use crate::io::{
    get_meta_path, AssetReader, AssetReaderError, EmptyPathStream, PathStream, Reader, VecReader,
};
use bevy_log::error;
use bevy_utils::BoxedFuture;
use std::{ffi::CString, path::Path};

/// [`AssetReader`] implementation for Android devices, built on top of Android's [`AssetManager`].
///
/// Implementation details:
///
/// - [`load_path`](AssetIo::load_path) uses the [`AssetManager`] to load files.
/// - [`read_directory`](AssetIo::read_directory) always returns an empty iterator.
/// - Watching for changes is not supported. The watcher method will do nothing.
///
/// [AssetManager]: https://developer.android.com/reference/android/content/res/AssetManager
pub struct AndroidAssetReader;

impl AssetReader for AndroidAssetReader {
    fn read<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, Result<Box<Reader<'a>>, AssetReaderError>> {
        Box::pin(async move {
            let asset_manager = bevy_winit::ANDROID_APP
                .get()
                .expect("Bevy must be setup with the #[bevy_main] macro on Android")
                .asset_manager();
            let mut opened_asset = asset_manager
                .open(&CString::new(path.to_str().unwrap()).unwrap())
                .ok_or(AssetReaderError::NotFound(path.to_path_buf()))?;
            let bytes = opened_asset.get_buffer()?;
            let reader: Box<Reader> = Box::new(VecReader::new(bytes.to_vec()));
            Ok(reader)
        })
    }

    fn read_meta<'a>(
        &'a self,
        path: &'a Path,
    ) -> BoxedFuture<'a, Result<Box<Reader<'a>>, AssetReaderError>> {
        Box::pin(async move {
            let meta_path = get_meta_path(path);
            let asset_manager = bevy_winit::ANDROID_APP
                .get()
                .expect("Bevy must be setup with the #[bevy_main] macro on Android")
                .asset_manager();
            let mut opened_asset = asset_manager
                .open(&CString::new(meta_path.to_str().unwrap()).unwrap())
                .ok_or(AssetReaderError::NotFound(meta_path))?;
            let bytes = opened_asset.get_buffer()?;
            let reader: Box<Reader> = Box::new(VecReader::new(bytes.to_vec()));
            Ok(reader)
        })
    }

    fn read_directory<'a>(
        &'a self,
        _path: &'a Path,
    ) -> BoxedFuture<'a, Result<Box<PathStream>, AssetReaderError>> {
        let stream: Box<PathStream> = Box::new(EmptyPathStream);
        error!("Reading directories is not supported with the AndroidAssetReader");
        Box::pin(async move { Ok(stream) })
    }

    fn is_directory<'a>(
        &'a self,
        _path: &'a Path,
    ) -> BoxedFuture<'a, std::result::Result<bool, AssetReaderError>> {
        error!("Reading directories is not supported with the AndroidAssetReader");
        Box::pin(async move { Ok(false) })
    }
}