//! Load a cubemap texture onto a cube like a skybox and cycle through different compressed texture formats

#[cfg(any(feature = "webgpu", not(target_arch = "wasm32")))]
use bevy::anti_alias::taa::TemporalAntiAliasing;

use bevy::{
    camera_controller::free_camera::{FreeCamera, FreeCameraPlugin},
    image::CompressedImageFormats,
    light::Skybox,
    pbr::ScreenSpaceAmbientOcclusion,
    prelude::*,
    render::{
        render_resource::{TextureViewDescriptor, TextureViewDimension},
        renderer::RenderDevice,
    },
};
use std::f32::consts::PI;

const CUBEMAPS: &[(&str, CompressedImageFormats)] = &[
    (
        "textures/Ryfjallet_cubemap.png",
        CompressedImageFormats::NONE,
    ),
    (
        "textures/Ryfjallet_cubemap_astc4x4.ktx2",
        CompressedImageFormats::ASTC_LDR,
    ),
    (
        "textures/Ryfjallet_cubemap_bc7.ktx2",
        CompressedImageFormats::BC,
    ),
    (
        "textures/Ryfjallet_cubemap_etc2.ktx2",
        CompressedImageFormats::ETC2,
    ),
];

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_plugins(FreeCameraPlugin)
        .add_systems(Startup, setup)
        .add_systems(
            Update,
            (
                cycle_cubemap_asset,
                asset_loaded.after(cycle_cubemap_asset),
                animate_light_direction,
            ),
        )
        .run();
}

#[derive(Resource)]
struct Cubemap {
    is_loaded: bool,
    index: usize,
    image_handle: Handle<Image>,
}

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    // directional 'sun' light
    commands.spawn((
        DirectionalLight {
            illuminance: 32000.0,
            ..default()
        },
        Transform::from_xyz(0.0, 2.0, 0.0).with_rotation(Quat::from_rotation_x(-PI / 4.)),
    ));

    let skybox_handle = asset_server.load(CUBEMAPS[0].0);
    // camera
    commands.spawn((
        Camera3d::default(),
        Msaa::Off,
        #[cfg(any(feature = "webgpu", not(target_arch = "wasm32")))]
        TemporalAntiAliasing::default(),
        ScreenSpaceAmbientOcclusion::default(),
        Transform::from_xyz(0.0, 0.0, 8.0).looking_at(Vec3::ZERO, Vec3::Y),
        FreeCamera::default(),
        Skybox {
            image: Some(skybox_handle.clone()),
            brightness: 1000.0,
            ..default()
        },
    ));

    // ambient light
    // NOTE: The ambient light is used to scale how bright the environment map is so with a bright
    // environment map, use an appropriate color and brightness to match
    commands.insert_resource(GlobalAmbientLight {
        color: Color::srgb_u8(210, 220, 240),
        brightness: 1.0,
        ..default()
    });

    commands.insert_resource(Cubemap {
        is_loaded: false,
        index: 0,
        image_handle: skybox_handle,
    });
}

const CUBEMAP_SWAP_DELAY: f32 = 3.0;

fn cycle_cubemap_asset(
    time: Res<Time>,
    mut next_swap: Local<f32>,
    mut cubemap: ResMut<Cubemap>,
    asset_server: Res<AssetServer>,
    render_device: Res<RenderDevice>,
) {
    let now = time.elapsed_secs();
    if *next_swap == 0.0 {
        *next_swap = now + CUBEMAP_SWAP_DELAY;
        return;
    } else if now < *next_swap {
        return;
    }
    *next_swap += CUBEMAP_SWAP_DELAY;

    let supported_compressed_formats =
        CompressedImageFormats::from_features(render_device.features());

    let mut new_index = cubemap.index;
    for _ in 0..CUBEMAPS.len() {
        new_index = (new_index + 1) % CUBEMAPS.len();
        if supported_compressed_formats.contains(CUBEMAPS[new_index].1) {
            break;
        }
        info!(
            "Skipping format which is not supported by current hardware: {:?}",
            CUBEMAPS[new_index]
        );
    }

    // Skip swapping to the same texture. Useful for when ktx2, zstd, or compressed texture support
    // is missing
    if new_index == cubemap.index {
        return;
    }

    cubemap.index = new_index;
    cubemap.image_handle = asset_server.load(CUBEMAPS[cubemap.index].0);
    cubemap.is_loaded = false;
}

fn asset_loaded(
    asset_server: Res<AssetServer>,
    mut images: ResMut<Assets<Image>>,
    mut cubemap: ResMut<Cubemap>,
    mut skyboxes: Query<&mut Skybox>,
) {
    if !cubemap.is_loaded && asset_server.load_state(&cubemap.image_handle).is_loaded() {
        info!("Swapping to {}...", CUBEMAPS[cubemap.index].0);
        let mut image = images.get_mut(&cubemap.image_handle).unwrap();
        // NOTE: PNGs do not have any metadata that could indicate they contain a cubemap texture,
        // so they appear as one texture. The following code reconfigures the texture as necessary.
        if image.texture_descriptor.array_layer_count() == 1 {
            let layers = image.height() / image.width();
            image
                .reinterpret_stacked_2d_as_array(layers)
                .expect("asset should be 2d texture and height will always be evenly divisible with the given layers");
            image.texture_view_descriptor = Some(TextureViewDescriptor {
                dimension: Some(TextureViewDimension::Cube),
                ..default()
            });
        }

        for mut skybox in &mut skyboxes {
            skybox.image = Some(cubemap.image_handle.clone());
        }

        cubemap.is_loaded = true;
    }
}

fn animate_light_direction(
    time: Res<Time>,
    mut query: Query<&mut Transform, With<DirectionalLight>>,
) {
    for mut transform in &mut query {
        transform.rotate_y(time.delta_secs() * 0.5);
    }
}
