package org.daisy.pipeline.nlp.impl.matchrules;
   
   import java.math.BigInteger;
   
   import org.daisy.pipeline.nlp.TextCategorizer.Category;
   import org.daisy.pipeline.nlp.TextCategorizer.MatchMode;
   import org.daisy.pipeline.nlp.impl.MatchRule;
   
   /**
   * Match ranges like "x-y" where x,y are integers such that x < y
   */
  public class NumberRangeMatchRule extends MatchRule {
  
  	public NumberRangeMatchRule(Category category, int priority, MatchMode matchMode) {
  		super(category, priority, false, matchMode);
  	}
  
  	@Override
  	protected String match(String input) {
  		if (input.charAt(0) <= '0' || input.charAt(0) > '9')
  			return null;
  		int k = 1;
  		for (; k < input.length() && input.charAt(k) >= '0' && input.charAt(k) <= '9'; ++k);
  		if (k == input.length() || input.charAt(k) != '-')
  			return null; //input is a regular number, not a range
  		int prevk = k++;
  		if (k >= input.length() || input.charAt(k) <= '0' || input.charAt(k) > '9')
  			return null;
  		for (++k; k < input.length() && input.charAt(k) >= '0' && input.charAt(k) <= '9'; ++k);
  		if (k == prevk + 2
  		        || !lowerThan(input.substring(0, prevk), input.substring(prevk + 1, k))
  		        || (mMatchMode == MatchMode.FULL_MATCH && k != input.length()))
  			return null;
  
  		return input.substring(0, k);
  	}
  	
  	private static boolean lowerThan(String x, String  y){
  		return (new BigInteger(x).compareTo(new BigInteger(y)) == -1);
  	}
  
  	@Override
  	public boolean threadsafe() {
  		return true;
  	}
  }