//! # Renderer Module
//!
//! The **Specialist** layer of the architecture. Owns rendering logic — RenderPipeline, shaders, and buffers — but does not own hardware resources (Device, Queue). Receives references to those resources when called by the orchestrator (main.rs).
//! Interacts with Context via `begin_frame()` / `end_frame()`: receives a TextureView as input, writes rendered output to it.

use crate::conf::BASIC_SHADER;

/// Renders geometry using a fixed RenderPipeline. This struct owns heavy objects
/// (RenderPipeline) compiled once at creation time, avoiding per-frame allocation.
pub struct Renderer {
    /// Pre-compiled pipeline defining vertex/fragment stages, layout, and blend state.
    render_pipeline: wgpu::RenderPipeline,
}

impl Renderer {
    /// Creates the renderer by compiling the shader module and building the render pipeline.
    /// Inputs: `device` for resource creation, `format` for color attachment format.
    /// Returns the initialized Renderer owning the pipeline. Called once at application startup
    /// by the orchestrator (main.rs). The pipeline is compiled only here; subsequent calls are cheap.
    pub fn new(device: &wgpu::Device, format: wgpu::TextureFormat) -> Self {
        // In wgpu 30, ShaderModuleDescriptor fields changed: label is Option<&str> (not Some(label)),
        // and source uses Cow<'_, str> instead of [u8]. include_str! + .into() converts &str → Cow<str>.
        let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
            label: Some(BASIC_SHADER),
            source: wgpu::ShaderSource::Wgsl(include_str!("../assets/shaders/basic_shader.wgsl").into()),
        });

        // push_constant_ranges → removed in wgpu 30; replaced by immediate_size for var<immediate> support.
        let render_pipeline_layout =
            device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
                label: Some("render_pipeline_layout"),
                bind_group_layouts: &[],
                immediate_size: 0, // no var<immediate> used
            });

        let render_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("Render Pipeline"),
            layout: Some(&render_pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                // entry_point is now Option<&str> — Some to specify the entry point explicitly, None to auto-detect.
                entry_point: Some("vs_main"),
                compilation_options: Default::default(), // new required field in wgpu 30
                buffers: &[],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: Some("fs_main"),
                compilation_options: Default::default(), // new required field in wgpu 30
                // targets is now &[Option<ColorTargetState>] — each target wrapped in Some.
                targets: &[Some(wgpu::ColorTargetState {
                    format,
                    blend: Some(wgpu::BlendState::REPLACE),
                    write_mask: wgpu::ColorWrites::ALL,
                })],
            }),
            primitive: wgpu::PrimitiveState::default(),
            depth_stencil: None,
            multisample: wgpu::MultisampleState::default(),
            // multiview → replaced by multiview_mask (NonZeroU32) and cache in wgpu 30.
            multiview_mask: None,
            cache: None,
        });

        Self { render_pipeline }
    }

    /// Renders a single frame by encoding commands into a temporary CommandEncoder and submitting them to the queue.
    /// Inputs: `device` for command buffer creation, `queue` for submission, `view` as render target (from Context).
    /// Called by the orchestrator after begin_frame() returns the TextureView. The pipeline is invoked once per call;
    /// no persistent state is retained between frames.
    pub fn render(&self, device: &wgpu::Device, queue: &wgpu::Queue, view: &wgpu::TextureView) {
        // create command encoder
        let mut encoder = device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
            label: Some("render encoder"),
        });

        // RenderPass start — depth_slice is a new required field in wgpu 30 for multisampled textures.
        let mut render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
            label: Some("render pass"),
            color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                view,
                resolve_target: None,
                depth_slice: None, // new field; None means no multisample resolve needed
                ops: wgpu::Operations {
                    load: wgpu::LoadOp::Clear(wgpu::Color::BLACK),
                    store: wgpu::StoreOp::Store,
                },
            })],
            ..Default::default()
        });

        // Pipeline call — draw with empty vertex buffers (geometry defined in shader)
        render_pass.set_pipeline(&self.render_pipeline);
        render_pass.draw(0..3, 0..1);

        // Queue submit
        drop(render_pass);
        queue.submit(std::iter::once(encoder.finish()));
    }
}