use cgmath::prelude::*;
use cgmath::{Vector3, vec3};
use rand::prelude::*;
use std::f64::INFINITY;
use crate::camera::Camera;
use crate::scene::Scene;
use crate::utils::{print_colour};
use crate::ray::Ray;
use crate::hittable::Hittable;

fn ray_colour(rng: &mut ThreadRng, ray: &Ray, scene: &Scene, depth: i32) -> Vector3<f64> {
    if depth <= 0 { return vec3(0.0, 0.0, 0.0) }

    if let Some(t) = scene.is_hit(ray, 0.001, INFINITY) {
        if let Some(nray) = t.material.scatter(rng, ray, &t) {
            ray_colour(rng, &nray.ray, scene, depth-1).mul_element_wise(nray.attenuation)
        } else {
            vec3(0.0, 0.0, 0.0)
        }
    } else {
        let t = 0.5 * (ray.dir.normalize().y + 1.0);
        (1.0 - t) * vec3(1.0, 1.0, 1.0) + t * vec3(0.5, 0.7, 1.0)
    }
}

pub fn render(world: &Scene, camera: Camera, image_height: i32, image_width: i32,
          samples: i32, max_depth: i32, rng: &mut ThreadRng) {
    for j in 0 .. image_height {
        eprint!("\rScanlines: {:3} / {:3}", j+1, image_height);
        for i in 0 .. image_width  {
            let mut colour = vec3(0.0, 0.0, 0.0);
            for _ in 0 .. samples {
                let ru: f64 = rng.gen();
                let rv: f64 = rng.gen();
                let u = (i as f64 + ru) / image_width as f64;
                let v = ((image_height - 1 - j) as f64 + rv) / image_height as f64;
                let ray = camera.get_ray(rng, u, v);
                colour += ray_colour(rng, &ray, &world, max_depth);
            }
            print_colour(&colour, samples);
        }
    }
}