use wgpu::util::DeviceExt;


#[repr(C)]
#[derive(Default, Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
struct Material {
    pub albedo: [f32; 4],
}

impl Material {
    pub fn set_albedo(&mut self, r: f32, g: f32, b:f32)
    {
        self.albedo[0] = r;
        self.albedo[1] = g;
        self.albedo[2] = b;
    }
}


pub struct MaterialBuffer {
    materials: [Material; 256],
    pub buffer: wgpu::Buffer,
    pub bind_layout: wgpu::BindGroupLayout,
    pub bind_group: wgpu::BindGroup
}

impl MaterialBuffer {
    
    pub fn new(device: &wgpu::Device) -> Self {
        // Create values
        let mut materials: [Material; 256] = [Default::default(); 256];
        materials[0].set_albedo(0.41,0.33,0.20);
        materials[1].set_albedo(0.15,0.5,0.05);
        materials[2].set_albedo(0.8,0.8,0.8);

        // Create buffer
        let buffer = device.create_buffer_init(
            &wgpu::util::BufferInitDescriptor {
                label: Some("Materials buffer"),
                contents: bytemuck::cast_slice(&materials),
                usage: wgpu::BufferUsage::UNIFORM | wgpu::BufferUsage::COPY_DST,
            }
        );

        // Create bind group
        let bind_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
            entries: &[
                wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStage::FRAGMENT,
                    ty: wgpu::BindingType::Buffer {
                        ty: wgpu::BufferBindingType::Uniform,
                        has_dynamic_offset: false,
                        min_binding_size: None,
                    },
                    count: None,
                }
            ],
            label: Some("Materials buffer layout"),
        });
        let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &bind_layout,
            entries: &[
                wgpu::BindGroupEntry {
                    binding: 0,
                    resource: buffer.as_entire_binding(),
                }
            ],
            label: Some("Materials buffer group"),
        });

        // Done
        MaterialBuffer { buffer, materials, bind_layout, bind_group }
    }
}