loading-bytes 0.1.1

//! Abstraction over loading bytes on WASM or other.
use snafu::prelude::*;

/// Enumeration of all errors this library may result in.
#[derive(Debug, Snafu)]
pub enum LoadingBytesError {
    #[snafu(display("loading '{path}' by WASM error: {msg:#?}"))]
    Wasm {
        path: String,
        msg: wasm_bindgen::JsValue,
    },
    #[snafu(display("loading '{path}' by filesystem from CWD '{}' error: {source}", cwd.display()))]
    Fs {
        path: String,
        cwd: std::path::PathBuf,
        source: std::io::Error,
    },
}

/// Load the file at the given url fragment or path and return it as a vector of bytes, if
/// possible.
pub async fn load(path: &str) -> Result<Vec<u8>, LoadingBytesError> {
    #[cfg(target_arch = "wasm32")]
    {
        use wasm_bindgen::JsCast;

        let path = path.to_string();
        let mut opts = web_sys::RequestInit::new();
        opts.method("GET");
        let request = web_sys::Request::new_with_str_and_init(&path, &opts).map_err(|msg| {
            LoadingBytesError::Wasm {
                path: path.clone(),
                msg,
            }
        })?;
        let window = web_sys::window().unwrap();
        let resp_value = wasm_bindgen_futures::JsFuture::from(window.fetch_with_request(&request))
            .await
            .map_err(|msg| LoadingBytesError::Wasm {
                path: path.clone(),
                msg,
            })?;
        let resp: web_sys::Response =
            resp_value
                .dyn_into()
                .map_err(|msg| LoadingBytesError::Wasm {
                    path: path.clone(),
                    msg,
                })?;
        let array_promise = resp.array_buffer().map_err(|msg| LoadingBytesError::Wasm {
            path: path.clone(),
            msg,
        })?;
        let buffer = wasm_bindgen_futures::JsFuture::from(array_promise)
            .await
            .map_err(|msg| LoadingBytesError::Wasm {
                path: path.clone(),
                msg,
            })?;
        assert!(buffer.is_instance_of::<js_sys::ArrayBuffer>());
        let array: js_sys::Uint8Array = js_sys::Uint8Array::new(&buffer);
        let mut bytes: Vec<u8> = vec![0; array.length() as usize];
        array.copy_to(&mut bytes);
        Ok(bytes)
    }
    #[cfg(not(target_arch = "wasm32"))]
    {
        let bytes: Vec<u8> = async_fs::read(path).await.with_context(|_| FsSnafu {
            path: path.to_string(),
            cwd: std::env::current_dir().unwrap(),
        })?;
        Ok(bytes)
    }
}