/*
 * ParenMatcher.java
 *
 * Created on March 17, 2008, 10:06 AM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

package parenmatchapplet2;

/**
 *
 * @author suchenek
 */
public class ParenMatcher {
    
    private String inputString, outputString;
    
    private Boolean match (char c, char d)
    {
        switch (c)
        {
            case '(' : return (d == ')');
            case '{' : return (d == '}');
            case '[' : return (d == ']');
            case '<' : return (d == '>');
            default: return false;
        }
    }
    
   private Boolean opening (char d)   
   {
      return  ((d == '(') || (d == '{') || (d  == '[') || (d == '<')); 
   }
   
    public void ParenMatch()
    {
      
        Stack parenStack = new Stack(); 
      int n = inputString.length();
      char c, d;
      for (int i = 0; i<n; i++)
      {
          d = inputString.charAt(i);
          if (opening(d))
          {
              parenStack.push(d);              
          }
          else if (parenStack.isEmpty())
          {
              output("Non-matching symbol found.");
              return;
          }
          else
          {
              c = ((Character)parenStack.pop()).charValue();
              if (!match(c, d))
              {
                   output("Mismatched parens: " + c + " and " + d);
                   return;
              }
              
          }
      }
      if (parenStack.isEmpty())
           output("Parens are balanced.");
      else
           output("More left parens than right parens.");
    }
    
    private void output(String s)
    {
     outputString = s;   
    }
    
    public void setInput(String input)
    {
        inputString = input;
    }
    
    public String getOutput()
    {
       return outputString; 
    }
}