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//! The tick module is based on the reference implementation at: 
//! https://github.com/rustwasm/wasm-bindgen/blob/master/examples/request-animation-frame/src/lib.rs

use wasm_bindgen::prelude::*;
use wasm_bindgen::JsCast;
use std::cell::RefCell;
use std::cell::Cell;
use std::rc::Rc;
use web_sys::{Window};
use log::{info};
use crate::errors::{Error};
use crate::window::{get_window};

#[derive(Copy, Clone, Debug)]
pub struct Timestamp {
    pub time: f64,
    pub delta: f64,
    pub elapsed: f64,
}

/// similar to start_ticker but instead of a callback with the current time
/// it uses a Timestamp struct which contains commonly useful info
pub fn start_raf_ticker_timestamp<F>(mut on_tick:F) -> Result<impl (FnOnce() -> ()), Error> 
where F: (FnMut(Timestamp) -> ()) + 'static
{
    let mut last_time:Option<f64> = None;
    let mut first_time = 0f64;

    start_raf_ticker(move |time| {
            match last_time {
                Some(last_time) => {
                    on_tick(Timestamp{
                        time,
                        delta: time - last_time,
                        elapsed: time - first_time
                    });
                }
                None => {
                    on_tick(Timestamp{
                        time,
                        delta: 0.0, 
                        elapsed: 0.0, 
                    });
                    first_time = time;
                }
            }
            last_time = Some(time);
    })
}

/// Kick off a rAF loop. The returned function can be called to cancel it
pub fn start_raf_ticker<F>(mut on_tick:F) -> Result<impl (FnOnce() -> ()), Error> 
where F: (FnMut(f64) -> ()) + 'static
{

    let f = Rc::new(RefCell::new(None));
    let g = f.clone();

    //the main closure must be static - and so it needs to take in its deps via move
    //but keep_alive also exists in cancel() - so we're left with multiple owners
    let keep_alive = Rc::new(Cell::new(true));
    
    let mut raf_id:Option<i32> = None;

    //this window is passed into the loop
    let window = get_window()?; 
    {
        let keep_alive = Rc::clone(&keep_alive);
        *g.borrow_mut() = Some(Closure::wrap(Box::new(move |time| {
           
            if !keep_alive.get() {
                if let Some(id) = raf_id {
                    info!("clearing raf id: {}", id);

                    window.cancel_animation_frame(id).unwrap();
                }
                //stopping tick loop
                f.borrow_mut().take();
            } else {
                on_tick(time);
                raf_id = request_animation_frame(&window, f.borrow().as_ref().unwrap()).ok();
            }
        }) as Box<dyn FnMut(f64)-> ()>));
    }

    //this is just used to create the first invocation
    let window = get_window()?; 
    request_animation_frame(&window, g.borrow().as_ref().unwrap())?;
   
    let cancel = move || keep_alive.set(false);

    Ok(cancel)
}

fn request_animation_frame(window:&Window, f: &Closure<dyn FnMut(f64) -> ()>) -> Result<i32, Error> {
    window.request_animation_frame(f.as_ref().unchecked_ref()).map_err(|e| e.into())
}