use bevy_asset::{load_embedded_asset, AssetServer, 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},
};
use bevy_utils::default;

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

pub fn init_ui_pipeline(
    mut commands: Commands,
    render_device: Res<RenderDevice>,
    asset_server: Res<AssetServer>,
) {
    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),
            ),
        ),
    );

    commands.insert_resource(UiPipeline {
        view_layout,
        image_layout,
        shader: load_embedded_asset!(asset_server.as_ref(), "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(),
                shader_defs: shader_defs.clone(),
                buffers: vec![vertex_layout],
                ..default()
            },
            fragment: Some(FragmentState {
                shader: self.shader.clone(),
                shader_defs,
                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,
                })],
                ..default()
            }),
            layout: vec![self.view_layout.clone(), self.image_layout.clone()],
            label: Some("ui_pipeline".into()),
            ..default()
        }
    }
}