use bevy_asset::{load_embedded_asset, Handle};
use bevy_ecs::prelude::*;
use bevy_image::BevyDefault as _;
use bevy_render::{
    render_resource::{
        binding_types::{sampler, texture_2d, uniform_buffer},
        *,
    },
    renderer::RenderDevice,
    view::{ViewTarget, ViewUniform},
};

#[derive(Resource)]
pub struct UiPipeline {
    pub view_layout: BindGroupLayout,
    pub image_layout: BindGroupLayout,
    pub shader: Handle<Shader>,
}

impl FromWorld for UiPipeline {
    fn from_world(world: &mut World) -> Self {
        let render_device = world.resource::<RenderDevice>();

        let view_layout = render_device.create_bind_group_layout(
            "ui_view_layout",
            &BindGroupLayoutEntries::single(
                ShaderStages::VERTEX_FRAGMENT,
                uniform_buffer::<ViewUniform>(true),
            ),
        );

        let image_layout = render_device.create_bind_group_layout(
            "ui_image_layout",
            &BindGroupLayoutEntries::sequential(
                ShaderStages::FRAGMENT,
                (
                    texture_2d(TextureSampleType::Float { filterable: true }),
                    sampler(SamplerBindingType::Filtering),
                ),
            ),
        );

        UiPipeline {
            view_layout,
            image_layout,
            shader: load_embedded_asset!(world, "ui.wgsl"),
        }
    }
}

#[derive(Clone, Copy, Hash, PartialEq, Eq)]
pub struct UiPipelineKey {
    pub hdr: bool,
    pub anti_alias: bool,
}

impl SpecializedRenderPipeline for UiPipeline {
    type Key = UiPipelineKey;

    fn specialize(&self, key: Self::Key) -> RenderPipelineDescriptor {
        let vertex_layout = VertexBufferLayout::from_vertex_formats(
            VertexStepMode::Vertex,
            vec![
                // position
                VertexFormat::Float32x3,
                // uv
                VertexFormat::Float32x2,
                // color
                VertexFormat::Float32x4,
                // mode
                VertexFormat::Uint32,
                // border radius
                VertexFormat::Float32x4,
                // border thickness
                VertexFormat::Float32x4,
                // border size
                VertexFormat::Float32x2,
                // position relative to the center
                VertexFormat::Float32x2,
            ],
        );
        let shader_defs = if key.anti_alias {
            vec!["ANTI_ALIAS".into()]
        } else {
            Vec::new()
        };

        RenderPipelineDescriptor {
            vertex: VertexState {
                shader: self.shader.clone(),
                entry_point: "vertex".into(),
                shader_defs: shader_defs.clone(),
                buffers: vec![vertex_layout],
            },
            fragment: Some(FragmentState {
                shader: self.shader.clone(),
                shader_defs,
                entry_point: "fragment".into(),
                targets: vec![Some(ColorTargetState {
                    format: if key.hdr {
                        ViewTarget::TEXTURE_FORMAT_HDR
                    } else {
                        TextureFormat::bevy_default()
                    },
                    blend: Some(BlendState::ALPHA_BLENDING),
                    write_mask: ColorWrites::ALL,
                })],
            }),
            layout: vec![self.view_layout.clone(), self.image_layout.clone()],
            push_constant_ranges: Vec::new(),
            primitive: PrimitiveState {
                front_face: FrontFace::Ccw,
                cull_mode: None,
                unclipped_depth: false,
                polygon_mode: PolygonMode::Fill,
                conservative: false,
                topology: PrimitiveTopology::TriangleList,
                strip_index_format: None,
            },
            depth_stencil: None,
            multisample: MultisampleState {
                count: 1,
                mask: !0,
                alpha_to_coverage_enabled: false,
            },
            label: Some("ui_pipeline".into()),
            zero_initialize_workgroup_memory: false,
        }
    }
}