pub mod util;
pub mod shadows;

use macroquad::prelude::draw_texture;
use macroquad::prelude::DMat3;
use smallvec::SmallVec;
use smallvec::smallvec;
use std::collections::HashSet;
use macroquad::prelude::set_camera;
use macroquad::prelude::DVec2;
use macroquad::prelude::Camera2D;
use core::mem::swap;
use std::collections::HashMap;
use core::fmt;
use core::cell::Cell;
use std::collections::hash_map::Entry;
use core::f64::consts::PI;
use macroquad::prelude::mouse_position;
use macroquad::prelude::is_mouse_button_pressed;
use macroquad::prelude::Vec2;
use core::ops::DerefMut;
use core::ops::Deref;
use core::hash::Hasher;
use core::hash::Hash;
use macroquad::prelude::screen_height;
use macroquad::prelude::next_frame;
use macroquad::prelude::screen_width;
use macroquad::prelude::clear_background;
use macroquad::prelude::Color;
use macroquad::input::MouseButton;
use std::sync::Arc;

const FG: Color		= Color::new(0.7686, 0.7216, 0.4078, 1.0);

const SPEED: f64	= 0.1;
const BOING_RADIUS: f64    = 30.0;
const LIGHT_RADIUS: f32 = 128.;
const WALL_THICKNESS: f32 = 5.;

#[macroquad::main("BasicShapes")]
async fn main() {
	let mut dd = DelaunayDemo::default();
	let mut camera = dd.get_camera();
	set_camera(&camera);
	let mut iter = 0;

	for _ in 0..100 {
		dd.add_random_point().unwrap();
	}

	let gradient = shadows::get_gradient(LIGHT_RADIUS);

	loop {
		if iter == 100 {
			iter = 0;
			dd.resize((screen_width()/screen_height()) as f64);
			camera = dd.get_camera();
			set_camera(&mut camera);
		}

		let mouse_position: Vec2 = camera.screen_to_world(mouse_position().into());
		if is_mouse_button_pressed(MouseButton::Left) {
			dd.click(mouse_position);
		}
		if is_mouse_button_pressed(MouseButton::Right) {

			println!("{}", mouse_position);

			for triangle in &dd.triangles {
				if triangle.invalidated_by_point(mouse_position.as_f64()) {
					println!(
						"{:?} has center {} with r={}",
						triangle,
						triangle.circumcenter().0,
						triangle.circumcenter().1,
					);
				}
			}
		}

		clear_background(shadows::BLACK);

		draw_texture(
			gradient,
			mouse_position.x - LIGHT_RADIUS,
			mouse_position.y - LIGHT_RADIUS,
			FG
		);

		for (w1, w2) in dd.get_walls() {
			let w1 = w1.as_f32();
			let w2 = w2.as_f32();
			if shadows::wall_needs_to_be_drawn(w1, w2, mouse_position, LIGHT_RADIUS) {
				let perpendicular = (w1 - w2).perp();
				let shift = perpendicular / perpendicular.length() * WALL_THICKNESS;
				let points = [
					w1 + shift,
					w1 - shift,
					w2 + shift,
					w2 - shift,
				];
				shadows::draw_wall(points[0], points[1], mouse_position, LIGHT_RADIUS);
				shadows::draw_wall(points[1], points[2], mouse_position, LIGHT_RADIUS);
				shadows::draw_wall(points[2], points[3], mouse_position, LIGHT_RADIUS);
				shadows::draw_wall(points[3], points[0], mouse_position, LIGHT_RADIUS);
			}
		}

		dd.update();

		iter += 1;
		next_frame().await;
	}
}

pub struct DelaunayDemo {
	pub nodes: Vec<NodeRef>,
	pub triangles: Vec<Triangle>,
	pub spanning_tree: HashSet<Edge>,
	spanning_tree_conn: HashMap<usize, SmallVec<[usize; 8]>>, // usize is casted from a noderef
	adjacency: HashMap<Edge, (NeighborOne, NeighborTwo)>,
	poisoned: bool,
	random_state: u128,
	width: f64,
	height: f64,
}

#[derive(Debug)]
enum NeighborOne {
	Occupant(Triangle),
	Border,
}
#[derive(Debug)]
enum NeighborTwo {
	Friend(Triangle),
	Hole,
}
use NeighborOne::*;
use NeighborTwo::*;

impl From<Triangle> for NeighborOne {
	fn from(triangle: Triangle) -> NeighborOne {
		Occupant(triangle)
	}
}

impl From<&Triangle> for NeighborOne {
	fn from(triangle: &Triangle) -> NeighborOne {
		triangle.clone().into()
	}
}

impl From<Triangle> for NeighborTwo {
	fn from(triangle: Triangle) -> NeighborTwo {
		Friend(triangle)
	}
}

impl From<&Triangle> for NeighborTwo {
	fn from(triangle: &Triangle) -> NeighborTwo {
		triangle.clone().into()
	}
}

impl NeighborTwo {
	fn unwrap_mut(&mut self) -> &mut Triangle {
		if let Friend(triangle) = self {
			triangle
		} else {
			panic!("Tried to unwrap a neighbor that wasn't a friend");
		}
	}
}

impl Default for DelaunayDemo {
	fn default() -> Self {
		const HEIGHT: f64 = 900.0;
		const WIDTH: f64 = 1200.0;
		let nodes: Vec<NodeRef> = vec![
			Arc::new(Cell::new((-5.0 - BOING_RADIUS, 0.0 - BOING_RADIUS).into())),
			Arc::new(Cell::new((0.0 - BOING_RADIUS, HEIGHT + BOING_RADIUS).into())),
			Arc::new(Cell::new((WIDTH + BOING_RADIUS, 0.0 - BOING_RADIUS).into())),
			Arc::new(Cell::new((WIDTH + BOING_RADIUS, HEIGHT + BOING_RADIUS).into())),
		];
		let edges = (
			Edge(nodes[2].clone(), nodes[0].clone()),
			Edge(nodes[0].clone(), nodes[1].clone()),
			Edge(nodes[1].clone(), nodes[2].clone()),
			Edge(nodes[2].clone(), nodes[3].clone()),
			Edge(nodes[3].clone(), nodes[1].clone()),
		);
		let triangles = vec![
			Triangle::new(
				[edges.0.clone(), edges.1.clone(), edges.2.clone()],
			),
			Triangle::new(
				[edges.2.clone(), edges.3.clone(), edges.4.clone()],
			),
		];
		let adjacency = [
			(edges.0, (Border, (&triangles[0]).into())),
			(edges.1, (Border, (&triangles[0]).into())),
			(edges.2, ((&triangles[0]).into(), (&triangles[1]).into())),
			(edges.3, (Border, (&triangles[1]).into())),
			(edges.4, (Border, (&triangles[1]).into())),
		].into();
		let mut random = 0xACAB_1312;
		util::pcg64_iterstate(&mut random);
		let dd = DelaunayDemo {
			nodes,
			adjacency,
			triangles,
			height: HEIGHT,
			width: WIDTH,
			random_state: random,
			poisoned: false,
			spanning_tree: HashSet::with_capacity(100),
			spanning_tree_conn: HashMap::with_capacity(100),
		};

		/*let n_v_nodes = ((height / 50.0) - 1.0).round();
		let v_inc = height / n_v_nodes;
		for i in 0..(n_v_nodes as usize) {
			println!("A");
			let random = util::pcg64(&mut dd.random_state);
			let offset = (random as f64) / (u64::MAX as f64) * 10.0;
			dd.add_point((offset, (i + 1) as f64 * v_inc).into()).unwrap();
			println!("B");
			dd.add_point((width - offset, (i + 1) as f64 * v_inc).into()).unwrap();
		}
		let n_h_nodes = ((width / 50.0) - 1.0).round();
		let h_inc = width / n_h_nodes;
		for i in 0..(n_h_nodes as usize) {
			println!("C");
			let random = util::pcg64(&mut dd.random_state);
			let offset = (random as f64) / (u64::MAX as f64) * 10.0;
			dd.add_point(((i + 1) as f64 * h_inc, offset).into()).unwrap();
			println!("D");
			dd.add_point(((i + 1) as f64 * h_inc, height - offset).into()).unwrap();
		}*/

		dd
	}
}

#[derive(Copy, Clone, Debug)]
pub struct Node(DVec2, DVec2);

impl Deref for Node {
	type Target = DVec2;

	fn deref(&self) -> &DVec2 {
		&self.0
	}
}

impl DerefMut for Node {
	fn deref_mut(&mut self) -> &mut DVec2 {
		&mut self.0
	}
}

impl From<(f64, f64)> for Node {
	fn from((x, y): (f64, f64)) -> Node {
		Node(DVec2::new(x, y), DVec2::ZERO)
	}
}

type NodeRef = Arc<Cell<Node>>;

#[derive(Clone)]
pub struct Edge(NodeRef, NodeRef);

impl Edge {
	fn node_thats_not(&self, node: &NodeRef) -> Result<&NodeRef, String> {
		[&self.0, &self.1].into_iter()
			.filter(|n| !Arc::ptr_eq(n, node))
			.next()
			.ok_or_else(|| format!("Edge {:?} connects two identical nodes", self))
	}
}

impl PartialEq for Edge {
	fn eq(&self, other: &Edge) -> bool {
		let mut our_ptrs = [
			Arc::as_ptr(&self.0),
			Arc::as_ptr(&self.1),
		];
		let mut other_ptrs = [
			Arc::as_ptr(&other.0),
			Arc::as_ptr(&other.1),
		];
		our_ptrs.sort_unstable();
		other_ptrs.sort_unstable();

		our_ptrs[0] == other_ptrs[0] && our_ptrs[1] == other_ptrs[1]
	}
}

impl Eq for Edge {}

impl Hash for Edge {
	fn hash<H: Hasher>(&self, state: &mut H) {
		let mut ptrs = [
			Arc::as_ptr(&self.0),
			Arc::as_ptr(&self.1),
		];
		ptrs.sort_unstable();
		ptrs.hash(state);
	}
}

impl fmt::Debug for Edge {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		write!(f,
			"Edge({},{} -> {},{})",
			self.0.get().x,
			self.0.get().y,
			self.1.get().x,
			self.1.get().y,
		)
	}
}

#[derive(Clone)]
pub struct Triangle {
	nodes: [NodeRef; 3],
	edges: [Edge; 3],
}

impl Triangle {
	pub fn new(edges: [Edge; 3]) -> Triangle {
		let nodes = [
			edges[0].0.clone(),
			edges[0].1.clone(),
			if Arc::ptr_eq(&edges[1].0, &edges[0].0) || Arc::ptr_eq(&edges[1].0, &edges[0].1) {
				edges[1].1.clone()
			} else {
				edges[1].0.clone()
			}
		];
		Triangle {
			nodes,
			edges,
		}
	}

	pub fn new_from_points(nodes: [NodeRef; 3]) -> Triangle {
		let edges = [
			Edge(nodes[0].clone(), nodes[1].clone()),
			Edge(nodes[1].clone(), nodes[2].clone()),
			Edge(nodes[2].clone(), nodes[0].clone()),
		];
		Triangle {
			nodes,
			edges,
		}
	}

	pub fn circumcenter(&self) -> (DVec2, f64) {
		Self::calc_circumcenter(*self.nodes[0].get(), *self.nodes[1].get(), *self.nodes[2].get())
	}

	fn calc_circumcenter(a: DVec2, b: DVec2, c: DVec2) -> (DVec2, f64) {

		let mag_a2 = a.powf(2.).dot(DVec2::ONE);
		let mag_b2 = b.powf(2.).dot(DVec2::ONE);
		let mag_c2 = c.powf(2.).dot(DVec2::ONE);

		let s = DVec2::new(
			DMat3::from_cols_array(&[
				mag_a2, a.y, 1.,
				mag_b2, b.y, 1.,
				mag_c2, c.y, 1.,
			]).determinant() * 0.5,
			DMat3::from_cols_array(&[
				a.x, mag_a2, 1.,
				b.x, mag_b2, 1.,
				c.x, mag_c2, 1.,
			]).determinant() * 0.5,
		);

		let little_a = DMat3::from_cols_array(&[
			a.x, a.y, 1.,
			b.x, b.y, 1.,
			c.x, c.y, 1.,
		]).determinant();

		let circumcenter = s / little_a;
		let radius = circumcenter.distance(a);

		(circumcenter, radius)
	}

	pub fn invalidated_by_point(&self, point: DVec2) -> bool {
		let (c, r) = self.circumcenter();
		c.distance(point) < r
	}

	pub fn common_edge(&self, other: &Triangle) -> Result<&Edge, String> {
		let common_edge = self.edges.iter()
			.filter(|e| other.edges.contains(e))
			.collect::<Vec<_>>();

		if common_edge.len() > 1 {
			Err(format!(
				"Tried to call common_edge on two triangles which share more \
				than one common edge?: {:?} and {:?}.",
				self, other
			))
		} else if let Some(common_edge) = common_edge.first() {
			Ok(common_edge)
		} else {
			Err(format!(
				"Tried to call common_edge on two triangles which don't \
				share a common edges: {:?} and {:?}.",
				self, other
			))
		}
	}

	pub fn point_not_on(&self, edge: &Edge) -> Result<&NodeRef, String> {
		self.nodes.iter()
			.filter(|n|
				!Arc::ptr_eq(n, &edge.0) &&
				!Arc::ptr_eq(n, &edge.1)
			)
			.next()
			.ok_or_else(||format!(
				".point_not_on called on {:?} with edge {:?}, but no points were found \
				not on this edge",
				self, edge
			))
	}

	pub fn invalidated_by_neighbor(&self, other: &Triangle) -> Result<bool, String> {

		let common_edge = self.common_edge(other)?;

		let self_point = self.point_not_on(common_edge)?;
		let othr_point = other.point_not_on(common_edge)?;

		let common_distance = common_edge.0.get().distance(*common_edge.1.get());
		let self_sidea = common_edge.0.get().distance(*self_point.get());
		let self_sideb = common_edge.1.get().distance(*self_point.get());
		let othr_sidea = common_edge.0.get().distance(*othr_point.get());
		let othr_sideb = common_edge.1.get().distance(*othr_point.get());

		let self_angle = f64::acos(
			(
				self_sidea.powf(2.0)
				+ self_sideb.powf(2.0)
				- common_distance.powf(2.0)
			) / (2.0 * self_sidea * self_sideb)
		);
		let othr_angle = f64::acos(
			(
				othr_sidea.powf(2.0)
				+ othr_sideb.powf(2.0)
				- common_distance.powf(2.0)
			) / (2.0 * othr_sidea * othr_sideb)
		);

		return Ok(self_angle + othr_angle > PI)
	}
}

impl PartialEq for Triangle {
	fn eq(&self, other: &Triangle) -> bool {
		let mut our_ptrs = [
			Arc::as_ptr(&self.nodes[0]),
			Arc::as_ptr(&self.nodes[1]),
			Arc::as_ptr(&self.nodes[2]),
		];
		let mut other_ptrs = [
			Arc::as_ptr(&other.nodes[0]),
			Arc::as_ptr(&other.nodes[1]),
			Arc::as_ptr(&other.nodes[2]),
		];
		our_ptrs.sort_unstable();
		other_ptrs.sort_unstable();

		our_ptrs[0] == other_ptrs[0] &&
		our_ptrs[1] == other_ptrs[1] &&
		our_ptrs[2] == other_ptrs[2]
	}
}

impl Eq for Triangle {}

impl Hash for Triangle {
	fn hash<H: Hasher>(&self, state: &mut H) {
		let mut ptrs = [
			Arc::as_ptr(&self.nodes[0]),
			Arc::as_ptr(&self.nodes[1]),
			Arc::as_ptr(&self.nodes[2]),
		];
		ptrs.sort_unstable();
		ptrs.hash(state);
	}
}

impl fmt::Debug for Triangle {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		let coords: Vec<_> = self.nodes.iter()
			.flat_map(|n| [n.get().x, n.get().y])
			.collect();
		write!(
			f,
			"Triangle[({}, {}), ({}, {}), ({}, {}))",
			coords[0],
			coords[1],
			coords[2],
			coords[3],
			coords[4],
			coords[5],
		)
	}
}

impl DelaunayDemo {
	pub fn get_camera(&self) -> Camera2D {

		let width = self.width as f32;
		let height = self.height as f32;

		Camera2D {
			target: Vec2::new(width / 2.0, height / 2.0),
			zoom: Vec2::new(2./width, 2./height),
			.. Default::default()
		}
	}

	pub fn resize(&mut self, aspect_ratio: f64) {
		let minimum_dimension = f64::min(self.width, self.height);
		let (new_width, new_height) = if aspect_ratio < 1.0 {
			(minimum_dimension, minimum_dimension / aspect_ratio)
		} else {
			(minimum_dimension * aspect_ratio, minimum_dimension)
		};

		let resize_factor = DVec2::new(
			new_width / self.width,
			new_height / self.height,
		);

		if resize_factor != DVec2::ONE {

			for node in &self.nodes {
				let mut node_inner = node.get();
				node_inner.0 *= resize_factor;
				node.set(node_inner);
			}

			self.width = new_width;
			self.height = new_height;

			if let Err(msg) = self.re_delaunize() {
				eprintln!("POISONED: {}", msg);
				self.poisoned = true;
			}
		}
	}

	fn get_walls(&self) -> impl Iterator<Item=(DVec2, DVec2)> + '_ {
		self.adjacency.values()
			.filter_map(|n|
				if let (Occupant(tri1), Friend(tri2)) = n {
					Some((tri1, tri2))
				} else {
					None
				}
			)
			.filter(|(tri1, tri2)| !self.spanning_tree.contains(tri1.common_edge(tri2).unwrap()))
			.map(|(tri1, tri2)| (tri1.circumcenter().0, tri2.circumcenter().0))
	}

	fn update(&mut self) {
		if self.poisoned {
			return
		}
		for node in self.nodes.clone() {
			if node.get().1 != DVec2::ZERO {
				self.move_point(node);
			}
		}
		if let Err(msg) = self.re_delaunize() {
			eprintln!("POISONED: {}", msg);
			self.poisoned = true;
		}
	}

	fn click(&mut self, pos: Vec2) {
		if let Err(msg) = self.add_point_random_dir(pos.as_f64()) {
			self.poisoned = true;
			eprintln!("POISONED: {}", msg);
		}
	}

	fn add_random_point(&mut self) -> Result<(), String> {
		let random = util::pcg64(&mut self.random_state);
		let x = (random & 0xffffffff) as f64 / (0xffffffffu32 as f64) * self.width;
		let y = (random >> 32) as f64 / (0xffffffffu32 as f64) * self.height;
		self.add_point_random_dir((x, y).into())
	}

	fn add_point_random_dir(&mut self, pos: DVec2) -> Result<(), String> {
		let random = util::pcg64(&mut self.random_state);
		let angle = (random as f64) / (u64::MAX as f64) * (2.0 * std::f64::consts::PI);
		let direction = DVec2::new(
			f64::cos(angle),
			f64::sin(angle),
		);
		self.add_point(Node(pos, direction * SPEED))
	}

	fn add_point(&mut self, mut node: Node) -> Result<(), String> {

		// If this node is on top of an existing node, move it out of the way
		let mut cycle_completed = false;
		while !cycle_completed {
			cycle_completed = true;
			for other in &self.nodes {
				let other_pos = other.get();
				if
					node.distance(other_pos.0) < BOING_RADIUS
				{
					let direction = node.0 - other_pos.0;
					let offset = direction / direction.length() * BOING_RADIUS;

					node.0 += offset;
					node.0.x = node.0.x.rem_euclid(self.width);
					node.0.y = node.0.y.rem_euclid(self.width);

					cycle_completed = false;
					break;
				}
			}
		}

		// Remove invalid triangles and coalesce their edges
		let mut orphaned_edges: Vec<_> = Vec::with_capacity(self.triangles.len() * 3);
		let mut i = 0;
		while i < self.triangles.len() {
			let triangle = &self.triangles[i];
			if triangle.invalidated_by_point(*node) {
				orphaned_edges.extend(
					self.remove_triangle(i)?.edges
				);
			} else {
				i = i + 1;
			}
		}
		orphaned_edges.retain(|e| self.adjacency.contains_key(e));

		// For every edge form a new triangle with that edge and this point
		let node = Arc::new(Cell::new(node));
		let mut node_connected_edges = HashSet::with_capacity(orphaned_edges.len());
		for edge in orphaned_edges {
			let edges = [
				Edge(edge.0.clone(), node.clone()),
				Edge(edge.1.clone(), node.clone()),
				edge,
			];
			for edge in &edges[..2] {
				if self.is_point_inbounds(*edge.0.get()) {
					node_connected_edges.insert(edge.clone());
				}
			}
			self.create_triangle(edges)?;
		}

		// Update the spanning tree
		let our_id = node.as_ptr() as usize;
		if self.spanning_tree.is_empty() && self.nodes.len() == 5 {

			// Connect the two non-border points
			let other_node: &NodeRef = self.nodes.iter()
				.filter(|n| self.is_point_inbounds(*n.get()))
				.next()
				.unwrap();

			let joining_edge = Edge(other_node.clone(), node.clone());
			let node_a_id = other_node.as_ptr() as usize;
			let node_b_id = node.as_ptr() as usize;

			self.spanning_tree.insert(joining_edge);
			self.spanning_tree_conn.insert(node_a_id, smallvec![node_b_id]);
			self.spanning_tree_conn.insert(node_b_id, smallvec![node_a_id]);

		} else if !self.spanning_tree.is_empty() {
			// Pick a random edge off this node and add it to the spanning tree
			let random = util::pcg64(&mut self.random_state);
			let random = random as usize % node_connected_edges.len();
			let lucky_edge = node_connected_edges.into_iter()
				.skip(random)
				.next()
				.unwrap();
			let connected_node = lucky_edge.node_thats_not(&node)
				.unwrap()
				.as_ptr() as usize;

			self.spanning_tree.insert(lucky_edge.clone());
			self.spanning_tree_conn.insert(our_id, smallvec![connected_node]);
			if let Some(other_edges) = self.spanning_tree_conn.get_mut(&connected_node) {
				other_edges.push(our_id);
			} else {
				return Err(format!(
					"Found node {} in triangle list, but it does not have an entry in \
					the spanning tree connections list",
					*lucky_edge.node_thats_not(&node)?.get()
				));
			}
		}

		self.nodes.push(node);

		Ok(())
	}

	fn remove_triangle(&mut self, index: usize) -> Result<Triangle, String> {
		let triangle = self.triangles.remove(index);
		for edge in &triangle.edges {
			match self.adjacency.get_mut(edge) {
				Some((Occupant(side1), side2 @ Friend(_))) => {
					let side2_inner = side2.unwrap_mut();
					if side1 == &triangle {
						swap(side1, side2_inner);
					} else if side2_inner != &triangle {
						return Err(format!(
								"{:?} does not contain triangle \
								{:?}, but this triangle's list of edges includes this \
								edge.  Triangle was in the triangle index until now.",
								edge, triangle
						));
					}
					*side2 = Hole;
				},
				Some((Occupant(our_side), Hole)) => {
					if our_side != &triangle {
						return Err(format!(
							"{:?} does not contain triangle \
							{:?}, but this triangle's list of edges includes this \
							edge.  Triangle was in the triangle index until now.",
							edge, triangle
						));
					}
					self.remove_edge(&edge)?;
				},
				Some((Border, our_side @ Friend(_))) => {
					*our_side = Hole;
				},
				Some((Border, Hole)) => {
					return Err(format!(
							"{:?} removed from graph, but it's edge {:?} is \
							already marked as a border-hole edge", triangle, edge
					));
				}
				None => {
					return Err(format!(
							"{:?} removed from graph, but it's edge {:?} was \
							missing from adjacency graph", triangle, edge
					));
				},
			}
		}
		Ok(triangle)
	}

	fn remove_edge(&mut self, edge: &Edge) -> Result<Edge, String> {
		// Remove edge from the edge graph
		let edge = if let Some((edge, _)) = self.adjacency.remove_entry(edge) {
			edge
		} else {
			return Err(format!(
				"Tried to remove edge {:?} from the list of edges, but it wasn't present",
				edge
			));
		};

		// If the edge was part of the spanning tree and the tree is initialized
		if !self.spanning_tree.is_empty() && self.spanning_tree.remove(&edge) {
			let left_id = edge.0.as_ptr() as usize;
			let right_id = edge.1.as_ptr() as usize;
			// Remove it completely from the spanning tree
			for (node, to_node) in [(left_id, right_id), (right_id, left_id)] {
				if let Some(connected_nodes) = self.spanning_tree_conn.get_mut(&node) {
					connected_nodes.retain(|n| *n != to_node);
				} else {
					return Err(format!(
						"Edge {:?} was previously in edge graph, but it's node {} was not in \
						the connections list", edge, node
					));
				}
			}

			// Traverse the tree on either side of the edge
			let tree_a = self.traverse_spanning_tree(edge.0.as_ptr() as usize)?;
			let tree_b = self.traverse_spanning_tree(edge.1.as_ptr() as usize)?;

			// Find a list of edges that:
			// - Have one node from each tree
			// - Do not connect to an out-of-bounds node
			let candidate_edges: Vec<_> = self.adjacency.keys()
				.filter(|e|
					(
						tree_a.contains(&(e.0.as_ptr() as usize)) &&
						tree_b.contains(&(e.1.as_ptr() as usize))
					) || (
						tree_a.contains(&(e.1.as_ptr() as usize)) &&
						tree_b.contains(&(e.0.as_ptr() as usize))
					)
				)
				.filter(|e|
					self.is_point_inbounds(*e.0.get()) &&
					self.is_point_inbounds(*e.1.get())
				)
				.collect();

			// Pick one at random and add it to the spanning tree
			let random = util::pcg64(&mut self.random_state);
			let random = random as usize % candidate_edges.len();
			let new_edge = candidate_edges[random];

			let node_a = new_edge.0.as_ptr() as usize;
			let node_b = new_edge.1.as_ptr() as usize;
			self.spanning_tree.insert(new_edge.clone());
			for (from, to) in [(node_a, node_b), (node_b, node_a)] {
				let connected = self.spanning_tree_conn.get_mut(&from).unwrap();
				connected.push(to);
			}
		}

		Ok(edge)
	}

	fn traverse_spanning_tree(&self, root: usize) -> Result<HashSet<usize>, String> {
		let mut visited = HashSet::with_capacity(self.nodes.len());
		let mut to_traverse: SmallVec<[usize; 40]> = smallvec![root];

		while let Some(node) = to_traverse.pop() {
			visited.insert(node);

			if let Some(c) = self.spanning_tree_conn.get(&node) {
				to_traverse.extend(
					c.iter()
						.filter(|c| !visited.contains(c))
						.map(|c| *c)
				);
			} else {
				return Err(format!(
					"Spanning tree connection database lists a connection to node id {}, \
					but that node lacks an entry in the database", node
				));
			};

		}

		Ok(visited)
	}

	fn is_point_inbounds(&self, p: DVec2) -> bool {
		p.x > 0. &&
		p.y > 0. &&
		p.x < self.width &&
		p.y < self.height
	}

	fn create_triangle(&mut self, edges: [Edge; 3]) -> Result<&Triangle, String> {
		let triangle = Triangle::new(edges.clone());
		for edge in edges {
			match self.adjacency.entry(edge) {
				Entry::Occupied(mut entry) => {
					match entry.get_mut() {
						(Occupant(tri1), Friend(tri2)) => {
							let (tri1, tri2) = (tri1.clone(), tri2.clone());
							return Err(format!(
								"Tried to create a triangle with edge {:?}, \
								but this edge is already in use by triangles {:?} and \
								{:?}.",
								entry.key(), tri1, tri2
							));
						},
						(Border, Friend(tri)) => {
							let tri = tri.clone();
							return Err(format!(
								"Tried to create a triangle with edge {:?}, \
								but this edge is already in use by triangle {:?} and \
								is a border.",
								entry.key(), tri
							));
						},
						(Occupant(_) | Border, new_home @ Hole) => {
							*new_home = Friend(triangle.clone());
						},
					}
				},
				Entry::Vacant(entry) => {
					entry.insert(((&triangle).into(), Hole));
				}
			}
		}
		self.triangles.push(triangle);
		Ok(self.triangles.last().unwrap())
	}

	fn move_point(&mut self, node: NodeRef) {

		// Update position
		let current_pos = node.get();
		let mut new_pos = Node(current_pos.0 + current_pos.1, current_pos.1);

		// Check if it is going to hit another point
		for other in &self.nodes {
			// If we are currently inside the boing radius of the node (e.g. because we spawned
			// there), then move out.
			if
				!Arc::ptr_eq(other, &node)
				&& current_pos.distance(other.get().0) < BOING_RADIUS
			{
				let other_pos = other.get();
				let direction = current_pos.0 - other_pos.0;
				let offset = direction / direction.length() * BOING_RADIUS / 2.;

				node.set(Node(current_pos.0 + offset, current_pos.1));
				other.set(Node(other_pos.0 - offset, other_pos.1));
				return self.move_point(node);
			}

			// If we are going to walk into the boing radius of another node, boing!
			if
				!Arc::ptr_eq(other, &node)
				&& new_pos.distance(other.get().0) < BOING_RADIUS
			{
				let mut node_inner = node.get();
				let mut other_inner = other.get();

				swap(&mut other_inner.1, &mut node_inner.1);

				other.set(other_inner);
				node.set(node_inner);
				return;
			}
		}

		// Check for a bounce
		if new_pos.0.y > self.height {
			new_pos.0.y = 2.0 * self.height - new_pos.0.y;
			new_pos.1.y = -new_pos.1.y;
		}
		if new_pos.0.y < 0.0 {
			new_pos.0.y = -new_pos.0.y;
			new_pos.1.y = -new_pos.1.y;
		}
		if new_pos.0.x > self.width {
			new_pos.0.x = 2.0 * self.width - new_pos.0.x;
			new_pos.1.x = -new_pos.1.x;
		}
		if new_pos.0.x < 0.0 {
			new_pos.0.x = -new_pos.0.x;
			new_pos.1.x = -new_pos.1.x;
		}

		node.set(new_pos);
	}

	fn get_neighbors(&self, triangle: &Triangle) -> Result<Vec<&Triangle>, String> {
		triangle.edges.iter()
			.filter_map(|e|
				 match self.adjacency.get(e) {
					 Some((Occupant(a), Friend(b))) => {
						 if a != triangle && b == triangle {
							 Some(Ok(a))
						 } else if a == triangle && b != triangle {
							 Some(Ok(b))
						 } else if a == triangle && b == triangle {
							Some(Err(format!(
								"{:?} has {:?} in adjacency graph which lists itself as \
								its own neighbor",
								triangle, e
							)))
						 } else {
							Some(Err(format!(
								"{:?} has {:?}, but the adjacency graph reports that the \
								triangles next to this edge are {:?} and {:?}",
								triangle, e, a, b
							)))
						 }
					 },
					 Some((Border, Friend(tri))) => {
						 if tri == triangle {
							 None
						 } else {
							Some(Err(format!(
								"{:?} has {:?}, but the adjacency graph reports that \
								this edge is an edge between the graph hull and {:?}",
								triangle, e, tri
							)))
						 }
					 },
					 Some((Occupant(tri), Hole)) => {
						 if tri == triangle {
							 None
						 } else {
							Some(Err(format!(
								"{:?} has {:?}, but the adjacency graph reports that \
								this edge is an edge between a polygonal hole and {:?}",
								triangle, e, tri
							)))
						 }
					 },
					 Some((Border, Hole)) => {
						Some(Err(format!(
							"{:?} has {:?}, but the adjacency graph lists this edge as \
							being between the graph hull and a polygonal hole (aka, it \
							has no neighbors",
							triangle, e
						)))
					 },
					 None => {
						Some(Err(format!(
							"get_neighbors called on {:?}, but its edge {:?} is not \
							present in the adjacency graph.",
							triangle, e
						)))
					 },
				 }
			 )
			.collect()
	}

	fn flip_triangles(
		&mut self,
		tri1: &Triangle,
		tri2: &Triangle
	) -> Result<(Triangle, &Triangle), String> {
		let mut indices = self.triangles.iter()
			.enumerate()
			.filter(|(_, t)| t == &tri1 || t == &tri2)
			.map(|(i, _)| i);
		let err = || format!(
			"flip_triangles called on {:?} and {:?}, but not both of these were found in \
			the list of triangles",
			tri1, tri2
		);

		let mut indices = [
			indices.next().ok_or_else(err)?,
			indices.next().ok_or_else(err)?,
		];
		indices.sort_unstable();

		let tri1 = self.remove_triangle(indices[1])?;
		let tri2 = self.remove_triangle(indices[0])?;

		let common_edge = tri1.common_edge(&tri2)?;

		let tri1_point = tri1.point_not_on(common_edge)?;
		let tri2_point = tri2.point_not_on(common_edge)?;

		Ok((
			self.create_triangle([
				Edge(tri1_point.clone(), common_edge.0.clone()),
				Edge(tri2_point.clone(), common_edge.0.clone()),
				Edge(tri1_point.clone(), tri2_point.clone()),
			])?.clone(),
			self.create_triangle([
				Edge(tri1_point.clone(), common_edge.1.clone()),
				Edge(tri2_point.clone(), common_edge.1.clone()),
				Edge(tri1_point.clone(), tri2_point.clone()),
			])?,
		))
	}

	fn re_delaunize(&mut self) -> Result<(), String> {
		let mut i = 0;
		while i < self.triangles.len() {
			let triangle = &self.triangles[i];
			let neighbors: Vec<_> = self.get_neighbors(triangle)?
				.into_iter()
				.cloned()
				.collect();
			let mut flipped = false;
			for neighbor in neighbors {
				if triangle.invalidated_by_neighbor(&neighbor)? {
					let triangle = triangle.clone();
					self.flip_triangles(&triangle, &neighbor)?;
					i = 0;
					flipped = true;
					break;
				}
			}
			if !flipped {
				i = i + 1;
			}
		}
		Ok(())
	}
}