use crate::znx_base::ZnxInfos;
use crate::{Backend, DataView, DataViewMut, Module, ZnxSliceSize, ZnxView, ZnxViewMut, alloc_aligned};
use rand::seq::SliceRandom;
use rand_core::RngCore;
use rand_distr::{Distribution, weighted::WeightedIndex};
use sampling::source::Source;

pub struct Scalar<D> {
    data: D,
    n: usize,
    cols: usize,
}

impl<D> ZnxInfos for Scalar<D> {
    fn cols(&self) -> usize {
        self.cols
    }

    fn rows(&self) -> usize {
        1
    }

    fn n(&self) -> usize {
        self.n
    }

    fn size(&self) -> usize {
        1
    }
}

impl<D> ZnxSliceSize for Scalar<D> {
    fn sl(&self) -> usize {
        self.n()
    }
}

impl<D> DataView for Scalar<D> {
    type D = D;
    fn data(&self) -> &Self::D {
        &self.data
    }
}

impl<D> DataViewMut for Scalar<D> {
    fn data_mut(&mut self) -> &mut Self::D {
        &mut self.data
    }
}

impl<D: AsRef<[u8]>> ZnxView for Scalar<D> {
    type Scalar = i64;
}

impl<D: AsMut<[u8]> + AsRef<[u8]>> Scalar<D> {
    pub fn fill_ternary_prob(&mut self, col: usize, prob: f64, source: &mut Source) {
        let choices: [i64; 3] = [-1, 0, 1];
        let weights: [f64; 3] = [prob / 2.0, 1.0 - prob, prob / 2.0];
        let dist: WeightedIndex<f64> = WeightedIndex::new(&weights).unwrap();
        self.at_mut(col, 0)
            .iter_mut()
            .for_each(|x: &mut i64| *x = choices[dist.sample(source)]);
    }

    pub fn fill_ternary_hw(&mut self, col: usize, hw: usize, source: &mut Source) {
        assert!(hw <= self.n());
        self.at_mut(col, 0)[..hw]
            .iter_mut()
            .for_each(|x: &mut i64| *x = (((source.next_u32() & 1) as i64) << 1) - 1);
        self.at_mut(col, 0).shuffle(source);
    }
}

impl<D: From<Vec<u8>>> Scalar<D> {
    pub(crate) fn bytes_of<S: Sized>(n: usize, cols: usize) -> usize {
        n * cols * size_of::<S>()
    }

    pub(crate) fn new<S: Sized>(n: usize, cols: usize) -> Self {
        let data = alloc_aligned::<u8>(Self::bytes_of::<S>(n, cols));
        Self {
            data: data.into(),
            n,
            cols,
        }
    }

    pub(crate) fn new_from_bytes<S: Sized>(n: usize, cols: usize, bytes: impl Into<Vec<u8>>) -> Self {
        let data: Vec<u8> = bytes.into();
        assert!(data.len() == Self::bytes_of::<S>(n, cols));
        Self {
            data: data.into(),
            n,
            cols,
        }
    }
}

pub type ScalarOwned = Scalar<Vec<u8>>;

pub trait ScalarAlloc {
    fn bytes_of_scalar(&self, cols: usize) -> usize;
    fn new_scalar(&self, cols: usize) -> ScalarOwned;
    fn new_scalar_from_bytes(&self, cols: usize, bytes: Vec<u8>) -> ScalarOwned;
}

impl<B: Backend> ScalarAlloc for Module<B> {
    fn bytes_of_scalar(&self, cols: usize) -> usize {
        ScalarOwned::bytes_of::<i64>(self.n(), cols)
    }
    fn new_scalar(&self, cols: usize) -> ScalarOwned {
        ScalarOwned::new::<i64>(self.n(), cols)
    }
    fn new_scalar_from_bytes(&self, cols: usize, bytes: Vec<u8>) -> ScalarOwned {
        ScalarOwned::new_from_bytes::<i64>(self.n(), cols, bytes)
    }
}

pub trait ScalarToRef {
    fn to_ref(&self) -> Scalar<&[u8]>;
}

pub trait ScalarToMut {
    fn to_mut(&mut self) -> Scalar<&mut [u8]>;
}

impl ScalarToMut for Scalar<Vec<u8>> {
    fn to_mut(&mut self) -> Scalar<&mut [u8]> {
        Scalar {
            data: self.data.as_mut_slice(),
            n: self.n,
            cols: self.cols,
        }
    }
}

impl ScalarToRef for Scalar<Vec<u8>> {
    fn to_ref(&self) -> Scalar<&[u8]> {
        Scalar {
            data: self.data.as_slice(),
            n: self.n,
            cols: self.cols,
        }
    }
}

impl ScalarToMut for Scalar<&mut [u8]> {
    fn to_mut(&mut self) -> Scalar<&mut [u8]> {
        Scalar {
            data: self.data,
            n: self.n,
            cols: self.cols,
        }
    }
}

impl ScalarToRef for Scalar<&mut [u8]> {
    fn to_ref(&self) -> Scalar<&[u8]> {
        Scalar {
            data: self.data,
            n: self.n,
            cols: self.cols,
        }
    }
}

impl ScalarToRef for Scalar<&[u8]> {
    fn to_ref(&self) -> Scalar<&[u8]> {
        Scalar {
            data: self.data,
            n: self.n,
            cols: self.cols,
        }
    }
}