use futures::channel::mpsc;
use futures::stream::Stream;
use gloo::events::EventListener;
use std::{
    future::Future,
    pin::Pin,
    task::{Context, Poll},
};
use wasm_bindgen::prelude::*;
use web_sys::{EventTarget, Node};

// From: https://docs.rs/gloo-events/latest/gloo_events/struct.EventListener.html

pub struct OnClick {
    receiver: mpsc::UnboundedReceiver<()>,
    // Automatically removed from the DOM on drop.
    listener: EventListener,
}

impl OnClick {
    pub fn new(target: &EventTarget) -> Self {
        Self::new_with_filter(target, |_| true)
    }

    pub fn new_with_filter<F>(target: &EventTarget, filter: F) -> Self
    where
        F: Fn(&Node) -> bool + 'static,
    {
        let (sender, receiver) = mpsc::unbounded();

        let listener = EventListener::new(target, "click", move |event| {
            let mut send = true;
            if let Some(event_target) = event.target() {
                if let Some(node) = event_target.dyn_ref::<Node>() {
                    send = filter(node);
                }
            }
            if send {
                sender.unbounded_send(()).unwrap_throw();
            }
        });

        Self { receiver, listener }
    }
}

// Multiple clicks.
impl Stream for OnClick {
    type Item = ();

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
        Pin::new(&mut self.receiver).poll_next(cx)
    }
}

// Just one click.
impl Future for OnClick {
    type Output = ();

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        Pin::new(&mut self.receiver)
            .poll_next(cx)
            .map(Option::unwrap)
    }
}