use std::sync::Arc;
use vulkano::command_buffer::allocator::StandardCommandBufferAllocator;
use vulkano::device::{Device, DeviceCreateInfo, DeviceExtensions, DeviceFeatures, Queue, QueueCreateInfo, QueueFlags};
use vulkano::device::physical::PhysicalDeviceType;
use vulkano::instance::{Instance, InstanceCreateFlags, InstanceCreateInfo};
use vulkano::memory::allocator::StandardMemoryAllocator;
use vulkano::swapchain::{acquire_next_image, Surface, SwapchainCreateInfo, SwapchainPresentInfo};
use vulkano::{sync, Validated, Version, VulkanError, VulkanLibrary};
use vulkano::command_buffer::{AutoCommandBufferBuilder, CommandBufferUsage, RenderingAttachmentInfo, RenderingInfo};
use vulkano::render_pass::{AttachmentLoadOp, AttachmentStoreOp};
use vulkano::sync::GpuFuture;
use winit::application::ApplicationHandler;
use winit::event::WindowEvent;
use winit::event_loop::{ActiveEventLoop, EventLoop};
use winit::window::{Window, WindowId};
use crate::renderer::render_context::RenderContext;
use crate::renderer::{window_size_dependent_setup, Scene};

pub struct App {
    instance: Arc<Instance>,
    device: Arc<Device>,
    queue: Arc<Queue>,
    memory_allocator: Arc<StandardMemoryAllocator>,
    command_buffer_allocator: Arc<StandardCommandBufferAllocator>,
    rcx: Option<RenderContext>,
    scene: Option<Scene>,
}

impl App {
    pub fn new(event_loop: &EventLoop<()>) -> Self {
        let library = VulkanLibrary::new().unwrap();

        // The first step of any Vulkan program is to create an instance.
        //
        // When we create an instance, we have to pass a list of extensions that we want to enable.
        //
        // All the window-drawing functionalities are part of non-core extensions that we need to
        // enable manually. To do so, we ask `Surface` for the list of extensions required to draw
        // to a window.
        let required_extensions = Surface::required_extensions(event_loop).unwrap();

        // Now creating the instance.
        let instance = Instance::new(
            library,
            InstanceCreateInfo {
                // Enable enumerating devices that use non-conformant Vulkan implementations.
                // (e.g. MoltenVK)
                flags: InstanceCreateFlags::ENUMERATE_PORTABILITY,
                enabled_extensions: required_extensions,
                enabled_layers: vec![
                    String::from("VK_LAYER_KHRONOS_validation"),
                    String::from("VK_LAYER_MANGOHUD_overlay_x86_64"),
                    String::from("VK_LAYER_NV_optimus"),
                ],
                ..Default::default()
            },
        )
            .unwrap();

        // Choose device extensions that we're going to use. In order to present images to a
        // surface, we need a `Swapchain`, which is provided by the `khr_swapchain` extension.
        let mut device_extensions = DeviceExtensions {
            khr_swapchain: true,
            ..DeviceExtensions::empty()
        };

        // We then choose which physical device to use. First, we enumerate all the available
        // physical devices, then apply filters to narrow them down to those that can support our
        // needs.
        let (physical_device, queue_family_index) = instance
            .enumerate_physical_devices()
            .unwrap()
            .filter(|p| {
                // For this example, we require at least Vulkan 1.3, or a device that has the
                // `khr_dynamic_rendering` extension available.
                p.api_version() >= Version::V1_3 || p.supported_extensions().khr_dynamic_rendering
            })
            .filter(|p| {
                // Some devices may not support the extensions or features that your application,
                // or report properties and limits that are not sufficient for your application.
                // These should be filtered out here.
                p.supported_extensions().contains(&device_extensions)
            })
            .filter_map(|p| {
                // For each physical device, we try to find a suitable queue family that will
                // execute our draw commands.
                //
                // Devices can provide multiple queues to run commands in parallel (for example a
                // draw queue and a compute queue), similar to CPU threads. This is something you
                // have to have to manage manually in Vulkan. Queues of the same type belong to the
                // same queue family.
                //
                // Here, we look for a single queue family that is suitable for our purposes. In a
                // real-world application, you may want to use a separate dedicated transfer queue
                // to handle data transfers in parallel with graphics operations. You may also need
                // a separate queue for compute operations, if your application uses those.
                p.queue_family_properties()
                    .iter()
                    .enumerate()
                    .position(|(i, q)| {
                        // We select a queue family that supports graphics operations. When drawing
                        // to a window surface, as we do in this example, we also need to check
                        // that queues in this queue family are capable of presenting images to the
                        // surface.
                        q.queue_flags.intersects(QueueFlags::GRAPHICS)
                            && p.presentation_support(i as u32, event_loop).unwrap()
                    })
                    // The code here searches for the first queue family that is suitable. If none
                    // is found, `None` is returned to `filter_map`, which disqualifies this
                    // physical device.
                    .map(|i| (p, i as u32))
            })
            // All the physical devices that pass the filters above are suitable for the
            // application. However, not every device is equal, some are preferred over others.
            // Now, we assign each physical device a score, and pick the device with the lowest
            // ("best") score.
            //
            // In this example, we simply select the best-scoring device to use in the application.
            // In a real-world setting, you may want to use the best-scoring device only as a
            // "default" or "recommended" device, and let the user choose the device themself.
            .min_by_key(|(p, _)| {
                // We assign a lower score to device types that are likely to be faster/better.
                match p.properties().device_type {
                    PhysicalDeviceType::DiscreteGpu => 0,
                    PhysicalDeviceType::IntegratedGpu => 1,
                    PhysicalDeviceType::VirtualGpu => 2,
                    PhysicalDeviceType::Cpu => 3,
                    PhysicalDeviceType::Other => 4,
                    _ => 5,
                }
            })
            .expect("no suitable physical device found");

        // Some little debug infos.
        println!(
            "Using device: {} (type: {:?})",
            physical_device.properties().device_name,
            physical_device.properties().device_type,
        );

        // If the selected device doesn't have Vulkan 1.3 available, then we need to enable the
        // `khr_dynamic_rendering` extension manually. This extension became a core part of Vulkan
        // in version 1.3 and later, so it's always available then and it does not need to be
        // enabled. We can be sure that this extension will be available on the selected physical
        // device, because we filtered out unsuitable devices in the device selection code above.
        if physical_device.api_version() < Version::V1_3 {
            device_extensions.khr_dynamic_rendering = true;
        }

        // Now initializing the device. This is probably the most important object of Vulkan.
        //
        // An iterator of created queues is returned by the function alongside the device.
        let (device, mut queues) = Device::new(
            // Which physical device to connect to.
            physical_device,
            DeviceCreateInfo {
                // The list of queues that we are going to use. Here we only use one queue, from
                // the previously chosen queue family.
                queue_create_infos: vec![QueueCreateInfo {
                    queue_family_index,
                    ..Default::default()
                }],

                // A list of optional features and extensions that our program needs to work
                // correctly. Some parts of the Vulkan specs are optional and must be enabled
                // manually at device creation. In this example the only things we are going to
                // need are the `khr_swapchain` extension that allows us to draw to a window, and
                // `khr_dynamic_rendering` if we don't have Vulkan 1.3 available.
                enabled_extensions: device_extensions,

                // In order to render with Vulkan 1.3's dynamic rendering, we need to enable it
                // here. Otherwise, we are only allowed to render with a render pass object, as in
                // the standard triangle example. The feature is required to be supported by the
                // device if it supports Vulkan 1.3 and higher, or if the `khr_dynamic_rendering`
                // extension is available, so we don't need to check for support.
                enabled_features: DeviceFeatures {
                    dynamic_rendering: true,
                    ..DeviceFeatures::empty()
                },

                ..Default::default()
            },
        )
            .unwrap();

        // Since we can request multiple queues, the `queues` variable is in fact an iterator. We
        // only use one queue in this example, so we just retrieve the first and only element of
        // the iterator.
        let queue = queues.next().unwrap();

        let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));

        // Before we can start creating and recording command buffers, we need a way of allocating
        // them. Vulkano provides a command buffer allocator, which manages raw Vulkan command
        // pools underneath and provides a safe interface for them.
        let command_buffer_allocator = Arc::new(StandardCommandBufferAllocator::new(
            device.clone(),
            Default::default(),
        ));

        Self {
            instance,
            device,
            queue,
            memory_allocator,
            command_buffer_allocator,
            rcx: None,
            scene: None,
        }
    }
}

impl ApplicationHandler for App {
    fn resumed(&mut self, event_loop: &ActiveEventLoop) {
        let window_attributes = winit::window::Window::default_attributes()
            .with_title("Rust ASH Test")
            .with_inner_size(winit::dpi::PhysicalSize::new(
                f64::from(800),
                f64::from(600),
            ));

        let window = Arc::new(
            event_loop
                .create_window(window_attributes)
                .unwrap(),
        );

        let surface = Surface::from_window(self.instance.clone(), window.clone()).unwrap();

        self.rcx = Some(RenderContext::new(window, surface, &self.device));
        self.scene = Some(Scene::initialize(&self.device, &self.rcx.as_ref().unwrap().swapchain, &self.memory_allocator));
    }

    fn window_event(&mut self, event_loop: &ActiveEventLoop, _id: WindowId, event: WindowEvent) {
        let rcx = self.rcx.as_mut().unwrap();

        match event {
            WindowEvent::CloseRequested => {
                log::debug!("The close button was pressed; stopping");
                event_loop.exit();
            }
            WindowEvent::Resized(_) => {
                rcx.recreate_swapchain = true;
            }
            WindowEvent::RedrawRequested => {
                let window_size = rcx.window.inner_size();

                // Do not draw the frame when the screen size is zero. On Windows, this can occur
                // when minimizing the application.
                if window_size.width == 0 || window_size.height == 0 {
                    return;
                }

                // It is important to call this function from time to time, otherwise resources
                // will keep accumulating and you will eventually reach an out of memory error.
                // Calling this function polls various fences in order to determine what the GPU
                // has already processed, and frees the resources that are no longer needed.
                rcx.previous_frame_end.as_mut().unwrap().cleanup_finished();

                // Whenever the window resizes we need to recreate everything dependent on the
                // window size. In this example that includes the swapchain, the framebuffers and
                // the dynamic state viewport.
                if rcx.recreate_swapchain {
                    let (new_swapchain, new_images) = rcx
                        .swapchain
                        .recreate(SwapchainCreateInfo {
                            image_extent: window_size.into(),
                            ..rcx.swapchain.create_info()
                        })
                        .expect("failed to recreate swapchain");

                    rcx.swapchain = new_swapchain;

                    // Now that we have new swapchain images, we must create new image views from
                    // them as well.
                    rcx.attachment_image_views = window_size_dependent_setup(&new_images);

                    rcx.viewport.extent = window_size.into();

                    rcx.recreate_swapchain = false;
                }

                // Before we can draw on the output, we have to *acquire* an image from the
                // swapchain. If no image is available (which happens if you submit draw commands
                // too quickly), then the function will block. This operation returns the index of
                // the image that we are allowed to draw upon.
                //
                // This function can block if no image is available. The parameter is an optional
                // timeout after which the function call will return an error.
                let (image_index, suboptimal, acquire_future) = match acquire_next_image(
                    rcx.swapchain.clone(),
                    None,
                )
                    .map_err(Validated::unwrap)
                {
                    Ok(r) => r,
                    Err(VulkanError::OutOfDate) => {
                        rcx.recreate_swapchain = true;
                        return;
                    }
                    Err(e) => panic!("failed to acquire next image: {e}"),
                };

                // `acquire_next_image` can be successful, but suboptimal. This means that the
                // swapchain image will still work, but it may not display correctly. With some
                // drivers this can be when the window resizes, but it may not cause the swapchain
                // to become out of date.
                if suboptimal {
                    rcx.recreate_swapchain = true;
                }

                // In order to draw, we have to record a *command buffer*. The command buffer
                // object holds the list of commands that are going to be executed.
                //
                // Recording a command buffer is an expensive operation (usually a few hundred
                // microseconds), but it is known to be a hot path in the driver and is expected to
                // be optimized.
                //
                // Note that we have to pass a queue family when we create the command buffer. The
                // command buffer will only be executable on that given queue family.
                let mut builder = AutoCommandBufferBuilder::primary(
                    self.command_buffer_allocator.clone(),
                    self.queue.queue_family_index(),
                    CommandBufferUsage::OneTimeSubmit,
                )
                    .unwrap();

                builder
                    // Before we can draw, we have to *enter a render pass*. We specify which
                    // attachments we are going to use for rendering here, which needs to match
                    // what was previously specified when creating the pipeline.
                    .begin_rendering(RenderingInfo {
                        // As before, we specify one color attachment, but now we specify the image
                        // view to use as well as how it should be used.
                        color_attachments: vec![Some(RenderingAttachmentInfo {
                            // `Clear` means that we ask the GPU to clear the content of this
                            // attachment at the start of rendering.
                            load_op: AttachmentLoadOp::Clear,
                            // `Store` means that we ask the GPU to store the rendered output in
                            // the attachment image. We could also ask it to discard the result.
                            store_op: AttachmentStoreOp::Store,
                            // The value to clear the attachment with. Here we clear it with a blue
                            // color.
                            //
                            // Only attachments that have `AttachmentLoadOp::Clear` are provided
                            // with clear values, any others should use `None` as the clear value.
                            clear_value: Some([0.0, 0.0, 0.0, 1.0].into()),
                            ..RenderingAttachmentInfo::image_view(
                                // We specify image view corresponding to the currently acquired
                                // swapchain image, to use for this attachment.
                                rcx.attachment_image_views[image_index as usize].clone(),
                            )
                        })],
                        ..Default::default()
                    })
                    .unwrap()
                    // We are now inside the first subpass of the render pass.
                    //
                    // TODO: Document state setting and how it affects subsequent draw commands.
                    .set_viewport(0, [rcx.viewport.clone()].into_iter().collect())
                    .unwrap();

                if let Some(scene) = self.scene.as_ref() {
                    scene.render(&mut builder);
                }

                builder
                    // We leave the render pass.
                    .end_rendering()
                    .unwrap();

                // Finish recording the command buffer by calling `end`.
                let command_buffer = builder.build().unwrap();

                let future = rcx
                    .previous_frame_end
                    .take()
                    .unwrap()
                    .join(acquire_future)
                    .then_execute(self.queue.clone(), command_buffer)
                    .unwrap()
                    // The color output is now expected to contain our triangle. But in order to
                    // show it on the screen, we have to *present* the image by calling
                    // `then_swapchain_present`.
                    //
                    // This function does not actually present the image immediately. Instead it
                    // submits a present command at the end of the queue. This means that it will
                    // only be presented once the GPU has finished executing the command buffer
                    // that draws the triangle.
                    .then_swapchain_present(
                        self.queue.clone(),
                        SwapchainPresentInfo::swapchain_image_index(
                            rcx.swapchain.clone(),
                            image_index,
                        ),
                    )
                    .then_signal_fence_and_flush();

                match future.map_err(Validated::unwrap) {
                    Ok(future) => {
                        rcx.previous_frame_end = Some(future.boxed());
                    }
                    Err(VulkanError::OutOfDate) => {
                        rcx.recreate_swapchain = true;
                        rcx.previous_frame_end = Some(sync::now(self.device.clone()).boxed());
                    }
                    Err(e) => {
                        println!("failed to flush future: {e}");
                        rcx.previous_frame_end = Some(sync::now(self.device.clone()).boxed());
                    }
                }
            }
            _ => {}
        }
    }

    fn about_to_wait(&mut self, _event_loop: &ActiveEventLoop) {
        let rcx = self.rcx.as_mut().unwrap();
        rcx.window.request_redraw();
    }
}