//! Throttle provider
use std::iter;
use std::num::NonZeroUsize;

/// Buffer size for `DefaultBufferSize`
pub const DEFAULT_BUFFER_SIZE: usize = 4096;

/// `BufferProvider` that only provides the `DEFAULT_BUFFER_SIZE`.
#[derive(Debug, Clone, PartialEq, Eq, Hash, Copy)]
pub struct DefaultBufferSize;

/// `BufferProvider` that never provides a chunking buffer size.
///
/// Therefore, buffers are always consumed as-is.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct NoBufferProvider;

impl BufferProvider for NoBufferProvider
{
    #[inline(always)]
    fn get_next_buffer_size(&mut self) -> Option<NonZeroUsize> {
	None
    }
}

impl BufferProvider for DefaultBufferSize
{
    #[inline(always)] 
    fn get_next_buffer_size(&mut self) -> Option<NonZeroUsize> {
	NonZeroUsize::new(DEFAULT_BUFFER_SIZE)
    }
}

/// The type that dictates the amount of time to wait between each read.
pub type Duration = std::time::Duration;

pub trait BufferProvider
{
    /// Try to get the next buffer size.
    ///
    /// # Implementations
    /// * *Should* always return `Some` *at least* once with no upper bound on the number of `Some`s that can be returned.
    /// * *Should* return `Some` until there are no more left (*can* be infinite.)
    /// * After a `None`, there **must never** be another non-`None` value.
    fn get_next_buffer_size(&mut self) -> Option<NonZeroUsize>;
}

/// Iterator adaptor for `BufferProvider`'s `gen_next_buffer_size()`.
#[derive(Debug, Clone)]
pub struct BufferProviderIter<T: ?Sized>(T);

impl<T: ?Sized + BufferProvider> Iterator for BufferProviderIter<T>
{
    type Item = NonZeroUsize;
    #[inline] 
    fn next(&mut self) -> Option<Self::Item>
    {
	self.0.get_next_buffer_size()
    }
}

pub trait BufferProviderIterExt<'a>
{
    type Iter: iter::Iterator<Item= NonZeroUsize> + 'a;
    fn get_all_buffer_sizes(self) -> Self::Iter;
}

pub trait BufferProviderDynIterExt<'a>
{
    fn gen_all_buffer_sizes(self: Box<Self>) -> Box<dyn Iterator<Item = NonZeroUsize> +'a>;
}

impl<'a, T: BufferProvider + 'a> BufferProviderDynIterExt<'a> for T
{
    #[inline]
    fn gen_all_buffer_sizes(self: Box<Self>) -> Box<dyn Iterator<Item = NonZeroUsize> +'a> {
	Box::new(BufferProviderIter(*self))
    }
}

impl<'a, T: BufferProvider + 'a> BufferProviderIterExt<'a> for T
{
    type Iter = BufferProviderIter<T>;
    #[inline(always)] 
    fn get_all_buffer_sizes(self) -> Self::Iter {
	BufferProviderIter(self)
    }
}

impl BufferProvider for usize
{
    #[inline(always)] 
    fn get_next_buffer_size(&mut self) -> Option<NonZeroUsize> {
	NonZeroUsize::new(*self)
    }
}

impl BufferProvider for (usize, usize)
{
    #[inline] 
    fn get_next_buffer_size(&mut self) -> Option<NonZeroUsize> {
	use rand::prelude::*;
	NonZeroUsize::new(rand::thread_rng().gen_range(self.0..self.1))
    }
}

pub trait DurationProvider
{
    /// Try to get the next `Duration` from this provider. If there is not one available, `None` will be returned.
    ///
    /// # Implementations
    /// * *Should* always return `Some` *at least* once with no upper bound on the number of `Some`s that can be returned.
    /// * *Should* return `Some` until there are no more left (*can* be infinite.)
    /// * After a `None`, there **must never** be another non-`None` value.
    fn get_next_duration(&mut self) -> Option<Duration>;
}

/// An iterator adaptor for a `DurationProvider`.
#[derive(Debug, Clone)]
pub struct DurationProviderIter<T: ?Sized>(T);

impl<T> DurationProviderIter<T>
{
    /// Consume into the backing `DurationProvider`
    #[inline(always)] 
    pub fn into_inner(self) -> T
    {
	self.0
    }
}

impl<T: ?Sized + DurationProvider> Iterator for DurationProviderIter<T>
{
    type Item = Duration;
    #[inline(always)] 
    fn next(&mut self) -> Option<Self::Item>
    {
	self.0.get_next_duration()
    }
}


pub trait DurationProviderIterExt<'a>
{
    type Iter: iter::Iterator<Item=Duration> + 'a;
    fn get_all_durations(self) -> Self::Iter;
}

pub trait DurationProviderExt<'a>
{
    fn get_all_durations_dyn(self: Box<Self>) -> Box<dyn iter::Iterator<Item=Duration> + 'a>;
}

impl<'a, T: DurationProvider + 'a> DurationProviderIterExt<'a> for T
{
    type Iter = DurationProviderIter<Self>;
    #[inline(always)] 
    fn get_all_durations(self) -> Self::Iter {
	DurationProviderIter(self)
    }
}

impl<'a, T: ?Sized + DurationProvider + 'a> DurationProviderExt<'a> for T
{
    #[inline] 
    fn get_all_durations_dyn(self: Box<Self>) -> Box<dyn iter::Iterator<Item=Duration> + 'a>
    {
	#[derive(Debug)]
	struct Iter<T: ?Sized>(Box<T>);
	impl<T: DurationProvider+?Sized> Iterator for Iter<T>
	{
	    type Item = Duration;
	    fn next(&mut self) -> Option<Self::Item>
	    {
		self.0.get_next_duration()
	    }
	}

	Box::new(Iter(self))
    }
}

impl DurationProvider for Duration
{
    #[inline(always)] 
    fn get_next_duration(&mut self) -> Option<Duration> {
	Some(*self)
    }
}

pub trait ThrottleProvider
{
    type Timer: DurationProvider;
    fn get_timeout(&self) -> Self::Timer;
}


pub trait DynThrottleProvider<'a>
{
    fn get_timeout(&self) -> Box<dyn DurationProvider + 'a>;
}

impl<'a, T: ?Sized> DynThrottleProvider<'a> for T
where T: ThrottleProvider,
      T::Timer: 'a
{
    #[inline(always)] 
    fn get_timeout(&self) -> Box<dyn DurationProvider + 'a>
    {
	Box::new(ThrottleProvider::get_timeout(&self))
    }
}

impl<'a> DurationProvider for Box<dyn DurationProvider + 'a>
{
    #[inline(always)] 
    fn get_next_duration(&mut self) -> Option<Duration> {
	(**self).get_next_duration()
    }
}

impl<'a> ThrottleProvider for Box<dyn DynThrottleProvider<'a> + 'a>
{
    type Timer = Box<dyn DurationProvider + 'a>;
    #[inline(always)] 
    fn get_timeout(&self) -> Self::Timer {
	DynThrottleProvider::get_timeout(self)
    }
}

impl<'a> BufferProvider for Box<dyn BufferProvider + 'a>
{
    #[inline(always)] 
    fn get_next_buffer_size(&mut self) -> Option<NonZeroUsize> {
	(**self).get_next_buffer_size()
    }
}

impl<'a, T: ?Sized> ThrottleProvider for &'a T
where T: ThrottleProvider
{
    type Timer = T::Timer;
    #[inline(always)] 
    fn get_timeout(&self) -> Self::Timer {
	T::get_timeout(self)
    }
}

impl ThrottleProvider for Duration
{
    type Timer = Self;
    fn get_timeout(&self) -> Self::Timer {
	self.clone()
    }
}

/// Provides a buffer size adaptor that returns a buffer size from a uniformly-distributed `BufferProvider` range each time `get_next_buffer_size()` is called.
#[derive(Debug, Clone, PartialEq, Eq, Hash, Copy)]
pub struct UniformBufferProvider<T: ?Sized, R: std::ops::RangeBounds<T>>(R, std::marker::PhantomData<T>);

impl<T: ?Sized, R> From<R> for UniformBufferProvider<T, R>
where T: BufferProvider,
      R: std::ops::RangeBounds<T>
{
    #[inline(always)] 
    fn from(from: R) -> Self
    {
	Self(from, std::marker::PhantomData)
    }
}


impl<T: ?Sized, R: Clone> BufferProvider for UniformBufferProvider<T, R>
where T: BufferProvider + rand::distributions::uniform::SampleUniform,
      R: std::ops::RangeBounds<T>+ rand::distributions::uniform::SampleRange<T>,
//for<'r> &'r R: ,
{
    #[inline] 
    fn get_next_buffer_size(&mut self) -> Option<NonZeroUsize> {
	use rand::prelude::*;
	rand::thread_rng().gen_range(self.0.clone()).get_next_buffer_size()
    }
}

/// Provides a duration adaptor that returns a `Duration` from a uniformly-distributed `T` range each time `get_next_duration()` is called. 
#[derive(Debug, Clone, PartialEq, Eq, Hash, Copy)]
pub struct UniformDurationProvider<T: ?Sized, R: std::ops::RangeBounds<T>>(R, std::marker::PhantomData<T>);

#[cfg(feature="none")] 
const _:() = {
    use rand::distributions::uniform::{
	self,
	UniformSampler,
	SampleUniform,
	SampleRange,
	Uniform,
    };
    use std::{
	ops::{
	    RangeBounds,
	    Bound,
	},
    };
    #[derive(Debug)]
    struct UniformDurationProviderSampler<T:?Sized, R: std::ops::RangeBounds<T>>(UniformDurationProvider<T, R>);

    impl<T: ?Sized, R: RangeBounds<T>> UniformSampler for UniformDurationProviderSampler<T, R>
    where R: SampleRange<T>,
	  T: SampleUniform,
    {
	type X = UniformDurationProvider<T, R>;
	fn new_inclusive<B1, B2>(low: B1, high: B2) -> Self
	where
            B1: uniform::SampleBorrow<Self::X> + Sized,
            B2: uniform::SampleBorrow<Self::X> + Sized {
	    Self(<Self::X as UniformSampler>::X::new_inclusive(low, high))
	}
	fn sample<Rng: rand::Rng + ?Sized>(&self, rng: &mut Rng) -> Self::X {
	    //use rand::prelude::*;
	    //UniformDurationProvider(self.0.sample(rng))
	    todo!()
	}
	fn new<B1, B2>(low: B1, high: B2) -> Self
	where
            B1: uniform::SampleBorrow<Self::X> + Sized,
            B2: uniform::SampleBorrow<Self::X> + Sized {
	    <Self::X as UniformSampler>::new(low, high)
	}
	
    }
};

#[cfg(feature="FUCK THIS")] 
const _:() = {
    use rand::distributions::uniform::{
	self,
	UniformSampler,
	SampleUniform,
	SampleRange,
	Uniform,
    };
    use std::{
	ops::{
	    RangeBounds,
	    Bound,
	},
	marker::PhantomData
    };
    use crate::ext::*;
    #[derive(Debug, Clone, Copy)]
    struct UDPSampler<R>(uniform::UniformDuration, PhantomData<R>);

    impl<D> UniformSampler for UDPSampler<D>
	where D: RangeBounds<Duration>
    {
	type X = UniformDurationProvider<Duration, D>;
	
	fn new_inclusive<B1, B2>(low: B1, high: B2) -> Self
	where
            B1: uniform::SampleBorrow<Self::X> + Sized,
            B2: uniform::SampleBorrow<Self::X> + Sized
	{
	    Self(uniform::UniformDuration::new_inclusive(low.borrow().0.start_bound(), high.borrow().0.end_bound()), PhantomData)
	}
	fn sample<R: rand::Rng + ?Sized>(&self, rng: &mut R) -> Self::X {
	    todo!()
	}
	fn new<B1, B2>(low: B1, high: B2) -> Self
	where
            B1: uniform::SampleBorrow<Self::X> + Sized,
            B2: uniform::SampleBorrow<Self::X> + Sized
	{
	    Self(uniform::UniformDuration::new(low, high), PhantomData)
	}
    }
    
    impl<R> SampleUniform for UniformDurationProvider<Duration, R>
    where R: RangeBounds<Duration> + SampleRange<Duration>
    {
	type Sampler = UDPSampler<R>;
    }
};

impl<T, R> rand::distributions::uniform::SampleRange<T> for UniformDurationProvider<T, R>
where R: std::ops::RangeBounds<T> + rand::distributions::uniform::SampleRange<T>,
      T: rand::distributions::uniform::SampleUniform
{
    #[inline(always)] 
    fn sample_single<Rng: rand::RngCore + ?Sized>(self, rng: &mut Rng) -> T {
	self.0.sample_single(rng)
    }
    #[inline]
    fn is_empty(&self) -> bool {
	use super::ext::*;
	self.0.start_bound().map_impl(into_addr) == self.0.end_bound().map_impl(into_addr)
    }
}

impl<T: ?Sized, R> From<R> for UniformDurationProvider<T, R>
where T: DurationProvider,
      R: std::ops::RangeBounds<T>
{
    #[inline(always)] 
    fn from(from: R) -> Self
    {
	Self(from, std::marker::PhantomData)
    }
}


impl<T: ?Sized, R: Clone> DurationProvider for UniformDurationProvider<T, R>
where T: DurationProvider + rand::distributions::uniform::SampleUniform,
      R: std::ops::RangeBounds<T>+ rand::distributions::uniform::SampleRange<T>,
//for<'r> &'r R: rand::distributions::uniform::SampleRange<T>
{
    #[inline] 
    fn get_next_duration(&mut self) -> Option<Duration> {
	use rand::prelude::*;
	rand::thread_rng().gen_range(self.0.clone()).get_next_duration()
    }
}

/// Provides a throttle adaptor that returns a uniformly-distributed `T` each time `get_timeout()` is called. 
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct UniformThrottleProvider<T: ?Sized, R: std::ops::RangeBounds<T>>(R, std::marker::PhantomData<T>);

/// Provides a single `DurationProvider` on each call to `get_timeout()`.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct SingleThrottleProvider<D: ?Sized>(D);

impl<D: DurationProvider> From<D> for SingleThrottleProvider<D>
{
    #[inline(always)] 
    fn from(from: D) -> Self
    {
	Self(from)
    }
}



/// Always provides no timeout duration.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct NoThrottleProvider;

/// Never provides a timeout duration
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct NoDurationProvider;

impl DurationProvider for NoDurationProvider
{
    #[inline(always)] 
    fn get_next_duration(&mut self) -> Option<Duration> {
	None
    }
}

impl ThrottleProvider for NoThrottleProvider
{
    type Timer = NoDurationProvider;
    #[inline(always)] 
    fn get_timeout(&self) -> Self::Timer {
	NoDurationProvider
    }
}

impl<D: Clone + DurationProvider> ThrottleProvider for SingleThrottleProvider<D>
{
    type Timer = D;
    #[inline(always)] 
    fn get_timeout(&self) -> Self::Timer {
	self.0.clone()
    }
}

/*impl From<Duration> for SingleThrottleProvider<Duration>
{
    #[inline(always)] 
    fn from(from: Duration) -> Self
    {
	Self(from)
    }
}*/


//TODO: Split this into multiple: From<Range/Inclusive>: same.
//      And From<x..>,From<..{,=}x>: x..BUFFER_MAX_LEN, 0..{,=}x
// (seperate impls needed for type signature. which is annoying...)
//
// XXX: Alternatively, we could add `new_from_range<R2>(range: R2)` methods for UniformThrottleProvider<_, R> where R determines which we use. This is probably the better way of doing it.
impl<T: ?Sized, R> From<R> for UniformThrottleProvider<T, R>
where T: DurationProvider,
      R: std::ops::RangeBounds<T>
{
    #[inline(always)] 
    fn from(from: R) -> Self
    {
	Self(from, std::marker::PhantomData)
    }
}

impl<T, R: Clone> ThrottleProvider for UniformThrottleProvider<T, R>
where T: DurationProvider + rand::distributions::uniform::SampleUniform,
      R: std::ops::RangeBounds<T> + rand::distributions::uniform::SampleRange<T>,
//for <'r> &'r R: rand::distributions::uniform::SampleRange<T>,
{
    type Timer = T;
    #[inline] 
    fn get_timeout(&self) -> Self::Timer {
	use rand::prelude::*;
	rand::thread_rng().gen_range(self.0.clone())
    }
}

pub mod prelude
{
    pub use super::{
	ThrottleProvider,
	DynThrottleProvider,

	Duration,
	DurationProvider,

	BufferProvider,

	DurationProviderExt as _,
	DurationProviderIterExt as _,
	BufferProviderIterExt as _,
	BufferProviderDynIterExt as _,

	DurationProviderIter,
	BufferProviderIter,
	
	UniformDurationProvider,
	UniformThrottleProvider,
	UniformBufferProvider,

	SingleThrottleProvider,
	
	DefaultBufferSize,
	
	NoThrottleProvider,
	NoDurationProvider,
	NoBufferProvider,
    };
}