use super::{Texture, TextureFormat};
use anyhow::Result;
use bevy_asset::{AssetLoader, LoadContext, LoadedAsset};
use bevy_math::Vec2;
use bevy_utils::BoxedFuture;

/// Loads HDR textures as Texture assets
#[derive(Clone, Default)]
pub struct HdrTextureLoader;

impl AssetLoader for HdrTextureLoader {
    fn load<'a>(
        &'a self,
        bytes: &'a [u8],
        load_context: &'a mut LoadContext,
    ) -> BoxedFuture<'a, Result<()>> {
        Box::pin(async move {
            let format = TextureFormat::Rgba32Float;
            debug_assert_eq!(
                format.pixel_size(),
                4 * 4,
                "Format should have 32bit x 4 size"
            );

            let decoder = image::hdr::HdrDecoder::new(bytes)?;
            let info = decoder.metadata();
            let rgb_data = decoder.read_image_hdr()?;
            let mut rgba_data = Vec::with_capacity(rgb_data.len() * format.pixel_size());

            for rgb in rgb_data {
                let alpha = 1.0f32;

                rgba_data.extend_from_slice(&rgb.0[0].to_ne_bytes());
                rgba_data.extend_from_slice(&rgb.0[1].to_ne_bytes());
                rgba_data.extend_from_slice(&rgb.0[2].to_ne_bytes());
                rgba_data.extend_from_slice(&alpha.to_ne_bytes());
            }

            let texture = Texture::new(
                Vec2::new(info.width as f32, info.height as f32),
                rgba_data,
                format,
            );

            load_context.set_default_asset(LoadedAsset::new(texture));
            Ok(())
        })
    }

    fn extensions(&self) -> &[&str] {
        static EXTENSIONS: &[&str] = &["hdr"];
        EXTENSIONS
    }
}