use anyhow::{Result, anyhow};
use pollster::FutureExt;
use wgpu::{
    Backends, BindGroup, BindGroupDescriptor, BindGroupLayoutDescriptor, BlendState, Color,
    ColorTargetState, ColorWrites, CommandEncoderDescriptor, Device, DeviceDescriptor, Features,
    FragmentState, FrontFace, Instance, InstanceDescriptor, Limits, LoadOp, MaintainBase,
    MultisampleState, Operations, PipelineCompilationOptions, PipelineLayoutDescriptor,
    PolygonMode, PowerPreference, PrimitiveState, PrimitiveTopology, Queue,
    RenderPassColorAttachment, RenderPassDescriptor, RenderPipeline, RenderPipelineDescriptor,
    RequestAdapterOptions, StoreOp, Surface, SurfaceConfiguration, TextureViewDescriptor,
    VertexState, include_wgsl,
};
use winit::window::Window;

pub struct Renderer<'a> {
    surface: Surface<'a>,
    pipeline: RenderPipeline,
    bind_group: BindGroup,
    queue: Queue,
    device: Device,
    surface_configuration: SurfaceConfiguration,
}
impl<'a> Renderer<'a> {
    pub fn new(window: &'a Window) -> Result<Self> {
        let instance = Instance::new(InstanceDescriptor {
            backends: Backends::all(),
            ..Default::default()
        });

        let surface = instance.create_surface(window)?;
        let adapter = instance
            .request_adapter(&RequestAdapterOptions {
                compatible_surface: Some(&surface),
                power_preference: PowerPreference::HighPerformance,
                ..Default::default()
            })
            .block_on()
            .ok_or(anyhow!("no adapter found"))?;

        let (device, queue) = adapter
            .request_device(
                &DeviceDescriptor {
                    required_features: Features::default(),
                    required_limits: Limits::downlevel_defaults(),
                    ..Default::default()
                },
                None,
            )
            .block_on()?;

        let surface_configuration = surface
            .get_default_config(&adapter, 256, 256)
            .ok_or(anyhow!("no default config"))?;

        let module = device.create_shader_module(include_wgsl!("shader.wgsl"));

        let bind_group_layout = device.create_bind_group_layout(&BindGroupLayoutDescriptor {
            entries: &[],
            label: None,
        });
        let bind_group = device.create_bind_group(&BindGroupDescriptor {
            label: None,
            layout: &bind_group_layout,
            entries: &[],
        });
        let pipeline_layout = device.create_pipeline_layout(&PipelineLayoutDescriptor {
            label: None,
            bind_group_layouts: &[&bind_group_layout],
            push_constant_ranges: &[],
        });
        let pipeline = device.create_render_pipeline(&RenderPipelineDescriptor {
            label: None,
            layout: Some(&pipeline_layout),
            fragment: Some(FragmentState {
                module: &module,
                entry_point: Some("fs_main"),
                targets: &[Some(ColorTargetState {
                    blend: Some(BlendState::PREMULTIPLIED_ALPHA_BLENDING),
                    format: surface_configuration.format,
                    write_mask: ColorWrites::all(),
                })],
                compilation_options: PipelineCompilationOptions::default(),
            }),
            vertex: VertexState {
                module: &module,
                entry_point: Some("vs_main"),
                buffers: &[],
                compilation_options: PipelineCompilationOptions::default(),
            },
            primitive: PrimitiveState {
                topology: PrimitiveTopology::TriangleList,
                front_face: FrontFace::Ccw,
                cull_mode: None, //Some(Face::Back),
                polygon_mode: PolygonMode::Fill,
                ..Default::default()
            },
            depth_stencil: Default::default(),
            multisample: MultisampleState::default(),
            multiview: None,
            cache: None,
        });

        surface.configure(&device, &surface_configuration);

        Ok(Self {
            surface,
            pipeline,
            bind_group,
            device,
            queue,
            surface_configuration,
        })
    }

    pub fn resize(&mut self, width: u32, height: u32) {
        self.surface_configuration.width = width;
        self.surface_configuration.height = height;
        self.surface
            .configure(&self.device, &self.surface_configuration);
    }

    pub fn draw(&mut self) -> Result<()> {
        let target = self.surface.get_current_texture()?;
        let target_view = target
            .texture
            .create_view(&TextureViewDescriptor::default());

        let mut commands = self
            .device
            .create_command_encoder(&CommandEncoderDescriptor { label: None });

        {
            let mut rpass = commands.begin_render_pass(&RenderPassDescriptor {
                label: None,
                color_attachments: &[Some(RenderPassColorAttachment {
                    view: &target_view,
                    resolve_target: None,
                    ops: Operations {
                        store: StoreOp::Store,
                        load: LoadOp::Clear(Color::BLUE),
                    },
                })],
                ..Default::default()
            });

            rpass.set_bind_group(0, &self.bind_group, &[]);
            rpass.set_pipeline(&self.pipeline);
            rpass.draw(0..3, 0..1);
        }

        let i = self.queue.submit(Some(commands.finish()));
        self.device.poll(MaintainBase::WaitForSubmissionIndex(i));

        target.present();

        Ok(())
    }
}