use std::ops::{Add, Mul, Sub};
use generic_array::{ArrayLength, GenericArray};
use rand::{Rng, RngCore};
use generic_array::typenum::Unsigned;

pub trait GF: Add<Output=Self> + Sub<Output=Self> + Mul<Output=Self> + Copy + Clone + Eq + TryFrom<usize> {
    const ORDER: usize;
    type ChunkSize: ArrayLength;


    /// Additive identity
    const ZERO: Self;
    /// Multiplicative identity
    const ONE: Self;

    /// Multiplicative inverse
    fn minv(self) -> Self;

    fn decode(chunk: GenericArray<u8, Self::ChunkSize>) -> Self;
    fn encode(self) -> GenericArray<u8, Self::ChunkSize>;

    fn decode_slice(s: &[u8]) -> Self {
        let mut chunk = GenericArray::<u8, Self::ChunkSize>::default();
        for i in 0..Self::ChunkSize::to_usize() {
            chunk[i] = s.get(i).copied().unwrap_or(0);
        }
        Self::decode(chunk)
    }
    fn sample(rng: &mut (impl Rng + ?Sized)) -> Self;
}