use core::cmp::Ordering;
use core::fmt::{Debug, Formatter};
use crate::upcast::IntoUsize;

//noinspection SpellCheckingInspection
/// Converts reference of struct to binary slice
pub fn slicify<T>(value: &T) -> &[u8] {
    let ptr = value as *const T as *const u8;
    unsafe { core::slice::from_raw_parts(ptr, core::mem::size_of::<T>()) }
}

/// Converts reference of struct to binary slice
pub unsafe fn slicify_mut<T>(value: &mut T) -> &mut [u8] {
    let ptr = value as *mut T as *mut u8;
    core::slice::from_raw_parts_mut(ptr, core::mem::size_of::<T>())
}

/// converts a non mutable reference into a mutable one
#[allow(invalid_reference_casting)]
pub unsafe fn mutify<T>(nr: &T) -> &mut T {
    &mut *(nr as *const T as *mut T)
}

/// converts a reference of any lifetime to 'static
pub unsafe fn statify<'a, T>(nr: &'a T) -> &'static T {
    &*(nr as *const T)
}

/// converts mutable a reference of any lifetime to 'static
pub unsafe fn statify_mut<'a, T>(nr: &'a mut T) -> &'static mut T {
    &mut *(nr as *mut T)
}

/// gets the distance between two references
pub fn distance(p1: impl IntoUsize, p2: impl IntoUsize) -> usize {
    let (p1, p2) = (p1.into_usize(), p2.into_usize());
    match p1.cmp(&p2) {
        Ordering::Less => p2 - p1,
        Ordering::Greater => p1 - p2,
        Ordering::Equal => 0,
    }
}

mod pointer_iterator {

    pub trait Pointer {
        type IterType;
        fn into_iter(self) -> Self::IterType;
    }

    pub struct PIter<T>(*const T);
    pub struct PIterMut<T>(*mut T);

    impl<T: 'static> Iterator for PIter<T> {
        type Item = &'static T;
        fn next(&mut self) -> Option<Self::Item> {
            unsafe {
                let r = Some(&*self.0);
                self.0 = self.0.offset(1isize);
                r
            }
        }
    }

    impl<T: 'static> Iterator for PIterMut<T> {
        type Item = &'static mut T;
        fn next(&mut self) -> Option<Self::Item> {
            unsafe {
                let r = Some(&mut *self.0);
                self.0 = self.0.offset(1isize);
                r
            }
        }
    }
    impl<T> Pointer for *const T { 
        type IterType = PIter<T>;
        fn into_iter(self) -> Self::IterType { PIter(self) }
    }
    impl<T> Pointer for *mut T { 
        type IterType = PIterMut<T>;
        fn into_iter(self) -> Self::IterType { PIterMut(self) }
    }
}

pub fn iterate<T: pointer_iterator::Pointer>(pointer: T) -> T::IterType {
    pointer.into_iter()
}

pub fn fill_with<T, F: FnMut(usize) -> T>(slice: &mut [T], mut func: F) {
    slice.iter_mut().enumerate().for_each(|(i,v)|*v = func(i))
}

pub struct FixedVec<const MAX_LEN: usize, T> {
    length: usize,
    buffer: [core::mem::MaybeUninit<T>;MAX_LEN],
}

impl<const MAX_LEN: usize, T: Sized> FixedVec<MAX_LEN, T> {
    pub fn push(&mut self, value: T) -> Option<()> {
        if self.length >= MAX_LEN { return None }
        unsafe { *self.buffer[self.length].as_mut_ptr() = value };
        self.length += 1;
        Some(())
    }

    pub fn pop(&mut self) -> Option<T> {
        if self.length == 0 { return None }
        self.length -= 1;
        Some(unsafe { self.buffer[self.length].assume_init_read() })
    }

    pub fn extend<Iter: Iterator<Item=T>>(&mut self, mut iter: Iter) -> Result<usize, usize> {
        let mut count = 0;
        loop {
            if self.length == MAX_LEN {
                return Err(count);
            }
            match iter.next() {
                None => return Ok(count),
                Some(value) => {
                    unsafe { *self.buffer[self.length].as_mut_ptr() = value };
                    self.length += 1;
                    count += 1;
                }
            }

        }
    }

    pub fn as_slice(&self) -> &[T] {
        // length can't be larger than MaxLen, use unsafe to dodge the panic
        unsafe { core::slice::from_raw_parts(self.buffer.as_ptr() as *const T, self.length) }
    }

}

impl<const MAX_LEN: usize, T: Debug> Debug for FixedVec<MAX_LEN, T> {
    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
        Debug::fmt(self.as_slice(), f)
    }
}

impl<const MAX_LEN: usize, T> Drop for FixedVec<MAX_LEN, T> {
    fn drop(&mut self) {
        for e in &mut self.buffer[..self.length] {
            unsafe { e.assume_init_drop() }
        }
    }
}