RC9/qpid/java/client/src/main/java/org/apache/qpid/filter/UnaryExpression.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.filter;

import org.apache.qpid.QpidException;
import org.apache.qpid.client.message.AbstractJMSMessage;

import java.math.BigDecimal;
import java.util.List;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;

/**
 * An expression which performs an operation on two expression values
 */
public abstract class UnaryExpression implements Expression
{

    private static final BigDecimal BD_LONG_MIN_VALUE = BigDecimal.valueOf(Long.MIN_VALUE);
    protected Expression right;

    public static Expression createNegate(Expression left)
    {
        return new UnaryExpression(left)
        {
            public Object evaluate(AbstractJMSMessage message) throws QpidException
            {
                Object rvalue = right.evaluate(message);
                if (rvalue == null)
                {
                    return null;
                }

                if (rvalue instanceof Number)
                {
                    return UnaryExpression.negate((Number) rvalue);
                }

                return null;
            }

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

    public static BooleanExpression createInExpression(PropertyExpression right, List elements, final boolean not)
    {

        // Use a HashSet if there are many elements.
        Collection t;
        if (elements.size() == 0)
        {
            t = null;
        }
        else if (elements.size() < 5)
        {
            t = elements;
        }
        else
        {
            t = new HashSet(elements);
        }

        final Collection inList = t;

        return new BooleanUnaryExpression(right)
        {
            public Object evaluate(AbstractJMSMessage message) throws QpidException
            {

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

                if (rvalue.getClass() != String.class)
                {
                    return null;
                }

                if (((inList != null) && inList.contains(rvalue)) ^ not)
                {
                    return Boolean.TRUE;
                }
                else
                {
                    return Boolean.FALSE;
                }

            }

            public String toString()
            {
                StringBuffer answer = new StringBuffer();
                answer.append(right);
                answer.append(" ");
                answer.append(getExpressionSymbol());
                answer.append(" ( ");

                int count = 0;
                for (Iterator i = inList.iterator(); i.hasNext();)
                {
                    Object o = (Object) i.next();
                    if (count != 0)
                    {
                        answer.append(", ");
                    }

                    answer.append(o);
                    count++;
                }

                answer.append(" )");

                return answer.toString();
            }

            public String getExpressionSymbol()
            {
                if (not)
                {
                    return "NOT IN";
                }
                else
                {
                    return "IN";
                }
            }
        };
    }

    abstract static class BooleanUnaryExpression extends UnaryExpression implements BooleanExpression
    {
        public BooleanUnaryExpression(Expression left)
        {
            super(left);
        }

        public boolean matches(AbstractJMSMessage message) throws QpidException
        {
            Object object = evaluate(message);

            return (object != null) && (object == Boolean.TRUE);
        }
    }

    ;

    public static BooleanExpression createNOT(BooleanExpression left)
    {
        return new BooleanUnaryExpression(left)
        {
            public Object evaluate(AbstractJMSMessage message) throws QpidException
            {
                Boolean lvalue = (Boolean) right.evaluate(message);
                if (lvalue == null)
                {
                    return null;
                }

                return lvalue.booleanValue() ? Boolean.FALSE : Boolean.TRUE;
            }

            public String getExpressionSymbol()
            {
                return "NOT";
            }
        };
    }
    public static BooleanExpression createBooleanCast(Expression left)
    {
        return new BooleanUnaryExpression(left)
        {
            public Object evaluate(AbstractJMSMessage message) throws QpidException
            {
                Object rvalue = right.evaluate(message);
                if (rvalue == null)
                {
                    return null;
                }

                if (!rvalue.getClass().equals(Boolean.class))
                {
                    return Boolean.FALSE;
                }

                return ((Boolean) rvalue).booleanValue() ? Boolean.TRUE : Boolean.FALSE;
            }

            public String toString()
            {
                return right.toString();
            }

            public String getExpressionSymbol()
            {
                return "";
            }
        };
    }

    private static Number negate(Number left)
    {
        Class clazz = left.getClass();
        if (clazz == Integer.class)
        {
            return new Integer(-left.intValue());
        }
        else if (clazz == Long.class)
        {
            return new Long(-left.longValue());
        }
        else if (clazz == Float.class)
        {
            return new Float(-left.floatValue());
        }
        else if (clazz == Double.class)
        {
            return new Double(-left.doubleValue());
        }
        else if (clazz == BigDecimal.class)
        {
            // We ussually get a big deciamal when we have Long.MIN_VALUE constant in the
            // Selector.  Long.MIN_VALUE is too big to store in a Long as a positive so we store it
            // as a Big decimal.  But it gets Negated right away.. to here we try to covert it back
            // to a Long.
            BigDecimal bd = (BigDecimal) left;
            bd = bd.negate();

            if (UnaryExpression.BD_LONG_MIN_VALUE.compareTo(bd) == 0)
            {
                return new Long(Long.MIN_VALUE);
            }

            return bd;
        }
        else
        {
            throw new RuntimeException("Don't know how to negate: " + left);
        }
    }

    public UnaryExpression(Expression left)
    {
        this.right = left;
    }

    public Expression getRight()
    {
        return right;
    }

    public void setRight(Expression expression)
    {
        right = expression;
    }

    /**
     * @see Object#toString()
     */
    public String toString()
    {
        return "(" + getExpressionSymbol() + " " + right.toString() + ")";
    }

    /**
     * TODO: more efficient hashCode()
     *
     * @see Object#hashCode()
     */
    public int hashCode()
    {
        return toString().hashCode();
    }

    /**
     * TODO: more efficient hashCode()
     *
     * @see Object#equals(Object)
     */
    public boolean equals(Object o)
    {

        if ((o == null) || !this.getClass().equals(o.getClass()))
        {
            return false;
        }

        return toString().equals(o.toString());

    }

    /**
     * Returns the symbol that represents this binary expression.  For example, addition is
     * represented by "+"
     *
     * @return
     */
    public abstract String getExpressionSymbol();

}