use std::cmp::max;
use std::sync::Arc;

use pollster::FutureExt;
use wgpu::{Adapter, Device, Instance, PresentMode, Queue, Surface, SurfaceCapabilities};
use winit::application::ApplicationHandler;
use winit::dpi::PhysicalSize;
use winit::event::WindowEvent;
use winit::event_loop::{ActiveEventLoop, EventLoop};
use winit::window::{Window, WindowId};

pub async fn run() {
    let event_loop = EventLoop::new().unwrap();

    let mut window_state = StateApplication::new();
    let _ = event_loop.run_app(&mut window_state);
}

struct StateApplication<'a> {
    state: Option<State<'a>>,
}

impl<'a> StateApplication<'a> {
    pub fn new() -> Self {
        Self {
            state: None,
        }
    }
}

impl<'a> ApplicationHandler for StateApplication<'a>{
    fn resumed(&mut self, event_loop: &ActiveEventLoop) {
        let window = event_loop.create_window(Window::default_attributes().with_title("Hello!")).unwrap();
        self.state = Some(State::new(window));
    }

    fn window_event(&mut self, event_loop: &ActiveEventLoop, window_id: WindowId, event: WindowEvent) {
        let window = self.state.as_ref().unwrap().window();

        if window.id() == window_id {
            match event {
                WindowEvent::CloseRequested => {
                    event_loop.exit();
                }
                WindowEvent::Resized(physical_size) => {
                    self.state.as_mut().unwrap().resize(physical_size);
                }
                WindowEvent::RedrawRequested => {
                    self.state.as_mut().unwrap().update();
                    self.state.as_mut().unwrap().render().unwrap();
                }
                WindowEvent::KeyboardInput { .. } => {
                    if let Some(state) = self.state.as_mut() {
                        if state.input(&event) {
                            return;
                        }
                    }
                }
                _ => {}
            }
        }
    }

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

struct State<'a> {
    surface: Surface<'a>,
    device: Device,
    queue: Queue,
    config: wgpu::SurfaceConfiguration,

    size: PhysicalSize<u32>,
    window: Arc<Window>,
}

impl<'a> State<'a> {
    pub fn new (window: Window) -> Self {
        let window_arc = Arc::new(window);
        let size = window_arc.inner_size();
        let instance = Self::create_gpu_instance();
        let surface = instance.create_surface(window_arc.clone()).unwrap();
        let adapter = Self::create_adapter(instance, &surface);
        let (device, queue) = Self::create_device(&adapter);
        let surface_caps = surface.get_capabilities(&adapter);
        let config = Self::create_surface_config(size, surface_caps);
        surface.configure(&device, &config);

        Self {
            surface,
            device,
            queue,
            config,
            size,
            window: window_arc,
        }
    }

    pub fn input(&mut self, event: &WindowEvent) -> bool {
        false
    }

    fn update(&mut self) {
        // TODO: Update logic here
    }

    fn create_surface_config(size: PhysicalSize<u32>, capabilities: SurfaceCapabilities) -> wgpu::SurfaceConfiguration {
        let surface_format = capabilities.formats.iter()
            .find(|f| f.is_srgb())
            .copied()
            .unwrap_or(capabilities.formats[0]);

        wgpu::SurfaceConfiguration {
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            format: surface_format,
            width: size.width,
            height: size.height,
            present_mode: PresentMode::AutoNoVsync,
            alpha_mode: capabilities.alpha_modes[0],
            view_formats: vec![],
            desired_maximum_frame_latency: 2,
        }
    }

    fn create_device(adapter: &Adapter) -> (Device, Queue) {
        adapter.request_device(
            &wgpu::DeviceDescriptor {
                required_features: wgpu::Features::empty(),
                required_limits: wgpu::Limits::default(),
                memory_hints: Default::default(),
                label: None,
                trace: Default::default(),
            }).block_on().unwrap()
    }

    fn create_adapter(instance: Instance, surface: &Surface) -> Adapter {
        instance.request_adapter(
            &wgpu::RequestAdapterOptions {
                power_preference: wgpu::PowerPreference::default(),
                compatible_surface: Some(&surface),
                force_fallback_adapter: false,
            }
        ).block_on().unwrap()
    }

    fn create_gpu_instance() -> Instance {
        Instance::new(&wgpu::InstanceDescriptor {
            backends: wgpu::Backends::PRIMARY,
            ..Default::default()
        })
    }

    pub fn resize(&mut self, new_size: PhysicalSize<u32>) {
        self.size = new_size;

        self.config.width = max(new_size.width, 1);
        self.config.height = max(new_size.height, 1);

        self.surface.configure(&self.device, &self.config);

        println!("Resized to {:?} from state!", new_size);
    }

    pub fn render(&mut self) -> Result<(), wgpu::SurfaceError> {
        let output = self.surface.get_current_texture().unwrap();
        let view = output.texture.create_view(&wgpu::TextureViewDescriptor::default());

        let mut encoder = self.device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
            label: Some("Render Encoder"),
        });

        {
            let _render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                label: Some("Render Pass"),
                color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                    view: &view,
                    resolve_target: None,
                    ops: wgpu::Operations {
                        load: wgpu::LoadOp::Clear(wgpu::Color {
                            r: 1.0,
                            g: 0.2,
                            b: 0.3,
                            a: 1.0,
                        }),
                        store: wgpu::StoreOp::Store,
                    }
                })],
                depth_stencil_attachment: None,
                occlusion_query_set: None,
                timestamp_writes: None,
            });
        }

        self.queue.submit(std::iter::once(encoder.finish()));
        output.present();

        Ok(())
    }

    pub fn window(&self) -> &Window {
        &self.window
    }
}

fn main() {
    pollster::block_on(run());
}