//! Demonstrates the ability to manually override which instance of PanOrbitCamera receives input
//! events, which is necessary when rendering to a texture/image instead of a window/viewport.
//!
//! In this example, input controls the camera that is rendering the texture applied to the cube,
//! rather than the main window camera.
//!
//! This example is based off Bevy's render_to_texture example.

use std::f32::consts::PI;

use bevy::window::PrimaryWindow;
use bevy::{
    prelude::*,
    render::{
        camera::RenderTarget,
        render_resource::{
            Extent3d, TextureDescriptor, TextureDimension, TextureFormat, TextureUsages,
        },
        view::RenderLayers,
    },
};
use bevy_panorbit_camera::{ActiveCameraData, PanOrbitCamera, PanOrbitCameraPlugin};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_plugins(PanOrbitCameraPlugin)
        .add_systems(Startup, setup)
        .add_systems(Update, cube_rotator_system)
        .run();
}

// Marks the first pass cube (rendered to a texture.)
#[derive(Component)]
struct FirstPassCube;

// Marks the main pass cube, to which the texture is applied.
#[derive(Component)]
struct MainPassCube;

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
    mut images: ResMut<Assets<Image>>,
    mut active_cam: ResMut<ActiveCameraData>,
    windows: Query<&Window, With<PrimaryWindow>>,
) {
    let size = Extent3d {
        width: 512,
        height: 512,
        ..default()
    };

    // This is the texture that will be rendered to.
    let mut image = Image {
        texture_descriptor: TextureDescriptor {
            label: None,
            size,
            dimension: TextureDimension::D2,
            format: TextureFormat::Bgra8UnormSrgb,
            mip_level_count: 1,
            sample_count: 1,
            usage: TextureUsages::TEXTURE_BINDING
                | TextureUsages::COPY_DST
                | TextureUsages::RENDER_ATTACHMENT,
            view_formats: &[],
        },
        ..default()
    };

    // fill image.data with zeroes
    image.resize(size);

    let image_handle = images.add(image);

    let cube_handle = meshes.add(Cuboid::new(4.0, 4.0, 4.0));
    let cube_material_handle = materials.add(StandardMaterial {
        base_color: Color::srgb(0.8, 0.7, 0.6),
        reflectance: 0.02,
        unlit: false,
        ..default()
    });

    // This specifies the layer used for the first pass, which will be attached to the first pass camera and cube.
    let first_pass_layer = RenderLayers::layer(1);

    // The cube that will be rendered to the texture.
    commands.spawn((
        Mesh3d(cube_handle),
        MeshMaterial3d(cube_material_handle),
        Transform::from_translation(Vec3::new(0.0, 0.0, 1.0)),
        FirstPassCube,
        first_pass_layer.clone(),
    ));

    // Light
    // NOTE: Currently lights are shared between passes - see https://github.com/bevyengine/bevy/issues/3462
    commands.spawn((
        PointLight::default(),
        Transform::from_translation(Vec3::new(0.0, 0.0, 10.0)),
    ));

    // The camera for the first pass cube that will be rendered to the texture. This is the camera
    // that is controlled by PanOrbitCamera.
    let pan_orbit_id = commands
        .spawn((
            Camera {
                // render before the "main pass" camera
                clear_color: ClearColorConfig::Custom(Color::WHITE),
                order: -1,
                target: RenderTarget::Image(image_handle.clone()),
                ..default()
            },
            Transform::from_translation(Vec3::new(0.0, 0.0, 15.0)).looking_at(Vec3::ZERO, Vec3::Y),
            PanOrbitCamera::default(),
            first_pass_layer,
        ))
        .id();

    let cube_size = 4.0;
    let cube_handle = meshes.add(Cuboid::new(cube_size, cube_size, cube_size));

    // This material has the texture that has been rendered.
    let material_handle = materials.add(StandardMaterial {
        base_color_texture: Some(image_handle),
        reflectance: 0.02,
        unlit: false,
        ..default()
    });

    // Main pass cube, with material containing the rendered first pass texture.
    commands.spawn((
        Mesh3d(cube_handle),
        MeshMaterial3d(material_handle),
        Transform::from_xyz(0.0, 0.0, 1.5).with_rotation(Quat::from_rotation_x(-PI / 5.0)),
        MainPassCube,
    ));

    // The main pass camera.
    commands.spawn((
        Camera3d::default(),
        Transform::from_xyz(0.0, 0.0, 15.0).looking_at(Vec3::ZERO, Vec3::Y),
    ));

    // Set up manual override of PanOrbitCamera. Note that this must run after PanOrbitCameraPlugin
    // is added, otherwise ActiveCameraData will be overwritten.
    // Note: you probably want to update the `viewport_size` and `window_size` whenever they change,
    // I haven't done this here for simplicity.
    let primary_window = windows
        .get_single()
        .expect("There is only ever one primary window");
    active_cam.set_if_neq(ActiveCameraData {
        // Set the entity to the entity ID of the camera you want to control. In this case, it's
        // the inner (first pass) cube that is rendered to the texture/image.
        entity: Some(pan_orbit_id),
        // What you set these values to will depend on your use case, but generally you want the
        // viewport size to match the size of the render target (image, viewport), and the window
        // size to match the size of the window that you are interacting with.
        viewport_size: Some(Vec2::new(size.width as f32, size.height as f32)),
        window_size: Some(Vec2::new(primary_window.width(), primary_window.height())),
        // Setting manual to true ensures PanOrbitCameraPlugin will not overwrite this resource
        manual: true,
    });
}

/// Rotates the outer cube (main pass)
fn cube_rotator_system(time: Res<Time>, mut query: Query<&mut Transform, With<MainPassCube>>) {
    for mut transform in &mut query {
        transform.rotate_x(1.0 * time.delta_secs());
        transform.rotate_y(0.7 * time.delta_secs());
    }
}