#![allow(clippy::many_single_char_names)]
use crate::{num::DefaultFloat, Matrix};
use num::{Float, One, Zero};
use std::{
  mem::{forget, MaybeUninit},
  ops::{
    Add, AddAssign, BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign, Div, DivAssign,
    Index, IndexMut, Mul, MulAssign, Neg, Not, Rem, RemAssign, Sub, SubAssign,
  },
};

/// Vector over floats and a const-size.
/// Often used through Vec2, Vec3, and Vec4 instead of the raw struct.
#[derive(Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct Vector<const N: usize, T = DefaultFloat>(pub [T; N]);

/// 2D vector with default float type (f32).
pub type Vec2<T = DefaultFloat> = Vector<2, T>;
/// 3D vector with default float type (f32).
pub type Vec3<T = DefaultFloat> = Vector<3, T>;
/// 4D vector with default float type (f32).
/// Often implicitly created by Vec3::homogeneous.
pub type Vec4<T = DefaultFloat> = Vector<4, T>;

impl<T: Copy, const N: usize> Vector<N, T> {
  /// Creates a vector of the value v (every element = v).
  pub fn of(v: T) -> Self { Vector([v; N]) }

  /// Applies this function to every vector value.
  #[inline]
  pub fn apply_fn<F, S>(self, mut f: F) -> Vector<N, S>
  where
    F: FnMut(T) -> S, {
    let mut out: [MaybeUninit<S>; N] = unsafe { MaybeUninit::uninit().assume_init() };
    for i in 0..N {
      out[i] = MaybeUninit::new(f(self[i]));
    }
    let ptr = &mut out as *mut _ as *mut [S; N];
    let res = unsafe { ptr.read() };
    forget(out);
    Vector(res)
  }

  pub fn cast<S: From<T>>(self) -> Vector<N, S> { self.apply_fn(|v| v.into()) }
  /// X component of this vector, panics if out of range
  pub fn x(&self) -> T { self[0] }
  /// Y component of this vector, panics if out of range
  pub fn y(&self) -> T { self[1] }
  /// Z component of this vector, panics if out of range
  pub fn z(&self) -> T { self[2] }
  /// W componenent of this vector, panics if out of range
  pub fn w(&self) -> T { self[3] }
}

impl<T, const N: usize> Vector<N, T> {
  pub fn with<F>(mut f: F) -> Self
  where
    F: FnMut(usize) -> T, {
    let mut out: [MaybeUninit<T>; N] = unsafe { MaybeUninit::uninit().assume_init() };
    for (i, v) in out.iter_mut().enumerate().take(N) {
      *v = MaybeUninit::new(f(i));
    }
    let ptr = &mut out as *mut _ as *mut [T; N];
    let res = unsafe { ptr.read() };
    forget(out);
    Vector(res)
  }
  pub fn iter(&self) -> impl Iterator<Item = &T> { self.0.iter() }
  pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut T> { self.0.iter_mut() }
}

impl<T: Copy, const N: usize> Vector<N, T> {
  /// Extend this vector to a larger vector.
  /// Must increase the size of the vector or keep it the same size.
  pub fn extend<const M: usize>(&self, v: T) -> Vector<M, T> {
    assert!(M >= N);
    let mut out: Vector<M, T> = Vector::of(v);
    for i in 0..N {
      out[i] = self[i];
    }
    out
  }
}

impl<T: Float, const N: usize> Vector<N, T> {
  pub fn linspace(a: T, b: T) -> Self {
    let delta = (a - b) / (T::from(N).unwrap());
    Self::with(|i| a + delta * T::from(i).unwrap())
  }
  /// Takes the dot product of two vectors
  #[inline]
  pub fn dot(&self, o: &Self) -> T { (0..N).fold(T::zero(), |acc, n| acc + self[n] * o[n]) }
  /// Computes the sqr_magnitude of the vector
  pub fn sqr_magn(&self) -> T { self.dot(self) }
  /// Takes the magnitude of the vector
  pub fn magn(&self) -> T { self.sqr_magn().sqrt() }
  /// Returns a unit vector in the same direction as self.
  /// Consider division instead of calling this method if you need efficiency.
  pub fn norm(&self) -> Self { *self / self.magn() }
  pub fn cos_similarity(&self, o: &Self) -> T { self.dot(o) / (self.magn() * o.magn()) }
  pub fn reflect(&self, across: &Self) -> Self {
    *self - (*across) * self.dot(across) * (T::one() + T::one())
  }
  pub fn refract(&self, norm: &Self, eta: T) -> Option<Self> {
    let cos_l = self.dot(norm);
    let discrim = T::one() - eta * eta * (T::one() - cos_l * cos_l);
    if discrim.is_sign_negative() {
      return None;
    }
    let cos_r = discrim.sqrt();
    Some(*self * eta - *norm * (eta * cos_l + cos_r))
  }
  /// Computes a vector from a list of strings.
  pub fn from_str_radix(strs: [&str; N], radix: u32) -> Result<Self, T::FromStrRadixErr> {
    let mut out = Self::zero();
    for i in 0..N {
      out[i] = T::from_str_radix(strs[i], radix)?;
    }
    Ok(out)
  }
  /// Linearly interpolates from self to v according to alpha, where 0 => self, and 1 => v.
  pub fn lerp(&self, v: &Self, alpha: T) -> Self { *self * (T::one() - alpha) + *v * alpha }
  /// Computes the max component of this vector
  pub fn max_component(&self) -> usize {
    let mut max_pos = 0;
    for i in 1..N {
      if self[i] > self[max_pos] {
        max_pos = i;
      }
    }
    max_pos
  }
  /// Computes the minimum component of this vector
  pub fn min_component(&self) -> usize {
    let mut min_pos = 0;
    for i in 1..N {
      if self[i] < self[min_pos] {
        min_pos = i;
      }
    }
    min_pos
  }
  /// Clamps self between min and max
  pub fn clamp(&mut self, min: T, max: T) {
    for i in 0..N {
      self[i] = self[i].min(max).max(min);
    }
  }
  pub fn dist(&self, o: &Self) -> T { (*self - *o).magn() }
  /// Shrink this vector to a lower dimension
  /// Must lower or keep the same size.
  pub fn reduce<const M: usize>(&self) -> Vector<M, T> {
    assert!(M <= N);
    let mut out: Vector<M, T> = Vector::zero();
    for i in 0..M {
      out[i] = self[i];
    }
    out
  }

  /// Takes the minimal and maximal elements from self and o and returns those vectors
  pub fn sift(&self, o: &Self) -> (Self, Self) {
    let mut min = *self;
    let mut max = *o;
    for i in 0..N {
      if self[i] > o[i] {
        max[i] = self[i];
        min[i] = o[i];
      }
    }
    (min, max)
  }

  pub fn project_onto(&self, onto: &Self) -> Self {
    let similarity = self.magn() * self.dot(onto);
    onto.norm() * similarity
  }
  pub fn col_vector(self) -> Matrix<N, 1, T> { Matrix(Vector([self])) }
  pub fn row_vector(self) -> Matrix<1, N, T> { self.col_vector().t() }

  /// Computes the bisector of two vectors = (a,b) => |a|*b + |b|*a;
  pub fn bisector(&self, o: &Self) -> Self { *self * o.magn() + *o * self.magn() }
  /// Convolves self with other, returning a vector of the same size
  pub fn convolve<const M: usize>(&self, o: &Vector<M, T>) -> Self {
    let mut out: Self = Vector::zero();
    for i in 0..N {
      for j in 0..M {
        if let Some(k) = j.checked_sub(M / 2).filter(|&k| k < N) {
          out[i] = out[i] + self[k] * o[j];
        }
      }
    }
    out
  }
  pub fn scatter_fn<S: Copy, const M: usize>(
    &self,
    idx: &Vector<N, usize>,
    base: S,
    acc: impl Fn(S, T) -> S,
  ) -> Vector<M, S> {
    let mut out = Vector::of(base);
    for i in 0..N {
      assert!(
        idx[i] < M,
        "Index in index vector larger than expected output"
      );
      out[idx[i]] = acc(out[i], self[i]);
    }
    out
  }
}

impl<const N: usize> Vector<N, bool> {
  pub fn any(&self) -> bool { self.iter().any(|&l| l) }
  pub fn all(&self) -> bool { self.iter().all(|&l| l) }
}

impl<T> Vec3<T> {
  pub const fn new(a: T, b: T, c: T) -> Self { Vector([a, b, c]) }
}

impl<T: Float> Vec3<T> {
  /// Takes the cross product of self with other
  pub fn cross(&self, o: &Self) -> Self {
    let [a, b, c] = self.0;
    let [x, y, z] = o.0;
    Vec3::new(b * z - c * y, c * x - a * z, a * y - b * x)
  }
  /// Whether or not self is aligned on the right or left hand side of normal w.r.t o.
  pub fn sided(&self, o: &Self, normal: &Self) -> bool {
    self.cross(o).dot(normal).is_sign_positive()
  }

  /// Returns the homogeneous form of this vector.
  pub fn homogeneous(&self) -> Vec4<T> {
    let &Vector([x, y, z]) = self;
    Vec4::new(x, y, z, T::one())
  }

  pub fn homogenize(&self) -> Vec2<T> {
    let &Vector([x, y, z]) = self;
    Vec2::new(x / z, y / z)
  }
}

impl<T> Vec2<T> {
  pub const fn new(a: T, b: T) -> Self { Vector([a, b]) }
}

impl<T: Copy> Vec2<T> {
  pub fn flip(&self) -> Self {
    let [i, j] = self.0;
    Vec2::new(j, i)
  }
}

impl<T: Float> Vec2<T> {
  /// Rotates this vector around the origin by theta (in radians)
  pub fn rot(&self, theta: T) -> Self {
    let &Vector([x, y]) = self;
    let (s, c) = theta.sin_cos();
    Vec2::new(c * x - s * y, s * x + c * y)
  }
  pub fn signed_angle(&self, dst: &Self) -> T {
    let [i, j] = self.0;
    let [x, y] = dst.0;
    (i * y - j * x).atan2(self.dot(dst))
  }
  pub fn perp(&self) -> Self {
    let [i, j] = self.0;
    Vec2::new(j, -i)
  }
  pub fn homogeneous(&self) -> Vec3<T> {
    let [i, j] = self.0;
    Vec3::new(i, j, T::one())
  }
}

impl<T> Vec4<T> {
  pub const fn new(a: T, b: T, c: T, w: T) -> Self { Vector([a, b, c, w]) }
}

impl<T: Float> Vec4<T> {
  pub fn homogenize(&self) -> Vec3<T> {
    let &Vector([x, y, z, w]) = self;
    Vec3::new(x, y, z) / w
  }
}

// Trait implementations for convenience
impl<T, const N: usize> AsRef<[T]> for Vector<N, T> {
  #[inline]
  fn as_ref(&self) -> &[T] { &self.0 }
}

// Op implementations
impl<T: Float, const N: usize> One for Vector<N, T> {
  #[inline]
  fn one() -> Self { Vector([T::one(); N]) }
  #[inline]
  fn is_one(&self) -> bool { self.iter().all(T::is_one) }
}

impl<T: Zero + Copy, const N: usize> Zero for Vector<N, T> {
  #[inline]
  fn zero() -> Self { Vector([T::zero(); N]) }
  #[inline]
  fn is_zero(&self) -> bool { self.iter().all(T::is_zero) }
}

use std::slice::SliceIndex;
impl<R: SliceIndex<[T]>, T, const N: usize> Index<R> for Vector<N, T> {
  type Output = R::Output;
  #[inline]
  fn index(&self, r: R) -> &Self::Output { &self.0[r] }
}

impl<R: SliceIndex<[T]>, T, const N: usize> IndexMut<R> for Vector<N, T> {
  #[inline]
  fn index_mut(&mut self, i: R) -> &mut Self::Output { &mut self.0[i] }
}

impl<T: Neg<Output = T> + Copy, const N: usize> Neg for Vector<N, T> {
  type Output = Self;
  #[inline]
  fn neg(self) -> Self::Output { self.apply_fn(|v| -v) }
}

impl<T: Not<Output = T> + Copy, const N: usize> Not for Vector<N, T> {
  type Output = Self;
  #[inline]
  fn not(self) -> Self::Output { self.apply_fn(|v| !v) }
}

macro_rules! vec_op {
  ($($t: ident, $func: ident, $op: tt;)*) => {
    $(
    impl<T: $t + Copy, const N: usize> $t for Vector<N, T> {
      type Output = Vector<N, T::Output>;
      #[inline]
      fn $func(self, o: Self) -> Self::Output {
        Self::Output::with(|i| self[i] $op o[i])
      }
    }
    )*
  };
}

vec_op!(
  Add, add, +;
  Mul, mul, *;
  Sub, sub, -;
  Div, div, /;
  Rem, rem, %;

  // Boolean operations
  BitAnd, bitand, &;
  BitOr, bitor, |;
  BitXor, bitxor, ^;
);

macro_rules! scalar_op {
  ($($t: ident, $func: ident, $op: tt;)*) => {
    $(
    impl<T: $t + Copy, const N: usize> $t<T> for Vector<N, T> {
      type Output = Vector<N, T::Output>;
      #[inline]
      fn $func(self, o: T) -> Self::Output {
        Self::Output::with(|i| self[i] $op o)
      }
    }
    )*
  };
}
scalar_op!(
  Add, add, +;
  Mul, mul, *;
  Sub, sub, -;
  Div, div, /;
  Rem, rem, %;

  // Boolean operations
  BitAnd, bitand, &;
  BitOr, bitor, |;
  BitXor, bitxor, ^;
);

macro_rules! assign_op {
  ($( $t: ident, $func: ident, $op: tt; )* ) => {
    $(
    impl<T: $t + Copy, const N: usize> $t<T> for Vector<N, T> {
      #[inline]
      fn $func(&mut self, o: T) {
        for i in 0..N {
          self[i] $op o;
        }
      }
    }
    impl<T: $t + Copy, const N: usize> $t for Vector<N, T> {
      #[inline]
      fn $func(&mut self, o: Self) {
        for i in 0..N {
          self[i] $op o[i];
        }
      }
    }
    )*
  };
}

assign_op!(
  AddAssign, add_assign, +=;
  SubAssign, sub_assign, -=;
  MulAssign, mul_assign, *=;
  DivAssign, div_assign, /=;
  RemAssign, rem_assign, %=;

  // boolean operations
  BitAndAssign, bitand_assign, &=;
  BitOrAssign, bitor_assign, |=;
  BitXorAssign, bitxor_assign, ^=;
);

macro_rules! elemwise_impl {
  ($func: ident, $call: path, $name: expr) => {
    #[doc="Element-wise "]
    #[doc=$name]
    #[doc="."]
    #[inline]
    pub fn $func(&self) -> Self { self.apply_fn($call) }
  };
  ($($func: ident, $call: path;)*) => {
    $(elemwise_impl!($func, $call, stringify!($func));)*
  };
}

macro_rules! curried_elemwise_impl {
  ($func: ident, $call: path, $name: expr) => {
    #[doc="Element-wise "]
    #[doc=$name]
    #[doc="."]
    #[inline]
    pub fn $func(&self, v: T) -> Self { self.apply_fn(|u| $call(u, v)) }
  };
  ($func: ident, $call: path) => {
    curried_elemwise_impl!($func, $call, stringify!($func));
  };
}
impl<T: Float, const N: usize> Vector<N, T> {
  // Trigonometric stuff
  elemwise_impl!(
    cos, T::cos;
    sin, T::sin;
    tan, T::tan;

    acos, T::acos;
    asin, T::asin;
    atan, T::atan;

    acosh, T::acosh;
    asinh, T::asinh;
    atanh, T::atanh;
  );

  #[inline]
  pub fn sin_cos(&self) -> (Self, Self) {
    let sscs = self.apply_fn(|u| u.sin_cos());
    (Self::with(|i| sscs[i].0), Self::with(|i| sscs[i].1))
  }

  curried_elemwise_impl!(atan2, T::atan2);
  curried_elemwise_impl!(hypot, T::hypot);

  // Rounding stuff
  elemwise_impl!(
    ceil, T::ceil;
    floor, T::floor;
    round, T::round;
  );

  // Decomposition stuff
  elemwise_impl!(
    fract, T::fract;
    trunc, T::trunc;
  );

  // Sign value stuff
  elemwise_impl!(
    abs, T::abs;
    signum, T::signum;
  );
  curried_elemwise_impl!(abs_sub, T::abs_sub);

  #[inline]
  pub fn is_sign_positive(&self) -> Vector<N, bool> { self.apply_fn(T::is_sign_positive) }
  #[inline]
  pub fn is_sign_negative(&self) -> Vector<N, bool> { self.apply_fn(T::is_sign_negative) }

  // Reciprocal
  elemwise_impl!(
    recip, T::recip;
  );

  // Logarithmic stuff
  elemwise_impl!(
    log2, T::log2;
    log10, T::log10;
    ln, T::ln;
    ln_1p, T::ln_1p;
    exp, T::exp;
    exp2, T::exp2;
    exp_m1, T::exp_m1;
    sqrt, T::sqrt;
    cbrt, T::cbrt;
  );
  curried_elemwise_impl!(powf, T::powf);
  pub fn powi(&self, v: i32) -> Self { self.apply_fn(|u| u.powi(v)) }
  curried_elemwise_impl!(log, T::log);

  // Min/max stuff
  curried_elemwise_impl!(max, T::max);
  curried_elemwise_impl!(min, T::min);

  // Degree related stuff
  elemwise_impl!(
    to_degrees, T::to_degrees;
    to_radians, T::to_radians;
  );
}

//// Trait Implementations for Vector below

impl<T: Clone, const N: usize> Clone for Vector<N, T> {
  fn clone(&self) -> Self { Self::with(|i| self[i].clone()) }
  fn clone_from(&mut self, source: &Self) {
    for i in 0..N {
      self[i].clone_from(&source[i]);
    }
  }
}

#[test]
fn example() {
  let a = Vec3::of(0.0);
  let b = a + 1.0;
  let c = b.sin();
  let _dot = b.dot(&c);

  let x = c.x();
  let y = c.y();
  let z = c.z();

  let Vector([i, j, k]) = c;
  assert_eq!(x, i);
  assert_eq!(y, j);
  assert_eq!(z, k);
}