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Google App Engine compliant variation of FreeMarker. FreeMarker is a "template engine"; a generic tool to generate text output based on templates.
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/*
 * 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.ext.beans;

import java.lang.reflect.Array;

import freemarker.ext.util.ModelFactory;
import freemarker.template.ObjectWrapper;
import freemarker.template.TemplateCollectionModel;
import freemarker.template.TemplateModel;
import freemarker.template.TemplateModelException;
import freemarker.template.TemplateModelIterator;
import freemarker.template.TemplateSequenceModel;

/**
 * A class that will wrap an arbitrary array into {@link TemplateCollectionModel}
 * and {@link TemplateSequenceModel} interfaces. It supports element retrieval through the array[index]
 * syntax and can be iterated as a list.
 */
public class ArrayModel
extends
    BeanModel
implements
    TemplateCollectionModel,
    TemplateSequenceModel {
    static final ModelFactory FACTORY =
        new ModelFactory()
        {
            public TemplateModel create(Object object, ObjectWrapper wrapper) {
                return new ArrayModel(object, (BeansWrapper) wrapper);
            }
        };
        
    // Cached length of the array
    private final int length;

    /**
     * Creates a new model that wraps the specified array object.
     * @param array the array object to wrap into a model.
     * @param wrapper the {@link BeansWrapper} associated with this model.
     * Every model has to have an associated {@link BeansWrapper} instance. The
     * model gains many attributes from its wrapper, including the caching 
     * behavior, method exposure level, method-over-item shadowing policy etc.
     * @throws IllegalArgumentException if the passed object is not a Java array.
     */
    public ArrayModel(Object array, BeansWrapper wrapper) {
        super(array, wrapper);
        Class clazz = array.getClass();
        if (!clazz.isArray())
            throw new IllegalArgumentException("Object is not an array, it's " + array.getClass().getName());
        length = Array.getLength(array);
    }


    public TemplateModelIterator iterator() {
        return new Iterator();
    }

    public TemplateModel get(int index)
    throws TemplateModelException {
        try {
            return wrap(Array.get(object, index));
        } catch (IndexOutOfBoundsException e) {
            return null; 
//            throw new TemplateModelException("Index out of bounds: " + index);
        }
    }

    private class Iterator
    implements 
        TemplateSequenceModel,
        TemplateModelIterator {
        private int position = 0;

        public boolean hasNext() {
            return position < length;
        }

        public TemplateModel get(int index)
        throws TemplateModelException {
            return ArrayModel.this.get(index);
        }

        public TemplateModel next()
        throws TemplateModelException {
            return position < length ? get(position++) : null;
        }

        public int size() {
            return ArrayModel.this.size();
        }
    }

    @Override
    public int size() {
        return length;
    }

    @Override
    public boolean isEmpty() {
        return length == 0;
    }
}