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package com.sun.enterprise.cli.framework;

public class StringEditDistance 
 {
 
     /**
      * Computes the edit distance between two strings.
      *
      * <p>
      * The complexity is O(nm) where n=a.length() and m=b.length().
      */
     public static int editDistance( String a, String b )
     {
         return new StringEditDistance(a,b).calc();
     }
  
         /**
          * Finds the string in the <code>group</code> closest to
          * <code>key</code> and returns it.
          *
          * @return null if group.length==0.
          */
     public static String findNearest( String key, String[] group )
     {
         int c = Integer.MAX_VALUE;
         String r = null;
         for( int i=0; i<group.length; i++ ) {
             int ed = editDistance(key,group[i]);
             if( c>ed ) {
                 c = ed;
                 r = group[i];
             }
         }
         return r;
     }
 
 
         /** cost vector. */
     private int[] cost;
 
         /** back buffer. */
     private int[] back;
 
 
         /** Two strings to be compared. */
     private final String a,b;
  
     private StringEditDistance( String a, String b ) {
         this.a=a;
         this.b=b;
         cost = new int[a.length()+1];
         back = new int[a.length()+1];
             // back buffer
         for( int i=0; i<=a.length(); i++ )
             cost[i] = i;
     }
 
 
         /**
          * Swaps two buffers.
          */
     private void flip() {
         int[] t = cost;
         cost = back;
         back = t;
     }
  
     private int min(int a,int b,int c) {
          return Math.min(a,Math.min(b,c));
     }
 
 
     private int calc() {
         for( int j=0; j<b.length(); j++ ) {
             flip();
             cost[0] = j+1;
             for( int i=0; i<a.length(); i++ ) {
                 int match = (a.charAt(i)==b.charAt(j))?0:1;
                 cost[i+1] = min( back[i]+match, cost[i]+1, back[i+1]+1 );
             }
         }
         return cost[a.length()];
     }
  
}
 
