//! Extensions and macros
use std::cell::RefCell;
use std::ptr;

#[macro_export] macro_rules! basic_enum {
    ($(#[$meta:meta])* $vis:vis $name:ident $(; $tcomment:literal)?: $($var:ident $(=> $comment:literal)?),+ $(,)?) => {
        $(#[$meta])*
	    #[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Copy)]
	$(#[doc = $tcomment])?
	    $vis enum $name {
		$(
		    $(#[doc = $comment])?
			$var
		),+
	    }
    }
}


/// Create a `Yes` or `No` enum.
#[macro_export] macro_rules! bool_type {
    ($vis:vis $name:ident $(; $comment:literal)? => $yes:ident, $no:ident) => {
	basic_enum!(#[repr(u8)] $vis $name $(; $comment)?: $yes => "# First variant\n\nYes/true", $no => "# Second variant\n\nNo/false");

	impl From<bool> for $name
	{
	    #[inline] fn from(from: bool) -> Self
	    {
		if from {
		    Self::$yes
		} else {
		    Self::$no
		}
	    }
	}

	impl From<$name> for bool
	{
	    #[inline] fn from(from: $name) -> Self
	    {
		match from {
		    $name::$yes => true,
		    $name::$no => false,
		}
	    }
	}

	impl $name
	{
	    /// Create from a bool value.
	    #[inline] pub const fn new(from: bool) -> Self
	    {
		if from {
		    Self::$yes
		} else {
		    Self::$no
		}
	    }

	    /// Is this false?
	    #[inline] pub const fn is_no(self) -> bool
	    {
		!self.is_yes()
	    }
	    /// Is this true?
	    #[inline] pub const fn is_yes(self) -> bool
	    {
		match self {
		    Self::$yes => true,
		    Self::$no => false,
		}	
	    }

	    /// Return Some(T) if self is true.
	    #[inline] pub fn some<T>(self, value: T) -> Option<T>
	    {
		self.and_then(move || value)
	    }
	    
	    /// Map this value
	    #[inline] pub fn map<F, T>(self, f: F) -> T
	    where F: FnOnce(bool) -> T
	    {
		f(self.is_yes())
	    }

	    /// Run this closure if value is false
	    #[inline] pub fn or_else<F, T>(self, f: F) -> Option<T>
	    where F: FnOnce() -> T
	    {
		if let Self::$no = self {
		    Some(f())
		} else {
		    None
		}
	    }
	    /// Run this closure if value is true
	    #[inline] pub fn and_then<F, T>(self, f: F) -> Option<T>
	    where F: FnOnce() -> T
	    {
		if let Self::$yes = self {
		    Some(f())
		} else {
		    None
		}
	    }

	    /// Return `yes` if true and `no` if false
	    #[inline] pub fn either<T>(self, yes: T, no: T) -> T
	    {
		self.and_either(move || yes, move || no)
	    }
	    /// Run closure `yes` if value is true, `no` if value is false.
	    #[inline] pub fn and_either<F, G, T>(self, yes: F, no: G) -> T
	    where F: FnOnce() -> T,
	    G: FnOnce() -> T,
	    {
		match self {
		    Self::$yes => yes(),
		    Self::$no => no(),
		}
	    }
	}
    };
    ($vis:vis $name:ident $(; $comment:literal)?) => {
		  $crate::bool_type!($vis $name $(; $comment)? => Yes, No);
    }
}

/// Max size of bytes we'll allocate to the stack at runtime before using a heap allocated buffer.
pub const STACK_SIZE_LIMIT: usize = 4096;

/// Allocate `size` bytes. Allocates on the stack if size is lower than `STACK_SIZE_LIMIT`, otherwise allocates on the heap.
pub fn alloca_limit<F, T>(size: usize, f: F) -> T
where F: FnOnce(&mut [u8]) -> T
{
    if size > STACK_SIZE_LIMIT {
	thread_local! {
	    static BUFFER: RefCell<Vec<u8>> = RefCell::new(vec![0u8; STACK_SIZE_LIMIT*2]);
	}
	BUFFER.with(move |buf| {
	    // If the borrow fails then `f` has recursively called into this function, so for that we allocate a new buffer instead of reusing this static one.
	    if let Ok(mut buf) = buf.try_borrow_mut() {
		if buf.len() < size {
		    buf.resize(size, 0);
		}
		let res = f(&mut buf[..size]);
		bytes::blank(&mut buf[..size]);
		res
	    } else {
		f(&mut vec![0u8; size])		
	    }
	})
    } else {
	stackalloc::alloca_zeroed(size, f)
	    
	// I don't think this is okay to do.
	//stackalloc::alloca(size, move |buf| f(unsafe { stackalloc::helpers::slice_assume_init_mut(buf) }))
    }
}

/// Create an accessor method. for a field in a structure.
///
/// The supported accessor types are: `ref`, `mut`, and `move`.
#[macro_export] macro_rules! accessor {
    ($vis:vis ref $name:ident -> $ty:ty => $internal:ident $(; $comment:literal)?) => {
	$(#[doc=$comment])?
	    #[inline] $vis fn $name(&self) -> &$ty {
		&self.$internal
	    }
    };
    ($vis:vis ref $name:ident -> $ty:ty => $internal:tt $(; $comment:literal)?) => {
	$(#[doc=$comment])?
	    #[inline] $vis fn $name(&self) -> &$ty {
		&self.$internal
	    }
    };
    ($vis:vis mut $name:ident -> $ty:ty => $internal:ident $(; $comment:literal)?) => {
	$(#[doc=$comment])?
	    #[inline] $vis fn $name(&self) -> &mut $ty {
		&mut self.$internal
	    }
    };
    ($vis:vis mut $name:ident -> $ty:ty => $internal:tt $(; $comment:literal)?) => {
	$(#[doc=$comment])?
	    #[inline] $vis fn $name(&self) -> &mut $ty {
		&mut self.$internal
	    }
    };
    ($vis:vis move $name:ident -> $ty:ty => $internal:ident $(; $comment:literal)?) => {
	$(#[doc=$comment])?
	    #[inline] $vis fn $name(&self) -> $ty {
		self.$internal
	    }
    };
    ($vis:vis move $name:ident -> $ty:ty => $internal:tt $(; $comment:literal)?) => {
	$(#[doc=$comment])?
	    #[inline] $vis fn $name(&self) -> $ty {
		self.$internal
	    }
    };
}


#[macro_export] macro_rules! lazy_format {
    ($msg:literal $($tt:tt)*) => {
	{
	    use ::std::fmt::{self, Write, Formatter};
	    use ::std::sync::Mutex;
	    use ::std::io;
	    
	    let pfn = move |fmt| {
		write!(fmt, $msg $($tt)*)?;
		let mut sfmt = String::new();
		write!(&mut sfmt, $msg $($tt)*)?;
		Ok(sfmt)
	    };

	    enum LazyFormatInner<F>
	    {
		//todo: redo this entire thing

		Pending(F),
		Complete(String),
		Error(fmt::Error),
		Panicked,
	    }

	    struct LazyFormat<F>(Mutex<LazyFormatInner<F>>);
	    
	    impl<F: FnOnce(&mut fmt::Formatter<'_>) -> io::Result<String>> fmt::Display for LazyFormat<F>
	    {
		fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
		{
		    //todo: redo this entire thing
		    /*
		    let mut inner = self.0.lock().unwrap();
		    let this = std::mem::replace(inner, LazyFormatInner::Panicked);
		    //TODO: impl fmt::Write wrapper that multi-writes to 2 outputs
		    let string = match this {
		    LazyFormatInner::Pending(func) => func(f),
		    LazyFormatInner::Complete(string) => write!(f, "{}", string).map(move |_| string),
		    LazyFormatInner::Error(err) => return Err(err),
		    LazyFormatInner::Panicked => panic!(),
		};
		    match string {
		    Err(err) => {
		     *inner = LazyFormatInner::Error(err),
		},
		}*/
		}
	    }
	}
    }
}

#[cfg(not(feature="log"))] #[macro_export] macro_rules! trace {
    ($fmt:literal $($tt:tt)*) => {
	{
	    ((), $($tt)*);
	}
    }
}

pub mod bytes
{
    use super::*;
    /// `bzero` this slice
    pub fn blank(slice: &mut [u8])
    {
	unsafe {
	    ptr::write_bytes(slice.as_mut_ptr(), 0, slice.len());
	}
    }
}

mod slice;
pub use slice::*;