use self::Blocker::*;
pub use self::Failure::*;
use core::intrinsics::abort;
use core::mem;
use core::ptr;
use crate::sync::atomic::{AtomicUsize, Ordering};
use crate::sync::mpsc::blocking::{self, SignalToken, WaitToken};
use crate::sync::{Mutex, MutexGuard};
use crate::time::Instant;
const MAX_REFCOUNT: usize = (isize::MAX) as usize;
pub struct Packet<T> {
    
    
    channels: AtomicUsize,
    lock: Mutex<State<T>>,
}
unsafe impl<T: Send> Send for Packet<T> {}
unsafe impl<T: Send> Sync for Packet<T> {}
struct State<T> {
    disconnected: bool, 
    queue: Queue,       
    blocker: Blocker,   
    buf: Buffer<T>,     
    cap: usize,         
    
    
    
    
    
    
    canceled: Option<&'static mut bool>,
}
unsafe impl<T: Send> Send for State<T> {}
enum Blocker {
    BlockedSender(SignalToken),
    BlockedReceiver(SignalToken),
    NoneBlocked,
}
struct Queue {
    head: *mut Node,
    tail: *mut Node,
}
struct Node {
    token: Option<SignalToken>,
    next: *mut Node,
}
unsafe impl Send for Node {}
struct Buffer<T> {
    buf: Vec<Option<T>>,
    start: usize,
    size: usize,
}
#[derive(Debug)]
pub enum Failure {
    Empty,
    Disconnected,
}
fn wait<'a, 'b, T>(
    lock: &'a Mutex<State<T>>,
    mut guard: MutexGuard<'b, State<T>>,
    f: fn(SignalToken) -> Blocker,
) -> MutexGuard<'a, State<T>> {
    let (wait_token, signal_token) = blocking::tokens();
    match mem::replace(&mut guard.blocker, f(signal_token)) {
        NoneBlocked => {}
        _ => unreachable!(),
    }
    drop(guard); 
    wait_token.wait(); 
    lock.lock().unwrap() 
}
fn wait_timeout_receiver<'a, 'b, T>(
    lock: &'a Mutex<State<T>>,
    deadline: Instant,
    mut guard: MutexGuard<'b, State<T>>,
    success: &mut bool,
) -> MutexGuard<'a, State<T>> {
    let (wait_token, signal_token) = blocking::tokens();
    match mem::replace(&mut guard.blocker, BlockedReceiver(signal_token)) {
        NoneBlocked => {}
        _ => unreachable!(),
    }
    drop(guard); 
    *success = wait_token.wait_max_until(deadline); 
    let mut new_guard = lock.lock().unwrap(); 
    if !*success {
        abort_selection(&mut new_guard);
    }
    new_guard
}
fn abort_selection<T>(guard: &mut MutexGuard<'_, State<T>>) -> bool {
    match mem::replace(&mut guard.blocker, NoneBlocked) {
        NoneBlocked => true,
        BlockedSender(token) => {
            guard.blocker = BlockedSender(token);
            true
        }
        BlockedReceiver(token) => {
            drop(token);
            false
        }
    }
}
fn wakeup<T>(token: SignalToken, guard: MutexGuard<'_, State<T>>) {
    
    
    drop(guard);
    token.signal();
}
impl<T> Packet<T> {
    pub fn new(capacity: usize) -> Packet<T> {
        Packet {
            channels: AtomicUsize::new(1),
            lock: Mutex::new(State {
                disconnected: false,
                blocker: NoneBlocked,
                cap: capacity,
                canceled: None,
                queue: Queue { head: ptr::null_mut(), tail: ptr::null_mut() },
                buf: Buffer {
                    buf: (0..capacity + if capacity == 0 { 1 } else { 0 }).map(|_| None).collect(),
                    start: 0,
                    size: 0,
                },
            }),
        }
    }
    
    
    fn acquire_send_slot(&self) -> MutexGuard<'_, State<T>> {
        let mut node = Node { token: None, next: ptr::null_mut() };
        loop {
            let mut guard = self.lock.lock().unwrap();
            
            if guard.disconnected || guard.buf.size() < guard.buf.capacity() {
                return guard;
            }
            
            let wait_token = guard.queue.enqueue(&mut node);
            drop(guard);
            wait_token.wait();
        }
    }
    pub fn send(&self, t: T) -> Result<(), T> {
        let mut guard = self.acquire_send_slot();
        if guard.disconnected {
            return Err(t);
        }
        guard.buf.enqueue(t);
        match mem::replace(&mut guard.blocker, NoneBlocked) {
            
            
            
            
            NoneBlocked if guard.cap == 0 => {
                let mut canceled = false;
                assert!(guard.canceled.is_none());
                guard.canceled = Some(unsafe { mem::transmute(&mut canceled) });
                let mut guard = wait(&self.lock, guard, BlockedSender);
                if canceled { Err(guard.buf.dequeue()) } else { Ok(()) }
            }
            
            NoneBlocked => Ok(()),
            
            BlockedReceiver(token) => {
                wakeup(token, guard);
                Ok(())
            }
            BlockedSender(..) => panic!("lolwut"),
        }
    }
    pub fn try_send(&self, t: T) -> Result<(), super::TrySendError<T>> {
        let mut guard = self.lock.lock().unwrap();
        if guard.disconnected {
            Err(super::TrySendError::Disconnected(t))
        } else if guard.buf.size() == guard.buf.capacity() {
            Err(super::TrySendError::Full(t))
        } else if guard.cap == 0 {
            
            
            match mem::replace(&mut guard.blocker, NoneBlocked) {
                NoneBlocked => Err(super::TrySendError::Full(t)),
                BlockedSender(..) => unreachable!(),
                BlockedReceiver(token) => {
                    guard.buf.enqueue(t);
                    wakeup(token, guard);
                    Ok(())
                }
            }
        } else {
            
            
            
            assert!(guard.buf.size() < guard.buf.capacity());
            guard.buf.enqueue(t);
            match mem::replace(&mut guard.blocker, NoneBlocked) {
                BlockedReceiver(token) => wakeup(token, guard),
                NoneBlocked => {}
                BlockedSender(..) => unreachable!(),
            }
            Ok(())
        }
    }
    
    
    
    
    pub fn recv(&self, deadline: Option<Instant>) -> Result<T, Failure> {
        let mut guard = self.lock.lock().unwrap();
        let mut woke_up_after_waiting = false;
        
        
        if !guard.disconnected && guard.buf.size() == 0 {
            if let Some(deadline) = deadline {
                guard =
                    wait_timeout_receiver(&self.lock, deadline, guard, &mut woke_up_after_waiting);
            } else {
                guard = wait(&self.lock, guard, BlockedReceiver);
                woke_up_after_waiting = true;
            }
        }
        
        
        if guard.disconnected && guard.buf.size() == 0 {
            return Err(Disconnected);
        }
        
        assert!(guard.buf.size() > 0 || (deadline.is_some() && !woke_up_after_waiting));
        if guard.buf.size() == 0 {
            return Err(Empty);
        }
        let ret = guard.buf.dequeue();
        self.wakeup_senders(woke_up_after_waiting, guard);
        Ok(ret)
    }
    pub fn try_recv(&self) -> Result<T, Failure> {
        let mut guard = self.lock.lock().unwrap();
        
        if guard.disconnected && guard.buf.size() == 0 {
            return Err(Disconnected);
        }
        if guard.buf.size() == 0 {
            return Err(Empty);
        }
        
        let ret = Ok(guard.buf.dequeue());
        self.wakeup_senders(false, guard);
        ret
    }
    
    
    
    
    
    fn wakeup_senders(&self, waited: bool, mut guard: MutexGuard<'_, State<T>>) {
        let pending_sender1: Option<SignalToken> = guard.queue.dequeue();
        
        
        
        let pending_sender2 = if guard.cap == 0 && !waited {
            match mem::replace(&mut guard.blocker, NoneBlocked) {
                NoneBlocked => None,
                BlockedReceiver(..) => unreachable!(),
                BlockedSender(token) => {
                    guard.canceled.take();
                    Some(token)
                }
            }
        } else {
            None
        };
        mem::drop(guard);
        
        pending_sender1.map(|t| t.signal());
        pending_sender2.map(|t| t.signal());
    }
    
    
    pub fn clone_chan(&self) {
        let old_count = self.channels.fetch_add(1, Ordering::SeqCst);
        
        if old_count > MAX_REFCOUNT {
            unsafe {
                abort();
            }
        }
    }
    pub fn drop_chan(&self) {
        
        match self.channels.fetch_sub(1, Ordering::SeqCst) {
            1 => {}
            _ => return,
        }
        
        let mut guard = self.lock.lock().unwrap();
        if guard.disconnected {
            return;
        }
        guard.disconnected = true;
        match mem::replace(&mut guard.blocker, NoneBlocked) {
            NoneBlocked => {}
            BlockedSender(..) => unreachable!(),
            BlockedReceiver(token) => wakeup(token, guard),
        }
    }
    pub fn drop_port(&self) {
        let mut guard = self.lock.lock().unwrap();
        if guard.disconnected {
            return;
        }
        guard.disconnected = true;
        
        
        
        
        
        let _data = if guard.cap != 0 { mem::take(&mut guard.buf.buf) } else { Vec::new() };
        let mut queue =
            mem::replace(&mut guard.queue, Queue { head: ptr::null_mut(), tail: ptr::null_mut() });
        let waiter = match mem::replace(&mut guard.blocker, NoneBlocked) {
            NoneBlocked => None,
            BlockedSender(token) => {
                *guard.canceled.take().unwrap() = true;
                Some(token)
            }
            BlockedReceiver(..) => unreachable!(),
        };
        mem::drop(guard);
        while let Some(token) = queue.dequeue() {
            token.signal();
        }
        waiter.map(|t| t.signal());
    }
}
impl<T> Drop for Packet<T> {
    fn drop(&mut self) {
        assert_eq!(self.channels.load(Ordering::SeqCst), 0);
        let mut guard = self.lock.lock().unwrap();
        assert!(guard.queue.dequeue().is_none());
        assert!(guard.canceled.is_none());
    }
}
impl<T> Buffer<T> {
    fn enqueue(&mut self, t: T) {
        let pos = (self.start + self.size) % self.buf.len();
        self.size += 1;
        let prev = mem::replace(&mut self.buf[pos], Some(t));
        assert!(prev.is_none());
    }
    fn dequeue(&mut self) -> T {
        let start = self.start;
        self.size -= 1;
        self.start = (self.start + 1) % self.buf.len();
        let result = &mut self.buf[start];
        result.take().unwrap()
    }
    fn size(&self) -> usize {
        self.size
    }
    fn capacity(&self) -> usize {
        self.buf.len()
    }
}
impl Queue {
    fn enqueue(&mut self, node: &mut Node) -> WaitToken {
        let (wait_token, signal_token) = blocking::tokens();
        node.token = Some(signal_token);
        node.next = ptr::null_mut();
        if self.tail.is_null() {
            self.head = node as *mut Node;
            self.tail = node as *mut Node;
        } else {
            unsafe {
                (*self.tail).next = node as *mut Node;
                self.tail = node as *mut Node;
            }
        }
        wait_token
    }
    fn dequeue(&mut self) -> Option<SignalToken> {
        if self.head.is_null() {
            return None;
        }
        let node = self.head;
        self.head = unsafe { (*node).next };
        if self.head.is_null() {
            self.tail = ptr::null_mut();
        }
        unsafe {
            (*node).next = ptr::null_mut();
            Some((*node).token.take().unwrap())
        }
    }
}