use std::sync::{Arc};
use log::info;
use pollster::FutureExt;
use wgpu::{Adapter, Device, Instance, PresentMode, Queue, Surface, SurfaceCapabilities, SurfaceConfiguration, SurfaceError};
use winit::dpi::PhysicalSize;
use winit::window::{Window};
use crate::camera::Camera;
use crate::geometry_manager::GeometryManager;
use crate::globals_manager::GlobalsManager;
use crate::instance_manager::{InstanceManager, RenderInstance};
use crate::light_manager::{LightManager};
use crate::material_manager::{GpuMaterial, MaterialManager};
use crate::render_manager::{RenderManager};

pub struct SampleCount(pub u32);
type RenderResult = Result<(), SurfaceError>;

impl SampleCount {
    pub fn get(&self) -> u32 {
        self.0
    }
}

pub struct EngineState<'a> {
    surface: Surface<'a>,
    device: Device,
    queue: Queue,
    config: SurfaceConfiguration,
    sample_count: SampleCount,
    size: PhysicalSize<u32>,

    window: Arc<Window>,
    pub camera: Camera,

    pub globals_manager: GlobalsManager,
    pub geometry_manager: GeometryManager,
    pub instance_manager: InstanceManager,
    pub light_manager: LightManager,
    pub material_manager: MaterialManager,
    pub render_manager: RenderManager,
}

impl<'a> EngineState<'a> {
    pub(crate) fn new(window: Window) -> Self {
        let window = Arc::new(window);
        let size = window.inner_size();

        let instance = Self::create_gpu_instance();

        let surface = instance.create_surface(window.clone()).unwrap();

        let adapter = Self::create_adapter(instance, &surface);

        let (device, queue) = Self::create_device(&adapter);

        let capabilities = surface.get_capabilities(&adapter);
        let config = Self::create_surface_config(size, capabilities);
        surface.configure(&device, &config);

        let sample_count = SampleCount(Self::probe_msaa_support(&device, &config));
        info!("MSAA sample count: {}", sample_count.get());

        let camera = Camera::new(config.width as f32 / config.height as f32);

        let globals_manager = GlobalsManager::new(&device, config.width, config.height, &camera);
        let geometry_manager = GeometryManager::new(&device);
        let instance_manager = InstanceManager::new(&device);
        let mut light_manager = LightManager::new(&device, 100);

        let mut material_manager = MaterialManager::new(&device);

        let render_manager = RenderManager::new(
            &device,
            &config,
            &globals_manager,
            &mut light_manager,
            &material_manager,
            &camera,
            sample_count.get(),
        );
        
        Self {
            surface,
            device,
            queue,
            config,
            sample_count,
            size,
            window,
            camera,
            globals_manager,
            geometry_manager,
            instance_manager,
            light_manager,
            material_manager,
            render_manager,
        }
    }

    fn probe_msaa_support(device: &Device, config: &SurfaceConfiguration) -> u32 {
        pollster::block_on(async {
            for &count in &[16, 8, 4, 2] {
                device.push_error_scope(wgpu::ErrorFilter::Validation);

                let _ = device.create_texture(&wgpu::TextureDescriptor {
                    label: Some("MSAA Probe"),
                    size: wgpu::Extent3d {
                        width: 4,
                        height: 4,
                        depth_or_array_layers: 1,
                    },
                    mip_level_count: 1,
                    sample_count: count,
                    dimension: wgpu::TextureDimension::D2,
                    format: config.format,
                    usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
                    view_formats: &[],
                });

                if device.pop_error_scope().await.is_none() {
                    return count;
                }
            }

            2 // fallback
        })
    }

    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]);

        SurfaceConfiguration {
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            format: surface_format,
            width: size.width,
            height: size.height,
            present_mode: PresentMode::AutoVsync,
            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::TEXTURE_ADAPTER_SPECIFIC_FORMAT_FEATURES,
                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(crate) fn resize(&mut self, new_size: PhysicalSize<u32>) {
        if new_size.width > 0 && new_size.height > 0 {
            self.size = new_size;
            self.config.width = new_size.width;
            self.config.height = new_size.height;
            self.surface.configure(&self.device, &self.config);

            self.camera.set_aspect(new_size.width as f32 / new_size.height as f32);
            self.globals_manager.resize(&self.queue, new_size.width, new_size.height, &self.camera);
            self.render_manager.resize(&self.device, new_size.width, new_size.height);
        }
    }

    pub fn update(&mut self) {}

    pub fn render(&mut self) -> RenderResult {
        let output = self.surface.get_current_texture()?;
        let view = output.texture.create_view(&Default::default());

        self.render_manager.render_frame(
            &self.device,
            &self.queue,
            output,
            &view,
            self.config.format,
            &mut self.globals_manager,
            &self.camera,
            &mut self.light_manager,
            &self.geometry_manager,
            &self.instance_manager,
            &mut self.material_manager
        )
    }
    
    pub fn set_materials(&mut self, materials: Vec<GpuMaterial>) {
        self.material_manager.set_materials(&self.device, materials);
    }
    
    pub fn set_instances(&mut self, instances: Vec<RenderInstance>) {
        self.instance_manager.set_instances(&self.device, &self.queue, instances);
    }

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

    pub fn camera_mut(&mut self) -> &mut crate::camera::Camera {
        &mut self.camera
    }

    pub fn camera(&self) -> &crate::camera::Camera {
        &self.camera
    }
}