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

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

use crate::{
    io::Output,
    utils::Triangle,
    
};

mod gpu;
use self::gpu::Gpu;

mod swap_system;
use self::swap_system::SwapSystem;

mod pipeline;
use self::pipeline::Pipeline;

//--Renderer implementation-------------------------------------------------------------------------
#[derive(Debug)]
pub struct Renderer<B: gfx_hal::Backend> {
    instance: ManuallyDrop<B::Instance>,
    gpu: ManuallyDrop<Gpu<B>>,
    swap_systems: Vec<SwapSystem<B>>,
    pipelines: Vec<Pipeline<B>>,
}

impl<B> Drop for Renderer<B>
where
    B: gfx_hal::Backend,
{
    fn drop(&mut self) {
        use gfx_hal::{
            Instance,
            device::Device,
        };

        debug!("Dropping Pipelines...");
        for pipeline in self.pipelines.drain(..) {
            pipeline.drop(&mut self.gpu);
        }

        debug!("Waiting for device to idle...");
        let _ = self.gpu
            .device()
            .wait_idle();

        info!("Dropping Renderer..."); 
        unsafe {
            for mut swap_system in self.swap_systems.drain(..) {
                self.instance.destroy_surface(swap_system.drop(&mut self.gpu));
            }
            ManuallyDrop::drop(&mut self.gpu);
            ManuallyDrop::drop(&mut self.instance);
        }
        trace!("Renderer dropped !");
    }
}

impl<B> Renderer<B>
where
    B: gfx_hal::Backend,
{
    pub fn new<'a, W: 'a, O: 'a, I>(outputs: &mut I) -> Result<Renderer<B>, &'static str>
    where 
        W: raw_window_handle::HasRawWindowHandle,
        O: Output<W>,
        I: Iterator<Item = &'a RefCell<O>>,
    {
        use gfx_hal::Instance;

        info!("Creating renderer...");
        let instance = B::Instance::create("IV", 1)
            .map_err(|_| "Could not create instance")?;
        let (mut gpu, mut surfaces) = Gpu::new(&instance, outputs)
            .map_err(|err| err)?; 
        let swap_systems = {
            surfaces
                .drain(..)
                .map(|surface| SwapSystem::new(&mut gpu, surface))
                .collect::<Result<Vec<_>,  &str>>()?
        };
        let pipelines = vec!(Pipeline::new(&mut gpu, &swap_systems[0]) //TODO improve that
            .map_err(|err| err)?);

        debug!("Renderer created !");
        Ok( Renderer {
            instance: ManuallyDrop::new(instance),
            gpu: ManuallyDrop::new(gpu),
            swap_systems,
            pipelines,
        })
    }

    pub fn draw_clear_frame<W, O>(&mut self, output: &RefCell<O>, color: [f32; 4])
        -> Result<(), &'static str> 
    where
        W: raw_window_handle::HasRawWindowHandle,
        O: Output<W>,
    {
        use gfx_hal::{
            window::AcquireError,
            device::Device,
            queue::Submission,
        };

        let swap_system = &mut self.swap_systems[output.borrow_mut().get_id()];

        let mut frame = match swap_system.acquire_frame(&self.gpu) {
            Ok(frame) => frame,
            Err(err) => match err {
                AcquireError::NotReady => {
                    return Err("Frame acquisition failed because all Frames are in use");
                },
                AcquireError::OutOfDate => {
                    swap_system.recreate(&mut self.gpu)?;
                    debug!("SwapSystem : {:#?}", swap_system);
                    return Ok(());
                },
                _ => Err("Could not acquire Frame from SwapSystem")?,
        }};

        trace!("Waiting for Frame...");
        unsafe {
            let _ = self.gpu.device()
                .wait_for_fence(&frame.fences[0], !0)
                .map_err(|_| "Failed to wait for Fence")?;
            let _ = self.gpu.device()
                .reset_fence(&frame.fences[0])
                .map_err(|_| "Failed to reset fence")?;
        }

        trace!("Recording CommandBuffer...");
        unsafe {
            use gfx_hal::command::{
                CommandBufferFlags, 
                SubpassContents, 
                ClearValue, 
                ClearColor,
                CommandBuffer,
            };

            frame.command_buffer.begin_primary(CommandBufferFlags::ONE_TIME_SUBMIT);

            let clear_value = ClearValue {color: ClearColor{float32: color}};

            frame.command_buffer.begin_render_pass(
                &swap_system.render_pass,
                &frame.framebuffer.as_ref().unwrap(),
                swap_system.render_area,
                iter::once(clear_value),
                SubpassContents::Inline,
            );
            frame.command_buffer.end_render_pass();
            frame.command_buffer.finish();
        }

        trace!("Submiting to queue...");
        let submission = Submission {
            command_buffers: iter::once(&*frame.command_buffer),
            wait_semaphores: None,
            signal_semaphores: iter::once(&frame.signal_semaphores[0]),
        };

        unsafe {
            use gfx_hal::queue::CommandQueue;

            self.gpu.queue_mut().submit(submission, Some(&frame.fences[0]));
        }

        let result = swap_system.present_frame(frame, &mut self.gpu);
        if result.is_err() {
            swap_system.recreate(&mut self.gpu).unwrap();
        }

        Ok(())
    }

    pub fn draw_triangle_frame<W, O>(&mut self, 
                                     output: &RefCell<O>, 
                                     triangle: Triangle, 
                                     colors: [[f32; 3]; 3])
        -> Result<(), &'static str> 
    where
        W: raw_window_handle::HasRawWindowHandle,
        O: Output<W>,
    {
        use gfx_hal::{
            window::AcquireError,
            queue::Submission,
        };

        let swap_system = &mut self.swap_systems[output.borrow_mut().get_id()];

        let mut frame = match swap_system.acquire_frame(&self.gpu) {
            Ok(frame) => frame,
            Err(err) => match err {
                AcquireError::NotReady => {
                    return Err("Frame acquisition failed because all Frames are in use");
                },
                AcquireError::OutOfDate => {
                    swap_system.recreate(&mut self.gpu)?;
                    debug!("SwapSystem : {:#?}", swap_system);
                    return Ok(());
                },
                _ => Err("Could not acquire Frame from SwapSystem")?,
        }};

        trace!("Uploading triangle data...");
        let points = triangle.points_flat();
        self.pipelines[0].write_vertex_buffer(&self.gpu, 0, (&points).to_vec())?; //TODO meh
        let colors_flat = colors.iter().flatten().copied().collect();
        self.pipelines[0].write_vertex_buffer(&self.gpu, 1, colors_flat)?;

        trace!("Recording CommandBuffer...");
        unsafe {
            use gfx_hal::command::{
                CommandBufferFlags, 
                SubpassContents, 
                ClearValue, 
                ClearColor,
                CommandBuffer,
            };

            frame.command_buffer.begin_primary(CommandBufferFlags::ONE_TIME_SUBMIT);

            const TRIANGLE_CLEAR: ClearValue = 
                ClearValue {color : ClearColor{float32 : [0.5, 0.5, 0.5, 1.0]}};

            frame.command_buffer.begin_render_pass(
                &swap_system.render_pass,
                &frame.framebuffer.as_ref().unwrap(),
                swap_system.render_area,
                iter::once(TRIANGLE_CLEAR),
                SubpassContents::Inline,
            );
            frame.command_buffer.bind_graphics_pipeline(self.pipelines[0].raw_pipeline());

            // storing const data via the CommandBuffer
            //let buffer_ref: &B::Buffer = &self.buffer;
            //let buffers: Vec<[_; 1]> = vec![(buffer_ref, 0)].into();
            frame.command_buffer.bind_vertex_buffers(0, self.pipelines[0].raw_vertex_buffers());

            frame.command_buffer.draw(0..3, 0..1);
            frame.command_buffer.end_render_pass();
            frame.command_buffer.finish();
        }

        trace!("Submiting to queue...");
        let submission = Submission {
            command_buffers: iter::once(&*frame.command_buffer),
            wait_semaphores: None,
            signal_semaphores: iter::once(&frame.signal_semaphores[0]),
        };

        unsafe {
            use gfx_hal::queue::CommandQueue;

            self.gpu.queue_mut().submit(submission, Some(&frame.fences[0]));
        }

        let result = swap_system.present_frame(frame, &mut self.gpu);
        if result.is_err() {
            swap_system.recreate(&mut self.gpu).unwrap();
        }

        Ok(())

    }
}