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

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 thread_render(
    world: &Scene,
    camera: &Camera,
    rng: &mut ThreadRng,
    image_height: i32,
    image_width: i32,
    samples: i32,
    max_depth: i32,
    i: i32,
    j: i32,
) -> Vector3<f64> {
    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);
    }
    colour
}

pub fn render(
    world: &Scene,
    camera: &Camera,
    image_height: i32,
    image_width: i32,
    samples: i32,
    max_depth: i32,
    threads: i32,
) {
    for j in 0..image_height {
        eprint!("\rScanlines: {:3} / {:3}", j + 1, image_height);
        for i in 0..image_width {
            let colours = (0..threads).into_par_iter().map(|_| {
                let mut trng = thread_rng();
                thread_render(
                    world,
                    camera,
                    &mut trng,
                    image_height,
                    image_width,
                    samples / threads,
                    max_depth,
                    i,
                    j,
                )
            });
            let colour = colours.sum::<Vector3<f64>>();
            print_colour(&colour, samples);
        }
    }
}