/**
 * 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.activemq.apollo.filter;

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: 1.3 $
 */
public abstract class UnaryExpression implements Expression {

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

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

    public static Expression createNegate(Expression left) {
        return new UnaryExpression(left) {
            public Object evaluate(Filterable message) throws FilterException {
                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<Object> elements, final boolean not) {

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

        return new BooleanUnaryExpression(right) {
            public Object evaluate(Filterable message) throws FilterException {

                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<Object> 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(Filterable message) throws FilterException {
            Object object = evaluate(message);
            return object != null && object == Boolean.TRUE;
        }
    };

    public static BooleanExpression createNOT(BooleanExpression left) {
        return new BooleanUnaryExpression(left) {
            public Object evaluate(Filterable message) throws FilterException {
                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(Filterable message) throws FilterException {
                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 Long.valueOf(Long.MIN_VALUE);
            }
            return bd;
        } else {
            throw new RuntimeException("Don't know how to negate: " + 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
     */
    public abstract String getExpressionSymbol();

}
