public class SigmoidStrengthFun implements ICommStrengthFunc {

	double m_lfWeight;
	double m_lfRad;
	
	public SigmoidStrengthFun() {
		
	}
	
	public SigmoidStrengthFun(double lfRad, double lfWeight) {
		m_lfWeight = lfWeight;
		m_lfRad = lfRad;
	}
	
	public SigmoidStrengthFun(SigmoidStrengthFun src) {
		m_lfWeight = src.m_lfWeight;
		m_lfRad = src.m_lfRad;
	}
	
	public double getGrad(double lfDist) {
		double lfExpVal = Math.exp(m_lfWeight*(lfDist-m_lfRad));
		double lfTmp = (1.0+lfExpVal);
		return -m_lfWeight*lfExpVal/(lfTmp*lfTmp);
	}

	public double getStrength(double lfDist) {
		return 1.0/(1.0+Math.exp(m_lfWeight*(lfDist-m_lfRad)));
	}

	public boolean isMonotonic() {
		return true;
	}

	public ICommStrengthFunc makeCopy() {
		return new SigmoidStrengthFun(this);
	}

	public double maxDerivRange(double lfMin, double lfMax) {
		if(lfMin < 0.0) { 
			lfMin = 0.0;
		}
		if(lfMax < 0.0) {
			lfMax = 0.0;
		}
		if(lfMin < m_lfRad && lfMax > m_lfRad) {
			return getGrad(m_lfRad);
		}
		if(Math.abs(lfMin-m_lfRad) > Math.abs(lfMax - m_lfRad)) {
			return getGrad(lfMax);
		}
		return getGrad(lfMin);
	}

	public double maxStrengthRange(double lfMinD, double lfMaxD) {
		if(lfMinD > 0.0) {
			return getStrength(lfMinD);
		}
		return getStrength(0.0);
	}

	public double minDerivRange(double lfMin, double lfMax) {
		if(lfMin < 0.0) { 
			lfMin = 0.0;
		}
		if(lfMax < 0.0) {
			lfMax = 0.0;
		}
		if(Math.abs(lfMin-m_lfRad) < Math.abs(lfMax - m_lfRad)) {
			return getGrad(lfMax);
		}
		return getGrad(lfMin);
	}

	public double minStrengthRange(double lfMinD, double lfMaxD) {
		if(lfMaxD > 0.0) {
			return getStrength(lfMaxD);
		}
		return getStrength(0.0);
	}

}