use std::{
    fmt,
    hash::{DefaultHasher, Hasher},
};

use crate::{
    alloc_aligned,
    layouts::{
        Data, DataMut, DataRef, DataView, DataViewMut, DigestU64, FillUniform, ReaderFrom, ScalarZnx, ToOwnedDeep, WriterTo,
        ZnxInfos, ZnxSliceSize, ZnxView, ZnxViewMut, ZnxZero,
    },
    source::Source,
};

use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
use rand::RngCore;

#[repr(C)]
#[derive(PartialEq, Eq, Clone, Copy, Hash)]
pub struct VecZnx<D: Data> {
    pub data: D,
    pub n: usize,
    pub cols: usize,
    pub size: usize,
    pub max_size: usize,
}

impl<D: DataRef> VecZnx<D> {
    pub fn as_scalar_znx_ref(&self, col: usize, limb: usize) -> ScalarZnx<&[u8]> {
        ScalarZnx {
            data: bytemuck::cast_slice(self.at(col, limb)),
            n: self.n,
            cols: 1,
        }
    }
}

impl<D: DataMut> VecZnx<D> {
    pub fn as_scalar_znx_mut(&mut self, col: usize, limb: usize) -> ScalarZnx<&mut [u8]> {
        ScalarZnx {
            n: self.n,
            cols: 1,
            data: bytemuck::cast_slice_mut(self.at_mut(col, limb)),
        }
    }
}

impl<D: Data + Default> Default for VecZnx<D> {
    fn default() -> Self {
        Self {
            data: D::default(),
            n: 0,
            cols: 0,
            size: 0,
            max_size: 0,
        }
    }
}

impl<D: DataRef> DigestU64 for VecZnx<D> {
    fn digest_u64(&self) -> u64 {
        let mut h: DefaultHasher = DefaultHasher::new();
        h.write(self.data.as_ref());
        h.write_usize(self.n);
        h.write_usize(self.cols);
        h.write_usize(self.size);
        h.write_usize(self.max_size);
        h.finish()
    }
}

impl<D: DataRef> ToOwnedDeep for VecZnx<D> {
    type Owned = VecZnx<Vec<u8>>;
    fn to_owned_deep(&self) -> Self::Owned {
        VecZnx {
            data: self.data.as_ref().to_vec(),
            n: self.n,
            cols: self.cols,
            size: self.size,
            max_size: self.max_size,
        }
    }
}

impl<D: DataRef> fmt::Debug for VecZnx<D> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{self}")
    }
}

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

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

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

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

impl<D: Data> ZnxSliceSize for VecZnx<D> {
    fn sl(&self) -> usize {
        self.n() * self.cols()
    }
}

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

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

impl<D: DataRef> ZnxView for VecZnx<D> {
    type Scalar = i64;
}

impl VecZnx<Vec<u8>> {
    pub fn rsh_tmp_bytes(n: usize) -> usize {
        n * std::mem::size_of::<i64>()
    }
}

impl<D: DataMut> ZnxZero for VecZnx<D> {
    fn zero(&mut self) {
        self.raw_mut().fill(0)
    }
    fn zero_at(&mut self, i: usize, j: usize) {
        self.at_mut(i, j).fill(0);
    }
}

impl VecZnx<Vec<u8>> {
    pub fn bytes_of(n: usize, cols: usize, size: usize) -> usize {
        n * cols * size * size_of::<i64>()
    }

    pub fn alloc(n: usize, cols: usize, size: usize) -> Self {
        let data: Vec<u8> = alloc_aligned::<u8>(Self::bytes_of(n, cols, size));
        Self {
            data,
            n,
            cols,
            size,
            max_size: size,
        }
    }

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

impl<D: Data> VecZnx<D> {
    pub fn from_data(data: D, n: usize, cols: usize, size: usize) -> Self {
        Self {
            data,
            n,
            cols,
            size,
            max_size: size,
        }
    }
}

impl<D: DataRef> fmt::Display for VecZnx<D> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        writeln!(
            f,
            "VecZnx(n={}, cols={}, size={})",
            self.n, self.cols, self.size
        )?;

        for col in 0..self.cols {
            writeln!(f, "Column {col}:")?;
            for size in 0..self.size {
                let coeffs = self.at(col, size);
                write!(f, "  Size {size}: [")?;

                let max_show = 100;
                let show_count = coeffs.len().min(max_show);

                for (i, &coeff) in coeffs.iter().take(show_count).enumerate() {
                    if i > 0 {
                        write!(f, ", ")?;
                    }
                    write!(f, "{coeff}")?;
                }

                if coeffs.len() > max_show {
                    write!(f, ", ... ({} more)", coeffs.len() - max_show)?;
                }

                writeln!(f, "]")?;
            }
        }
        Ok(())
    }
}

impl<D: DataMut> FillUniform for VecZnx<D> {
    fn fill_uniform(&mut self, log_bound: usize, source: &mut Source) {
        match log_bound {
            64 => source.fill_bytes(self.data.as_mut()),
            0 => panic!("invalid log_bound, cannot be zero"),
            _ => {
                let mask: u64 = (1u64 << log_bound) - 1;
                for x in self.raw_mut().iter_mut() {
                    let r = source.next_u64() & mask;
                    *x = ((r << (64 - log_bound)) as i64) >> (64 - log_bound);
                }
            }
        }
    }
}

pub type VecZnxOwned = VecZnx<Vec<u8>>;
pub type VecZnxMut<'a> = VecZnx<&'a mut [u8]>;
pub type VecZnxRef<'a> = VecZnx<&'a [u8]>;

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

impl<D: DataRef> VecZnxToRef for VecZnx<D> {
    fn to_ref(&self) -> VecZnx<&[u8]> {
        VecZnx {
            data: self.data.as_ref(),
            n: self.n,
            cols: self.cols,
            size: self.size,
            max_size: self.max_size,
        }
    }
}

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

impl<D: DataMut> VecZnxToMut for VecZnx<D> {
    fn to_mut(&mut self) -> VecZnx<&mut [u8]> {
        VecZnx {
            data: self.data.as_mut(),
            n: self.n,
            cols: self.cols,
            size: self.size,
            max_size: self.max_size,
        }
    }
}

impl<D: DataMut> ReaderFrom for VecZnx<D> {
    fn read_from<R: std::io::Read>(&mut self, reader: &mut R) -> std::io::Result<()> {
        self.n = reader.read_u64::<LittleEndian>()? as usize;
        self.cols = reader.read_u64::<LittleEndian>()? as usize;
        self.size = reader.read_u64::<LittleEndian>()? as usize;
        self.max_size = reader.read_u64::<LittleEndian>()? as usize;
        let len: usize = reader.read_u64::<LittleEndian>()? as usize;
        let buf: &mut [u8] = self.data.as_mut();
        if buf.len() != len {
            return Err(std::io::Error::new(
                std::io::ErrorKind::UnexpectedEof,
                format!("self.data.len()={} != read len={}", buf.len(), len),
            ));
        }
        reader.read_exact(&mut buf[..len])?;
        Ok(())
    }
}

impl<D: DataRef> WriterTo for VecZnx<D> {
    fn write_to<W: std::io::Write>(&self, writer: &mut W) -> std::io::Result<()> {
        writer.write_u64::<LittleEndian>(self.n as u64)?;
        writer.write_u64::<LittleEndian>(self.cols as u64)?;
        writer.write_u64::<LittleEndian>(self.size as u64)?;
        writer.write_u64::<LittleEndian>(self.max_size as u64)?;
        let buf: &[u8] = self.data.as_ref();
        writer.write_u64::<LittleEndian>(buf.len() as u64)?;
        writer.write_all(buf)?;
        Ok(())
    }
}