use std::rc::Rc;
use std::sync::Mutex;

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

use render_loop::RenderLoop;
use state::State;
use web_sys::Event;

mod line;
mod point;
mod render_loop;
mod state;

type JSResult<T> = Result<T, JsValue>;
type HandlerClosure = Closure<dyn FnMut(Event) -> JSResult<()>>;

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

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

fn canvas() -> JSResult<web_sys::HtmlCanvasElement> {
    let x = document().query_selector("canvas")?.ok_or("no canvas")?;
    Ok(x.dyn_into::<web_sys::HtmlCanvasElement>()?)
}

fn fps() -> JSResult<web_sys::HtmlElement> {
    let x = document().query_selector("#fps")?.ok_or("no fps counter")?;
    Ok(x.dyn_into::<web_sys::HtmlElement>()?)
}

fn go() -> JSResult<web_sys::HtmlElement> {
    let x = document().query_selector("button")?.ok_or("no go button")?;
    Ok(x.dyn_into::<web_sys::HtmlElement>()?)
}

#[wasm_bindgen(start)]
pub fn init() -> JSResult<()> {
    console_log::init_with_level(Level::Debug)
        .map_err(|e| format!("couldn't init console: {e}"))?;
    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)?;

    let render_loop = RenderLoop::new(move |t| {
        s.render_frame(t)?;
        s.update()?;
        Ok(!*paused.lock().unwrap())
    });

    let a: HandlerClosure = Closure::new(move |e| {
        debug!("go clicked: {:?}", e);
        let mut p = p1.lock().unwrap();
        *p = !*p;
        let text = if *p {
            "go"
        } else {
            render_loop.start()?;
            "pause"
        };
        go()?.set_text_content(Some(text));
        Ok(())
    });
    go()?.set_onclick(Some(a.as_ref().unchecked_ref()));
    // otherwise it gets dropped after we're done, invalidating the
    // handler.
    a.forget();

    Ok(())
}