/*
 * 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 freemarker.template.utility;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 */
public class OptimizerUtil {
    private static final BigInteger INTEGER_MIN = new BigInteger(Integer.toString(Integer.MIN_VALUE));
    private static final BigInteger INTEGER_MAX = new BigInteger(Integer.toString(Integer.MAX_VALUE));
    private static final BigInteger LONG_MIN = new BigInteger(Long.toString(Long.MIN_VALUE));
    private static final BigInteger LONG_MAX = new BigInteger(Long.toString(Long.MAX_VALUE));

    private OptimizerUtil() {
    }
    
    public static List optimizeListStorage(List list) {
        switch(list.size())
        {
            case 0:
            {
                return Collections.EMPTY_LIST;
            }
            case 1:
            {
                return Collections.singletonList(list.get(0));
            }
            default:
            {
                if (list instanceof ArrayList) {
                    ((ArrayList) list).trimToSize();
                }
                return list;
            }
        }
    }
    
    
This is needed to reverse the extreme conversions in arithmetic 
operations so that numbers can be meaningfully used with models that
don't know what to do with a BigDecimal. Of course, this will make
impossible for these models (i.e. Jython) to receive a BigDecimal even if 
it was originally placed as such in the data model. However, since 
arithmetic operations aggressively erase the information regarding the 
original number type, we have no other choice to ensure expected operation
in majority of cases.
/**
     * This is needed to reverse the extreme conversions in arithmetic 
     * operations so that numbers can be meaningfully used with models that
     * don't know what to do with a BigDecimal. Of course, this will make
     * impossible for these models (i.e. Jython) to receive a BigDecimal even if 
     * it was originally placed as such in the data model. However, since 
     * arithmetic operations aggressively erase the information regarding the 
     * original number type, we have no other choice to ensure expected operation
     * in majority of cases.
     */
    public static Number optimizeNumberRepresentation(Number number) {
        if (number instanceof BigDecimal) {
            BigDecimal bd = (BigDecimal) number;
            if (bd.scale() == 0) {
                // BigDecimal -> BigInteger
                number = bd.unscaledValue();
            } else {
                double d = bd.doubleValue();
                if (d != Double.POSITIVE_INFINITY && d != Double.NEGATIVE_INFINITY) {
                    // BigDecimal -> Double
                    return Double.valueOf(d);
                }
            }
        }
        if (number instanceof BigInteger) {
            BigInteger bi = (BigInteger) number;
            if (bi.compareTo(INTEGER_MAX) <= 0 && bi.compareTo(INTEGER_MIN) >= 0) {
                // BigInteger -> Integer
                return Integer.valueOf(bi.intValue());
            }
            if (bi.compareTo(LONG_MAX) <= 0 && bi.compareTo(LONG_MIN) >= 0) {
                // BigInteger -> Long
                return Long.valueOf(bi.longValue());
            }
        }
        return number;
    }
}