#include "metal_backend.h"

#include <mbgl/mtl/mtl_fwd.hpp>
#include <mbgl/mtl/renderable_resource.hpp>

#include <Metal/Metal.hpp>
#include <QuartzCore/CAMetalLayer.hpp>

namespace mbgl {

using namespace mtl;

class MetalRenderableResource final: public mtl::RenderableResource {
public:
    MetalRenderableResource(MetalBackend &backend):
    rendererBackend(backend),
    commandQueue(NS::TransferPtr(backend.getDevice()->newCommandQueue())),
    swapchain(NS::TransferPtr(CA::MetalLayer::layer()))
    {
        swapchain->setDevice(backend.getDevice().get());
    }
    
    void setBackendSize(mbgl::Size size_) {
        size = size_;
        swapchain->setDrawableSize({static_cast<CGFloat>(size.width), static_cast<CGFloat>(size.height)});
        buffersInvalid = true;
    }
    
    mbgl::Size getSize() const {
        return size;
    }
    
    void bind() override {
        surface = NS::TransferPtr(swapchain->nextDrawable());
        auto texSize = mbgl::Size{
            static_cast<uint32_t>(swapchain->drawableSize().width),
            static_cast<uint32_t>(swapchain->drawableSize().height)};
        
        commandBuffer = NS::TransferPtr(commandQueue->commandBuffer());
        renderPassDescriptor = NS::TransferPtr(MTL::RenderPassDescriptor::renderPassDescriptor());
        renderPassDescriptor->colorAttachments()->object(0)->setTexture(surface->texture());
        
        if (buffersInvalid || !depthTexture || !stencilTexture) {
            buffersInvalid = false;
            depthTexture = rendererBackend.getContext().createTexture2D();
            depthTexture->setSize(texSize);
            depthTexture->setFormat(gfx::TexturePixelType::Depth, gfx::TextureChannelDataType::Float);
            depthTexture->setSamplerConfiguration(
                                                  {gfx::TextureFilterType::Linear, gfx::TextureWrapType::Clamp, gfx::TextureWrapType::Clamp});
            static_cast<mtl::Texture2D*>(depthTexture.get())->setUsage(
                                                                       MTL::TextureUsageShaderRead | MTL::TextureUsageShaderWrite | MTL::TextureUsageRenderTarget);
            
            stencilTexture = rendererBackend.getContext().createTexture2D();
            stencilTexture->setSize(texSize);
            stencilTexture->setFormat(gfx::TexturePixelType::Stencil, gfx::TextureChannelDataType::UnsignedByte);
            stencilTexture->setSamplerConfiguration(
                                                    {gfx::TextureFilterType::Linear, gfx::TextureWrapType::Clamp, gfx::TextureWrapType::Clamp});
            static_cast<mtl::Texture2D*>(stencilTexture.get())
            ->setUsage(MTL::TextureUsageShaderRead | MTL::TextureUsageShaderWrite | MTL::TextureUsageRenderTarget);
        }
        
        if (depthTexture) {
            depthTexture->create();
            if (auto* depthTarget = renderPassDescriptor->depthAttachment()) {
                depthTarget->setTexture(static_cast<mtl::Texture2D*>(depthTexture.get())->getMetalTexture());
            }
        }
        if (stencilTexture) {
            stencilTexture->create();
            if (auto* stencilTarget = renderPassDescriptor->stencilAttachment()) {
                stencilTarget->setTexture(static_cast<mtl::Texture2D*>(stencilTexture.get())->getMetalTexture());
            }
        }
    }
    
    void swap() override {
        commandBuffer->presentDrawable(surface.get());
        commandBuffer->commit();
        commandBuffer.reset();
        renderPassDescriptor.reset();
    }
    
    const mtl::RendererBackend& getBackend() const override {
        return rendererBackend;
    }
    
    const mtl::MTLCommandBufferPtr& getCommandBuffer() const override {
        return commandBuffer;
    }
    
    mtl::MTLBlitPassDescriptorPtr getUploadPassDescriptor() const override {
        return NS::TransferPtr(MTL::BlitPassDescriptor::alloc()->init());
    }
    
    const mtl::MTLRenderPassDescriptorPtr& getRenderPassDescriptor() const override {
        return renderPassDescriptor;
    }
    
    const CAMetalLayerPtr& getSwapchain() const {
        return swapchain;
    }
    
private:
    MetalBackend &rendererBackend;
    MTLCommandQueuePtr commandQueue;
    MTLCommandBufferPtr commandBuffer;
    MTLRenderPassDescriptorPtr renderPassDescriptor;
    CAMetalDrawablePtr surface;
    CAMetalLayerPtr swapchain;
    gfx::Texture2DPtr depthTexture;
    gfx::Texture2DPtr stencilTexture;
    mbgl::Size size;
    bool buffersInvalid = true;
};

} // namespace mbgl

MetalBackend::MetalBackend(NSWindow *window):
mbgl::mtl::RendererBackend(mbgl::gfx::ContextMode::Unique),
mbgl::gfx::Renderable(mbgl::Size{0, 0}, std::make_unique<mbgl::MetalRenderableResource>(*this))
{
    window.contentView.layer = (__bridge CALayer *)getDefaultRenderable().getResource<mbgl::MetalRenderableResource>().getSwapchain().get();
    window.contentView.wantsLayer = YES;
}

mbgl::gfx::Renderable &MetalBackend::getDefaultRenderable() {
    return *this;
}

void MetalBackend::activate() {}
void MetalBackend::deactivate() {}
void MetalBackend::updateAssumedState() {}

void MetalBackend::setSize(mbgl::Size size_) {
    getResource<mbgl::MetalRenderableResource>().setBackendSize(size_);
}

mbgl::Size MetalBackend::getSize() const { return getResource<mbgl::MetalRenderableResource>().getSize(); }