//! # Material Module
//!
//! Defines `Material`, a lightweight appearance descriptor that pairs a shader identifier with
//! a shared RenderPipeline. Materials are created via PipelineCache to ensure pipeline reuse—
//! multiple materials referencing the same shader_id point to the identical compiled GPU pipeline.

use crate::pipeline_cache::PipelineCache;
use std::sync::Arc;

/// Lightweight appearance descriptor: links a shader ID to a shared RenderPipeline.
/// Does not own the pipeline; holds an Arc for zero-copy sharing across objects using the same shader.
pub struct Material {
    /// Unique shader identifier used to look up or create a compiled RenderPipeline in PipelineCache.
    pub shader_id: String,
    /// Shared reference to the compiled GPU render pipeline. Multiple Materials can share one through Arc cloning.
    pub pipeline: Arc<wgpu::RenderPipeline>,
}

impl Material {
    /// Creates a new Material by requesting the cache to provide (or create) its RenderPipeline.
    /// Inputs: device (GPU command source for pipeline creation), format (surface texture format),
    ///         shader_id (unique key into PipelineCache), cache (mutable ref for potential insertion).
    /// Returns a Material holding the Arc-wrapped pipeline. Called at scene initialization time.
    pub fn new(
        device: &wgpu::Device,
        format: wgpu::TextureFormat,
        shader_id: &str,
        cache: &mut PipelineCache,
    ) -> Self {
        // Request pipeline from cache — returns cached instance if already exists, creates new otherwise
        let pipeline = cache.get_or_create(device, format, shader_id);
        Self {
            shader_id: shader_id.to_string(),
            pipeline,
        }
    }
}