//	Vamos Automotive Simulator
//  Copyright (C) 2001--2002 Sam Varner
//
//  This program is free software; you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation; either version 2 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

#ifndef _SPLINE_H_
#define _SPLINE_H_

#include <vamos/geometry/Interpolator.h>
#include <vamos/geometry/Two_Point.h>
#include <vector>

namespace Vamos_Geometry
{
  class Spline : public Interpolator
  {
	// The array of points to interpolate betwen.
	std::vector <Two_Point> m_points;

	// The array of calculated second derivatives.
	std::vector <double> m_second_deriv;

	// The first derivative of the spline at the first point.
	double m_first_slope;

	// The first derivative of the spline at the last point.
	double m_last_slope;

	// True if the second derivatives have been calculated.
	bool m_calculated;

	// The first derivative at the interpolated point calculated
	// during the last call to interpolate().
	double m_slope;

	// Calculate the coefficients for interpolation.
	void calculate ();

  public:
	// Construct an empty curve.
	Spline (double first_slope = 0.0, 
			double last_slope = 0.0);

	// Construct a cuvre from an array of points.
	Spline (const std::vector <Two_Point>& points,
			double first_slope = 0.0, 
			double last_slope = 0.0);

	// Add a point to the curve.
	void load (const Two_Point& point);

	// Add multiple points to the curve.
	void load (const std::vector <Two_Point>& points);
  
	// Remove all points from the curve.
	void clear ();

	// Scale all of the x values by FACTOR.
	void scale (double factor);

	// Return the y value at the x value DIST
	double interpolate (double dist);

	// Return the normal to the tanget at DIST.
	Two_Point normal (double dist);
  };
}

#endif
