//! [Legion](https://github.com/amethyst/legion) integration.

use crate::camera::Camera;
use crate::pass::{self, debug, mesh};
use crate::scene;
use crate::viewport::{Viewport, ViewportInfo};
use crate::Renderer;
use legion::systems::Builder;
use legion::world::SubWorld;
use legion::*;
use rayon::prelude::*;
use std::sync::Arc;

/// Callbacks trait for acquiring renderer input dynamically.
pub trait RenderCallbacks: 'static + Send + Sync {
    fn get_viewports(&mut self) -> Vec<(&dyn Viewport, Camera)>;
    fn present(&mut self);
}

/// Initializes the Cyborg renderer within a Legion world.
///
/// Uses the provided [Builder] to run all rendering code.
///
/// Required pre-initialized resources:
/// - [Renderer]
/// - [ViewportInfo] (TODO: dynamic viewport targeting)
/// - [mesh::ShaderInfo]
pub fn build_renderer<T: RenderCallbacks>(
    callbacks: T,
    resources: &mut Resources,
    builder: &mut Builder,
) {
    puffin::profile_function!();

    let renderer = resources.get_mut::<Renderer>().unwrap();
    let viewport_info = resources.get::<ViewportInfo>().unwrap();
    let mesh_shaders = resources.get::<mesh::ShaderInfo>().unwrap();

    let device = renderer.get_device();
    let layouts = renderer.get_layouts();

    let mesh_pass = mesh::MeshPass::new(
        device.to_owned(),
        layouts.to_owned(),
        viewport_info.to_owned(),
        mesh_shaders.to_owned(),
    );

    let debug_pass = debug::DebugPass::new(
        device.to_owned(),
        layouts.to_owned(),
        viewport_info.to_owned(),
    );

    let frames_in_flight = renderer.get_frames_in_flight();
    let mesh_pass = pass::RenderPassBox::new(Arc::new(mesh_pass), frames_in_flight);
    let debug_pass = pass::RenderPassBox::new(Arc::new(debug_pass), frames_in_flight);

    // drop borrowed resources so that new ones can be inserted
    drop(renderer);
    drop(viewport_info);
    drop(mesh_shaders);

    resources.insert(mesh_pass);
    resources.insert(debug_pass);

    resources.insert(callbacks);

    builder.add_system(draw_transformed_meshes_system());
    builder.add_system(draw_debug_system());
    builder.add_system(draw_debug_transformed_system());
    builder.add_system(render_system::<T>());
    builder.add_system(present_system::<T>());
}

#[system]
fn render<T: RenderCallbacks>(
    #[resource] callbacks: &mut T,
    #[resource] renderer: &mut Renderer,
    #[resource] mesh_pass: &mut pass::RenderPassBox<mesh::MeshPass>,
    #[resource] debug_pass: &mut pass::RenderPassBox<debug::DebugPass>,
) {
    puffin::profile_function!();

    let viewports = {
        puffin::profile_scope!("RenderCallbacks::get_viewports()");
        callbacks.get_viewports()
    };

    if viewports.len() > 1 {
        eprintln!("Cyborg does not currently support more than one viewport at a time!");
        return;
    } else if let Some((viewport, camera)) = viewports.get(0) {
        let mut passes: Vec<&mut dyn pass::RenderPassBoxTrait> = Vec::new();
        passes.push(mesh_pass);
        passes.push(debug_pass);
        renderer.render(passes.as_mut_slice(), *viewport, camera);
    }
}

#[system]
fn present<T: RenderCallbacks>(#[resource] callbacks: &mut T) {
    puffin::profile_function!();

    callbacks.present();
}

#[system]
fn draw_transformed_meshes(
    #[resource] mesh_pass: &pass::RenderPassBox<mesh::MeshPass>,
    world: &SubWorld,
    query: &mut Query<(&scene::Transform, &scene::Mesh)>,
) {
    query.par_iter_chunks(world).for_each(|mesh_chunk| {
        puffin::profile_function!();

        let meshes: Vec<_> = mesh_chunk
            .into_iter()
            .map(|(transform, mesh)| mesh::TransformedMesh {
                transform: transform.transform,
                mesh: mesh.mesh,
            })
            .collect();

        mesh_pass.add_transformed_meshes(&meshes);
    });
}

#[system(for_each)]
#[filter(!component::<scene::Transform>())]
fn draw_debug(
    #[resource] debug_pass: &pass::RenderPassBox<debug::DebugPass>,
    draw_list: &scene::DebugDrawList,
) {
    puffin::profile_function!();

    debug_pass.add_draw_list(draw_list);
}

#[system]
fn draw_debug_transformed(
    #[resource] debug_pass: &pass::RenderPassBox<debug::DebugPass>,
    world: &SubWorld,
    query: &mut Query<(&scene::DebugDrawList, &scene::Transform)>,
) {
    puffin::profile_function!();

    query.par_iter_chunks(world).for_each(|draw_list_chunk| {
        let mut sub_list = scene::DebugDrawList::default();
        for (draw_list, transform) in draw_list_chunk {
            let vertices_start = sub_list.vertices.len();
            sub_list.merge(draw_list);
            for vertex in sub_list.vertices[vertices_start..].iter_mut() {
                let position = glam::Vec3::from_slice(&vertex.position);
                let transformed = transform.transform.transform_point3(position);
                vertex.position = transformed.to_array();
            }
        }

        debug_pass.add_draw_list(&sub_list);
    });
}