use strafesnet_common::integer::{Planar64,Planar64Vec3};

type Indices=arrayvec::ArrayVec<usize,4>;

struct Ray{
	origin:Planar64Vec3,
	direction:Planar64Vec3,
}

/// Information about a contact restriction
pub struct Contact{
	pub position:Planar64Vec3,
	pub velocity:Planar64Vec3,
	pub normal:Planar64Vec3,
}
impl Contact{
	const fn relative_to(&self,point:Planar64Vec3)->Self{
		Self{
			position:self.position-point,
			velocity:self.velocity,
			normal:self.normal,
		}
	}
}

const fn solve0()->Planar64Vec3{
	Planar64Vec3::ZERO
}

fn solve1(c0:&Contact)->Option<Planar64Vec3>{
	let d0=c0.normal.dot(c0.position);
	let det=c0.normal.dot(c0.velocity);
	if det.get().abs()<0{
		None
	}else{
		Some(c0.normal*d0/det)
	}
}

const fn is_space_enclosed_0_1()->bool{
	false
}

fn is_space_enclosed_2(
	a:Planar64Vec3,
	b:Planar64Vec3,
)->bool{
	a.cross(b)==Planar64Vec3::ZERO
	&&a.dot(b)<Planar64::ZERO
}
fn is_space_enclosed_3(
	a:Planar64Vec3,
	b:Planar64Vec3,
	c:Planar64Vec3
)->bool{
	a.cross(b).dot(c)==Planar64::ZERO
	&&{
		let det_abac=a.cross(b).dot(a.cross(c));
		let det_abbc=a.cross(b).dot(b.cross(c));
		let det_acbc=a.cross(c).dot(b.cross(c));
		return det_abac*det_abbc<=Planar64::ZERO
			&& det_abbc*det_acbc<=Planar64::ZERO
			&&-det_acbc*det_abac<=Planar64::ZERO
			||is_space_enclosed_2(a,b)
			||is_space_enclosed_2(a,c)
			||is_space_enclosed_2(b,c)
	}
}
fn is_space_enclosed_4(
	a:Planar64Vec3,
	b:Planar64Vec3,
	c:Planar64Vec3,
	d:Planar64Vec3,
)->bool{
	let det_abc=a.cross(b).dot(c);
	let det_abd=a.cross(b).dot(d);
	let det_acd=a.cross(c).dot(d);
	let det_bcd=b.cross(c).dot(d);
	return det_abc*det_abd<Planar64::ZERO
		&&-det_abc*det_acd<Planar64::ZERO
		&& det_abd*det_acd<Planar64::ZERO
		&& det_abc*det_bcd<Planar64::ZERO
		&&-det_abd*det_bcd<Planar64::ZERO
		&& det_acd*det_bcd<Planar64::ZERO
		||is_space_enclosed_3(a,b,c)
		||is_space_enclosed_3(a,b,d)
		||is_space_enclosed_3(a,c,d)
		||is_space_enclosed_3(b,c,d)
}

fn test_positivity(direction:Planar64Vec3,c:&Contact)->bool{
	Planar64::ZERO<=(direction-c.velocity).dot(c.normal)
}

const fn get_push_ray_0(point:Planar64Vec3)->Option<Ray>{
	Some(Ray{origin:point,direction:Planar64Vec3::ZERO})
}
const fn get_best_push_ray_and_indices_0(point:Planar64Vec3)->Option<(Ray,Indices)>{
	match get_push_ray_0(point){
		Some(ray)=>Some((ray,Indices::new_const())),
		None=>None,
	}
}

fn get_push_ray_1(point:Planar64Vec3,c0:&Contact)->Option<Ray>{
	let direction=solve1(c0)?;
	let s0=decompose1(direction,c0.velocity)?;
	if s0<Planar64::ZERO{
		return None;
	}
	let origin=point+solve1(
		&c0.relative_to(point),
	)?;
	Some(Ray{origin,direction})
}
fn get_best_push_ray_and_indices_1(pnv_list:&Vec<Contact>,point:Planar64Vec3,i0:usize)->Option<(Ray,Indices)>{
	get_push_ray_1(point,&pnv_list[i0])
		.map(|ray|(ray,Indices::from_iter([i0])))
}

fn get_push_ray_2(point:Planar64Vec3,c0:&Contact,c1:&Contact)->Option<Ray>{
	let direction=solve2(c0,c1)?;
	let (s0,s1)=decompose2(direction,c0.velocity,c1.velocity)?;
	if s0<Planar64::ZERO||s1<Planar64::ZERO{
		return None;
	}
	let origin=point+solve2(
		&c0.relative_to(point),
		&c1.relative_to(point),
	)?;
	Some(Ray{origin,direction})
}
fn get_best_push_ray_and_indices_2(pnv_list:&Vec<Contact>,point:Planar64Vec3,i0:usize,i1:usize)->Option<(Ray,Indices)>{
	if let Some(ray)=get_push_ray_2(point,&pnv_list[i0],&pnv_list[i1]){
		return Some((ray,Indices::from_iter([i0,i1])));
	}
	if let Some(ray)=get_push_ray_1(point,&pnv_list[i0]){
		if test_positivity(ray.direction,&pnv_list[i0]){
			return Some((ray,Indices::from_iter([i0])));
		}
	}
	return None;
}

fn get_push_ray_3(point:Planar64Vec3,c0:&Contact,c1:&Contact,c2:&Contact)->Option<Ray>{
	let direction=solve3(c0,c1,c2)?;
	let (s0,s1,s2)=decompose3(direction,c0.velocity,c1.velocity,c2.velocity)?;
	if s0<Planar64::ZERO||s1<Planar64::ZERO||s2<Planar64::ZERO{
		return None;
	}
	let origin=point+solve3(
		&c0.relative_to(point),
		&c1.relative_to(point),
		&c2.relative_to(point),
	)?;
	Some(Ray{origin,direction})
}
fn get_best_push_ray_and_indices_3(pnv_list:&Vec<Contact>,point:Planar64Vec3,i0:usize,i1:usize,i2:usize)->Option<(Ray,Indices)>{
	get_push_ray_3(point,&pnv_list[i0],&pnv_list[i1],&pnv_list[i2])
		.map(|ray|(ray,Indices::from_iter([i0,i1,i2])))
}

fn get_best_push_ray_and_indices(
	pnv_list:&Vec<Contact>,
	point:Planar64Vec3,
	indices:Indices,
)->Option<(Ray,Indices)>{
	let is_space_enclosed=match indices.as_slice(){
		&[i0,i1,i2,i3]=>is_space_enclosed_4(pnv_list[i0].normal,pnv_list[i1].normal,pnv_list[i2].normal,pnv_list[i3].normal),
		&[i0,i1,i2]=>is_space_enclosed_3(pnv_list[i0].normal,pnv_list[i1].normal,pnv_list[i2].normal),
		&[i0,i1]=>is_space_enclosed_2(pnv_list[i0].normal,pnv_list[i1].normal),
		&[_]|&[]=>is_space_enclosed_0_1(),
	};
}

pub fn push_solve(pnv_list:&Vec<Contact>,point:Planar64Vec3){
	//
}

pub fn push_solve_with_output(pnv_list:&Vec<Contact>,point:Planar64Vec3,output:&mut Vec<Planar64Vec3>){
	//
}