/**
 *
 * 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>
//

import org.apache.qpid.AMQException;
import org.apache.qpid.server.queue.AMQMessage;

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

/**
 * An expression which performs an operation on two expression values
 * 
 * @version $Revision$
 */
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(AMQMessage message) throws AMQException
            {
                Object rvalue = right.evaluate(message);
                if (rvalue == null) {
                    return null;
                }
                if (rvalue instanceof Number) {
                    return 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(AMQMessage message) throws AMQException {
            	
                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(AMQMessage message) throws AMQException {
            Object object = evaluate(message);
            return object!=null && object==Boolean.TRUE;            
        }
    };

        
    public static BooleanExpression createNOT(BooleanExpression left) {
        return new BooleanUnaryExpression(left) {
            public Object evaluate(AMQMessage message) throws AMQException {
                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 createXPath(final String xpath) {
        return new XPathExpression(xpath);
    }

    public static BooleanExpression createXQuery(final String xpath) {
        return new XQueryExpression(xpath);
    }

    public static BooleanExpression createBooleanCast(Expression left) {
        return new BooleanUnaryExpression(left) {
            public Object evaluate(AMQMessage message) throws AMQException {
                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( 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 java.lang.Object#toString()
     */
    public String toString() {
        return "(" + getExpressionSymbol() + " " + right.toString() + ")";
    }

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

    /**
     * TODO: more efficient hashCode()
     *
     * @see java.lang.Object#equals(java.lang.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
     */
    abstract public String getExpressionSymbol();

}
