/**
Plane in hessian form.

Copyright:
Copyright (c) 2007-2018 Juan Linietsky, Ariel Manzur.  
Copyright (c) 2014-2018 Godot Engine contributors (cf. AUTHORS.md)  
Copyright (c) 2017-2018 Godot-D contributors  

License: $(LINK2 https://opensource.org/licenses/MIT, MIT License)


*/
module godot.core.plane;

import godot.core.defs;
import godot.core.vector3;

import std.math;

enum ClockDirection
{
	clockwise,
	counterClockwise,
	
	cw = clockwise,
	ccw = counterClockwise
}

/**
Plane represents a normalized plane equation. Basically, “normal” is the normal of the plane (a,b,c normalized), and “d” is the distance from the origin to the plane (in the direction of “normal”). “Over” or “Above” the plane is considered the side of the plane towards where the normal is pointing.
*/
struct Plane
{
	@nogc nothrow:
	
	Vector3 normal = Vector3(0,0,0);
	real_t d = 0;
	
	Vector3 center() const
	{
		return normal*d;
	}
	
	Plane opUnary(string op : "-")() const
	{
		return Plane(-normal, -d);
	}
	
	Vector3 project(in Vector3 p_point) const
	{
		return p_point - normal * distanceTo(p_point);
	}
	
	
	void normalize()
	{
		real_t l = normal.length();
		if (l==0)
		{
			this=Plane(Vector3(0,0,0),0);
			return;
		}
		normal/=l;
		d/=l;
	}
	
	Plane normalized() const
	{
		Plane p = this;
		p.normalize();
		return p;
	}
	
	Vector3 getAnyPoint() const
	{
		return normal*d;
	}
	
	Vector3 getAnyPerpendicularNormal() const
	{
		enum Vector3 p1 = Vector3(1,0,0);
		enum Vector3 p2 = Vector3(0,1,0);
		Vector3 p;
	
		if (fabs(normal.dot(p1)) > 0.99) // if too similar to p1
			p=p2; // use p2
		else
			p=p1; // use p1
	
		p-=normal * normal.dot(p);
		p.normalize();
	
		return p;
	}
	
	
	/* intersections */
	
	bool intersect3(in Plane p_plane1, in Plane p_plane2, Vector3* r_result = null) const
	{
		const Plane p_plane0 = this;
		Vector3 normal0=p_plane0.normal;
		Vector3 normal1=p_plane1.normal;
		Vector3 normal2=p_plane2.normal;
		
		real_t denom=normal0.cross(normal1).dot(normal2);
		
		if (fabs(denom)<=CMP_EPSILON)
			return false;
		
		if (r_result)
		{
			*r_result = ( (normal1.cross(normal2) * p_plane0.d) +
			              (normal2.cross(normal0) * p_plane1.d) +
			              (normal0.cross(normal1) * p_plane2.d) )/denom;
		}
		return true;
	}
	
	
	bool intersectsRay(in Vector3 p_from, in Vector3 p_dir, Vector3* p_intersection = null)  const
	{
		Vector3 segment=p_dir;
		real_t den=normal.dot( segment );
		
		//printf("den is %i\n",den);
		if (fabs(den)<=CMP_EPSILON)
		{
			return false;
		}
		
		real_t dist=(normal.dot( p_from ) - d) / den;
		//printf("dist is %i\n",dist);
		
		if (dist>CMP_EPSILON)
		{ //this is a ray, before the emiting pos (p_from) doesnt exist
			return false;
		}
		
		dist=-dist;
		if(p_intersection) *p_intersection = p_from + segment * dist;
		
		return true;
	}
	
	bool intersectsSegment(in Vector3 p_begin, in Vector3 p_end, Vector3* p_intersection) const
	{
		Vector3 segment= p_begin - p_end;
		real_t den=normal.dot( segment );
		
		//printf("den is %i\n",den);
		if (fabs(den)<=CMP_EPSILON) return false;
		
		real_t dist=(normal.dot( p_begin ) - d) / den;
		//printf("dist is %i\n",dist);
		
		if (dist<-CMP_EPSILON || dist > (1.0 +CMP_EPSILON)) return false;
		
		dist=-dist;
		if(p_intersection) *p_intersection = p_begin + segment * dist;
		
		return true;
	}
	
	/* misc */
	
	bool isAlmostLike(in Plane p_plane) const
	{
		return (normal.dot( p_plane.normal ) > _PLANE_EQ_DOT_EPSILON && fabs(d-p_plane.d) < _PLANE_EQ_D_EPSILON);
	}
	
	
	/+String opCast(T : String)() const
	{
		// return normal.operator String() + ", " + rtos(d);
		return String(); // @Todo
	}+/
	
	
	
	bool isPointOver(in Vector3 p_point) const
	{
		return (normal.dot(p_point) > d);
	}
	
	real_t distanceTo(in Vector3 p_point) const
	{
		return (normal.dot(p_point)-d);
	}
	
	bool hasPoint(in Vector3 p_point,real_t _epsilon = CMP_EPSILON) const
	{
		real_t dist=normal.dot(p_point) - d;
		dist=fabs(dist);
		return ( dist <= _epsilon);
	
	}
	
	this(in Vector3 p_normal, real_t p_d)
	{
		normal=p_normal;
		d=p_d;
	}
	
	this(in Vector3 p_point, in Vector3 p_normal)
	{
		normal=p_normal;
		d=p_normal.dot(p_point);
	}
	
	this(in Vector3 p_point1, in Vector3 p_point2, in Vector3 p_point3,ClockDirection p_dir = ClockDirection.ccw)
	{
		if (p_dir == ClockDirection.clockwise)
			normal=(p_point1-p_point3).cross(p_point1-p_point2);
		else
			normal=(p_point1-p_point2).cross(p_point1-p_point3);
		normal.normalize();
		d = normal.dot(p_point1);
	}
}