#[allow(unused_imports)]
use log::{debug, error, info, trace, warn};

use std::{
    mem::ManuallyDrop,
    iter,
};

use core::ptr::read;

use gfx_hal::{
    Instance,
    device::Device,
    queue::QueueGroup,
    Backend,
    pool::CommandPool,
    pso::Rect,
};

use gfx_backend_vulkan as vk_back;

use winit::window::Window;

pub mod render;

#[derive(Debug)]
pub struct HalState {
    //items need to communicate with the GPU
    instance: ManuallyDrop<<vk_back::Backend as Backend>::Instance>,
    surface: ManuallyDrop<<vk_back::Backend as Backend>::Surface>,
    adapter: ManuallyDrop<gfx_hal::adapter::Adapter<vk_back::Backend>>,
    device: vk_back::Device,
    queue_group: ManuallyDrop<QueueGroup<vk_back::Backend>>,
    render_pass: ManuallyDrop<<vk_back::Backend as Backend>::RenderPass>,
    swapchain: ManuallyDrop<<vk_back::Backend as Backend>::Swapchain>,
    extent: gfx_hal::window::Extent2D,
    format: gfx_hal::format::Format,
    render_area: Rect,

    //items needed to render the images
    sems_image_available: Vec<<vk_back::Backend as Backend>::Semaphore>,
    sems_render_finished: Vec<<vk_back::Backend as Backend>::Semaphore>,
    fences: Vec<<vk_back::Backend as Backend>::Fence>,
    image_views: Vec<<vk_back::Backend as Backend>::ImageView>,
    framebuffers: Vec<<vk_back::Backend as Backend>::Framebuffer>,

    command_pool: ManuallyDrop<<vk_back::Backend as Backend>::CommandPool>,
    command_buffers: Vec<<vk_back::Backend as Backend>::CommandBuffer>,

    //items needed to keep track of the images
    image_count: usize,
    current_image: usize,
}

impl core::ops::Drop for HalState {

    //----------------------------------------------------------------------------------------------
    fn drop(&mut self) {

        let _ = self.device.wait_idle();

        //destroy all underlying ressources
        debug!("Destroying HAL ressources");
        unsafe {
            self.command_pool.free(self.command_buffers.drain(..));
            self.device.destroy_command_pool(
                ManuallyDrop::into_inner(read(&mut self.command_pool)));
            for buffer in self.framebuffers.drain(..) {
                self.device.destroy_framebuffer(buffer);
            }
            for view in self.image_views.drain(..) {
                self.device.destroy_image_view(view);
            }
            for fence in self.fences.drain(..) {
                self.device.destroy_fence(fence);
            }
            for sem in self.sems_image_available.drain(..) {
                self.device.destroy_semaphore(sem);
            }
            for sem in self.sems_render_finished.drain(..) {
                self.device.destroy_semaphore(sem);
            }
            self.device.destroy_swapchain(ManuallyDrop::into_inner(read(&mut self.swapchain)));
            self.device.destroy_render_pass(ManuallyDrop::into_inner(read(&mut self.render_pass)));
            ManuallyDrop::drop(&mut self.queue_group);
            ManuallyDrop::drop(&mut self.adapter);
            self.instance.destroy_surface(ManuallyDrop::into_inner(read(&mut self.surface)));
            ManuallyDrop::drop(&mut self.instance);
        }
        info!("HAL ressources destroyed");
    }
}

impl HalState {

    //----------------------------------------------------------------------------------------------
    pub fn recreate_swapchain(&mut self) -> Result<(), &'static str> {
        use gfx_hal::window::{
            SwapchainConfig,
            Surface,
        };

        debug!("Recreating swapchain");

        //destroying previous swapchain
        unsafe {
            for buffer in self.framebuffers.drain(..) {
                self.device.destroy_framebuffer(buffer);
            }
            for view in self.image_views.drain(..) {
                self.device.destroy_image_view(view);
            }

            self.device.destroy_swapchain(ManuallyDrop::into_inner(read(&mut self.swapchain)));
        }
        let capabilities = self.surface.capabilities(&self.adapter.physical_device);
        info!("{:#?}", capabilities);

        //creating new swapchain
        let swapchain_config = SwapchainConfig::from_caps(&capabilities, self.format, self.extent);
            info!("{:?}", swapchain_config);

            let (swapchain, backbuffer) = unsafe {
                self.device
                    .create_swapchain(&mut self.surface, swapchain_config, None)
                    .map_err(|_| "Failed to create swapchain and backbuffer")?
            };

        let image_views : Vec<_> = {
            use gfx_hal::{
                image::{ViewKind, SubresourceRange},
                format::{Swizzle, Aspects},
            };

            backbuffer
                .iter()
                .map(|img| unsafe {
                    self.device
                        .create_image_view(
                            &img,
                            ViewKind::D2,
                            self.format,
                            Swizzle::NO,
                            SubresourceRange {
                                aspects : Aspects::COLOR,
                                levels : 0..1,
                                layers : 0..1,
                            },
                        )
                        .map_err(|_| "Could not create ImageViews")
                })
                .collect::<Result<Vec<_>, &str>>()?
        };

        let framebuffers: Vec<_> = {

            image_views
                .iter()
                .map(|image_view|
                    unsafe {
                        self.device
                            .create_framebuffer(&self.render_pass, 
                                                iter::once(image_view), 
                                                self.extent.to_extent())
                            .map_err(|_| "Could not create FrameBuffer")
                    },
                )
                .collect::<Result<Vec<_>, &str>>()?
        };

        self.swapchain = ManuallyDrop::new(swapchain);
        self.image_views = image_views;
        self.framebuffers = framebuffers;
        Ok(())
    }

    //----------------------------------------------------------------------------------------------
    pub fn new(window: &Window) -> Result<HalState, &'static str> {
        use gfx_hal::adapter::Gpu;

        // create top level
        let instance = vk_back::Instance::create("IV", 1)
            .map_err(|_| "Could not create instance")?;

        let mut surface = unsafe {
            instance
                .create_surface(window)
                .map_err(|_| "Could not create Surface")?
        };

        let (adapter, device, queue_group) = {
            use gfx_hal::{
                window::Surface,
                queue::family::QueueFamily,
            };

            // find a adapter with a suitable queue family
            // TODO add weight for adapters
            let adapter = 
                Instance::enumerate_adapters(&instance)
                .into_iter();
//                .find(|a| {
//                    a.queue_families
//                        .iter()
//                        .any(|qf| 
//                            QueueFamily::queue_type(qf).supports_graphics()
//                            && Surface::supports_queue_family(&surface, &qf)
//                )})
//                .ok_or("Could not find a graphical adapter")?;

            debug!("Adapters : {:#?}", adapter);

            let adapter = 
                Instance::enumerate_adapters(&instance)
                .into_iter()
                .find(|a| {
                    a.queue_families
                        .iter()
                        .any(|qf| 
                            QueueFamily::queue_type(qf).supports_graphics()
                            && Surface::supports_queue_family(&surface, &qf)
                )})
                .ok_or("Could not find a graphical adapter")?;

            info!("Selected adapter : {}", adapter.info.name);

            // get the suitable queue family index
            let queue_family = adapter
                .queue_families
                .iter()
                .find(|qf| 
                    QueueFamily::queue_type(*qf).supports_graphics()
                    && Surface::supports_queue_family(&surface, &qf))
                .ok_or("Could not find suitable queue_family")?;

            // get the related physical device and queue family list
            let Gpu {device, queue_groups} = unsafe {
                use gfx_hal::{
                    adapter::PhysicalDevice,
                    Features,
                };

                adapter
                    .physical_device
                    .open(&[(&queue_family, &[1.0; 1])], Features::empty())
                    .map_err(|_| "Could not open physical device")?
            };

            // retrieve the selected queue family
            let queue_group = queue_groups
                .into_iter()
                .find(|qg| qg.family == queue_family.id())
                .ok_or("Could not take ownership of the queue")?;

            // check our harvest
            if queue_group.queues.len() <= 0 {
                return Err("The QueueGroup does not have any CommandQueues available");
            };

            (adapter, device, queue_group)
        };

        let (swapchain, extent, backbuffer, format, image_count) = {
            use gfx_hal::window::{
                SwapchainConfig,
                Surface,
            };

            let capabilities = surface.capabilities(&adapter.physical_device);
            debug!("{:#?}", capabilities);

            // select optimal presentation mode (vsync, triple buffuring, ...)
            let present_mode = {
                use gfx_hal::window::PresentMode;

                [PresentMode::MAILBOX, PresentMode::FIFO, 
                 PresentMode::RELAXED, PresentMode::IMMEDIATE]
                    .iter()
                    .cloned()
                    .find(|pm| capabilities.present_modes.contains(*pm))
                    .ok_or("No PresentMode found")?
            };

            // select optimal alpha composition
//            let composite_alpha_mode = {
//                use gfx_hal::window::CompositeAlphaMode;
//
//                [CompositeAlphaMode::OPAQUE, CompositeAlphaMode::INHERIT, 
//                 CompositeAlphaMode::PREMULTIPLIED, CompositeAlphaMode::POSTMULTIPLIED]
//                    .iter()
//                    .cloned()
//                    .find(|cam| capabilities.composite_alpha_modes.contains(*cam))
//                    .ok_or("No CompositeAlphaMode found")?
//            };

            // select optimal format (sRGB)
            let format = {
                use gfx_hal::format::{Format, ChannelType};

                match surface.supported_formats(&adapter.physical_device) {
                    None => Format::Rgba8Srgb,
                    Some(formats) => formats
                        .iter()
                        .find(|f| f.base_format().1 == ChannelType::Srgb)
                        .cloned()
                        .ok_or("Could no find suitabe format")?
            }};

            let extent = capabilities.extents.end().clone();

            // verify swapchain size
            let image_count = {
                use gfx_hal::window::PresentMode;

                capabilities.image_count.end()
                    .min(capabilities.image_count.start()
                    .max(match present_mode {
                        PresentMode::MAILBOX => &3,
                        PresentMode::FIFO => &2,
                        _ => &1,
                    })).clone()
            };
            debug!("image count : {}", image_count);

//            // a surface support at least one layer
//            let image_layers = 1;
//
//            // verify surface compatibility
//            let image_usage = {
//                use gfx_hal::image::Usage;
//
//                if capabilities.usage.contains(Usage::COLOR_ATTACHMENT) {
//                    Ok(Usage::COLOR_ATTACHMENT)
//                } else {
//                    Err("This surface does not support color")
//                }
//            }?;

            let swapchain_config = SwapchainConfig::from_caps(&capabilities, format, extent);
            debug!("{:?}", swapchain_config);

            let (swapchain, backbuffer) = unsafe {
                device
                    .create_swapchain(&mut surface, swapchain_config, None)
                    .map_err(|_| "Failed to create swapchain and backbuffer")?
            };

            (swapchain, extent, backbuffer, format, image_count as usize)
        };

        // creating semaphores and fences
        let (sems_image_available, sems_render_finished, fences) = {

            let mut sems_image_available : Vec<<vk_back::Backend as Backend>::Semaphore> = vec![];
            let mut sems_render_finished : Vec<<vk_back::Backend as Backend>::Semaphore> = vec![];
            let mut fences :Vec<<vk_back::Backend as Backend>::Fence> = vec![];

            for _ in 0..image_count {
                sems_image_available
                    .push(device
                        .create_semaphore()
                        .map_err(|_| "Could not create sempahore")?
                    );
                sems_render_finished
                    .push(device
                        .create_semaphore()
                        .map_err(|_| "Could not create sempahore")?
                    );
                fences
                    .push(device
                        .create_fence(true)
                        .map_err(|_| "Could not create fence")?
                    );
            }

            (sems_image_available, sems_render_finished, fences)
        };

        // creating RenderPass
        let render_pass = {
            use gfx_hal::{
                pass::{Attachment, AttachmentOps, AttachmentLoadOp, AttachmentStoreOp, SubpassDesc},
                image::Layout,
            };

            let color_attachment = Attachment {
                format : Some(format),
                samples : 1,
                ops : AttachmentOps {
                    load : AttachmentLoadOp::Clear,
                    store : AttachmentStoreOp::Store,
                },
                stencil_ops : AttachmentOps::DONT_CARE,
                layouts : (Layout::Undefined..Layout::Present),
            };

            let subpass = SubpassDesc {
                colors : &[(0, Layout::ColorAttachmentOptimal)],
                depth_stencil : None,
                inputs : &[],
                resolves : &[],
                preserves : &[],
            };

            unsafe {
                device.create_render_pass(&[color_attachment], &[subpass], &[])
                    .map_err(|_| "Could not create render pass")?
            }
        };

        // add ImageView "headers" to images in BackBuffer
        let image_views : Vec<_> = {
            use gfx_hal::{
                image::{ViewKind, SubresourceRange},
                format::{Swizzle, Aspects},
            };

            backbuffer
                .iter()
                .map(|img| unsafe {
                    device
                        .create_image_view(
                            &img,
                            ViewKind::D2,
                            format,
                            Swizzle::NO,
                            SubresourceRange {
                                aspects : Aspects::COLOR,
                                levels : 0..1,
                                layers : 0..1,
                            },
                        )
                        .map_err(|_| "Could not create ImageViews")
                })
                .collect::<Result<Vec<_>, &str>>()?
        };

        let framebuffers: Vec<_> = {

            image_views
                .iter()
                .map(|image_view|
                    unsafe {
                        device
                            .create_framebuffer(&render_pass, vec![image_view], extent.to_extent())
                            .map_err(|_| "Could not create FrameBuffer")
                    },
                )
                .collect::<Result<Vec<_>, &str>>()?
        };

        let mut command_pool = unsafe {
            use gfx_hal::pool::CommandPoolCreateFlags;

            device
                .create_command_pool(queue_group.family, CommandPoolCreateFlags::RESET_INDIVIDUAL)
                .map_err(|_| "Could not create CommandPool")?
        };

        let command_buffers: Vec<_> = unsafe {
            use gfx_hal::command::Level;

            framebuffers
                .iter()
                .map(|_| command_pool.allocate_one(Level::Primary))
                .collect()
        };

        info!("HAL successfully initialized");

        Ok(
            HalState {
                instance: ManuallyDrop::new(instance),
                surface: ManuallyDrop::new(surface),
                adapter: ManuallyDrop::new(adapter),
                device: device,
                queue_group: ManuallyDrop::new(queue_group),
                render_pass: ManuallyDrop::new(render_pass),
                swapchain: ManuallyDrop::new(swapchain),
                extent: extent,
                format: format,
                render_area: Rect{x: 0, y: 0, w: 1280, h: 720},
                sems_image_available,
                sems_render_finished,
                fences,
                image_views,
                framebuffers,

                command_pool: ManuallyDrop::new(command_pool),
                command_buffers,

                image_count,
                current_image: 0,
            }
        )
    }
}