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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.util.Collection;
import java.util.List;

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 special case of {@link BeanModel} that can wrap Java collections
 * and that implements the {@link TemplateCollectionModel} in order to be usable 
 * in a <#list> block.
 */
public class CollectionModel
extends
    StringModel
implements
    TemplateCollectionModel,
    TemplateSequenceModel {
    static final ModelFactory FACTORY =
        new ModelFactory()
        {
            public TemplateModel create(Object object, ObjectWrapper wrapper) {
                return new CollectionModel((Collection) object, (BeansWrapper) wrapper);
            }
        };


    /**
     * Creates a new model that wraps the specified collection object.
     * @param collection the collection 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.
     */
    public CollectionModel(Collection collection, BeansWrapper wrapper) {
        super(collection, wrapper);
    }

    /**
     * Retrieves the i-th object from the collection, wrapped as a TemplateModel.
     * @throws TemplateModelException if the index is out of bounds, or the
     * underlying collection is not a List.
     */
    public TemplateModel get(int index)
    throws TemplateModelException {
        // Don't forget to keep getSupportsIndexedAccess in sync with this!
        if (object instanceof List) {
            try {
                return wrap(((List) object).get(index));
            } catch (IndexOutOfBoundsException e) {
                return null;
//                throw new TemplateModelException("Index out of bounds: " + index);
            }
        } else {
            throw new TemplateModelException("Underlying collection is not a list, it's " + object.getClass().getName());
        }
    }
    
    /**
     * Tells if {@link #get(int)} will always fail for this object.
     * As this object implements {@link TemplateSequenceModel},
     * {@link #get(int)} should always work, but due to a design flaw, for
     * non-{@link List} wrapped objects {@link #get(int)} will always fail.
     * This method exists to ease working this problem around.
     * 
     * @since 2.3.17 
     */
    public boolean getSupportsIndexedAccess() {
        return object instanceof List;
    }
    
    public TemplateModelIterator iterator() {
        return new IteratorModel(((Collection) object).iterator(), wrapper);
    }

    @Override
    public int size() {
        return ((Collection) object).size();
    }
    
}