public class CommFuncSimpleSpline implements ICommStrengthFunc {

	double m_lfMin;
	double m_lfMax;
	double m_lfMed;
	double m_lfScale;
	
	public CommFuncSimpleSpline() {
		m_lfMin = 0.0;
		m_lfMax = 1.0;
		m_lfMed = 0.5;
		m_lfScale = 1.0;
	}
	
	public CommFuncSimpleSpline(double lfMinRange, double lfMaxRange) {
		if(lfMinRange > lfMaxRange) {
			double lfTmp = lfMinRange;
			lfMinRange = lfMaxRange;
			lfMaxRange = lfTmp;
		}
		m_lfMin = lfMinRange;
		m_lfMax = lfMaxRange;
		m_lfMed = (m_lfMax + m_lfMin)*0.5;
		m_lfScale = 1.0/(m_lfMax - m_lfMin);
	}
	
	double getScaledParam(double lfDist) {
		return m_lfScale*(lfDist - m_lfMin);
	}
	
	public double getGrad(double lfDist) {
		if(lfDist <= m_lfMin || lfDist >= m_lfMax) {
			return 0.0;
		}
		double lfSDist = 1.0-getScaledParam(lfDist);
		// 3x^2 - 2x^3
		// 6x - 6x^2
		// 3 a^2 x^2 - 2 a^3 x^3
		// 6 a^2 x - 6 a^3 x^2
		// 6 a (ax)( 1 - (ax) )
		return -1.0*m_lfScale*6.0*lfSDist*(1.0-lfSDist);
	}

	public double getStrength(double lfDist) {
		if(lfDist < m_lfMin) {
			return 1.0;
		}
		if( lfDist > m_lfMax) {
			return 0.0;
		}
		double lfSDist = 1.0-getScaledParam(lfDist);
		// 3x^2 - 2x^3
		// 6x - 6x^2
		return lfSDist*lfSDist*(3.0-2.0*lfSDist);
	}

	public boolean isMonotonic() {
		return true;
	}

	public ICommStrengthFunc makeCopy() {
		return new CommFuncSimpleSpline(m_lfMin, m_lfMax);
	}

	public double maxDerivRange(double lfMin, double lfMax) {
		if((lfMin - m_lfMed ) * ( lfMax - m_lfMed) <= 0.0) {
			return getGrad(m_lfMed);
		}
		return Math.min(getGrad(lfMin), getGrad(lfMax));
	}

	public double maxStrengthRange(double lfMinD, double lfMaxD) {
		return getStrength(Math.min(lfMaxD, lfMinD));
	}

	public double minDerivRange(double lfMin, double lfMax) {
		return Math.max(getGrad(lfMin), getGrad(lfMax));
	}

	public double minStrengthRange(double lfMinD, double lfMaxD) {
		return getStrength(Math.max(lfMaxD, lfMinD));
	}

}