bevy_ratatui_camera 0.16.0

use bevy::{
    asset::RenderAssetUsages,
    image::TextureFormatPixelInfo,
    prelude::*,
    render::{
        render_resource::{
            Buffer, BufferDescriptor, BufferUsages, Extent3d, MapMode, PollType, TextureDimension,
            TextureFormat, TextureUsages,
        },
        renderer::RenderDevice,
    },
};
use crossbeam_channel::{Receiver, Sender};

#[derive(Clone, Debug)]
pub struct ImageSender {
    pub sender: Sender<Vec<u8>>,
    pub sender_image: Handle<Image>,
    pub buffer: Buffer,
}

#[derive(Debug)]
pub struct ImageReceiver {
    pub receiver: Receiver<Vec<u8>>,
    pub receiver_image: Image,
}

pub fn create_image_pipe(
    images: &mut Assets<Image>,
    render_device: &RenderDevice,
    dimensions: UVec2,
) -> (ImageSender, ImageReceiver) {
    let (sender, receiver, buffer, sender_image, receiver_image) =
        create_image_copy_objects(render_device, images, dimensions);

    let camera_sender = ImageSender {
        sender,
        sender_image,
        buffer,
    };

    let camera_receiver = ImageReceiver {
        receiver,
        receiver_image,
    };

    (camera_sender, camera_receiver)
}

fn create_image_copy_objects(
    render_device: &RenderDevice,
    images: &mut Assets<Image>,
    dimensions: UVec2,
) -> (
    Sender<Vec<u8>>,
    Receiver<Vec<u8>>,
    Buffer,
    Handle<Image>,
    Image,
) {
    let (sender, receiver) = crossbeam_channel::unbounded();
    let (sender_texture, receiver_texture) = create_image_copy_textures(dimensions);
    let buffer = create_image_copy_buffer(render_device, dimensions);
    let sender_handle = images.add(sender_texture);

    (sender, receiver, buffer, sender_handle, receiver_texture)
}

fn create_image_copy_textures(dimensions: UVec2) -> (Image, Image) {
    let size = Extent3d {
        width: dimensions.x,
        height: dimensions.y,
        ..Default::default()
    };

    let mut sender_texture = Image::new_fill(
        size,
        TextureDimension::D2,
        &[0; 4],
        TextureFormat::bevy_default(),
        RenderAssetUsages::default(),
    );

    let receiver_texture = sender_texture.clone();

    sender_texture.texture_descriptor.usage |=
        TextureUsages::COPY_SRC | TextureUsages::RENDER_ATTACHMENT | TextureUsages::TEXTURE_BINDING;

    (sender_texture, receiver_texture)
}

fn create_image_copy_buffer(render_device: &RenderDevice, dimensions: UVec2) -> Buffer {
    let buffer_descriptor = BufferDescriptor {
        label: None,
        size: calculate_buffer_size(dimensions.x, dimensions.y),
        usage: BufferUsages::MAP_READ | BufferUsages::COPY_DST,
        mapped_at_creation: false,
    };

    render_device.create_buffer(&buffer_descriptor)
}

pub fn calculate_buffer_size(width: u32, height: u32) -> u64 {
    let padded_row_bytes = RenderDevice::align_copy_bytes_per_row(width as usize) * 4;
    padded_row_bytes as u64 * height as u64
}

pub fn send_image_buffer(render_device: &RenderDevice, buffer: &Buffer, sender: &Sender<Vec<u8>>) {
    let buffer_slice = buffer.slice(..);

    let (s, r) = crossbeam_channel::bounded(1);

    buffer_slice.map_async(MapMode::Read, move |r| match r {
        Ok(r) => s.send(r).expect("failed to send map update"),
        Err(err) => panic!("failed to map buffer: {err}"),
    });

    let _ = render_device.poll(PollType::wait());

    r.recv().expect("failed to receive the map_async message");

    let _ = sender.send(buffer_slice.get_mapped_range().to_vec());

    buffer.unmap();
}

pub fn receive_image(image_receiver: &mut ImageReceiver) {
    let mut image_data = Vec::new();
    while let Ok(data) = image_receiver.receiver.try_recv() {
        image_data = data;
    }

    if !image_data.is_empty() {
        let row_bytes = image_receiver.receiver_image.width() as usize
            * image_receiver
                .receiver_image
                .texture_descriptor
                .format
                .pixel_size()
                .expect("Image receiver received a compressed image.");

        let aligned_row_bytes = RenderDevice::align_copy_bytes_per_row(row_bytes);

        if row_bytes == aligned_row_bytes {
            image_receiver
                .receiver_image
                .data
                .clone_from(&Some(image_data));
        } else {
            image_receiver.receiver_image.data = Some(
                image_data
                    .chunks(aligned_row_bytes)
                    .take(image_receiver.receiver_image.height() as usize)
                    .flat_map(|row| &row[..row_bytes.min(row.len())])
                    .cloned()
                    .collect(),
            );
        }
    }
}