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use std::sync::mpsc;
use std::mem;
use std::rc::Rc;
use std::cell::UnsafeCell;
use crossbeam::channel as crossbeam;

use crate::traits::StreamExt;
use crate::priv_traits::SinkInner;
use crate::parameter::Parameter;
use crate::stream::Stream;


pub struct TryIter<'a, T>{
    receiver: mpsc::Receiver<T>,
    _parent: Option<Box<dyn StreamExt<'a,T> + 'a>>,
}

unsafe impl<'a, T> Send for TryIter<'a, T>{}

impl<'a, T> Iterator for TryIter<'a, T>{
    type Item = T;
    fn next(&mut self) -> Option<T>{
        self.receiver.try_recv().ok()
    }
}

//TODO: can we use unique here instead of rc?
impl<'a, T> TryIter<'a, T>{
    pub fn new<'p, S: StreamExt<'p, T> + 'p>(parent: S) -> TryIter<'a,T> where T: 'p, 'p: 'a{
        let (tx,rx) = mpsc::channel();
        // let parent = parent.on_value(move |t| { tx.send(t).is_ok(); } );
        let sender = NoDropRemoveParent{
            sender: tx,
            is_alive: true,
        };
        let sender = Rc::new(UnsafeCell::new(sender));
        unsafe{ (*parent.inner_rc().get()).push(sender) };
        TryIter{
            receiver: rx,
            _parent: Some(unsafe{ mem::transmute(parent.to_box()) }),
        }
    }

    pub fn new_initial<'p, S: StreamExt<'p, T> + 'p>(parent: S, initial: T) -> TryIter<'a,T> where T: 'p, 'p: 'a{
        let (tx,rx) = mpsc::channel();
        tx.send(initial).unwrap();
        let sender = NoDropRemoveParent{
            sender: tx,
            is_alive: true,
        };
        let sender = Rc::new(UnsafeCell::new(sender));
        unsafe{ (*parent.inner_rc().get()).push(sender) };
        TryIter{
            receiver: rx,
            _parent: Some(unsafe{ mem::transmute(parent.to_box()) }),
        }
    }

    pub fn into_parameter(self, initial: T) -> Parameter<'a,T>{
        Parameter::from_parent(self, initial)
    }

    pub fn from_mpsc(receiver: mpsc::Receiver<T>) -> TryIter<'static, T>{
        TryIter{
            receiver,
            _parent: None,
        }
    }
}

pub struct TryIterLastFrame<'a, T>{
    receiver: crossbeam::Receiver<T>,
    _last_frame: Stream<'a, ()>,
    _parent: Option<Box<dyn StreamExt<'a,T> + 'a>>,
}

unsafe impl<'a, T> Send for TryIterLastFrame<'a, T>{}

impl<'a, T> Iterator for TryIterLastFrame<'a, T>{
    type Item = T;
    fn next(&mut self) -> Option<T>{
        self.receiver.try_recv().ok()
    }
}

//TODO: can we use unique here instead of rc?
impl<'a, T> TryIterLastFrame<'a, T>{
    pub fn new<'p, S, F>(parent: S, frame: F) -> TryIterLastFrame<'a,T>
    where T: 'p,
        'p: 'a,
        S: StreamExt<'p, T> + 'p,
        F: StreamExt<'p, ()> + 'p,
    {
        let (tx,rx) = crossbeam::unbounded();
        // let parent = parent.on_value(move |t| { tx.send(t).is_ok(); } );
        let sender = NoDropRemoveParent2{
            sender: tx,
            is_alive: true,
        };
        let _last_frame = {
            let rx = rx.clone();
            frame.on_value(move |_| mem::drop(rx.try_iter().by_ref().last()) )
        };
        let sender = Rc::new(UnsafeCell::new(sender));
        unsafe{ (*parent.inner_rc().get()).push(sender) };
        TryIterLastFrame{
            receiver: rx,
            _last_frame,
            _parent: Some(unsafe{ mem::transmute(parent.to_box()) }),
        }
    }
}

struct NoDropRemoveParent<T>{
    sender: mpsc::Sender<T>,
    is_alive: bool,
}

impl<'a,T> SinkInner<'a,T> for NoDropRemoveParent<T>{
    #[inline]
    fn call(&mut self, t: T) -> Result<(),()>{
        if self.sender.send(t).is_ok(){
            Ok(())
        }else{
            self.is_alive = false;
            Err(())
        }
    }

    fn is_alive(&self) -> bool {
        self.is_alive
    }
}


struct NoDropRemoveParent2<T>{
    sender: crossbeam::Sender<T>,
    is_alive: bool,
}

impl<'a,T> SinkInner<'a,T> for NoDropRemoveParent2<T>{
    #[inline]
    fn call(&mut self, t: T) -> Result<(),()>{
        if self.sender.send(t).is_ok(){
            Ok(())
        }else{
            self.is_alive = false;
            Err(())
        }
    }

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