/*
Copyright @ 2004, The Institute for Genomic Research (TIGR).
All rights reserved.
*/

/***************************************************************************
 * Author:  Jianwei(Jerry) Li.
 * Name:  MathExpression (Version 1.0)
 * Date:  Created: 10/12/2004 and modified: 11/04/2004
 * Descp: A Java class that evaluate a formula passed in.
 ***************************************************************************/
package org.tigr.util.formula;

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

import org.tigr.util.formula.node.EvaluateException;

public class MathExpression {

  private boolean gTreeReady, gUninary, gInt;
  private ExpressionParser gParser;
  private String gExpr;

  public MathExpression(){
    gTreeReady = false;
    gUninary = false;
    gInt = true;
  }

  public MathExpression(String formula) {
    this();
    setExpression(formula);
    parseFormula();
  }

  public void setExpression(String expr) throws ExpressionException{
    if(expr == null) {
      throw new ExpressionException(this, "Invalid expression : " + expr);
    }
    gExpr = expr;
  }

  public void IntegerResult(boolean b) { gInt = b; }

  /***************************************************************************
   * <b>Description: </b>
   *   returns the formula expression.
   **************************************************************************/
  public String getExpression() { return gExpr; }

  public String evaluate() throws EvaluateException {
    String result = null;
    if(getExpression() == null) {
      throw new EvaluateException("Invalid empty expression");
    }

    if(gTreeReady){
      result = gParser.evaluate();
    }

    if(result == null) {
      throw new EvaluateException("No evaluation");
    }
    return result;
  }

  /****************************************************************************
   * <b>Description: </b>
   *    evaluates the formula with passed variables.
   * <p><b>Parameter: </b>
   * <br> vals -- the values.
   * <p><b> Return: </b> the results in a string format.
   ***************************************************************************/
  public String evaluate(String[] vals) throws EvaluateException {
    int indx;
    String result = null;

    if(gExpr == null) {
      throw new EvaluateException("Invalid empty expression");
    }

    indx = isUninary(gExpr);
    if(indx >= 0){
      return vals[indx];
    }

    if(gTreeReady){
      result = gParser.evaluate(vals, gInt);
    }
    if(result == null) {
      throw new EvaluateException("No evaluation");
    }
    return result;
  }

  /****************************************************************************
   * <b>Description: </b>
   *    check if the formula a uninary one.
   * <p><b>Parameter: </b>
   * <br> forumula -- the formula to be checked.
   * <p><b>Return: </b> -1 if it is not; otherwise, a positive number.
   ***************************************************************************/
  private int isUninary(String formula){
    int num = -1;
    try{
      num = Integer.parseInt(formula);
    } catch (NumberFormatException ne){
      return (-1);
    }
    return num;
  }

  private void parseFormula(){
    if(gExpr.equals("")){
      gUninary = true;
      return;
    }
    gParser = new ExpressionParser(gExpr);
    int indx = isUninary(gExpr);
    if(indx >= 0){
      gUninary = true;
    } else {
      gTreeReady = gParser.execute();
    }
  }
}