/*
 * 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.cache;

import java.io.IOException;

import freemarker.core.TemplateConfiguration;
import freemarker.template.Configuration;

Returns the merged results of all the child factories. The factories are merged in the order as they were added. null results from the child factories will be ignored. If all child factories return null, the result of this factory will be null too. 
Since:
2.3.24/**
 * Returns the merged results of all the child factories. The factories are merged in the order as they were added.
 * {@code null} results from the child factories will be ignored. If all child factories return {@code null}, the result
 * of this factory will be {@code null} too.
 * 
 * @since 2.3.24
 */
public class MergingTemplateConfigurationFactory extends TemplateConfigurationFactory {
    
    private final TemplateConfigurationFactory[] templateConfigurationFactories;
    
    public MergingTemplateConfigurationFactory(TemplateConfigurationFactory... templateConfigurationFactories) {
        this.templateConfigurationFactories = templateConfigurationFactories;
    }

    @Override
    public TemplateConfiguration get(String sourceName, Object templateSource)
            throws IOException, TemplateConfigurationFactoryException {
        TemplateConfiguration mergedTC = null;
        TemplateConfiguration resultTC = null;
        for (TemplateConfigurationFactory tcf : templateConfigurationFactories) {
            TemplateConfiguration tc = tcf.get(sourceName, templateSource);
            if (tc != null) {
                if (resultTC == null) {
                    resultTC = tc;
                } else {
                    if (mergedTC == null) {
                        Configuration cfg = getConfiguration();
                        if (cfg == null) {
                            throw new IllegalStateException(
                                    "The TemplateConfigurationFactory wasn't associated to a Configuration yet.");
                        }
                        
                        mergedTC = new TemplateConfiguration();
                        mergedTC.setParentConfiguration(cfg);
                        mergedTC.merge(resultTC);
                        resultTC = mergedTC;
                    }
                    mergedTC.merge(tc);
                }
            }
        }
        return resultTC;
    }
    
    @Override
    protected void setConfigurationOfChildren(Configuration cfg) {
        for (TemplateConfigurationFactory templateConfigurationFactory : templateConfigurationFactories) {
            templateConfigurationFactory.setConfiguration(cfg);
        }
    }

}