package org.lsst.ccs.utilities.dsp;
   
   /**
    * 
    * @author aubourg
    * 
    */
   public class FIRFilter implements DigitalFilter {
   	/**
  	 * 
  	 */
  	private static final long serialVersionUID = 2786444222861355300L;
  
  	double rate; // Hz
  
  	int order;
  
  	double[] history;
  
  	int ip; // last point in history
  
  	double[] aCoeff;
  
  	protected FIRFilter(double[] coeff) {
  		aCoeff = coeff;
  		order = coeff.length - 1;
  		history = new double[order + 1];
  		ip = 0;
  	}
  
  	public void reset() {
  		for (int i = 0; i <= order; i++) {
  			history[i] = 0;
  		}
  		ip = 0;
  	}
  
  	public double getRate() {
  		return rate;
  	}
  
  	public int getDelay() {
  		return (order) / 2;
  	}
  
  	public double flush() {
  		return apply(0);
  	}
  
  	public double apply(double signal) {
  		ip++;
  		if (ip >= order) {
  			ip = 0;
  		}
  		history[ip] = signal;
  		double resp = 0;
  		for (int i = 0; i <= order; i++) {
  			int j = (ip - i) % (order + 1);
  			if (j < 0) {
  				j += order + 1;
  			}
  			// System.out.println("apply "+i+" "+j+" "+aCoeff[i]+"
  			// "+history[j]+" "+(aCoeff[i] * history[j]));
  			resp += aCoeff[i] * history[j];
  		}
  		return resp;
  	}
  
  	public double freqResp(double freq) {
  		// TODO Auto-generated method stub
  		return 0;
  	}
  
  	public int getOrder() {
  		return order;
  	}
  
  	public void print() {
  		System.out.println("FIRFilter order " + order);
  		for (int i = 0; i <= order; i++) {
  			System.out.println("  a[" + i + "] = " + aCoeff[i]);
  		}
  		System.out.println("---");
  	}
  
  	@Override
  	public Object clone() {
  		try {
  			FIRFilter f = (FIRFilter) super.clone();
  			f.history = new double[order + 1];
  			return f;
  		} catch (CloneNotSupportedException e) {
  			return null;
  		}
  	}
  }