// Welcome to the deferred lighting example!
//
// The idea behind deferred lighting is to render the scene in two steps.
//
// First you draw all the objects of the scene. But instead of calculating the color they will have
// on the screen, you output their characteristics such as their diffuse color and their normals,
// and write this to images.
//
// After all the objects are drawn, you should obtain several images that contain the
// characteristics of each pixel.
//
// Then you apply lighting to the scene. In other words you draw to the final image by taking these
// intermediate images and the various lights of the scene as input.
//
// This technique allows you to apply tons of light sources to a scene, which would be too
// expensive otherwise. It has some drawbacks, which are the fact that transparent objects must be
// drawn after the lighting, and that the whole process consumes more memory.

use crate::{
    frame::{FrameSystem, Pass},
    triangle_draw_system::TriangleDrawSystem,
};
use cgmath::{Matrix4, SquareMatrix, Vector3};
use std::{error::Error, sync::Arc};
use vulkano::{
    command_buffer::allocator::{
        StandardCommandBufferAllocator, StandardCommandBufferAllocatorCreateInfo,
    },
    device::{
        physical::PhysicalDeviceType, Device, DeviceCreateInfo, DeviceExtensions, QueueCreateInfo,
        QueueFlags,
    },
    image::{view::ImageView, ImageUsage},
    instance::{Instance, InstanceCreateFlags, InstanceCreateInfo},
    memory::allocator::StandardMemoryAllocator,
    swapchain::{
        acquire_next_image, Surface, Swapchain, SwapchainCreateInfo, SwapchainPresentInfo,
    },
    sync::{self, GpuFuture},
    Validated, VulkanError, VulkanLibrary,
};
use winit::{
    event::{Event, WindowEvent},
    event_loop::{ControlFlow, EventLoop},
    window::WindowBuilder,
};

mod frame;
mod triangle_draw_system;

fn main() -> Result<(), impl Error> {
    // Basic initialization. See the triangle example if you want more details about this.

    let event_loop = EventLoop::new().unwrap();

    let library = VulkanLibrary::new().unwrap();
    let required_extensions = Surface::required_extensions(&event_loop).unwrap();
    let instance = Instance::new(
        library,
        InstanceCreateInfo {
            flags: InstanceCreateFlags::ENUMERATE_PORTABILITY,
            enabled_extensions: required_extensions,
            ..Default::default()
        },
    )
    .unwrap();

    let window = Arc::new(WindowBuilder::new().build(&event_loop).unwrap());
    let surface = Surface::from_window(instance.clone(), window.clone()).unwrap();

    let device_extensions = DeviceExtensions {
        khr_swapchain: true,
        ..DeviceExtensions::empty()
    };
    let (physical_device, queue_family_index) = instance
        .enumerate_physical_devices()
        .unwrap()
        .filter(|p| p.supported_extensions().contains(&device_extensions))
        .filter_map(|p| {
            p.queue_family_properties()
                .iter()
                .enumerate()
                .position(|(i, q)| {
                    q.queue_flags.intersects(QueueFlags::GRAPHICS)
                        && p.surface_support(i as u32, &surface).unwrap_or(false)
                })
                .map(|i| (p, i as u32))
        })
        .min_by_key(|(p, _)| match p.properties().device_type {
            PhysicalDeviceType::DiscreteGpu => 0,
            PhysicalDeviceType::IntegratedGpu => 1,
            PhysicalDeviceType::VirtualGpu => 2,
            PhysicalDeviceType::Cpu => 3,
            PhysicalDeviceType::Other => 4,
            _ => 5,
        })
        .unwrap();

    println!(
        "Using device: {} (type: {:?})",
        physical_device.properties().device_name,
        physical_device.properties().device_type,
    );

    let (device, mut queues) = Device::new(
        physical_device,
        DeviceCreateInfo {
            enabled_extensions: device_extensions,
            queue_create_infos: vec![QueueCreateInfo {
                queue_family_index,
                ..Default::default()
            }],
            ..Default::default()
        },
    )
    .unwrap();
    let queue = queues.next().unwrap();

    let (mut swapchain, mut images) = {
        let surface_capabilities = device
            .physical_device()
            .surface_capabilities(&surface, Default::default())
            .unwrap();
        let image_format = device
            .physical_device()
            .surface_formats(&surface, Default::default())
            .unwrap()[0]
            .0;

        let (swapchain, images) = Swapchain::new(
            device.clone(),
            surface,
            SwapchainCreateInfo {
                min_image_count: surface_capabilities.min_image_count.max(2),
                image_format,
                image_extent: window.inner_size().into(),
                image_usage: ImageUsage::COLOR_ATTACHMENT,
                composite_alpha: surface_capabilities
                    .supported_composite_alpha
                    .into_iter()
                    .next()
                    .unwrap(),
                ..Default::default()
            },
        )
        .unwrap();
        let images = images
            .into_iter()
            .map(|image| ImageView::new_default(image).unwrap())
            .collect::<Vec<_>>();
        (swapchain, images)
    };

    let memory_allocator = Arc::new(StandardMemoryAllocator::new_default(device.clone()));
    let command_buffer_allocator = Arc::new(StandardCommandBufferAllocator::new(
        device.clone(),
        StandardCommandBufferAllocatorCreateInfo {
            secondary_buffer_count: 32,
            ..Default::default()
        },
    ));

    // Here is the basic initialization for the deferred system.
    let mut frame_system = FrameSystem::new(
        queue.clone(),
        swapchain.image_format(),
        memory_allocator.clone(),
        command_buffer_allocator.clone(),
    );
    let triangle_draw_system = TriangleDrawSystem::new(
        queue.clone(),
        frame_system.deferred_subpass(),
        memory_allocator.clone(),
        command_buffer_allocator,
    );

    let mut recreate_swapchain = false;
    let mut previous_frame_end = Some(sync::now(device.clone()).boxed());

    event_loop.run(move |event, elwt| {
        elwt.set_control_flow(ControlFlow::Poll);

        match event {
            Event::WindowEvent {
                event: WindowEvent::CloseRequested,
                ..
            } => {
                elwt.exit();
            }
            Event::WindowEvent {
                event: WindowEvent::Resized(_),
                ..
            } => {
                recreate_swapchain = true;
            }
            Event::WindowEvent {
                event: WindowEvent::RedrawRequested,
                ..
            } => {
                let image_extent: [u32; 2] = window.inner_size().into();

                if image_extent.contains(&0) {
                    return;
                }

                previous_frame_end.as_mut().unwrap().cleanup_finished();

                if recreate_swapchain {
                    let (new_swapchain, new_images) = swapchain
                        .recreate(SwapchainCreateInfo {
                            image_extent,
                            ..swapchain.create_info()
                        })
                        .expect("failed to recreate swapchain");
                    let new_images = new_images
                        .into_iter()
                        .map(|image| ImageView::new_default(image).unwrap())
                        .collect::<Vec<_>>();

                    swapchain = new_swapchain;
                    images = new_images;
                    recreate_swapchain = false;
                }

                let (image_index, suboptimal, acquire_future) =
                    match acquire_next_image(swapchain.clone(), None).map_err(Validated::unwrap) {
                        Ok(r) => r,
                        Err(VulkanError::OutOfDate) => {
                            recreate_swapchain = true;
                            return;
                        }
                        Err(e) => panic!("failed to acquire next image: {e}"),
                    };

                if suboptimal {
                    recreate_swapchain = true;
                }

                let future = previous_frame_end.take().unwrap().join(acquire_future);
                let mut frame = frame_system.frame(
                    future,
                    images[image_index as usize].clone(),
                    Matrix4::identity(),
                );
                let mut after_future = None;
                while let Some(pass) = frame.next_pass() {
                    match pass {
                        Pass::Deferred(mut draw_pass) => {
                            let cb = triangle_draw_system.draw(draw_pass.viewport_dimensions());
                            draw_pass.execute(cb);
                        }
                        Pass::Lighting(mut lighting) => {
                            lighting.ambient_light([0.1, 0.1, 0.1]);
                            lighting
                                .directional_light(Vector3::new(0.2, -0.1, -0.7), [0.6, 0.6, 0.6]);
                            lighting.point_light(Vector3::new(0.5, -0.5, -0.1), [1.0, 0.0, 0.0]);
                            lighting.point_light(Vector3::new(-0.9, 0.2, -0.15), [0.0, 1.0, 0.0]);
                            lighting.point_light(Vector3::new(0.0, 0.5, -0.05), [0.0, 0.0, 1.0]);
                        }
                        Pass::Finished(af) => {
                            after_future = Some(af);
                        }
                    }
                }

                let future = after_future
                    .unwrap()
                    .then_swapchain_present(
                        queue.clone(),
                        SwapchainPresentInfo::swapchain_image_index(swapchain.clone(), image_index),
                    )
                    .then_signal_fence_and_flush();

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