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

use std::{
    mem::ManuallyDrop,
    ptr::read,
    collections::VecDeque,
};

use gfx_hal::{
    window::{Extent2D, AcquireError, PresentationSurface, SurfaceCapabilities, SwapchainConfig},
    pso::Rect as GfxRect,
    format::Format,
};

mod frame;
use frame::Frame;

use super::gpu::Gpu;

//--SwapSystem implementation-----------------------------------------------------------------------
#[derive(Debug)]
pub struct SwapSystem<B: gfx_hal::Backend> {
    surface: ManuallyDrop<B::Surface>,
    format: Format,
    extent: Extent2D,
    pub render_area: GfxRect, //TODO may not be needed (duplicate of extent)
    pub render_pass: ManuallyDrop<B::RenderPass>, //TODO move to Pipeline ?
    frames: VecDeque<Frame<B>>,
    frame_nb: usize,
}

impl<B> SwapSystem<B>
where
    B: gfx_hal::Backend,
{
    pub fn drop(&mut self, gpu: &mut Gpu<B>) -> B::Surface {
        use gfx_hal::device::Device;

        debug!("Dropping SwapSystem...");
        for mut frame in self.frames.drain(..) {
            frame.drop(gpu);
        }
        unsafe {
            gpu.device().destroy_render_pass(
                ManuallyDrop::into_inner(read(&mut self.render_pass)));
            //render_area extent and format can be dropped automatically
            self.surface.unconfigure_swapchain(gpu.device());
            trace!("SwapSystem dropped !");
            ManuallyDrop::take(&mut self.surface)
        }
    }

    pub fn new(gpu: &mut Gpu<B>, mut surface: B::Surface) 
        -> Result<SwapSystem<B>, &'static str> 
    {

        debug!("Creating SwapSystem...");
        trace!("Obtaining surface capabilities...");
        let capabilities = {
            use gfx_hal::window::Surface;

            surface.capabilities(&gpu.adapter().physical_device)
        };
        debug!("Surface capabitlities : {:#?}", capabilities);

        trace!("Selecting image format...");
        let format = {
            use gfx_hal::{
                format::ChannelType,
                window::Surface,
            };

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

        trace!("Getting surface's render area size...");
        let extent = capabilities.current_extent
            .unwrap_or(*capabilities.extents.end())
            .clone();
        let render_area = GfxRect{x: 0, y: 0, w: extent.width as i16, h: extent.height as i16};

        trace!("Generating Swapchain configuration...");
        let (swapchain_config, frame_nb) = 
            generate_swapchain_config(capabilities, &format, &extent)?;
        debug!("Swapchain configuration : {:#?}", swapchain_config);

        trace!("Configuring Swapchain...");
        let _ = unsafe {
            surface
                .configure_swapchain(gpu.device(), swapchain_config)
                .map_err(|_| "Failed to create swapchain and backbuffer")?
        };

        trace!("Creating RenderPass...");
        let render_pass = {
            use gfx_hal::{
                pass::{Attachment, AttachmentOps, AttachmentLoadOp, AttachmentStoreOp, SubpassDesc},
                image::Layout,
                device::Device,
            };

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

        warn!("Generating hard-coded number of frames !");
        let mut frames = VecDeque::with_capacity(frame_nb);
        for _ in 0..frame_nb {
            let frame = Frame::new(gpu)
                .map_err(|_| "Could not create frame")?;
            frames.push_back(frame);
        };

        let frame_nb = frames.len();

        trace!("Created SwapSystem !");
        Ok( SwapSystem {
            surface: ManuallyDrop::new(surface),
            format,
            extent,
            render_area,
            render_pass: ManuallyDrop::new(render_pass),
            frames,
            frame_nb,
        })
    }

    pub fn recreate(&mut self, gpu: &mut Gpu<B>) -> Result<(), &'static str> {

        trace!("Obtaining surface capabilities...");
        let capabilities = {
            use gfx_hal::window::Surface;

            self.surface.capabilities(&gpu.adapter().physical_device)
        };
        debug!("Surface capabitlities : {:#?}", capabilities);

        trace!("Getting surface's render area size...");
        self.extent = capabilities.current_extent
            .unwrap_or(*capabilities.extents.end())
            .clone();
        self.render_area = 
            GfxRect{x: 0, y: 0, w: self.extent.width as i16, h: self.extent.height as i16};

        trace!("Generating Swapchain configuration...");
        let (swapchain_config, _frame_nb) = //TODO check frame nb change
            generate_swapchain_config(capabilities, &self.format, &self.extent)?;
        debug!("Swapchain configuration : {:#?}", swapchain_config);

        trace!("Configuring Swapchain...");
        let _ = unsafe {
            self.surface
                .configure_swapchain(gpu.device(), swapchain_config)
                .map_err(|_| "Failed to create swapchain and backbuffer")?
        };

        Ok(())
    }

    pub fn acquire_frame(&mut self, gpu: &Gpu<B>) -> Result<Frame<B>, AcquireError> {

        trace!("Acquiring Frame...");
        let image = unsafe {
            match self.surface.acquire_image(core::u64::MAX) {
                Ok((image, suboptimal)) => {
                    match suboptimal {
                        Some(_) => return Err(AcquireError::OutOfDate),
                        None => image,
                }},
                Err(err) => return Err(err),
        }};
        //println!("Frame nb : {}", self.frames.len());
        //frames number diminish sometimes at resize...
        let mut frame = self.frames.pop_back().unwrap();

        trace!("Creating Framebuffer...");
        let framebuffer = unsafe {
            use gfx_hal::device::Device;
            use std::borrow::Borrow;

            gpu.device()
                .create_framebuffer(&self.render_pass,
                                    vec![image.borrow()],
                                    self.extent.clone().to_extent())
                .unwrap() //TODO improve that
        };

        frame.link_swapchain_image(gpu, image, framebuffer);
        
        Ok(frame)
    }

    pub fn present_frame(&mut self, mut frame: Frame<B>, gpu: &mut Gpu<B>) 
        -> Result<(), &'static str> {
        use gfx_hal::queue::CommandQueue;

        let image = frame
            .unlink_swapchain_image()
            .unwrap(); //TODO improve that
    
        trace!("Presenting Frame...");
        let _ = unsafe {
            gpu.queue_mut()
                .present(&mut self.surface, image, Some(&frame.signal_semaphores[0]))
                .map_err(|_| "Failed to present into the swapchain")?;
        };

        self.frames.push_front(frame);

        Ok(())
    }
}

fn generate_swapchain_config(capabilities: SurfaceCapabilities, 
                             format: &Format, 
                             extent: &Extent2D) 
    -> Result<(SwapchainConfig, usize), &'static str> {

    trace!("Generating Swapchain configuration...");
    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 values specified!")?
    };

    let composite_alpha_mode = {
        use gfx_hal::window::CompositeAlphaMode;

        [CompositeAlphaMode::OPAQUE, CompositeAlphaMode::INHERIT, 
        CompositeAlphaMode::PREMULTIPLIED, CompositeAlphaMode::POSTMULTIPLIED]
            .iter()
            .cloned()
            .find(|ca| capabilities.composite_alpha_modes.contains(*ca))
            .ok_or("No CompositeAlpha values specified!")?
    };

    let image_count = {
        use std::cmp::{min, max};
        use gfx_hal::window::PresentMode;

        let count = match present_mode {
            PresentMode::MAILBOX => 3,
            _ => 2, //TODO to be checked
        };
        max(capabilities.image_count.start().clone(), 
            min(capabilities.image_count.end().clone(), count))
    };

    warn!("Hard-coding number of layers per image !");
    let image_layers = 1;

    let image_usage = {
        use gfx_hal::image::Usage;

        if capabilities.usage.contains(Usage::COLOR_ATTACHMENT) {
            Usage::COLOR_ATTACHMENT 
        } else { 
            Err("The Surface isn't capable of supporting color!")?  
    }};

    Ok (( 
        SwapchainConfig {
            present_mode,
            composite_alpha_mode,
            format: format.clone(),
            extent: extent.clone(),
            image_count: image_count.clone(),
            image_layers,
            image_usage,
        },
        image_count as usize
    ))
}