Add.java

/*****************************************************************************
      SQLJEP - Java SQL Expression Parser 0.2
      November 1 2006
         (c) Copyright 2006, Alexey Gaidukov
      SQLJEP Author: Alexey Gaidukov

      SQLJEP is based on JEP 2.24 (http://www.singularsys.com/jep/)
           (c) Copyright 2002, Nathan Funk
 
      See LICENSE.txt for license information.
*****************************************************************************/

package com.meidusa.amoeba.sqljep.function;

import java.math.BigDecimal;
import java.sql.Timestamp;

import com.meidusa.amoeba.sqljep.function.PostfixCommand;
import com.meidusa.amoeba.sqljep.ASTFunNode;
import com.meidusa.amoeba.sqljep.JepRuntime;
import com.meidusa.amoeba.sqljep.ParseException;

public final class Add extends PostfixCommand {
	final static String DATE_ADDITION = "Wrong operation";
	final static BigDecimal DAY_MILIS = new BigDecimal(86400000);
	
	final public int getNumberOfParameters() {
		return 2;
	}
	
	/**
	 * Calculates the result of applying the "+" operator to the arguments from
	 * the stack and pushes it back on the stack.
	 */
	public Comparable<?>[] evaluate(ASTFunNode node, JepRuntime runtime) throws ParseException {
		node.childrenAccept(runtime.ev, null);
		Comparable<?>  param2 = runtime.stack.pop();
		Comparable<?>  param1 = runtime.stack.pop();
		return new Comparable<?>[]{param1,param2};
	}

	public static Comparable<?>  add(Comparable<?>  param1, Comparable<?>  param2) throws ParseException {
		if (param1 == null || param2 == null) {
			return null;
		}
		if (param1 instanceof String) {
			param1 = parse((String)param1);
		}
		if (param2 instanceof String) {
			param2 = parse((String)param2);
		}
		if (param1 instanceof Number && param2 instanceof Number) {
			// BigInteger type is not supported
			Number n1 = (Number)param1;
			Number n2 = (Number)param2;
			if (n1 instanceof BigDecimal || n2 instanceof BigDecimal) {
				BigDecimal b1 = getBigDecimal(n1);
				BigDecimal b2 = getBigDecimal(n2);
				return b1.add(b2);
			}
			if (n1 instanceof Double || n2 instanceof Double || n1 instanceof Float || n2 instanceof Float) {
				return n1.doubleValue() + n2.doubleValue();
			} else {	// Long, Integer, Short, Byte 
				long l1 = n1.longValue();
				long l2 = n2.longValue();
				long r = l1 + l2;
				if (l1 <= r && l2 <= r) {		// overflow check
					return r;
				} else {
					BigDecimal b1 = new BigDecimal(l1);
					BigDecimal b2 = new BigDecimal(l2);
					return b1.add(b2);
				}
			}
		}
		else if (param1 instanceof Timestamp || param2 instanceof Timestamp) {
			if (param1 instanceof Timestamp && param2 instanceof Timestamp) {
				throw new ParseException(DATE_ADDITION);
			}
			Timestamp d;
			Number n;
			if (param1 instanceof Timestamp) {
				d = (Timestamp)param1;
				if (param2 instanceof Number) {
					n = (Number)param2;
				} else {
					throw new ParseException(DATE_ADDITION);
				}
				return new Timestamp(d.getTime()+toDay(n));
			}
			else if (param2 instanceof Timestamp) {
				d = (Timestamp)param2;
				if (param1 instanceof Number) {
					n = (Number)param1;
				} else {
					throw new ParseException(DATE_ADDITION);
				}
				return new Timestamp(d.getTime()+toDay(n));
			}
			throw new ParseException(INTERNAL_ERROR);
		} else {
			throw new ParseException(WRONG_TYPE+"  ("+param1.getClass()+"+"+param2.getClass()+")");
		}
	}
	
	static long toDay(Number n) {
		if (n instanceof BigDecimal) {		// BigInteger is not supported
			BigDecimal dec = (BigDecimal)n;
			BigDecimal t = dec.multiply(DAY_MILIS);
			t = t.setScale(0, BigDecimal.ROUND_HALF_UP);
			return t.longValue();
		} else {		// Long, Integer, Short, Byte 
			return n.longValue()*86400000;
		}
	}

	public Comparable<?> getResult(Comparable<?>... comparables)
			throws ParseException {
		return add(comparables[0], comparables[1]);
	}
}