extern crate core;

pub mod camera;
pub mod color;
pub mod mesh;
pub mod primitives;
pub mod render_asset;
pub mod render_component;
pub mod render_graph;
pub mod render_phase;
pub mod render_resource;
pub mod renderer;
pub mod settings;
pub mod texture;
pub mod view;

pub mod prelude {
    #[doc(hidden)]
    pub use crate::{
        camera::{
            Camera, OrthographicCameraBundle, OrthographicProjection, PerspectiveCameraBundle,
            PerspectiveProjection,
        },
        color::Color,
        mesh::{shape, Mesh},
        render_resource::Shader,
        texture::Image,
        view::{ComputedVisibility, Msaa, Visibility},
    };
}

use bevy_utils::tracing::debug;
pub use once_cell;

use crate::{
    camera::CameraPlugin,
    color::Color,
    mesh::MeshPlugin,
    primitives::{CubemapFrusta, Frustum},
    render_graph::RenderGraph,
    render_resource::{PipelineCache, Shader, ShaderLoader},
    renderer::render_system,
    texture::ImagePlugin,
    view::{ViewPlugin, WindowRenderPlugin},
};
use bevy_app::{App, AppLabel, Plugin};
use bevy_asset::{AddAsset, AssetServer};
use bevy_ecs::prelude::*;
use std::ops::{Deref, DerefMut};

/// Contains the default Bevy rendering backend based on wgpu.
#[derive(Default)]
pub struct RenderPlugin;

/// The labels of the default App rendering stages.
#[derive(Debug, Hash, PartialEq, Eq, Clone, StageLabel)]
pub enum RenderStage {
    /// Extract data from the "app world" and insert it into the "render world".
    /// This step should be kept as short as possible to increase the "pipelining potential" for
    /// running the next frame while rendering the current frame.
    Extract,

    /// Prepare render resources from the extracted data for the GPU.
    Prepare,

    /// Create [`BindGroups`](crate::render_resource::BindGroup) that depend on
    /// [`Prepare`](RenderStage::Prepare) data and queue up draw calls to run during the
    /// [`Render`](RenderStage::Render) stage.
    Queue,

    // TODO: This could probably be moved in favor of a system ordering abstraction in Render or Queue
    /// Sort the [`RenderPhases`](crate::render_phase::RenderPhase) here.
    PhaseSort,

    /// Actual rendering happens here.
    /// In most cases, only the render backend should insert resources here.
    Render,

    /// Cleanup render resources here.
    Cleanup,
}

/// The Render App World. This is only available as a resource during the Extract step.
#[derive(Default)]
pub struct RenderWorld(World);

impl Deref for RenderWorld {
    type Target = World;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl DerefMut for RenderWorld {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

/// A Label for the rendering sub-app.
#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, AppLabel)]
pub struct RenderApp;

/// A "scratch" world used to avoid allocating new worlds every frame when
/// swapping out the [`RenderWorld`].
#[derive(Default)]
struct ScratchRenderWorld(World);

impl Plugin for RenderPlugin {
    /// Initializes the renderer, sets up the [`RenderStage`](RenderStage) and creates the rendering sub-app.
    fn build(&self, app: &mut App) {
        let options = app
            .world
            .get_resource::<settings::WgpuSettings>()
            .cloned()
            .unwrap_or_default();

        app.add_asset::<Shader>()
            .add_debug_asset::<Shader>()
            .init_asset_loader::<ShaderLoader>()
            .init_debug_asset_loader::<ShaderLoader>()
            .register_type::<Color>();

        if let Some(backends) = options.backends {
            let instance = wgpu::Instance::new(backends);
            let surface = {
                let windows = app.world.resource_mut::<bevy_window::Windows>();
                let raw_handle = windows.get_primary().map(|window| unsafe {
                    let handle = window.raw_window_handle().get_handle();
                    instance.create_surface(&handle)
                });
                raw_handle
            };
            let request_adapter_options = wgpu::RequestAdapterOptions {
                power_preference: options.power_preference,
                compatible_surface: surface.as_ref(),
                ..Default::default()
            };
            let (device, queue, adapter_info) = futures_lite::future::block_on(
                renderer::initialize_renderer(&instance, &options, &request_adapter_options),
            );
            debug!("Configured wgpu adapter Limits: {:#?}", device.limits());
            debug!("Configured wgpu adapter Features: {:#?}", device.features());
            app.insert_resource(device.clone())
                .insert_resource(queue.clone())
                .insert_resource(adapter_info.clone())
                .init_resource::<ScratchRenderWorld>()
                .register_type::<Frustum>()
                .register_type::<CubemapFrusta>();

            let pipeline_cache = PipelineCache::new(device.clone());
            let asset_server = app.world.resource::<AssetServer>().clone();

            let mut render_app = App::empty();
            let mut extract_stage =
                SystemStage::parallel().with_system(PipelineCache::extract_shaders);
            // don't apply buffers when the stage finishes running
            // extract stage runs on the app world, but the buffers are applied to the render world
            extract_stage.set_apply_buffers(false);
            render_app
                .add_stage(RenderStage::Extract, extract_stage)
                .add_stage(RenderStage::Prepare, SystemStage::parallel())
                .add_stage(RenderStage::Queue, SystemStage::parallel())
                .add_stage(RenderStage::PhaseSort, SystemStage::parallel())
                .add_stage(
                    RenderStage::Render,
                    SystemStage::parallel()
                        .with_system(PipelineCache::process_pipeline_queue_system)
                        .with_system(render_system.exclusive_system().at_end()),
                )
                .add_stage(RenderStage::Cleanup, SystemStage::parallel())
                .insert_resource(instance)
                .insert_resource(device)
                .insert_resource(queue)
                .insert_resource(adapter_info)
                .insert_resource(pipeline_cache)
                .insert_resource(asset_server)
                .init_resource::<RenderGraph>();

            app.add_sub_app(RenderApp, render_app, move |app_world, render_app| {
                #[cfg(feature = "trace")]
                let _render_span = bevy_utils::tracing::info_span!("renderer subapp").entered();
                {
                    #[cfg(feature = "trace")]
                    let _stage_span =
                        bevy_utils::tracing::info_span!("stage", name = "reserve_and_flush")
                            .entered();

                    // reserve all existing app entities for use in render_app
                    // they can only be spawned using `get_or_spawn()`
                    let meta_len = app_world.entities().meta_len();
                    render_app
                        .world
                        .entities()
                        .reserve_entities(meta_len as u32);

                    // flushing as "invalid" ensures that app world entities aren't added as "empty archetype" entities by default
                    // these entities cannot be accessed without spawning directly onto them
                    // this _only_ works as expected because clear_entities() is called at the end of every frame.
                    unsafe { render_app.world.entities_mut() }.flush_as_invalid();
                }

                {
                    #[cfg(feature = "trace")]
                    let _stage_span =
                        bevy_utils::tracing::info_span!("stage", name = "extract").entered();

                    // extract
                    extract(app_world, render_app);
                }

                {
                    #[cfg(feature = "trace")]
                    let _stage_span =
                        bevy_utils::tracing::info_span!("stage", name = "prepare").entered();

                    // prepare
                    let prepare = render_app
                        .schedule
                        .get_stage_mut::<SystemStage>(&RenderStage::Prepare)
                        .unwrap();
                    prepare.run(&mut render_app.world);
                }

                {
                    #[cfg(feature = "trace")]
                    let _stage_span =
                        bevy_utils::tracing::info_span!("stage", name = "queue").entered();

                    // queue
                    let queue = render_app
                        .schedule
                        .get_stage_mut::<SystemStage>(&RenderStage::Queue)
                        .unwrap();
                    queue.run(&mut render_app.world);
                }

                {
                    #[cfg(feature = "trace")]
                    let _stage_span =
                        bevy_utils::tracing::info_span!("stage", name = "sort").entered();

                    // phase sort
                    let phase_sort = render_app
                        .schedule
                        .get_stage_mut::<SystemStage>(&RenderStage::PhaseSort)
                        .unwrap();
                    phase_sort.run(&mut render_app.world);
                }

                {
                    #[cfg(feature = "trace")]
                    let _stage_span =
                        bevy_utils::tracing::info_span!("stage", name = "render").entered();

                    // render
                    let render = render_app
                        .schedule
                        .get_stage_mut::<SystemStage>(&RenderStage::Render)
                        .unwrap();
                    render.run(&mut render_app.world);
                }

                {
                    #[cfg(feature = "trace")]
                    let _stage_span =
                        bevy_utils::tracing::info_span!("stage", name = "cleanup").entered();

                    // cleanup
                    let cleanup = render_app
                        .schedule
                        .get_stage_mut::<SystemStage>(&RenderStage::Cleanup)
                        .unwrap();
                    cleanup.run(&mut render_app.world);

                    render_app.world.clear_entities();
                }
            });
        }

        app.add_plugin(WindowRenderPlugin)
            .add_plugin(CameraPlugin)
            .add_plugin(ViewPlugin)
            .add_plugin(MeshPlugin)
            // NOTE: Load this after renderer initialization so that it knows about the supported
            // compressed texture formats
            .add_plugin(ImagePlugin);
    }
}

/// Executes the [`Extract`](RenderStage::Extract) stage of the renderer.
/// This updates the render world with the extracted ECS data of the current frame.
fn extract(app_world: &mut World, render_app: &mut App) {
    let extract = render_app
        .schedule
        .get_stage_mut::<SystemStage>(&RenderStage::Extract)
        .unwrap();

    // temporarily add the render world to the app world as a resource
    let scratch_world = app_world.remove_resource::<ScratchRenderWorld>().unwrap();
    let render_world = std::mem::replace(&mut render_app.world, scratch_world.0);
    app_world.insert_resource(RenderWorld(render_world));

    extract.run(app_world);

    // add the render world back to the render app
    let render_world = app_world.remove_resource::<RenderWorld>().unwrap();
    let scratch_world = std::mem::replace(&mut render_app.world, render_world.0);
    app_world.insert_resource(ScratchRenderWorld(scratch_world));

    extract.apply_buffers(&mut render_app.world);
}