use std::{io, mem::size_of, vec};

use thiserror::Error;
use tracing::{debug, error, trace};
use wgpu::util::DeviceExt as _;

use crate::{
    camera::Camera,
    screen::{Screen, ScreenSize},
};

use super::{
    device::Device, draw_config::DrawConfig, drawables::Drawables,
    geometries::Geometries, navigation_cube::NavigationCubeRenderer,
    pipelines::Pipelines, transform::Transform, uniforms::Uniforms,
    vertices::Vertices, DeviceError, DEPTH_FORMAT, SAMPLE_COUNT,
};

/// Graphics rendering state and target abstraction
#[derive(Debug)]
pub struct Renderer {
    surface: wgpu::Surface,
    device: Device,

    surface_config: wgpu::SurfaceConfiguration,
    frame_buffer: wgpu::TextureView,
    depth_view: wgpu::TextureView,

    uniform_buffer: wgpu::Buffer,
    bind_group: wgpu::BindGroup,

    geometries: Geometries,
    pipelines: Pipelines,

    navigation_cube_renderer: NavigationCubeRenderer,
}

impl Renderer {
    /// Returns a new `Renderer`.
    pub async fn new(screen: &impl Screen) -> Result<Self, RendererInitError> {
        let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
            backends: wgpu::Backends::all(),
            ..Default::default()
        });

        // This is sound, as `window` is an object to create a surface upon.
        let surface = unsafe { instance.create_surface(screen.window()) }?;

        for adapter in instance.enumerate_adapters(wgpu::Backends::all()) {
            debug!("Available adapter: {:?}", adapter.get_info());
        }

        let result = Device::from_preferred_adapter(&instance, &surface).await;
        let (device, adapter, features) = match result {
            Ok((device, adapter, features)) => (device, adapter, features),
            Err(_) => {
                error!("Failed to acquire device from preferred adapter");

                match Device::try_from_all_adapters(&instance).await {
                    Ok((device, adapter, features)) => {
                        (device, adapter, features)
                    }
                    Err(err) => {
                        error!("Prepend `RUST_LOG=fj_viewer=debug` and re-run");
                        error!("Then open an issue and post your output");
                        error!(
                            "https://github.com/hannobraun/fornjot/issues/new"
                        );

                        return Err(err.into());
                    }
                }
            }
        };

        let color_format = 'color_format: {
            let capabilities = surface.get_capabilities(&adapter);
            let supported_formats = capabilities.formats;

            // We don't really care which color format we use, as long as we
            // find one that's supported. `egui_wgpu` prints a warning though,
            // unless we choose one of the following ones.
            let preferred_formats = [
                wgpu::TextureFormat::Rgba8Unorm,
                wgpu::TextureFormat::Bgra8Unorm,
            ];

            for format in preferred_formats {
                if supported_formats.contains(&format) {
                    break 'color_format format;
                }
            }

            // None of the preferred color formats are supported. Just use one
            // of the supported ones then.
            supported_formats
                .into_iter()
                .next()
                .expect("No color formats supported")
        };

        let ScreenSize { width, height } = screen.size();
        let surface_config = wgpu::SurfaceConfiguration {
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            format: color_format,
            width,
            height,
            present_mode: wgpu::PresentMode::AutoVsync,
            // I don't understand what this option does. It was introduced with
            // wgpu 0.14, but we had already been using premultiplied alpha
            // blending before that. See the `BlendState` configuration of the
            // render pipelines.
            //
            // For that reason, I tried to set this to `PreMultiplied`, but that
            // failed on Linux/Wayland (with in integrated AMD GPU). Setting it
            // to `Auto` seems to just work.
            //
            // @hannobraun
            alpha_mode: wgpu::CompositeAlphaMode::Auto,
            view_formats: vec![],
        };
        surface.configure(&device.device, &surface_config);

        let frame_buffer =
            Self::create_frame_buffer(&device.device, &surface_config);
        let depth_view =
            Self::create_depth_buffer(&device.device, &surface_config);

        let uniform_buffer = device.device.create_buffer_init(
            &wgpu::util::BufferInitDescriptor {
                label: None,
                contents: bytemuck::cast_slice(&[Uniforms::default()]),
                usage: wgpu::BufferUsages::UNIFORM
                    | wgpu::BufferUsages::COPY_DST,
            },
        );
        let bind_group_layout = device.device.create_bind_group_layout(
            &wgpu::BindGroupLayoutDescriptor {
                entries: &[wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStages::all(),
                    ty: wgpu::BindingType::Buffer {
                        ty: wgpu::BufferBindingType::Uniform,
                        has_dynamic_offset: false,
                        min_binding_size: wgpu::BufferSize::new(size_of::<
                            Uniforms,
                        >(
                        )
                            as u64),
                    },
                    count: None,
                }],
                label: None,
            },
        );
        let bind_group =
            device.device.create_bind_group(&wgpu::BindGroupDescriptor {
                layout: &bind_group_layout,
                entries: &[wgpu::BindGroupEntry {
                    binding: 0,
                    resource: wgpu::BindingResource::Buffer(
                        wgpu::BufferBinding {
                            buffer: &uniform_buffer,
                            offset: 0,
                            size: None,
                        },
                    ),
                }],
                label: None,
            });

        let geometries = Geometries::new(&device.device, &Vertices::empty());
        let pipelines = Pipelines::new(
            &device.device,
            &bind_group_layout,
            color_format,
            features,
        );

        let navigation_cube_renderer = NavigationCubeRenderer::new(
            &device.device,
            &device.queue,
            &surface_config,
        );

        Ok(Self {
            surface,
            device,

            surface_config,
            frame_buffer,
            depth_view,

            uniform_buffer,
            bind_group,

            geometries,
            pipelines,

            navigation_cube_renderer,
        })
    }

    /// Updates the geometry of the model being rendered.
    pub fn update_geometry(&mut self, mesh: Vertices) {
        self.geometries = Geometries::new(&self.device.device, &mesh);
    }

    /// Resizes the render surface.
    ///
    /// # Arguments
    /// - `size`: The target size for the render surface.
    pub fn handle_resize(&mut self, size: ScreenSize) {
        self.surface_config.width = size.width;
        self.surface_config.height = size.height;

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

        self.frame_buffer = Self::create_frame_buffer(
            &self.device.device,
            &self.surface_config,
        );
        self.depth_view = Self::create_depth_buffer(
            &self.device.device,
            &self.surface_config,
        );
    }

    /// Draws the renderer, camera, and config state to the window.
    pub fn draw(
        &mut self,
        camera: &Camera,
        config: &DrawConfig,
    ) -> Result<(), DrawError> {
        let aspect_ratio = f64::from(self.surface_config.width)
            / f64::from(self.surface_config.height);
        let uniforms = Uniforms {
            transform: Transform::for_vertices(camera, aspect_ratio),
            transform_normals: Transform::for_normals(camera),
        };

        self.device.queue.write_buffer(
            &self.uniform_buffer,
            0,
            bytemuck::cast_slice(&[uniforms]),
        );

        let surface_texture = match self.surface.get_current_texture() {
            Ok(surface_texture) => surface_texture,
            Err(wgpu::SurfaceError::Timeout) => {
                // I'm seeing this all the time now (as in, multiple times per
                // microsecond), with `PresentMode::AutoVsync`. Not sure what's
                // going on, but for now, it works to just ignore it.
                //
                // Issues for reference:
                // - https://github.com/gfx-rs/wgpu/issues/1218
                // - https://github.com/gfx-rs/wgpu/issues/1565
                return Ok(());
            }
            result => result?,
        };
        let color_view = surface_texture
            .texture
            .create_view(&wgpu::TextureViewDescriptor::default());

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

        // Need this block here, as a render pass only takes effect once it's
        // dropped.
        {
            let mut render_pass =
                encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                    color_attachments: &[Some(
                        wgpu::RenderPassColorAttachment {
                            view: &self.frame_buffer,
                            resolve_target: Some(&color_view),
                            ops: wgpu::Operations {
                                load: wgpu::LoadOp::Clear(wgpu::Color::WHITE),
                                // Not necessary, due to MSAA being enabled.
                                store: wgpu::StoreOp::Discard,
                            },
                        },
                    )],
                    depth_stencil_attachment: Some(
                        wgpu::RenderPassDepthStencilAttachment {
                            view: &self.depth_view,
                            depth_ops: Some(wgpu::Operations {
                                load: wgpu::LoadOp::Clear(1.0),
                                store: wgpu::StoreOp::Store,
                            }),
                            stencil_ops: None,
                        },
                    ),
                    ..Default::default()
                });
            render_pass.set_bind_group(0, &self.bind_group, &[]);

            let drawables = Drawables::new(&self.geometries, &self.pipelines);

            if config.draw_model {
                drawables.model.draw(&mut render_pass);
            }

            if let Some(drawable) = drawables.mesh {
                if config.draw_mesh {
                    drawable.draw(&mut render_pass);
                }
            }
        }

        self.navigation_cube_renderer.draw(
            &color_view,
            &mut encoder,
            &self.device.queue,
            aspect_ratio,
            camera.rotation,
        );

        let command_buffer = encoder.finish();
        self.device.queue.submit(Some(command_buffer));

        trace!("Presenting...");
        surface_texture.present();

        trace!("Finished drawing.");
        Ok(())
    }

    fn create_frame_buffer(
        device: &wgpu::Device,
        surface_config: &wgpu::SurfaceConfiguration,
    ) -> wgpu::TextureView {
        let texture = device.create_texture(&wgpu::TextureDescriptor {
            label: None,
            size: wgpu::Extent3d {
                width: surface_config.width,
                height: surface_config.height,
                depth_or_array_layers: 1,
            },
            mip_level_count: 1,
            sample_count: SAMPLE_COUNT,
            dimension: wgpu::TextureDimension::D2,
            format: surface_config.format,
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            view_formats: &[],
        });
        texture.create_view(&wgpu::TextureViewDescriptor::default())
    }

    fn create_depth_buffer(
        device: &wgpu::Device,
        surface_config: &wgpu::SurfaceConfiguration,
    ) -> wgpu::TextureView {
        let texture = device.create_texture(&wgpu::TextureDescriptor {
            label: None,
            size: wgpu::Extent3d {
                width: surface_config.width,
                height: surface_config.height,
                depth_or_array_layers: 1,
            },
            mip_level_count: 1,
            sample_count: SAMPLE_COUNT,
            dimension: wgpu::TextureDimension::D2,
            format: DEPTH_FORMAT,
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            view_formats: &[],
        });

        texture.create_view(&wgpu::TextureViewDescriptor::default())
    }
}

/// Error describing the set of render surface initialization errors
#[derive(Error, Debug)]
pub enum RendererInitError {
    /// General IO error
    #[error("I/O error")]
    Io(#[from] io::Error),

    /// Surface creating error
    #[error("Error creating surface")]
    CreateSurface(#[from] wgpu::CreateSurfaceError),

    /// Device error
    #[error(transparent)]
    Device(#[from] DeviceError),
}

/// Draw error
///
/// Returned by [`Renderer::draw`].
#[derive(Error, Debug)]
#[error("Error acquiring output surface: {0}")]
pub struct DrawError(#[from] wgpu::SurfaceError);