// https://www.scratchapixel.com/lessons/procedural-generation-virtual-worlds/procedural-patterns-noise-part-1/simple-pattern-examples.html

use rand::RngCore;

use crate::ppm::{Pixel, Ppm};
use crate::value_noise::ValueNoise;
use crate::vec2::Vec2;

pub fn generate_turbulence(
  width: usize,
  height: usize,
  rng: impl RngCore,
) -> Ppm {
  let mut noise_map = vec![0.0; width * height];
  let noise = ValueNoise::new(rng);

  let frequency = 0.02;
  let frequency_mult = 1.8;
  let amplitude_mult = 0.35;
  let num_layers = 5;
  let mut max_noise_val = 0.0f64;

  for j in 0..height {
    for i in 0..width {
      let mut noise_point = Vec2::new(i as f64, j as f64) * frequency;
      let mut amplitude = 1.0;

      for _ in 0..num_layers {
        noise_map[j * width + i] =
          (2.0 * noise.eval(noise_point) - 1.0).abs() * amplitude;
        noise_point = noise_point * frequency_mult;
        amplitude *= amplitude_mult;
      }

      max_noise_val = max_noise_val.max(noise_map[j * width + i]);
    }
  }

  let data = noise_map
    .into_iter()
    .map(|f| {
      let v = (f / max_noise_val * 192.0 + 32.0).floor() as u8;
      Pixel(v, v, v)
    })
    .collect();
  Ppm {
    width,
    height,
    data,
  }
}