use std::rc::Rc;
use wgpu;

use crate::vertexbuffer::VertexBuffer;
use crate::{SHADER_MAIN_FRAGMENT, SHADER_MAIN_VERTEX};

pub struct PipelineBuilder<'a> {
	// These are provided with new()
	label: &'a str,
	device: &'a wgpu::Device,

	// These have empty defaults
	triangle: bool,
	bind_group_layouts: &'a [&'a wgpu::BindGroupLayout],

	// These must be provided
	shader: Option<&'a str>,
	format: Option<wgpu::TextureFormat>,
	vertex_buffer: Option<&'a Rc<VertexBuffer>>,
}

impl<'a> PipelineBuilder<'a> {
	pub fn new(label: &'a str, device: &'a wgpu::Device) -> Self {
		Self {
			label,
			device,

			triangle: true,
			vertex_buffer: None,
			bind_group_layouts: &[],

			shader: None,
			format: None,
		}
	}

	pub fn set_shader(mut self, shader: &'a str) -> Self {
		self.shader = Some(shader);
		self
	}

	pub fn set_format(mut self, format: wgpu::TextureFormat) -> Self {
		self.format = Some(format);
		self
	}

	pub fn set_triangle(mut self, triangle: bool) -> Self {
		self.triangle = triangle;
		self
	}

	pub fn set_vertex_buffer(mut self, vertex_buffer: &'a Rc<VertexBuffer>) -> Self {
		self.vertex_buffer = Some(vertex_buffer);
		self
	}

	pub fn set_bind_group_layouts(
		mut self,
		bind_group_layouts: &'a [&'a wgpu::BindGroupLayout],
	) -> Self {
		self.bind_group_layouts = bind_group_layouts;
		self
	}

	pub fn build(self) -> wgpu::RenderPipeline {
		// All fields should be set.
		// Nones are not checked, they will panic.

		let shader = self
			.device
			.create_shader_module(wgpu::ShaderModuleDescriptor {
				label: Some(&format!("pipeline [{}] shader", self.label)),
				source: wgpu::ShaderSource::Wgsl(self.shader.unwrap().into()),
			});

		let pipeline_layout = self
			.device
			.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
				label: Some(&format!("pipeline [{}] layout", self.label)),
				bind_group_layouts: self.bind_group_layouts,
				push_constant_ranges: &[],
			});

		let pipeline = self
			.device
			.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
				label: Some(&format!("pipeline [{}]", self.label)),
				layout: Some(&pipeline_layout),
				depth_stencil: None,
				multiview: None,
				multisample: wgpu::MultisampleState {
					count: 1,
					mask: !0,
					alpha_to_coverage_enabled: false,
				},

				vertex: wgpu::VertexState {
					module: &shader,
					entry_point: SHADER_MAIN_VERTEX,
					buffers: &self.vertex_buffer.unwrap().layout,
				},

				fragment: Some(wgpu::FragmentState {
					module: &shader,
					entry_point: SHADER_MAIN_FRAGMENT,
					targets: &[Some(wgpu::ColorTargetState {
						format: self.format.unwrap(),
						blend: Some(wgpu::BlendState::ALPHA_BLENDING),
						write_mask: wgpu::ColorWrites::ALL,
					})],
				}),

				primitive: if self.triangle {
					wgpu::PrimitiveState {
						topology: wgpu::PrimitiveTopology::TriangleList,
						strip_index_format: None,
						front_face: wgpu::FrontFace::Ccw,
						cull_mode: Some(wgpu::Face::Back),
						polygon_mode: wgpu::PolygonMode::Fill,
						unclipped_depth: false,
						conservative: false,
					}
				} else {
					wgpu::PrimitiveState {
						topology: wgpu::PrimitiveTopology::PointList,
						strip_index_format: None,
						front_face: wgpu::FrontFace::Ccw,
						cull_mode: None,
						polygon_mode: wgpu::PolygonMode::Fill,
						unclipped_depth: false,
						conservative: false,
					}
				},
			});

		return pipeline;
	}
}