use bevy::prelude::*;

use bevy::render::camera::{Camera, CameraProjection};
use bevy::render::primitives::Frustum;
use bevy::render::view::VisibleEntities;





#[derive(Component, Debug, Clone, Reflect)]
#[reflect(Component, Default)]
pub struct OffAxisProjection {
    near: f32,
    pub far: f32,
    aspect: f32,
}

impl CameraProjection for OffAxisProjection {
    fn get_projection_matrix(&self) -> Mat4 {
        println!("Here we go! {:?}",self);
        Mat4::orthographic_rh(-self.aspect, self.aspect, -1.0, 1.0, self.near, self.far)
    }

    // what to do on window resize
    fn update(&mut self, width: f32, height: f32) {
        self.aspect = width / height;
    }

    // fn depth_calculation(&self) -> DepthCalculation {
    //     // for 2D (camera doesn't rotate)
    //     DepthCalculation::ZDifference

    //     // otherwise
    //     //DepthCalculation::Distance
    // }

    fn far(&self) -> f32 {
        self.far
    }
}

impl Default for OffAxisProjection {
    fn default() -> Self {
        Self {
            near: 0.0,
            far: 1000.0,
            aspect: 1.0,
        }
    }
}

pub fn offaxis_camera_setup(mut commands: Commands) {
    print!("Setup {0}", line!());

    // We need all the components that Bevy's built-in camera bundles would add

    let projection = OffAxisProjection::default();



    println!("Setup {0}", line!());

    // position the camera like bevy would do by default for 2D:
    let transform = Transform::from_xyz(0.0, 0.0, projection.far - 0.1);
    
    // frustum construction code copied from Bevy
    let view_projection = projection.get_projection_matrix() * transform.compute_matrix().inverse();

    let frustum = Frustum::from_view_projection(
        &view_projection,
        &transform.translation,
        &transform.back(),
        projection.far,
    );

    print!("Setup {0}\n", line!());

    commands.spawn((
        bevy::render::camera::CameraRenderGraph::new(bevy::core_pipeline::core_3d::graph::NAME),
        projection,
        frustum,
        transform,
        GlobalTransform::default(),
        VisibleEntities::default(),
        Camera::default(),
        Camera3d::default()
    ));

    println!("Setup {0}\t{1}\n", line!(), file!());
}

// fn main() {
//     // need to add a bevy-internal camera system to update
//     // the projection on window resizing

//     use bevy::render::camera::camera_system;

//     App::new()
//         .add_plugins(DefaultPlugins)
//         .add_startup_system(setup)
//         .add_system_to_stage(
//             CoreStage::PostUpdate,
//             camera_system::<SimpleOrthoProjection>,
//         )
//         .run();
// }