use super::*;
use futures::prelude::*;
use std::sync::atomic::{Ordering, AtomicBool};
use std::mem;
use tokio::time::{
    Duration,
    Interval,
    self,
};
use std::{
    pin::Pin,
    task::{Poll, Context},
};
use std::{fmt, error};

pub mod prelude
{
    pub use super::StreamGateExt as _;
    pub use super::StreamLagExt as _;
    pub use super::INodeExt as _;

    pub use super::OptionIterator;
    
    pub use super::MaybeVec;
}

pub trait INodeExt
{
    /// Get the `ino` of this fs object metadata.
    fn inode(&self) -> data::INode;
}

impl INodeExt for std::fs::Metadata
{
    #[inline] fn inode(&self) -> data::INode {
	data::INode::new(self)
    }
}

impl INodeExt for tokio::fs::DirEntry
{
    #[inline] fn inode(&self) -> data::INode {
	use std::os::unix::fs::DirEntryExt as _;

	unsafe { data::INode::new_unchecked(self.ino()) }
    }
}

/// A gated stream that releases every N items from the backing stream.
#[pin_project]
#[derive(Debug)]
pub struct GatedStream<S,T>
{
    #[pin] backing: stream::Fuse<S>,
    buffer: Vec<T>,
    release_at: usize,
    force_release: AtomicBool,
}

/// A gated stream that also releases on a timeout.
#[pin_project]
#[derive(Debug)]
pub struct TimedGatedStream<S, T>
{
    #[pin] backing: GatedStream<S, T>,
    interval: Interval, // no need to Pin this, it's Unpin, we call `poll_next_unpin`.
}

pub trait StreamLagExt: Sized
{
    /// Throttle this stream with this duration.
    fn lag(self, timeout: Duration) -> time::Throttle<Self>;
}

impl<S> StreamLagExt for S
where S: Stream
{
    #[inline] fn lag(self, timeout: Duration) -> time::Throttle<Self>
    {
	time::throttle(timeout, self)
    }
}

pub trait StreamGateExt<T>: Sized
{
    /// Gate this stream every `n` elements.
    ///
    /// # Panics
    /// If `n` is 0.
    fn gate(self, n: usize) -> GatedStream<Self, T>;

    /// Gate this stream every `n` elements or after `timeout` completes.
    ///
    /// # Panics
    /// If `n` is 0.
    fn gate_with_timeout(self, n: usize, timeout: Duration) -> TimedGatedStream<Self, T>;
}

impl<S> StreamGateExt<S::Item> for S
where S: Stream,
{
    fn gate(self, n: usize) -> GatedStream<Self, S::Item>
    {
	assert!(n > 0, "Size of gate must be above 0");
	GatedStream
	{
	    backing: self.fuse(),
	    buffer: Vec::with_capacity(n),
	    release_at: n,
	    force_release: AtomicBool::new(false),
	}
    }
    fn gate_with_timeout(self, n: usize, timeout: Duration) -> TimedGatedStream<Self, S::Item> {
	TimedGatedStream
	{
	    backing: self.gate(n),
	    interval: tokio::time::interval(timeout),
	}
    }
}

impl<S>  GatedStream<S, S::Item>
where S: Stream
{
    /// Force release of next block whether its full or not
    pub fn force_release(&self)
    {
	self.force_release.store(true, Ordering::SeqCst);
    }

    /// Consume into the inner stream and the current buffer.
    pub fn into_inner(self) -> (S, Vec<S::Item>)
    {
	(self.backing.into_inner(), self.buffer)
    }

    /// Size of the gated block
    pub fn block_size(&self) -> usize
    {
	self.release_at
    }
}
impl<S> Stream for GatedStream<S, S::Item>
where S: Stream
{
    type Item = Vec<S::Item>;//Box<[S::Item]>;
    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {

	while self.buffer.len() < self.release_at
	{
	    let this = self.as_mut().project();
	    match this.backing.poll_next(cx)
	    {
		Poll::Pending => break,
		Poll::Ready(None) => {
		    return if this.buffer.len() == 0 {
			Poll::Ready(None)
		    } else {
			let this = self.project();
			Poll::Ready(Some(mem::replace(this.buffer, Vec::with_capacity(*this.release_at)).into()))
		    };
		    
		},
		Poll::Ready(Some(item)) => this.buffer.push(item),
	    }
	}
	
	if self.buffer.len() > 0 && self.force_release.load(Ordering::Acquire) {
	    let this = self.project();
	    let output = mem::replace(this.buffer, Vec::with_capacity(*this.release_at));
	    this.force_release.store(false, Ordering::Release);
	    Poll::Ready(Some(output.into()))
	}
	else if self.buffer.len() == self.release_at
	{
	    let this = self.project();
	    Poll::Ready(Some(mem::replace(this.buffer, Vec::with_capacity(*this.release_at)).into()))
	} else {
	    Poll::Pending
	}
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
	let bshint = self.backing.size_hint();
	(bshint.0 / self.release_at, bshint.1.map(|x| x / self.release_at))
    }
}


impl<S> Stream for TimedGatedStream<S, S::Item>
where S: Stream
{
    type Item = Vec<S::Item>;//Box<[S::Item]>;
    #[inline] fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
	let this = self.project();
	match this.interval.poll_next_unpin(cx)
	{
	    Poll::Ready(_) => this.backing.force_release(),
	    _ => (),
	}
	
	this.backing.poll_next(cx)
    }
    #[inline] fn size_hint(&self) -> (usize, Option<usize>) {
	self.backing.size_hint()
    }
}

/// An iterator that can be constructed from an `Option<Iterator>`.
#[derive(Debug, Clone)]
pub struct OptionIterator<I>(Option<I>);

impl<I> OptionIterator<I>
{
    /// Consume into the inner `Option`.
    #[inline] pub fn into_inner(self) -> Option<I>
    {
	self.0
    }

    /// Does this `OptionIterator` have a value?
    pub fn is_some(&self) -> bool
    {
	self.0.is_some()
    }
}

impl<I: Iterator> From<Option<I>> for OptionIterator<I>
{
    fn from(from: Option<I>) -> Self
    {
	Self(from)
    }
}


impl<I: Iterator> Iterator for OptionIterator<I>
{
    type Item = I::Item;
    fn next(&mut self) -> Option<Self::Item>
    {
	self.0.map(|x| x.next()).flatten()
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
	match self.0 {
	    Some(i) => i.size_hint(),
	    _ => (0, Some(0)),
	}
    }
}

impl<I: Iterator> std::iter::FusedIterator for OptionIterator<I>
where I: std::iter::FusedIterator{}
impl<I: Iterator> ExactSizeIterator for OptionIterator<I>
where I: ExactSizeIterator{}
impl<I: Iterator> DoubleEndedIterator for OptionIterator<I>
where I: DoubleEndedIterator
{
    fn next_back(&mut self) -> Option<Self::Item> {
	self.0.map(|x| x.next_back()).flatten()
    }
}


/// Create a duration with time suffix `h`, `m`, `s`, `ms` or `ns`.
///
/// # Combination
/// These can also be combined.
/// ```
/// #use crate::duration;
/// duration!(1 h, 20 m, 30 s);
/// ```
#[macro_export ]macro_rules! duration
{
    (0 $($_any:tt)?) => (::std::time::Duration::from_secs(0));
    ($dur:literal ms) => (::std::time::Duration::from_millis($dur));
    ($dur:literal ns) => (::std::time::Duration::from_nanos($dur));
    ($dur:literal s) => (::std::time::Duration::from_secs($dur));
    ($dur:literal m) => (::std::time::Duration::from_secs($dur * 60));
    ($dur:literal h) => (::std::time::Duration::from_secs($dur * 60 * 60));
    
    ( $($dur:literal $unit:tt),*)=> {
        duration!(0 s) $(
            + duration!($dur $unit)
        )*
    };
}


#[cfg(test)]
mod tests
{
    use super::*;
    
    #[test]
    fn duration()
    {
	let dur = duration!(1 h) +
	    duration!(10 m) +
	    duration!(1 s) +
	    duration!(10 ms, 2 ns);
	println!("{:?}", dur);
	let dur2 = duration!(
	    1 h,
	    10 m,
	    1 s,
	    10 ms,
	    2 ns
	);
	println!("{:?}", dur2);
	assert_eq!(dur, dur2);
    }
    
    #[tokio::test]
    async fn stream_gating_with_timeout()
    {
	let mut stream = stream::iter(0i32..100)
	    .gate_with_timeout(16, Duration::from_millis(100))
	//    .gate(16)
	    .lag(Duration::from_millis(10));
	let mut sum = 0i32;
	while let Some(numbers) = stream.next().await
	{
	    eprintln!("{}: {:?}", numbers.len(), numbers);
	    sum+=numbers.into_iter().sum::<i32>();
	}
	println!("{}", sum);
	assert_eq!((0..100).sum::<i32>(),sum);
    }
    
    #[tokio::test]
    async fn stream_gating()
    {
	let mut stream = stream::iter(0i32..100)
	    .gate(16)
	    .lag(Duration::from_millis(10));
	let mut sum = 0i32;
	while let Some(numbers) = stream.next().await
	{
	    eprintln!("{}: {:?}", numbers.len(), numbers);
	    sum+=numbers.into_iter().sum::<i32>();
	}
	println!("{}", sum);
	assert_eq!((0..100).sum::<i32>(),sum);
    }
}

/// Explicitly drop this item.
///
/// If `defer-drop` feature is enabled, this may move the object to the background collector thread.
///
/// # Speicialisations
/// There can be special handling for `Vec<T>` types in this way.
/// ```
/// let large_vec = vec![String::from("Hello world"); 1000];
/// drop!(vec large_vec);
/// ```
/// It also has an `async` variant, that lets you await the background dropping task.
/// ```
/// let large_vec = vec![String::from("Hello world"); 1000];
/// drop!(async vec large_vec);
/// ```
#[macro_export] macro_rules! drop {
    (async vec $item:expr) => {
	#[cfg(feature="defer-drop")] {
	    $crate::defer_drop::drop_vec($item).await;
	}
	#[cfg(not(feature="defer-drop"))] {
	    drop($item);
	}
	()
    };
    (vec $item:expr) => {
	#[cfg(feature="defer-drop")] {
	    $crate::defer_drop::drop_vec_sync($item);
	}
	#[cfg(not(feature="defer-drop"))] {
	    drop($item);
	}
	()
    }
}

/// Base type from macro `eyre_assert`.
#[derive(Debug)]
pub struct SoftAssertionFailedError;

impl error::Error for SoftAssertionFailedError{}
impl fmt::Display for SoftAssertionFailedError
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
    {
	write!(f, "Assertion failed")
    }
}


/// A soft assertion that yields an `Err(eyre::Report)` if the condition fails.
#[macro_export] macro_rules! eyre_assert {
    ($cond:expr $(; $message:literal)?) => {
	if !$cond {
	    Err($crate::ext::SoftAssertionFailedError)
		$(.wrap_err(eyre!($message)))?
		.with_section(|| stringify!($cond).header("Expression was"))
	} else {
	    Ok(())
	}
    };
}

pub type MaybeVec<T> = smallvec::SmallVec<[T; 1]>;