use std::cell::RefCell;
use std::sync::{Mutex};
use std::rc::Rc;

use log::{Level, info, debug};
use wasm_bindgen::prelude::*;

use state::State;

mod line;
mod point;
mod state;

struct RenderLoop {
    animation_id: Option<i32>,
    pub closure: Option<Closure<dyn FnMut(f64)>>,
}

impl RenderLoop {
    pub fn new() -> Self {
        Self {
            animation_id: None,
            closure: None,
        }
    }
}

fn window() -> web_sys::Window {
    web_sys::window().expect("no window")
}

fn document() -> web_sys::Document {
    window().document().expect("no document")
}

fn canvas() -> Result<web_sys::HtmlCanvasElement, JsValue> {
    let x = document()
        .query_selector("canvas")?
        .expect("canvas element");
    Ok(x.dyn_into::<web_sys::HtmlCanvasElement>()?)
}

fn fps() -> Result<web_sys::HtmlElement, JsValue> {
    let x = document()
        .query_selector("#fps")?
        .expect("fps counter exists");
    Ok(x.dyn_into::<web_sys::HtmlElement>()?)
}

fn go() -> Result<web_sys::HtmlElement, JsValue> {
    let x = document()
        .query_selector("button")?
        .expect("go button exists");
    Ok(x.dyn_into::<web_sys::HtmlElement>()?)
}

#[wasm_bindgen(start)]
pub fn init() -> Result<(), JsValue> {
    console_log::init_with_level(Level::Debug).expect("couldn't init console log");
    info!("wasm init");

    let paused = Rc::new(Mutex::new(true));
    let p1 = paused.clone();

    let mut s = State::new(canvas()?, fps()?)?;
    s.render_frame(0.0)?;

    //
    // from https://users.rust-lang.org/t/wasm-web-sys-how-to-use-window-request-animation-frame-resolved/20882
    //

    let render_loop: Rc<RefCell<RenderLoop>> = Rc::new(RefCell::new(RenderLoop::new()));
    {
        let closure: Closure<dyn FnMut(f64)> = {
            let render_loop_clone = render_loop.clone();
            Closure::wrap(Box::new(move |t| {
                s.render_frame(t).expect("should render frame");
                let p = paused.lock().unwrap();
                if !*p {
                    let mut render_loop_mut = render_loop_clone.borrow_mut();
                    render_loop_mut.animation_id = if let Some(ref closure) = render_loop_mut.closure {
                        Some(
                            window()
                                .request_animation_frame(closure.as_ref().unchecked_ref())
                                .expect("req anim frame"),
                        )
                    } else {
                        None
                    }
                }
            }))
        };

        let mut render_loop_last = render_loop.borrow_mut();
        render_loop_last.animation_id = Some(
            window()
                .request_animation_frame(closure.as_ref().unchecked_ref())
                .expect("req anim frame"),
        );
        render_loop_last.closure = Some(closure);
    }

    //
    //
    //

    let a = Closure::<dyn FnMut()>::new(move || {
        let mut p = p1.lock().unwrap();
        debug!("go clicked: {}", *p);
        *p = !*p;
        let text = if *p {
            "go"
        } else {
            let render_loop_clone = render_loop.clone();
            let mut render_loop_mut = render_loop_clone.borrow_mut();
            render_loop_mut.animation_id = if let Some(ref closure) = render_loop_mut.closure {
                Some(
                    window()
                        .request_animation_frame(closure.as_ref().unchecked_ref())
                        .expect("req anim frame"),
                )
            } else {
                None
            };
            "pause"
        };
        go().expect("go button works").set_text_content(Some(text));
    });
    go()?.set_onclick(Some(a.as_ref().unchecked_ref()));
    // otherwise it gets dropped after we're done, invalidating the
    // handler.
    a.forget();

    Ok(())
}