//! wgpu rendering context
//!
//! Manages the wgpu device, queue, and surface for rendering.

use std::sync::Arc;
use winit::window::Window;

/// Rendering context holding wgpu state
pub struct RenderContext {
    pub surface: wgpu::Surface<'static>,
    pub device: wgpu::Device,
    pub queue: wgpu::Queue,
    pub config: wgpu::SurfaceConfiguration,
    pub size: winit::dpi::PhysicalSize<u32>,
    // Keep window alive
    _window: Arc<Window>,
}

impl RenderContext {
    /// Create a new render context from a window with VSync enabled
    pub async fn new(window: Arc<Window>) -> Self {
        Self::with_vsync(window, true).await
    }

    /// Create a new render context from a window with configurable VSync
    pub async fn with_vsync(window: Arc<Window>, vsync: bool) -> Self {
        let size = window.inner_size();

        // Create wgpu instance
        let instance = wgpu::Instance::new(&wgpu::InstanceDescriptor {
            backends: wgpu::Backends::all(),
            ..Default::default()
        });

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

        // Request adapter
        let adapter = instance
            .request_adapter(&wgpu::RequestAdapterOptions {
                power_preference: wgpu::PowerPreference::default(),
                compatible_surface: Some(&surface),
                force_fallback_adapter: false,
            })
            .await
            .expect("Failed to find an appropriate adapter");

        // Request device
        let (device, queue) = adapter
            .request_device(&wgpu::DeviceDescriptor {
                label: Some("Rust4D Device"),
                required_features: wgpu::Features::empty(),
                required_limits: wgpu::Limits::default(),
                memory_hints: wgpu::MemoryHints::default(),
                trace: wgpu::Trace::Off,
            })
            .await
            .expect("Failed to create device");

        // Configure surface
        let surface_caps = surface.get_capabilities(&adapter);
        let surface_format = surface_caps
            .formats
            .iter()
            .copied()
            .find(|f| f.is_srgb())
            .unwrap_or(surface_caps.formats[0]);

        let present_mode = if vsync {
            wgpu::PresentMode::AutoVsync
        } else {
            wgpu::PresentMode::AutoNoVsync
        };

        let config = wgpu::SurfaceConfiguration {
            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
            format: surface_format,
            width: size.width,
            height: size.height,
            present_mode,
            alpha_mode: surface_caps.alpha_modes[0],
            view_formats: vec![],
            desired_maximum_frame_latency: 2,
        };
        surface.configure(&device, &config);

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

    /// Handle window resize
    pub fn resize(&mut self, new_size: winit::dpi::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);
        }
    }

    /// Render a frame with a clear color
    pub fn render_clear(&self, color: wgpu::Color) -> Result<(), wgpu::SurfaceError> {
        let output = self.surface.get_current_texture()?;
        let view = output
            .texture
            .create_view(&wgpu::TextureViewDescriptor::default());

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

        {
            let _render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                label: Some("Clear Pass"),
                color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                    view: &view,
                    resolve_target: None,
                    ops: wgpu::Operations {
                        load: wgpu::LoadOp::Clear(color),
                        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(())
    }

    /// Get the aspect ratio
    pub fn aspect_ratio(&self) -> f32 {
        self.size.width as f32 / self.size.height as f32
    }
}