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//! # Galois Field
//!
//! finite field arithmetic
//!
//! ```
//! use gf::GF;
//!
//! let x = GF(123u8);
//! let y = GF(225u8);
//! println!("{}", x + y);
//! ```
#![no_std]
#![cfg_attr(feature = "unstable_simd", feature(portable_simd))]

use core::fmt;

mod gen_table;
mod impls;

#[cfg(feature = "unstable_simd")]
mod simd;
#[cfg(feature = "unstable_simd")]
pub use simd::GF256Simd;

/// # The Galois Field Type.
///
/// ```
/// use gf::GF;
///
/// let val = GF(4);
///
/// let typed_val1 = GF(5u8);
/// let typed_val2 = GF::<u8>(5);
/// assert_eq!(typed_val1, typed_val2)
/// ```
///
/// Supports all basic Mathematical Functions
#[derive(PartialEq, Eq, Clone, Copy, Default, Hash, Debug)]
#[repr(transparent)]
pub struct GF<T>(pub T);

pub type GF256 = GF<u8>;

impl<T> GF<T> {
    #[inline]
    pub fn from_ref(u: &T) -> &Self {
        unsafe { &*(u as *const T).cast::<Self>() }
    }

    #[inline]
    pub fn from_mut(u: &mut T) -> &mut Self {
        unsafe { &mut *(u as *mut T).cast::<Self>() }
    }

    #[inline]
    pub fn from_slice(slice: &[T]) -> &[Self] {
        unsafe { core::slice::from_raw_parts(slice.as_ptr().cast::<Self>(), slice.len()) }
    }

    #[inline]
    pub fn from_slice_mut(slice: &mut [T]) -> &mut [Self] {
        unsafe { core::slice::from_raw_parts_mut(slice.as_mut_ptr().cast::<Self>(), slice.len()) }
    }
}

impl<T: fmt::Display> fmt::Display for GF<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)
    }
}

impl<T: fmt::Binary> fmt::Binary for GF<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)
    }
}

impl<T: fmt::Octal> fmt::Octal for GF<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)
    }
}

impl<T: fmt::LowerHex> fmt::LowerHex for GF<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)
    }
}

impl<T: fmt::UpperHex> fmt::UpperHex for GF<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)
    }
}

#[cfg(test)]
mod tests {
    use crate::GF;
    #[test]
    fn add_sub() {
        assert_eq!((GF(5u8) + GF(60)) - GF(5), GF(60))
    }

    #[test]
    fn mul_div() {
        assert_eq!((GF(5u8) * GF(60)) / GF(5), GF(60))
    }

    #[test]
    fn pow() {
        assert_eq!(GF(5u8).pow(0), GF(1))
    }
    #[test]
    fn pow1() {
        assert_eq!(GF(5u8).pow(1), GF(5))
    }
    #[test]
    fn pow2() {
        assert_eq!(GF(4u8).pow(2), GF(4) * GF(4))
    }

    #[test]
    fn conv() {
        assert_eq!(GF::from(34u8), GF(34u8));
        let x: u8 = GF(34u8).into();
        assert!(x == 34);
    }
}