broker-core/src/main/java/org/apache/qpid/server/filter/ArithmeticExpression.java

/**
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.qpid.server.filter;
//
// Based on like named file from r450141 of the Apache ActiveMQ project <http://www.activemq.org/site/home.html>
//

/**
 * An expression which performs an operation on two expression values
 */
public abstract class ArithmeticExpression<T> extends BinaryExpression<T>
{

    protected static final int INTEGER = 1;
    protected static final int LONG = 2;
    protected static final int DOUBLE = 3;

    public ArithmeticExpression(Expression<T> left, Expression<T> right)
    {
        super(left, right);
    }

    public static <E> Expression<E> createPlus(Expression<E> left, Expression<E> right)
    {
        return new ArithmeticExpression<E>(left, right)
            {
                @Override
                protected Object evaluate(Object lvalue, Object rvalue)
                {
                    if (lvalue instanceof String)
                    {
                        String text = (String) lvalue;
                        String answer = text + rvalue;

                        return answer;
                    }
                    else if (lvalue instanceof Number)
                    {
                        return plus((Number) lvalue, asNumber(rvalue));
                    }

                    throw new SelectorParsingException("Cannot call plus operation on: " + lvalue + " and: " + rvalue);
                }

                @Override
                public String getExpressionSymbol()
                {
                    return "+";
                }
            };
    }

    public static <E> Expression<E> createMinus(Expression<E> left, Expression<E> right)
    {
        return new ArithmeticExpression<E>(left, right)
            {
                @Override
                protected Object evaluate(Object lvalue, Object rvalue)
                {
                    if (lvalue instanceof Number)
                    {
                        return minus((Number) lvalue, asNumber(rvalue));
                    }

                    throw new SelectorParsingException("Cannot call minus operation on: " + lvalue + " and: " + rvalue);
                }

                @Override
                public String getExpressionSymbol()
                {
                    return "-";
                }
            };
    }

    public static <E> Expression<E> createMultiply(Expression<E> left, Expression<E> right)
    {
        return new ArithmeticExpression<E>(left, right)
            {

                @Override
                protected Object evaluate(Object lvalue, Object rvalue)
                {
                    if (lvalue instanceof Number)
                    {
                        return multiply((Number) lvalue, asNumber(rvalue));
                    }

                    throw new SelectorParsingException("Cannot call multiply operation on: " + lvalue + " and: " + rvalue);
                }

                @Override
                public String getExpressionSymbol()
                {
                    return "*";
                }
            };
    }

    public static <E> Expression<E> createDivide(Expression<E> left, Expression<E> right)
    {
        return new ArithmeticExpression<E>(left, right)
            {

                @Override
                protected Object evaluate(Object lvalue, Object rvalue)
                {
                    if (lvalue instanceof Number)
                    {
                        return divide((Number) lvalue, asNumber(rvalue));
                    }

                    throw new SelectorParsingException("Cannot call divide operation on: " + lvalue + " and: " + rvalue);
                }

                @Override
                public String getExpressionSymbol()
                {
                    return "/";
                }
            };
    }

    public static <E> Expression<E> createMod(Expression<E> left, Expression<E> right)
    {
        return new ArithmeticExpression<E>(left, right)
            {

                @Override
                protected Object evaluate(Object lvalue, Object rvalue)
                {
                    if (lvalue instanceof Number)
                    {
                        return mod((Number) lvalue, asNumber(rvalue));
                    }

                    throw new SelectorParsingException("Cannot call mod operation on: " + lvalue + " and: " + rvalue);
                }

                @Override
                public String getExpressionSymbol()
                {
                    return "%";
                }
            };
    }

    protected Number plus(Number left, Number right)
    {
        switch (numberType(left, right))
        {

        case INTEGER:
            return Integer.valueOf(left.intValue() + right.intValue());

        case LONG:
            return Long.valueOf(left.longValue() + right.longValue());

        default:
            return Double.valueOf(left.doubleValue() + right.doubleValue());
        }
    }

    protected Number minus(Number left, Number right)
    {
        switch (numberType(left, right))
        {

        case INTEGER:
            return Integer.valueOf(left.intValue() - right.intValue());

        case LONG:
            return Long.valueOf(left.longValue() - right.longValue());

        default:
            return Double.valueOf(left.doubleValue() - right.doubleValue());
        }
    }

    protected Number multiply(Number left, Number right)
    {
        switch (numberType(left, right))
        {

        case INTEGER:
            return Integer.valueOf(left.intValue() * right.intValue());

        case LONG:
            return Long.valueOf(left.longValue() * right.longValue());

        default:
            return Double.valueOf(left.doubleValue() * right.doubleValue());
        }
    }

    protected Number divide(Number left, Number right)
    {
        return Double.valueOf(left.doubleValue() / right.doubleValue());
    }

    protected Number mod(Number left, Number right)
    {
        return Double.valueOf(left.doubleValue() % right.doubleValue());
    }

    private int numberType(Number left, Number right)
    {
        if (isDouble(left) || isDouble(right))
        {
            return DOUBLE;
        }
        else if ((left instanceof Long) || (right instanceof Long))
        {
            return LONG;
        }
        else
        {
            return INTEGER;
        }
    }

    private boolean isDouble(Number n)
    {
        return (n instanceof Float) || (n instanceof Double);
    }

    protected Number asNumber(Object value)
    {
        if (value instanceof Number)
        {
            return (Number) value;
        }
        else
        {
            throw new SelectorParsingException("Cannot convert value: " + value + " into a number");
        }
    }

    @Override
    public Object evaluate(T message)
    {
        Object lvalue = getLeft().evaluate(message);
        if (lvalue == null)
        {
            return null;
        }

        Object rvalue = getRight().evaluate(message);
        if (rvalue == null)
        {
            return null;
        }

        return evaluate(lvalue, rvalue);
    }

    protected abstract Object evaluate(Object lvalue, Object rvalue);

}