/**
* Read in filter data from file and store as
* data members.
* Method bandpassIntegral takes input R and C
* and combines with filter data to compute B.
*
* Glen Cowan
* RHUL Physics
* August 2011
*/

import java.io.*;
import java.util.*;

public class IntegrateFilterData {
  
//  data members
  
  int numPoints;
  final int MAXPOINTS = 1000;
  double[] x = new double[MAXPOINTS];
  double[] y = new double[MAXPOINTS];
  
// constructors

  public IntegrateFilterData(String file){
    this.readData(file);              // sets x[], y[], numPoints
  }
  
//-----------------------------------------------------------------
  
  public double bandpassIntegral (double R, double C) {
    
    final double pi = Math.PI;
    double bpi = 0.;
    for (int i=0; i<numPoints-1; i++){
      double fAve = 0.5 * (x[i] + x[i+1]);
      double alpha = 2.*pi*fAve*R*C;
      bpi += 0.5*(y[i] + y[i+1])*(x[i+1] - x[i]) / (1. + alpha*alpha);
    }
    return bpi;  
    
  }
  
//-----------------------------------------------------------------
  
  public void readData(String fileName) {
    
    final int MAXCOL = 10;
    
    BufferedReader br = null;
    try {
      br = new BufferedReader(new FileReader(fileName));
    }
    catch (FileNotFoundException e){
      System.out.println ("File " + fileName + " not found");
      return;    // --------------------------------> exit
    }
    
// Read in line from input file and assign values to array elements
    
    boolean readLines = true;
    int n = 0;               // index of line
    while ( readLines ) {
 
// try to read a line
      
      String s;
      try {
        s = br.readLine();
      }
      catch (IOException ioe) {
        System.out.println("Cannot read line " + ioe);
        s = null;
      }
      
      readLines = (s != null);
      
      if ( readLines ) { 
        
        boolean useLine = !( s.startsWith("!") || s.startsWith("#") );
        if ( useLine ) {
          
// parse line, put values into buffer
          
          StringTokenizer st = new StringTokenizer(s);
          double[] buffer = new double[MAXCOL];
          int column = 0;
          while (st.hasMoreTokens()) {
            String token = st.nextToken();
            buffer[column] = Double.parseDouble(token);
            column++;
          }
          
// here use columns 0 and 3
          
          x[n] = buffer[0];
          y[n] = buffer[3];
          n++;
          
        }
      }
    }                       // end of loop reading lines
    numPoints = n;
    
// close up
    
    try {
      br.close();
    }
    catch (IOException e){
      System.out.println ("Cannot close buffered reader " + e);
      return;    // ----------------------------------> exit
    }
    
  }       // end of readData
  
}         // end of class IntegrateFilterData