awsm 0.0.11

Wrappers for WASM
Documentation 
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use crate::errors::Error;
use crate::window::get_window;
use futures::channel::oneshot::{channel, Receiver, Sender};
use futures::task::{Context, Poll};
use futures::Future;
use log::info;
use std::pin::Pin;
use wasm_bindgen::prelude::*;
use wasm_bindgen::JsCast;
use web_sys::*;

pub struct Image {
    pub url: String,
    pub img: Option<HtmlImageElement>,
    state: ImageState,
    closure_holders: Option<(Closure<dyn FnMut()>, Closure<dyn FnMut(JsValue)>)>,
}

enum ImageState {
    Empty,
    Loading {
        receiver_err: Receiver<JsValue>,
        receiver_success: Receiver<()>,
    },
}

//See: https://github.com/rustwasm/wasm-bindgen/issues/1126
//
impl Future for Image {
    //impl Future for Image {
    type Output = Result<HtmlImageElement, Error>;

    fn poll(mut self: Pin<&mut Self>, ctx: &mut Context) -> Poll<Self::Output> {
        //fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
        match &mut self.state {
            ImageState::Empty => {
                let img = HtmlImageElement::new()?;
                let has_same_origin = same_origin(&self.url)?;
                if !has_same_origin {
                    img.set_cross_origin(Some(&"anonymous"));
                }

                img.set_src(&self.url);

                //success callback
                let waker = ctx.waker().clone();
                let (sender_success, receiver_success): (Sender<()>, Receiver<()>) = channel();
                let mut sender_success = Option::from(sender_success);
                let closure_success = Closure::wrap(Box::new(move || {
                    sender_success.take().unwrap().send(()).unwrap();
                    waker.wake_by_ref();
                }) as Box<dyn FnMut()>);

                img.set_onload(Some(closure_success.as_ref().unchecked_ref()));

                //error callback
                let waker = ctx.waker().clone();
                let (sender_err, receiver_err): (Sender<JsValue>, Receiver<JsValue>) = channel();
                let mut sender_err = Option::from(sender_err);
                let closure_err = Closure::wrap(Box::new(move |err| {
                    sender_err.take().unwrap().send(err).unwrap();
                    waker.wake_by_ref();
                }) as Box<dyn FnMut(JsValue)>);

                //self.closure_err = Some(closure_err);
                img.set_onerror(Some(closure_err.as_ref().unchecked_ref()));

                //Assign stuff to myself
                self.img = Some(img);
                self.state = ImageState::Loading {
                    receiver_err,
                    receiver_success,
                };
                self.closure_holders = Some((closure_success, closure_err));

                //notify the task that we're now loading
                ctx.waker().wake_by_ref();

                Poll::Pending
            }

            ImageState::Loading {
                receiver_err,
                receiver_success,
            } => {
                //if let Poll::Ready(value) = Receiver::poll(Pin::new(receiver_err), ctx) {

                let mut is_cancelled = false;

                let error_state = match receiver_err.try_recv() {
                    Ok(result) => result,
                    _ => {
                        is_cancelled = true;
                        None
                    }
                };

                let success_state = match receiver_success.try_recv() {
                    Ok(result) => result,
                    _ => {
                        is_cancelled = true;
                        None
                    }
                };

                if let Some(result) = error_state {
                    Poll::Ready(Err(result.into()))
                } else if let Some(_) = success_state {
                    Poll::Ready(Ok(self.img.as_ref().unwrap().clone()))
                } else {
                    if !is_cancelled {
                        //ctx.waker().wake_by_ref();
                    }
                    Poll::Pending
                }
            }
        }
    }
}

impl Image {
    pub fn new(url: &str) -> Self {
        //can't seem to avoid this
        //but realistically, loading images is a slow and memory intensive operation
        //and urls are going to be on the smaller side too... so, no biggie
        let url = url.to_owned();

        Self {
            url,
            img: None,
            state: ImageState::Empty,
            closure_holders: None,
        }
    }
}

pub fn same_origin(url: &str) -> Result<bool, JsValue> {
    //FOLLOWUP: https://github.com/rustwasm/wasm-bindgen/issues/1150
    if url.starts_with("http://") || url.starts_with("https://") {
        let location_origin = get_window()?.location().origin()?;
        let url_origin = Url::new(url)?.origin();
        Ok(url_origin == location_origin)
    } else {
        Ok(true)
    }
}