Subtract.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 static com.meidusa.amoeba.sqljep.function.Add.DATE_ADDITION;
import static com.meidusa.amoeba.sqljep.function.Add.DAY_MILIS;
import static com.meidusa.amoeba.sqljep.function.Add.toDay;

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 Subtract extends PostfixCommand {
	final public int getNumberOfParameters() {
		return 2;
	}
	
	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<?>  sub(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
			if (param1 instanceof BigDecimal || param2 instanceof BigDecimal) {
				BigDecimal b1 = getBigDecimal((Number)param1);
				BigDecimal b2 = getBigDecimal((Number)param2);
				return b1.subtract(b2);
			}
			if (param1 instanceof Double || param2 instanceof Double || param1 instanceof Float || param2 instanceof Float) {
				return ((Number)param1).doubleValue() - ((Number)param2).doubleValue();
			} else {	// Long, Integer, Short, Byte 
				long l1 = ((Number)param1).longValue();
				long l2 = ((Number)param2).longValue();
				long r = l1 - l2;
				if (l1 >= r) {		// overflow check
					return r;
				} else {
					BigDecimal b1 = new BigDecimal(l1);
					BigDecimal b2 = new BigDecimal(l2);
					return b1.subtract(b2);
				}
			}
		}
		else if (param1 instanceof Timestamp || param2 instanceof Timestamp) {
			if (param1 instanceof Timestamp && param2 instanceof Timestamp) {
				Timestamp d1 = (Timestamp)param1;
				Timestamp d2 = (Timestamp)param2;
				BigDecimal d = new BigDecimal(d1.getTime()-d2.getTime());
				return d.divide(DAY_MILIS, 40, BigDecimal.ROUND_HALF_UP);
			} else {
				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()+")");
		}
	}

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