use backend::{
    FFT64, MatZnxDftOps, MatZnxDftScratch, Module, ScalarZnx, ScalarZnxAlloc, ScalarZnxDft, ScalarZnxDftAlloc, ScalarZnxDftOps,
    Scratch, VecZnxAlloc, VecZnxBigAlloc, VecZnxBigOps, VecZnxBigScratch, VecZnxDftAlloc, VecZnxDftOps, VecZnxOps, ZnxView,
    ZnxViewMut, ZnxZero,
};
use itertools::izip;

use crate::{
    GLWECiphertext, GLWECiphertextToMut, Infos, LWECiphertext,
    blind_rotation::{key::BlindRotationKeyCGGI, lut::LookUpTable},
    lwe::ciphertext::LWECiphertextToRef,
};

pub fn cggi_blind_rotate_scratch_space(
    module: &Module<FFT64>,
    extension_factor: usize,
    basek: usize,
    k_lut: usize,
    k_brk: usize,
    rows: usize,
    rank: usize,
) -> usize {
    let cols: usize = rank + 1;
    let brk_size: usize = k_brk.div_ceil(basek);

    let acc_dft: usize = module.bytes_of_vec_znx_dft(cols, rows) * extension_factor;
    let acc_big: usize = module.bytes_of_vec_znx_big(1, brk_size);
    let vmp_res: usize = module.bytes_of_vec_znx_dft(cols, brk_size) * extension_factor;
    let acc_dft_add: usize = vmp_res;
    let xai_plus_y: usize = module.bytes_of_scalar_znx(1);
    let xai_plus_y_dft: usize = module.bytes_of_scalar_znx_dft(1);
    let vmp: usize = module.vmp_apply_tmp_bytes(brk_size, rows, rows, 2, 2, brk_size); // GGSW product: (1 x 2) x (2 x 2)

    let acc: usize;
    if extension_factor > 1 {
        acc = module.bytes_of_vec_znx(cols, k_lut.div_ceil(basek)) * extension_factor;
    } else {
        acc = 0;
    }

    return acc
        + acc_dft
        + acc_dft_add
        + vmp_res
        + xai_plus_y
        + xai_plus_y_dft
        + (vmp | (acc_big + (module.vec_znx_big_normalize_tmp_bytes() | module.vec_znx_idft_tmp_bytes())));
}

pub fn cggi_blind_rotate<DataRes, DataIn>(
    module: &Module<FFT64>,
    res: &mut GLWECiphertext<DataRes>,
    lwe: &LWECiphertext<DataIn>,
    lut: &LookUpTable,
    brk: &BlindRotationKeyCGGI<FFT64>,
    scratch: &mut Scratch,
) where
    DataRes: AsRef<[u8]> + AsMut<[u8]>,
    DataIn: AsRef<[u8]>,
{
    if lut.extension_factor() > 1 {
        cggi_blind_rotate_block_binary_extended(module, res, lwe, lut, brk, scratch);
    } else if brk.block_size() > 1 {
        cggi_blind_rotate_block_binary(module, res, lwe, lut, brk, scratch);
    } else {
        todo!("implement this case")
    }
}

// TODO: ENSURE DOMAIN EXTENSION AS
pub(crate) fn cggi_blind_rotate_block_binary_extended<DataRes, DataIn>(
    module: &Module<FFT64>,
    res: &mut GLWECiphertext<DataRes>,
    lwe: &LWECiphertext<DataIn>,
    lut: &LookUpTable,
    brk: &BlindRotationKeyCGGI<FFT64>,
    scratch: &mut Scratch,
) where
    DataRes: AsRef<[u8]> + AsMut<[u8]>,
    DataIn: AsRef<[u8]>,
{
    let extension_factor: usize = lut.extension_factor();
    let basek: usize = res.basek();
    let rows: usize = brk.rows();
    let cols: usize = res.rank() + 1;

    let (mut acc, scratch1) = scratch.tmp_slice_vec_znx(extension_factor, module, cols, res.size());
    let (mut acc_dft, scratch2) = scratch1.tmp_slice_vec_znx_dft(extension_factor, module, cols, rows);
    let (mut vmp_res, scratch3) = scratch2.tmp_slice_vec_znx_dft(extension_factor, module, cols, brk.size());
    let (mut acc_add_dft, scratch4) = scratch3.tmp_slice_vec_znx_dft(extension_factor, module, cols, brk.size());
    let (mut xai_plus_y, scratch5) = scratch4.tmp_scalar_znx(module, 1);
    let (mut xai_plus_y_dft, scratch6) = scratch5.tmp_scalar_znx_dft(module, 1);

    (0..extension_factor).for_each(|i| {
        acc[i].zero();
    });

    let mut lwe_2n: Vec<i64> = vec![0i64; lwe.n() + 1]; // TODO: from scratch space
    let lwe_ref: LWECiphertext<&[u8]> = lwe.to_ref();

    let two_n_ext: usize = 2 * lut.domain_size();

    negate_and_mod_switch_2n(two_n_ext, &mut lwe_2n, &lwe_ref);

    let a: &[i64] = &lwe_2n[1..];
    let b_pos: usize = ((lwe_2n[0] + two_n_ext as i64) % two_n_ext as i64) as usize;

    let b_hi: usize = b_pos / extension_factor;
    let b_lo: usize = b_pos % extension_factor;

    for (i, j) in (0..b_lo).zip(extension_factor - b_lo..extension_factor) {
        module.vec_znx_rotate(b_hi as i64 + 1, &mut acc[i], 0, &lut.data[j], 0);
    }
    for (i, j) in (b_lo..extension_factor).zip(0..extension_factor - b_lo) {
        module.vec_znx_rotate(b_hi as i64, &mut acc[i], 0, &lut.data[j], 0);
    }

    let block_size: usize = brk.block_size();

    izip!(
        a.chunks_exact(block_size),
        brk.data.chunks_exact(block_size)
    )
    .enumerate()
    .for_each(|(i, (ai, ski))| {
        (0..extension_factor).for_each(|i| {
            (0..cols).for_each(|j| {
                module.vec_znx_dft(1, 0, &mut acc_dft[i], j, &acc[i], j);
            });
            acc_add_dft[i].zero();
        });

        // TODO: first & last iterations can be optimized
        izip!(ai.iter(), ski.iter()).for_each(|(aii, skii)| {
            let ai_pos: usize = ((aii + two_n_ext as i64) % two_n_ext as i64) as usize;
            let ai_hi: usize = ai_pos / extension_factor;
            let ai_lo: usize = ai_pos % extension_factor;

            // vmp_res = DFT(acc) * BRK[i]
            (0..extension_factor).for_each(|i| {
                module.vmp_apply(&mut vmp_res[i], &acc_dft[i], &skii.data, scratch6);
            });

            // Trivial case: no rotation between polynomials, we can directly multiply with (X^{-ai} - 1)
            if ai_lo == 0 {
                // DFT X^{-ai}
                set_xai_plus_y(module, ai_hi, -1, &mut xai_plus_y_dft, &mut xai_plus_y);

                // Sets acc_add_dft[i] = (acc[i] * sk) * (X^{-ai} - 1)
                (0..extension_factor).for_each(|j| {
                    (0..cols).for_each(|i| {
                        module.svp_apply_inplace(&mut vmp_res[j], i, &xai_plus_y_dft, 0);
                        module.vec_znx_dft_add_inplace(&mut acc_add_dft[j], i, &vmp_res[j], i);
                    });
                });
            // Non trivial case: rotation between polynomials
            // In this case we can't directly multiply with (X^{-ai} - 1) because of the
            // ring homomorphism R^{N} -> prod R^{N/extension_factor}, so we split the
            // computation in two steps: acc_add_dft = (acc * sk) * (-1) + (acc * sk) * X^{-ai}
            } else {
                // Sets acc_add_dft[i] = acc[i] * sk
                (0..extension_factor).for_each(|i| {
                    (0..cols).for_each(|k| {
                        module.vec_znx_dft_sub_ab_inplace(&mut acc_add_dft[i], k, &vmp_res[i], k);
                    })
                });

                // DFT X^{-ai}
                set_xai_plus_y(module, ai_hi + 1, 0, &mut xai_plus_y_dft, &mut xai_plus_y);

                // Sets acc_add_dft[0..ai_lo] += (acc[extension_factor - ai_lo..extension_factor] * sk) * X^{-ai+1}
                for (i, j) in (0..ai_lo).zip(extension_factor - ai_lo..extension_factor) {
                    (0..cols).for_each(|k| {
                        module.svp_apply_inplace(&mut vmp_res[j], k, &xai_plus_y_dft, 0);
                        module.vec_znx_dft_add_inplace(&mut acc_add_dft[i], k, &vmp_res[j], k);
                    });
                }

                // DFT X^{-ai}
                set_xai_plus_y(module, ai_hi, 0, &mut xai_plus_y_dft, &mut xai_plus_y);

                // Sets acc_add_dft[ai_lo..extension_factor] += (acc[0..extension_factor - ai_lo] * sk) * X^{-ai}
                for (i, j) in (ai_lo..extension_factor).zip(0..extension_factor - ai_lo) {
                    (0..cols).for_each(|k| {
                        module.svp_apply_inplace(&mut vmp_res[j], k, &xai_plus_y_dft, 0);
                        module.vec_znx_dft_add_inplace(&mut acc_add_dft[i], k, &vmp_res[j], k);
                    });
                }
            }
        });

        {
            let (mut acc_add_big, scratch7) = scratch6.tmp_vec_znx_big(module, 1, brk.size());

            (0..extension_factor).for_each(|j| {
                (0..cols).for_each(|i| {
                    module.vec_znx_idft(&mut acc_add_big, 0, &acc_add_dft[j], i, scratch7);
                    module.vec_znx_big_add_small_inplace(&mut acc_add_big, 0, &acc[j], i);
                    module.vec_znx_big_normalize(basek, &mut acc[j], i, &acc_add_big, 0, scratch7);
                });
            });
        }
    });

    (0..cols).for_each(|i| {
        module.vec_znx_copy(&mut res.data, i, &acc[0], i);
    });
}

fn set_xai_plus_y(
    module: &Module<FFT64>,
    ai: usize,
    y: i64,
    res: &mut ScalarZnxDft<&mut [u8], FFT64>,
    buf: &mut ScalarZnx<&mut [u8]>,
) {
    let n: usize = module.n();

    {
        let raw: &mut [i64] = buf.at_mut(0, 0);
        if ai < n {
            raw[ai] = 1;
        } else {
            raw[(ai - n) & (n - 1)] = -1;
        }
        raw[0] += y;
    }

    module.svp_prepare(res, 0, buf, 0);

    {
        let raw: &mut [i64] = buf.at_mut(0, 0);

        if ai < n {
            raw[ai] = 0;
        } else {
            raw[(ai - n) & (n - 1)] = 0;
        }
        raw[0] = 0;
    }
}

pub(crate) fn cggi_blind_rotate_block_binary<DataRes, DataIn>(
    module: &Module<FFT64>,
    res: &mut GLWECiphertext<DataRes>,
    lwe: &LWECiphertext<DataIn>,
    lut: &LookUpTable,
    brk: &BlindRotationKeyCGGI<FFT64>,
    scratch: &mut Scratch,
) where
    DataRes: AsRef<[u8]> + AsMut<[u8]>,
    DataIn: AsRef<[u8]>,
{
    let mut lwe_2n: Vec<i64> = vec![0i64; lwe.n() + 1]; // TODO: from scratch space
    let mut out_mut: GLWECiphertext<&mut [u8]> = res.to_mut();
    let lwe_ref: LWECiphertext<&[u8]> = lwe.to_ref();
    let two_n: usize = module.n() << 1;
    let basek: usize = brk.basek();
    let rows = brk.rows();

    let cols: usize = out_mut.rank() + 1;

    negate_and_mod_switch_2n(2 * lut.domain_size(), &mut lwe_2n, &lwe_ref);

    let a: &[i64] = &lwe_2n[1..];
    let b: i64 = lwe_2n[0];

    out_mut.data.zero();

    // Initialize out to X^{b} * LUT(X)
    module.vec_znx_rotate(b, &mut out_mut.data, 0, &lut.data[0], 0);

    let block_size: usize = brk.block_size();

    // ACC + [sum DFT(X^ai -1) * (DFT(ACC) x BRKi)]

    let (mut acc_dft, scratch1) = scratch.tmp_vec_znx_dft(module, cols, rows);
    let (mut vmp_res, scratch2) = scratch1.tmp_vec_znx_dft(module, cols, brk.size());
    let (mut acc_add_dft, scratch3) = scratch2.tmp_vec_znx_dft(module, cols, brk.size());
    let (mut xai_plus_y, scratch4) = scratch3.tmp_scalar_znx(module, 1);
    let (mut xai_plus_y_dft, scratch5) = scratch4.tmp_scalar_znx_dft(module, 1);

    izip!(
        a.chunks_exact(block_size),
        brk.data.chunks_exact(block_size)
    )
    .for_each(|(ai, ski)| {
        (0..cols).for_each(|j| {
            module.vec_znx_dft(1, 0, &mut acc_dft, j, &out_mut.data, j);
        });

        acc_add_dft.zero();

        izip!(ai.iter(), ski.iter()).for_each(|(aii, skii)| {
            let ai_pos: usize = ((aii + two_n as i64) % two_n as i64) as usize;

            // vmp_res = DFT(acc) * BRK[i]
            module.vmp_apply(&mut vmp_res, &acc_dft, &skii.data, scratch5);

            // DFT(X^ai -1)
            set_xai_plus_y(module, ai_pos, -1, &mut xai_plus_y_dft, &mut xai_plus_y);

            // DFT(X^ai -1) * (DFT(acc) * BRK[i])
            (0..cols).for_each(|i| {
                module.svp_apply_inplace(&mut vmp_res, i, &xai_plus_y_dft, 0);
                module.vec_znx_dft_add_inplace(&mut acc_add_dft, i, &vmp_res, i);
            });
        });

        (0..cols).for_each(|i| {
            module.vec_znx_dft_add_inplace(&mut acc_dft, i, &acc_add_dft, i);
        });

        {
            let (mut acc_add_big, scratch6) = scratch5.tmp_vec_znx_big(module, 1, brk.size());

            (0..cols).for_each(|i| {
                module.vec_znx_idft(&mut acc_add_big, 0, &acc_add_dft, i, scratch6);
                module.vec_znx_big_add_small_inplace(&mut acc_add_big, 0, &out_mut.data, i);
                module.vec_znx_big_normalize(basek, &mut out_mut.data, i, &acc_add_big, 0, scratch6);
            });
        }
    });
}

pub(crate) fn negate_and_mod_switch_2n(n: usize, res: &mut [i64], lwe: &LWECiphertext<&[u8]>) {
    let basek: usize = lwe.basek();

    let log2n: usize = usize::BITS as usize - (n - 1).leading_zeros() as usize + 1;

    res.copy_from_slice(&lwe.data.at(0, 0));
    res.iter_mut().for_each(|x| *x = -*x);

    if basek > log2n {
        let diff: usize = basek - log2n;
        res.iter_mut().for_each(|x| {
            *x = div_ceil_signed_by_pow2(x, diff);
        })
    } else {
        let rem: usize = basek - (log2n % basek);
        let size: usize = log2n.div_ceil(basek);
        (1..size).for_each(|i| {
            if i == size - 1 && rem != basek {
                let k_rem: usize = basek - rem;
                izip!(lwe.data.at(0, i).iter(), res.iter_mut()).for_each(|(x, y)| {
                    *y = (*y << k_rem) + (x >> rem);
                });
            } else {
                izip!(lwe.data.at(0, i).iter(), res.iter_mut()).for_each(|(x, y)| {
                    *y = (*y << basek) + x;
                });
            }
        })
    }
}

#[inline(always)]
fn div_round_by_pow2(x: &i64, k: usize) -> i64 {
    if x >= &0 {
        (x + (1 << (k - 1))) >> k
    } else {
        (x + (-1 << (k - 1))) >> k
    }
}

// #[inline(always)]
// fn div_floor_signed_by_pow2(x: &i64, k: usize) -> i64{
// let bias: i64 = (1 << k) - 1;
// (x + ((x >> 63) & bias)) >> k
// }

#[inline(always)]
fn div_ceil_signed_by_pow2(x: &i64, k: usize) -> i64 {
    let bias: i64 = (1 << k) - 1;
    (x + ((x >> 63) & bias)) >> k
}