/*
   Matrix Math helper class.
   (C)2018 Marisa Kirisame, UnSX Team.
   Released under the GNU Lesser General Public License version 3 (or later).
   See https://www.gnu.org/licenses/lgpl-3.0.txt for its terms.
*/

Class dt_Matrix4
{
	private double m[16];

	dt_Matrix4 init()
	{
		int i;
		for ( i=0; i<16; i++ ) m[i] = 0;
		return self;
	}

	static dt_Matrix4 create()
	{
		return new("dt_Matrix4").init();
	}

	static dt_Matrix4 identity()
	{
		dt_Matrix4 o = dt_Matrix4.create();
		for ( int i=0; i<4; i++ ) o.set(i,i,1);
		return o;
	}

	double get( int c, int r )
	{
		return m[r*4+c];
	}

	void set( int c, int r, double v )
	{
		m[r*4+c] = v;
	}

	dt_Matrix4 add( dt_Matrix4 o )
	{
		dt_Matrix4 r = dt_Matrix4.create();
		int i, j;
		for ( i=0; i<4; i++ ) for ( j=0; j<4; j++ )
			r.set(j,i,get(j,i)+o.get(j,i));
		return r;
	}

	dt_Matrix4 scale( double s )
	{
		dt_Matrix4 r = dt_Matrix4.create();
		int i, j;
		for ( i=0; i<4; i++ ) for ( j=0; j<4; j++ )
			r.set(j,i,get(j,i)*s);
		return r;
	}

	dt_Matrix4 mul( dt_Matrix4 o )
	{
		dt_Matrix4 r = dt_Matrix4.create();
		int i, j;
		for ( i=0; i<4; i++ ) for ( j=0; j<4; j++ )
			r.set(j,i,get(0,i)*o.get(j,0)+get(1,i)*o.get(j,1)+get(2,i)*o.get(j,2)+get(3,i)*o.get(j,3));
		return r;
	}

	Vector3 vmat( Vector3 o )
	{
		double x, y, z, w;
		x = get(0,0)*o.x+get(1,0)*o.y+get(2,0)*o.z+get(3,0);
		y = get(0,1)*o.x+get(1,1)*o.y+get(2,1)*o.z+get(3,1);
		z = get(0,2)*o.x+get(1,2)*o.y+get(2,2)*o.z+get(3,2);
		w = get(0,3)*o.x+get(1,3)*o.y+get(2,3)*o.z+get(3,3);
		return (x,y,z)/w;
	}

	static dt_Matrix4 rotate( Vector3 axis, double theta )
	{
		dt_Matrix4 r = dt_Matrix4.identity();
		double s, c, oc;
		s = sin(theta);
		c = cos(theta);
		oc = 1.0-c;
		r.set(0,0,oc*axis.x*axis.x+c);
		r.set(1,0,oc*axis.x*axis.y-axis.z*s);
		r.set(2,0,oc*axis.x*axis.z+axis.y*s);
		r.set(0,1,oc*axis.y*axis.x+axis.z*s);
		r.set(1,1,oc*axis.y*axis.y+c);
		r.set(2,1,oc*axis.y*axis.z-axis.x*s);
		r.set(0,2,oc*axis.z*axis.x-axis.y*s);
		r.set(1,2,oc*axis.z*axis.y+axis.x*s);
		r.set(2,2,oc*axis.z*axis.z+c);
		return r;
	}

	static dt_Matrix4 perspective( double fov, double ar, double znear, double zfar )
	{
		dt_Matrix4 r = dt_Matrix4.create();
		double f = 1/tan(fov*0.5);
		r.set(0,0,f/ar);
		r.set(1,1,f);
		r.set(2,2,(zfar+znear)/(znear-zfar));
		r.set(3,2,(2*zfar*znear)/(znear-zfar));
		r.set(2,3,-1);
		return r;
	}

	// UE-like axes from rotation
	static Vector3, Vector3, Vector3 getaxes( double pitch, double yaw, double roll )
	{
		Vector3 x = (1,0,0), y = (0,-1,0), z = (0,0,1);	// y inverted for left-handed result
		dt_Matrix4 mRoll = dt_Matrix4.rotate((1,0,0),roll);
		dt_Matrix4 mPitch = dt_Matrix4.rotate((0,1,0),pitch);
		dt_Matrix4 mYaw = dt_Matrix4.rotate((0,0,1),yaw);
		dt_Matrix4 mRot = mRoll.mul(mYaw);
		mRot = mRot.mul(mPitch);
		x = mRot.vmat(x);
		y = mRot.vmat(y);
		z = mRot.vmat(z);
		return x, y, z;
	}
}