc);
    if (!voxelizeShader.IsValid()) {
        device->DestroyTexture(voxelTexture);
        voxelTexture = TextureHandle{};
        return false;
    }

    // Create cone tracing shader
    std::stringstream coneTracingSS;
    coneTracingSS << "#version 450\n";
    coneTracingSS << "layout(location = 0) in vec2 texCoord;\n";
    coneTracingSS << "layout(location = 0) out vec4 outColor;\n";
    coneTracingSS << "layout(binding = 0) uniform sampler3D voxelGrid;\n";
    coneTracingSS << "void main() {\n";
    coneTracingSS << "    // Cone tracing for indirect lighting\n";
    coneTracingSS << "    vec3 gi = vec3(0.1);\n";
    coneTracingSS << "    outColor = vec4(gi, 1.0);\n";
    coneTracingSS << "}\n";

    ShaderDesc coneTracingDesc{};
    coneTracingDesc.stage = ShaderStage::Fragment;
    coneTracingDesc.source = coneTracingSS.str();
    coneTracingDesc.isSpirV = false;

    voxelConeTracingShader = device->CreateShader(coneTracingDesc);
    if (!voxelConeTracingShader.IsValid()) {
        device->DestroyShader(voxelizeShader);
        device->DestroyTexture(voxelTexture);
        voxelizeShader = ShaderHandle{};
        voxelTexture = TextureHandle{};
        return false;
    }

    return true;
}

void GlobalIllumination::CleanupVoxelGI() {
    if (device) {
        if (voxelTexture.IsValid()) {
            device->DestroyTexture(voxelTexture);
            voxelTexture = TextureHandle{};
        }
        if (voxelizeShader.IsValid()) {
            device->DestroyShader(voxelizeShader);
            voxelizeShader = ShaderHandle{};
        }
        if (voxelConeTracingShader.IsValid()) {
            device->DestroyShader(voxelConeTracingShader);
            voxelConeTracingShader = ShaderHandle{};
        }
    }
}

// Enable/Disable
void GlobalIllumination::Enable(bool enable) {
    if (!initialized) return;
    enabled = enable;
}

} // namespace rendering
} // namespace pywrkgame
