use rand::distributions::{Distribution, Uniform};
use rand::Rng;
use crate::Point3;

pub struct Perlin {
    ranfloat: Vec<f64>,
    perm_x: Vec<usize>,
    perm_y: Vec<usize>,
    perm_z: Vec<usize>,
}

impl Perlin {
    const POINT_COUNT: usize = 256;

    pub fn new() -> Self {
        let range = Uniform::from(0.0..1.0);
        let mut rng = rand::thread_rng();
        let mut ranfloat = Vec::with_capacity(Perlin::POINT_COUNT);
        (0..Perlin::POINT_COUNT).for_each(|_i|ranfloat.push(range.sample(&mut rng)));
        Perlin {
            ranfloat,
            perm_x: Perlin::perlin_generate_perm(),
            perm_y: Perlin::perlin_generate_perm(),
            perm_z: Perlin::perlin_generate_perm(),
        }
    }

    pub fn noise(&self, point: &Point3) -> f64 {
        /*
        let i = ((4.0 * point.x()) as i32) & 255;
        let j = ((4.0 * point.y()) as i32) & 255;
        let k= ((4.0 * point.z()) as i32) & 255;
        let idx = self.perm_x[i as usize] ^ self.perm_y[j as usize] ^ self.perm_z[k as usize];
        self.ranfloat[idx]
        */
        let u = point.x() - point.x().floor();
        let v = point.y() - point.y().floor();
        let w = point.z() - point.z().floor();
        let i = point.x().floor() as i32;
        let j = point.y().floor() as i32;
        let k = point.z().floor() as i32;
        let mut c: [[[f64; 2]; 2]; 2] = [[[0.0; 2]; 2]; 2];

        for di in 0..2 {
            for dj in 0..2 {
                for dk in 0..2 {
                    let idx = self.perm_x[((i+di) & 255) as usize] ^
                        self.perm_y[((j+dj) & 255) as usize] ^
                        self.perm_z[((k+dk) & 255) as usize];
                    c[di as usize][dj as usize][dk as usize] = self.ranfloat[idx];
                }
            }
        }
        Perlin::trilinerar_interpolation(c, u, v, w)
    }

    fn perlin_generate_perm() -> Vec<usize> {
        let mut p = Vec::with_capacity(Perlin::POINT_COUNT);
        (0..Perlin::POINT_COUNT).for_each(|i| p.push(i));
        let mut rng = rand::thread_rng();
        (1..Perlin::POINT_COUNT).rev().for_each(|idx| {
            let target = rng.gen_range(0..=idx);
            p.swap(idx, target);
        });
        p
    }

    fn trilinerar_interpolation(c: [[[f64; 2]; 2]; 2], u: f64, v: f64, w: f64) -> f64 {
        let mut accum = 0.0;
        for i in 0..2 {
            for j in 0..2 {
                for k in 0..2 {
                    let ifl = i as f64;
                    let jfl = j as f64;
                    let kfl = k as f64;
                    accum += (ifl*u + (1.0-ifl)*(1.0-u)) *
                        (jfl*v + (1.0-jfl)*(1.0-v)) *
                        (kfl*w + (1.0-kfl)*(1.0-w)) *
                        c[i][j][k];
                }
            }
        }
        accum
    }
}