/*
 *
 * 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;
//
// Based on like named file from r450141 of the Apache ActiveMQ project <http://www.activemq.org/site/home.html>
//

import java.math.BigDecimal;

/**
 * Represents a constant expression
 */
public class ConstantExpression implements Expression
{

    static class BooleanConstantExpression extends ConstantExpression implements BooleanExpression
    {
        public BooleanConstantExpression(Object value)
        {
            super(value);
        }

        public boolean matches(FilterableMessage message)
        {
            Object object = evaluate(message);

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

    public static final BooleanConstantExpression NULL = new BooleanConstantExpression(null);
    public static final BooleanConstantExpression TRUE = new BooleanConstantExpression(Boolean.TRUE);
    public static final BooleanConstantExpression FALSE = new BooleanConstantExpression(Boolean.FALSE);

    private Object value;

    public static ConstantExpression createFromDecimal(String text)
    {

        // Strip off the 'l' or 'L' if needed.
        if (text.endsWith("l") || text.endsWith("L"))
        {
            text = text.substring(0, text.length() - 1);
        }

        Number value;
        try
        {
            value = new Long(text);
        }
        catch (NumberFormatException e)
        {
            // The number may be too big to fit in a long.
            value = new BigDecimal(text);
        }

        long l = value.longValue();
        if ((Integer.MIN_VALUE <= l) && (l <= Integer.MAX_VALUE))
        {
            value = value.intValue();
        }

        return new ConstantExpression(value);
    }

    public static ConstantExpression createFromHex(String text)
    {
        Number value = Long.parseLong(text.substring(2), 16);
        long l = value.longValue();
        if ((Integer.MIN_VALUE <= l) && (l <= Integer.MAX_VALUE))
        {
            value = value.intValue();
        }

        return new ConstantExpression(value);
    }

    public static ConstantExpression createFromOctal(String text)
    {
        Number value = Long.parseLong(text, 8);
        long l = value.longValue();
        if ((Integer.MIN_VALUE <= l) && (l <= Integer.MAX_VALUE))
        {
            value = value.intValue();
        }

        return new ConstantExpression(value);
    }

    public static ConstantExpression createFloat(String text)
    {
        Number value = new Double(text);

        return new ConstantExpression(value);
    }

    public ConstantExpression(Object value)
    {
        this.value = value;
    }

    public Object evaluate(FilterableMessage message)
    {
        return value;
    }

    public Object getValue()
    {
        return value;
    }

    /**
     * @see java.lang.Object#toString()
     */
    public String toString()
    {
        if (value == null)
        {
            return "NULL";
        }

        if (value instanceof Boolean)
        {
            return ((Boolean) value) ? "TRUE" : "FALSE";
        }

        if (value instanceof String)
        {
            return encodeString((String) value);
        }

        return value.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());

    }

    /**
     * Encodes the value of string so that it looks like it would look like
     * when it was provided in a selector.
     *
     * @param s
     * @return
     */
    public static String encodeString(String s)
    {
        StringBuffer b = new StringBuffer();
        b.append('\'');
        for (int i = 0; i < s.length(); i++)
        {
            char c = s.charAt(i);
            if (c == '\'')
            {
                b.append(c);
            }

            b.append(c);
        }

        b.append('\'');

        return b.toString();
    }

}