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use std::cell::UnsafeCell;
use std::rc::Rc;
use std::os::raw::c_void;
use std::collections::VecDeque;

use crate::Sender;
use crate::priv_traits::*;

pub struct Delay<'a, T>{
    last_values: VecDeque<T>,
    delay: usize,
    sender: Sender<'a,T>,
}

impl<'a,T> Delay<'a,T>{
    pub fn new(delay: usize) -> Delay<'a,T>{
        Delay{
            last_values: VecDeque::new(),
            delay: delay,
            sender: Sender::new(),
        }
    }
}

impl<'a,T> StreamInner<'a,T> for Delay<'a,T>{
    #[inline]
    fn push(&mut self, st: Rc<UnsafeCell<dyn SinkInner<'a,T>+'a>>){
        self.sender.push(st)
    }

    #[inline]
    fn send(&mut self, t: T){
        self.sender.send(t)
    }
}

impl<'a,T> Remove for Delay<'a,T>{
    fn remove_raw(&mut self, st: *const c_void){
        self.sender.remove_raw(st)
    }
}

impl<'a, T> SinkInner<'a, T> for Delay<'a,T>{
    #[inline]
    fn call(&mut self, t: T) -> Result<(),()>{
        self.last_values.push_back(t);
        if self.last_values.len() > self.delay{
            self.sender.send(self.last_values.pop_front().unwrap());
        }
        Ok(())
    }

    #[inline]
    fn is_alive(&self) -> bool {
        true
    }
}