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]
    }

    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
    }
}