use crate::cast_mut_u8_to_mut_i64_slice;
use crate::ffi::znx::{
    znx_automorphism_i64, znx_automorphism_inplace_i64, znx_normalize, znx_zero_i64_ref,
};
use crate::module::Module;
use itertools::izip;
use rand_distr::{Distribution, Normal};
use sampling::source::Source;
use std::cmp::min;

impl Module {
    pub fn new_vec_znx(&self, log_base2k: usize, log_q: usize) -> VecZnx {
        VecZnx::new(self.n(), log_base2k, log_q)
    }
}

#[derive(Clone)]
pub struct VecZnx {
    pub n: usize,
    pub log_base2k: usize,
    pub data: Vec<i64>,
}

impl VecZnx {
    pub fn new(n: usize, log_base2k: usize, limbs: usize) -> Self {
        Self {
            n: n,
            log_base2k: log_base2k,
            data: vec![i64::default(); Self::buffer_size(n, limbs)],
        }
    }

    pub fn buffer_size(n: usize, limbs: usize) -> usize {
        n * limbs
    }

    pub fn from_buffer(&mut self, n: usize, log_base2k: usize, limbs: usize, buf: &[i64]) {
        let size = Self::buffer_size(n, limbs);
        assert!(
            buf.len() >= size,
            "invalid buffer: buf.len()={} < self.buffer_size(n={}, limbs={})={}",
            buf.len(),
            n,
            limbs,
            size
        );
        self.n = n;
        self.log_base2k = log_base2k;
        self.data = Vec::from(&buf[..size])
    }

    pub fn log_n(&self) -> u64 {
        (u64::BITS - (self.n - 1).leading_zeros()) as _
    }

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

    pub fn limbs(&self) -> usize {
        self.data.len() / self.n
    }

    pub fn copy_from(&mut self, a: &VecZnx) {
        let size = min(self.data.len(), a.data.len());
        self.data[..size].copy_from_slice(&a.data[..size])
    }

    pub fn as_ptr(&self) -> *const i64 {
        self.data.as_ptr()
    }

    pub fn as_mut_ptr(&mut self) -> *mut i64 {
        self.data.as_mut_ptr()
    }

    pub fn at(&self, i: usize) -> &[i64] {
        &self.data[i * self.n..(i + 1) * self.n]
    }

    pub fn at_ptr(&self, i: usize) -> *const i64 {
        &self.data[i * self.n] as *const i64
    }

    pub fn at_mut_ptr(&mut self, i: usize) -> *mut i64 {
        &mut self.data[i * self.n] as *mut i64
    }

    pub fn at_mut(&mut self, i: usize) -> &mut [i64] {
        &mut self.data[i * self.n..(i + 1) * self.n]
    }

    pub fn zero(&mut self) {
        unsafe { znx_zero_i64_ref(self.data.len() as u64, self.data.as_mut_ptr()) }
    }

    pub fn from_i64(&mut self, data: &[i64], log_max: usize, log_k: usize) {
        let limbs: usize = (log_k + self.log_base2k - 1) / self.log_base2k;

        assert!(limbs <= self.limbs(), "invalid argument log_k: (log_k + self.log_base2k - 1)/self.log_base2k={} > self.limbs()={}", limbs, self.limbs());

        let size: usize = min(data.len(), self.n());
        let log_k_rem: usize = self.log_base2k - (log_k % self.log_base2k);

        // If 2^{log_base2k} * 2^{k_rem} < 2^{63}-1, then we can simply copy
        // values on the last limb.
        // Else we decompose values base2k.
        if log_max + log_k_rem < 63 || log_k_rem == self.log_base2k {
            (0..limbs - 1).for_each(|i| unsafe {
                znx_zero_i64_ref(size as u64, self.at_mut(i).as_mut_ptr());
            });
            self.at_mut(self.limbs() - 1)[..size].copy_from_slice(&data[..size]);
        } else {
            let mask: i64 = (1 << self.log_base2k) - 1;
            let steps: usize = min(limbs, (log_max + self.log_base2k - 1) / self.log_base2k);

            (0..steps).for_each(|i| unsafe {
                znx_zero_i64_ref(size as u64, self.at_mut(i).as_mut_ptr());
            });

            (limbs - steps..limbs)
                .rev()
                .enumerate()
                .for_each(|(i, i_rev)| {
                    let shift: usize = i * self.log_base2k;
                    izip!(self.at_mut(i_rev)[..size].iter_mut(), data[..size].iter())
                        .for_each(|(y, x)| *y = (x >> shift) & mask);
                })
        }

        // Case where self.prec % self.k != 0.
        if log_k_rem != self.log_base2k {
            let limbs = self.limbs();
            let steps: usize = min(limbs, (log_max + self.log_base2k - 1) / self.log_base2k);
            (limbs - steps..limbs).rev().for_each(|i| {
                self.at_mut(i)[..size]
                    .iter_mut()
                    .for_each(|x| *x <<= log_k_rem);
            })
        }
    }

    pub fn from_i64_single(&mut self, i: usize, value: i64, log_max: usize, log_k: usize) {
        assert!(i < self.n());
        let limbs: usize = (log_k + self.log_base2k - 1) / self.log_base2k;
        assert!(limbs <= self.limbs(), "invalid argument log_k: (log_k + self.log_base2k - 1)/self.log_base2k={} > self.limbs()={}", limbs, self.limbs());
        let log_k_rem: usize = self.log_base2k - (log_k % self.log_base2k);
        let limbs = self.limbs();

        // If 2^{log_base2k} * 2^{log_k_rem} < 2^{63}-1, then we can simply copy
        // values on the last limb.
        // Else we decompose values base2k.
        if log_max + log_k_rem < 63 || log_k_rem == self.log_base2k {
            (0..limbs - 1).for_each(|j| self.at_mut(j)[i] = 0);

            self.at_mut(self.limbs() - 1)[i] = value;
        } else {
            let mask: i64 = (1 << self.log_base2k) - 1;
            let steps: usize = min(limbs, (log_max + self.log_base2k - 1) / self.log_base2k);

            (0..limbs - steps).for_each(|j| self.at_mut(j)[i] = 0);

            (limbs - steps..limbs)
                .rev()
                .enumerate()
                .for_each(|(j, j_rev)| {
                    self.at_mut(j_rev)[i] = (value >> (j * self.log_base2k)) & mask;
                })
        }

        // Case where self.prec % self.k != 0.
        if log_k_rem != self.log_base2k {
            let limbs = self.limbs();
            let steps: usize = min(limbs, (log_max + self.log_base2k - 1) / self.log_base2k);
            (limbs - steps..limbs).rev().for_each(|j| {
                self.at_mut(j)[i] <<= log_k_rem;
            })
        }
    }

    pub fn normalize(&mut self, carry: &mut [u8]) {
        assert!(
            carry.len() >= self.n * 8,
            "invalid carry: carry.len()={} < self.n()={}",
            carry.len(),
            self.n()
        );

        let carry_i64: &mut [i64] = cast_mut_u8_to_mut_i64_slice(carry);

        unsafe {
            znx_zero_i64_ref(self.n() as u64, carry_i64.as_mut_ptr());
            (0..self.limbs()).rev().for_each(|i| {
                znx_normalize(
                    self.n as u64,
                    self.log_base2k as u64,
                    self.at_mut_ptr(i),
                    carry_i64.as_mut_ptr(),
                    self.at_mut_ptr(i),
                    carry_i64.as_mut_ptr(),
                )
            });
        }
    }

    pub fn to_i64(&self, data: &mut [i64], log_k: usize) {
        let limbs: usize = (log_k + self.log_base2k - 1) / self.log_base2k;
        assert!(
            data.len() >= self.n,
            "invalid data: data.len()={} < self.n()={}",
            data.len(),
            self.n
        );
        data.copy_from_slice(self.at(0));
        let rem: usize = self.log_base2k - (log_k % self.log_base2k);
        (1..limbs).for_each(|i| {
            if i == limbs - 1 && rem != self.log_base2k {
                let k_rem: usize = self.log_base2k - rem;
                izip!(self.at(i).iter(), data.iter_mut()).for_each(|(x, y)| {
                    *y = (*y << k_rem) + (x >> rem);
                });
            } else {
                izip!(self.at(i).iter(), data.iter_mut()).for_each(|(x, y)| {
                    *y = (*y << self.log_base2k) + x;
                });
            }
        })
    }

    pub fn to_i64_single(&self, i: usize, log_k: usize) -> i64 {
        let limbs: usize = (log_k + self.log_base2k - 1) / self.log_base2k;
        assert!(i < self.n());
        let mut res: i64 = self.data[i];
        let rem: usize = self.log_base2k - (log_k % self.log_base2k);
        (1..limbs).for_each(|i| {
            let x = self.data[i * self.n];
            if i == limbs - 1 && rem != self.log_base2k {
                let k_rem: usize = self.log_base2k - rem;
                res = (res << k_rem) + (x >> rem);
            } else {
                res = (res << self.log_base2k) + x;
            }
        });
        res
    }

    pub fn automorphism_inplace(&mut self, gal_el: i64) {
        unsafe {
            (0..self.limbs()).for_each(|i| {
                znx_automorphism_inplace_i64(self.n as u64, gal_el, self.at_mut_ptr(i))
            })
        }
    }
    pub fn automorphism(&mut self, gal_el: i64, a: &mut VecZnx) {
        unsafe {
            (0..self.limbs()).for_each(|i| {
                znx_automorphism_i64(self.n as u64, gal_el, a.at_mut_ptr(i), self.at_ptr(i))
            })
        }
    }

    pub fn fill_uniform(&mut self, source: &mut Source, log_k: usize) {
        let mut base2k: u64 = 1 << self.log_base2k;
        let mut mask: u64 = base2k - 1;
        let mut base2k_half: i64 = (base2k >> 1) as i64;

        let size: usize = self.n() * (self.limbs() - 1);

        self.data[..size]
            .iter_mut()
            .for_each(|x| *x = (source.next_u64n(base2k, mask) as i64) - base2k_half);

        let log_base2k_rem: usize = log_k % self.log_base2k;

        if log_base2k_rem != 0 {
            base2k = 1 << log_base2k_rem;
            mask = (base2k - 1) << (self.log_base2k - log_base2k_rem);
            base2k_half = ((mask >> 1) + 1) as i64;
        }

        self.data[size..]
            .iter_mut()
            .for_each(|x| *x = (source.next_u64n(base2k, mask) as i64) - base2k_half);
    }

    pub fn add_dist_f64<T: Distribution<f64>>(
        &mut self,
        source: &mut Source,
        dist: T,
        bound: f64,
        log_k: usize,
    ) {
        let log_base2k_rem: usize = log_k % self.log_base2k;

        if log_base2k_rem != 0 {
            self.at_mut(self.limbs() - 1).iter_mut().for_each(|a| {
                let mut dist_f64: f64 = dist.sample(source);
                while dist_f64.abs() > bound {
                    dist_f64 = dist.sample(source)
                }
                *a += (dist_f64.round() as i64) << log_base2k_rem
            });
        } else {
            self.at_mut(self.limbs() - 1).iter_mut().for_each(|a| {
                let mut dist_f64: f64 = dist.sample(source);
                while dist_f64.abs() > bound {
                    dist_f64 = dist.sample(source)
                }
                *a += dist_f64.round() as i64
            });
        }
    }

    pub fn add_normal(&mut self, source: &mut Source, sigma: f64, bound: f64, log_k: usize) {
        self.add_dist_f64(source, Normal::new(0.0, sigma).unwrap(), bound, log_k);
    }

    pub fn trunc_pow2(&mut self, k: usize) {
        if k == 0 {
            return;
        }

        self.data
            .truncate((self.limbs() - k / self.log_base2k) * self.n());

        let k_rem: usize = k % self.log_base2k;

        if k_rem != 0 {
            let mask: i64 = ((1 << (self.log_base2k - k_rem - 1)) - 1) << k_rem;
            self.at_mut(self.limbs() - 1)
                .iter_mut()
                .for_each(|x: &mut i64| *x &= mask)
        }
    }

    pub fn rsh(&mut self, k: usize, carry: &mut [u8]) {
        assert!(
            carry.len() >> 3 >= self.n(),
            "invalid carry: carry.len()/8={} < self.n()={}",
            carry.len() >> 3,
            self.n()
        );

        let limbs: usize = self.limbs();
        let limbs_steps: usize = k / self.log_base2k;

        self.data.rotate_right(self.n * limbs_steps);
        unsafe {
            znx_zero_i64_ref((self.n * limbs_steps) as u64, self.data.as_mut_ptr());
        }

        let k_rem = k % self.log_base2k;

        if k_rem != 0 {
            let carry_i64: &mut [i64] = cast_mut_u8_to_mut_i64_slice(carry);

            unsafe {
                znx_zero_i64_ref(self.n() as u64, carry_i64.as_mut_ptr());
            }

            let mask: i64 = (1 << k_rem) - 1;
            let log_base2k: usize = self.log_base2k;

            (limbs_steps..limbs).for_each(|i| {
                izip!(carry_i64.iter_mut(), self.at_mut(i).iter_mut()).for_each(|(ci, xi)| {
                    *xi += *ci << log_base2k;
                    *ci = *xi & mask;
                    *xi /= 1 << k_rem;
                });
            })
        }
    }

    pub fn switch_degree(&self, a: &mut VecZnx) {
        let (n_in, n_out) = (self.n(), a.n());
        let (gap_in, gap_out): (usize, usize);

        if n_in > n_out {
            (gap_in, gap_out) = (n_in / n_out, 1)
        } else {
            (gap_in, gap_out) = (1, n_out / n_in);
            a.zero();
        }

        let limbs = min(self.limbs(), a.limbs());

        (0..limbs).for_each(|i| {
            izip!(
                self.at(i).iter().step_by(gap_in),
                a.at_mut(i).iter_mut().step_by(gap_out)
            )
            .for_each(|(x_in, x_out)| *x_out = *x_in);
        });
    }

    pub fn print_limbs(&self, limbs: usize, n: usize) {
        (0..limbs).for_each(|i| println!("{}: {:?}", i, &self.at(i)[..n]))
    }
}

#[cfg(test)]
mod tests {
    use crate::VecZnx;
    use itertools::izip;
    use sampling::source::Source;

    #[test]
    fn test_set_get_i64_lo_norm() {
        let n: usize = 8;
        let log_base2k: usize = 17;
        let limbs: usize = 5;
        let log_k: usize = limbs * log_base2k - 5;
        let mut a: VecZnx = VecZnx::new(n, log_base2k, limbs);
        let mut have: Vec<i64> = vec![i64::default(); n];
        have.iter_mut()
            .enumerate()
            .for_each(|(i, x)| *x = (i as i64) - (n as i64) / 2);
        a.from_i64(&have, 10, log_k);
        let mut want = vec![i64::default(); n];
        a.to_i64(&mut want, log_k);
        izip!(want, have).for_each(|(a, b)| assert_eq!(a, b));
    }

    #[test]
    fn test_set_get_i64_hi_norm() {
        let n: usize = 8;
        let log_base2k: usize = 17;
        let limbs: usize = 5;
        let log_k: usize = limbs * log_base2k - 5;
        let mut a: VecZnx = VecZnx::new(n, log_base2k, limbs);
        let mut have: Vec<i64> = vec![i64::default(); n];
        let mut source = Source::new([1; 32]);
        have.iter_mut().for_each(|x| {
            *x = source
                .next_u64n(u64::MAX, u64::MAX)
                .wrapping_sub(u64::MAX / 2 + 1) as i64;
        });
        a.from_i64(&have, 63, log_k);
        //(0..a.limbs()).for_each(|i| println!("i:{} -> {:?}", i, a.at(i)));
        let mut want = vec![i64::default(); n];
        //(0..a.limbs()).for_each(|i| println!("i:{} -> {:?}", i, a.at(i)));
        a.to_i64(&mut want, log_k);
        izip!(want, have).for_each(|(a, b)| assert_eq!(a, b, "{} != {}", a, b));
    }
    #[test]
    fn test_normalize() {
        let n: usize = 8;
        let log_base2k: usize = 17;
        let limbs: usize = 5;
        let log_k: usize = limbs * log_base2k - 5;
        let mut a: VecZnx = VecZnx::new(n, log_base2k, limbs);
        let mut have: Vec<i64> = vec![i64::default(); n];
        let mut source = Source::new([1; 32]);
        have.iter_mut().for_each(|x| {
            *x = source
                .next_u64n(u64::MAX, u64::MAX)
                .wrapping_sub(u64::MAX / 2 + 1) as i64;
        });
        a.from_i64(&have, 63, log_k);
        let mut carry: Vec<u8> = vec![u8::default(); n * 8];
        a.normalize(&mut carry);

        let base_half = 1 << (log_base2k - 1);
        a.data
            .iter()
            .for_each(|x| assert!(x.abs() <= base_half, "|x|={} > 2^(k-1)={}", x, base_half));
        let mut want = vec![i64::default(); n];
        a.to_i64(&mut want, log_k);
        izip!(want, have).for_each(|(a, b)| assert_eq!(a, b, "{} != {}", a, b));
    }
}