use glam::*;
use itertools::{chain, iproduct};

use refraction::ifaces::{DebugTraceable, Traceable};
use refraction::tube::metric::Tube;
use refraction::tube::Space;
use refraction::types::{Location, Object, Ray};
use refraction::utils::put_object;

pub enum Line {
	Strip(Vec<Ray>),
	Loop(Vec<Ray>),
}

pub struct FancyLine {
	pub color: Vec3,
	pub pts: Vec<Ray>,
}

fn paint(onto: &mut Vec<FancyLine>, color: Vec3, lines: Vec<Line>) {
	onto.extend(lines.into_iter().map(move |line| FancyLine {
		color,
		pts: match line {
			Line::Strip(pts) => pts,
			Line::Loop(mut pts) => {
				pts.push(*pts.first().unwrap());
				pts
			}
		},
	}))
}

fn draw_line(a: Vec3, b: Vec3) -> Line {
	let dir = (b - a).normalize();
	Line::Strip(vec![Ray { pos: a, dir }, Ray { pos: b, dir }])
}

fn draw_rect(center: Vec3, u: Vec3, v: Vec3) -> Vec<Line> {
	let a = center - u - v;
	let b = center + u - v;
	let c = center + u + v;
	let d = center - u + v;
	vec![draw_line(a, b), draw_line(b, c), draw_line(c, d), draw_line(d, a)]
}

fn draw_ellipse(center: Vec3, u: Vec3, v: Vec3) -> Line {
	let segments = 47;
	let step = 2. * std::f32::consts::PI / segments as f32;
	Line::Loop(
		(0..segments)
			.map(|k| k as f32 * step)
			.map(Vec2::from_angle)
			.map(|d| Ray {
				pos: center + d.x * u + d.y * v,
				dir: -d.y * u + d.x * v,
			})
			.collect(),
	)
}

pub fn build() -> Vec<FancyLine> {
	let tube = Tube {
		inner_radius: 30.0,
		outer_radius: 50.0,
		internal_halflength: 100.0,
		external_halflength: 300.0,
	};

	let objs: Vec<_> = [-1.25, -1.00, -0.85, -0.50, 0.00, 0.40, 0.70, 0.95, 1.05]
		.iter()
		.enumerate()
		.map(|(k, &y)| Object {
			id: k as i32,
			loc: put_object(
				&tube,
				vec3(0.0, y * tube.external_halflength, 0.0),
				Mat3::from_mat2(Mat2::from_angle(y)),
			),
			r: 20.0,
		})
		.collect();
	let space = Space { tube, objs };
	let cam1 = put_object(&space.tube, vec3(-500., 0., 0.), Mat3::IDENTITY);
	let cam2 = put_object(
		&space.tube,
		vec3(-2.5 * tube.outer_radius, 1.25 * tube.external_halflength, 0.),
		mat3(vec3(1., -1., 0.), vec3(1., 1., 0.), vec3(0., 0., 1.)),
	);
	let cam3 = put_object(
		&space.tube,
		vec3(0.25 * tube.inner_radius, 0.25 * tube.external_halflength, 0.),
		mat3(vec3(0., -1., 0.), vec3(1., 0., 0.), vec3(0., 0., 1.)),
	);

	let mut gc = vec![];
	paint(&mut gc, vec3(0.6, 0.6, 0.6), tube.render());
	paint(&mut gc, vec3(0.0, 0.6, 1.0), draw_fan_2(&space, cam3, 1.0));
	paint(&mut gc, vec3(0.2, 1.0, 0.0), draw_fan_2(&space, cam2, 1.0));
	paint(&mut gc, vec3(1.0, 0.2, 0.0), draw_fan_2(&space, cam1, 1.0));
	gc
}

fn draw_ray_2(gc: &mut Vec<Line>, space: &Space, camera: Location, dir: Vec3) {
	let pos = vec3(0., 0., 0.);
	let (hits, path) = space.trace_dbg(camera, Ray { pos, dir });
	let hits2 = space.trace(camera, Ray { pos, dir });
	for (a, b) in hits.into_iter().zip(hits2.into_iter()) {
		assert_eq!(a.id, b.id);
		assert_eq!(a.pos, b.pos);
		assert_eq!(a.rel, b.rel);
	}

	let mut pts = path.points;
	let end_pos = *pts.last().expect("the starting point is always in the path");
	pts.extend(itertools::iterate(end_pos, |r| r.forward(100.0)).take(1000));
	gc.push(Line::Strip(pts));
}

fn draw_fan_2(space: &Space, camera: Location, spread: f32) -> Vec<Line> {
	let mut gc = vec![];
	for y in itertools_num::linspace(-spread, spread, 101) {
		draw_ray_2(&mut gc, space, camera, vec3(1., y, 0.));
	}
	gc
}

trait Renderable {
	fn render(&self) -> Vec<Line>;
}

impl Renderable for Tube {
	fn render(&self) -> Vec<Line> {
		let lines = 4;
		let step = 2. * std::f32::consts::PI / lines as f32;
		let r = 0.5 * (self.outer_radius + self.inner_radius);
		let w = 0.5 * (self.outer_radius - self.inner_radius);
		let l = vec3(0., self.external_halflength, 0.);
		let along = (0..lines)
			.map(|k| k as f32 * step)
			.map(Vec2::from_angle)
			.map(|d| vec3(d.x, 0., d.y))
			.flat_map(|d| draw_rect(r * d, w * d, l));
		let caps = iproduct!([self.inner_radius, self.outer_radius], [-l, l])
			.map(|(r, l)| draw_ellipse(l, vec3(r, 0., 0.), vec3(0., 0., r)));
		chain!(along, caps).collect()
	}
}