/*
    * Copyright 2002-2014 the original author or authors.
    *
    * Licensed 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.springframework.ui.freemarker;
  
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.Reader;
  
  import freemarker.cache.TemplateLoader;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import org.springframework.core.io.Resource;
  import org.springframework.core.io.ResourceLoader;
  
  /**
   * FreeMarker {@link TemplateLoader} adapter that loads via a Spring {@link ResourceLoader}.
   * Used by {@link FreeMarkerConfigurationFactory} for any resource loader path that cannot
   * be resolved to a {@link java.io.File}.
   *
   * @author Juergen Hoeller
   * @since 14.03.2004
   * @see FreeMarkerConfigurationFactory#setTemplateLoaderPath
   * @see freemarker.template.Configuration#setDirectoryForTemplateLoading
   */
  public class SpringTemplateLoader implements TemplateLoader {
  
  	protected final Log logger = LogFactory.getLog(getClass());
  
  	private final ResourceLoader resourceLoader;
  
  	private final String templateLoaderPath;
  
  
  	/**
  	 * Create a new SpringTemplateLoader.
  	 * @param resourceLoader the Spring ResourceLoader to use
  	 * @param templateLoaderPath the template loader path to use
  	 */
  	public SpringTemplateLoader(ResourceLoader resourceLoader, String templateLoaderPath) {
  		this.resourceLoader = resourceLoader;
  		if (!templateLoaderPath.endsWith("/")) {
  			templateLoaderPath += "/";
  		}
  		this.templateLoaderPath = templateLoaderPath;
  		if (logger.isInfoEnabled()) {
  			logger.info("SpringTemplateLoader for FreeMarker: using resource loader [" + this.resourceLoader +
  					"] and template loader path [" + this.templateLoaderPath + "]");
  		}
  	}
  
  
  	@Override
  	public Object findTemplateSource(String name) throws IOException {
  		if (logger.isDebugEnabled()) {
  			logger.debug("Looking for FreeMarker template with name [" + name + "]");
  		}
  		Resource resource = this.resourceLoader.getResource(this.templateLoaderPath + name);
  		return (resource.exists() ? resource : null);
  	}
  
  	@Override
  	public Reader getReader(Object templateSource, String encoding) throws IOException {
  		Resource resource = (Resource) templateSource;
  		try {
  			return new InputStreamReader(resource.getInputStream(), encoding);
  		}
  		catch (IOException ex) {
  			if (logger.isDebugEnabled()) {
  				logger.debug("Could not find FreeMarker template: " + resource);
  			}
  			throw ex;
  		}
  	}
  
  	@Override
  	public long getLastModified(Object templateSource) {
  		Resource resource = (Resource) templateSource;
  		try {
  			return resource.lastModified();
  		}
  		catch (IOException ex) {
  			if (logger.isDebugEnabled()) {
  				logger.debug("Could not obtain last-modified timestamp for FreeMarker template in " +
  						resource + ": " + ex);
 			}
 			return -1;
 		}
 	}
 
 	@Override
 	public void closeTemplateSource(Object templateSource) throws IOException {
 	}
 
 }