use std::marker::PhantomData;
use stdweb::web::event::*;
use stdweb::web::{Element, EventListenerHandle, IEventTarget};

macro_rules! declare_events {
    ($($name:ident : $type:ty ,)*) => {
        #[derive(Default)]
        pub struct Events {
            $(
                pub $name: Option<Box<dyn EventHandler<$type>>>,
            )*
        }

        #[macro_export]
        macro_rules! for_events {
            ($event:ident in $events:expr => $body:block) => {
                $(
                    if let Some(ref mut $event) = $events.$name $body
                )*
            }
        }
    }
}

// TODO? these are all the "on*" attributes defined in the HTML5 standard, with
// the ones I've been unable to match to stdweb event types commented out.
//
// This needs review.

declare_events! {
    abort: ResourceAbortEvent,
    // autocomplete: Event,
    // autocompleteerror: Event,
    blur: BlurEvent,
    // cancel: Event,
    // canplay: Event,
    // canplaythrough: Event,
    change: ChangeEvent,
    click: ClickEvent,
    // close: Event,
    contextmenu: ContextMenuEvent,
    // cuechange: Event,
    dblclick: DoubleClickEvent,
    drag: DragEvent,
    dragend: DragEndEvent,
    dragenter: DragEnterEvent,
    dragexit: DragExitEvent,
    dragleave: DragLeaveEvent,
    dragover: DragOverEvent,
    dragstart: DragStartEvent,
    drop: DragDropEvent,
    // durationchange: Event,
    // emptied: Event,
    // ended: Event,
    error: ResourceErrorEvent,
    focus: FocusEvent,
    input: InputEvent,
    // invalid: Event,
    keydown: KeyDownEvent,
    keypress: KeyPressEvent,
    keyup: KeyUpEvent,
    load: ResourceLoadEvent,
    // loadeddata: Event,
    // loadedmetadata: Event,
    loadstart: LoadStartEvent,
    mousedown: MouseDownEvent,
    mouseenter: MouseEnterEvent,
    mouseleave: MouseLeaveEvent,
    mousemove: MouseMoveEvent,
    mouseout: MouseOutEvent,
    mouseover: MouseOverEvent,
    mouseup: MouseUpEvent,
    mousewheel: MouseWheelEvent,
    // pause: Event,
    // play: Event,
    // playing: Event,
    progress: ProgressEvent,
    // ratechange: Event,
    // reset: Event,
    resize: ResizeEvent,
    scroll: ScrollEvent,
    // seeked: Event,
    // seeking: Event,
    // select: Event,
    // show: Event,
    // sort: Event,
    // stalled: Event,
    submit: SubmitEvent,
    // suspend: Event,
    // timeupdate: Event,
    // toggle: Event,
    // volumechange: Event,
    // waiting: Event,
}

/// Trait for event handlers.
pub trait EventHandler<EventType> {
    /// Build a callback function from this event handler.
    ///
    /// Returns `None` is this event handler can't be used to build a callback
    /// function. This is usually the case if the event handler is a string
    /// intended for server side rendering.
    // fn build(self) -> Option<Box<FnMut(EventType) + 'static>>;

    fn attach(&mut self, target: &Element) -> EventListenerHandle;

    /// Render this event handler as a string.
    ///
    /// Returns `None` if this event handler cannot be rendered. Normally, the
    /// only event handlers that can be rendered are string values intended for
    /// server side rendering.
    fn render(&self) -> Option<String>;
}

pub struct EFn<F, E>(Option<F>, PhantomData<E>);

impl<F, E> EFn<F, E>
where
    F: FnMut(E) + 'static,
    E: ConcreteEvent,
{
    pub fn new(f: F) -> Self {
        EFn(Some(f), PhantomData)
    }
}

impl<F, E> EventHandler<E> for EFn<F, E>
where
    F: FnMut(E) + 'static,
    E: ConcreteEvent,
{
    fn attach(&mut self, target: &Element) -> EventListenerHandle {
        let handler = self.0.take().unwrap();
        target.add_event_listener(handler)
    }

    fn render(&self) -> Option<String> {
        None
    }
}

impl<'a, EventType> EventHandler<EventType> for &'a str {
    fn attach(&mut self, _target: &Element) -> EventListenerHandle {
        panic!("Silly wabbit, strings as event handlers are only for printing.");
    }

    fn render(&self) -> Option<String> {
        Some(self.to_string())
    }
}