use bevy::{prelude::*, render::{render_asset::{RenderAssets, RenderAssetUsages}, renderer::RenderDevice, render_resource::{MapMode, Maintain, Extent3d, TextureDimension}}};

use pollster::FutureExt;

use crate::{render_assets::FramebufferExtractSource, components::FramebufferExtractDestination};

pub fn extract_framebuffers(
    mut extract_bundles: Query<(&Handle<FramebufferExtractSource>, &mut FramebufferExtractDestination)>, 
    sources: Res<RenderAssets<FramebufferExtractSource>>,
    device: Res<RenderDevice>,
) {
    for (source_handle, destination_handle) in extract_bundles.iter_mut() {
        let Some(gpu_source) = sources.get(source_handle) else {
            continue;
        };

        let mut image_bytes = {
            let slice = gpu_source.buffer.slice(..);

            {
                let (tx, rx) = oneshot::channel();
                device.map_buffer(&slice, MapMode::Read, move |res| {
                    tx.send(res).unwrap();
                });
                device.poll(Maintain::Wait);
                rx.block_on().unwrap().unwrap();
            }
             
            slice.get_mapped_range().to_vec()
        };

        gpu_source.buffer.unmap();

        let bytes_per_row = gpu_source.bytes_per_row as usize;
        let padded_bytes_per_row = gpu_source.padded_bytes_per_row as usize;
        let source_size = gpu_source.source_size;
        let destination_handle = destination_handle.clone();
        let source_format = gpu_source.format;

        std::thread::spawn(move || {
            if bytes_per_row != padded_bytes_per_row {
                let mut unpadded_bytes = Vec::<u8>::with_capacity(source_size.height as usize * bytes_per_row);
                for padded_row in image_bytes.chunks(padded_bytes_per_row) {
                    unpadded_bytes.extend_from_slice(&padded_row[..bytes_per_row]);
                }
                image_bytes = unpadded_bytes;
            }

            *destination_handle.0.lock().unwrap() = Image::new(
                Extent3d {
                    width: source_size.width,
                    height: source_size.height,
                    depth_or_array_layers: 1,
                },
                TextureDimension::D2,
                image_bytes,
                source_format,
                RenderAssetUsages::MAIN_WORLD | RenderAssetUsages::RENDER_WORLD,
            );
        });
    }

}