/*
    * Copyright 2002-2013 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.scripting.support;
  
  import java.io.IOException;
  import java.io.Reader;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import org.springframework.core.io.Resource;
  import org.springframework.core.io.support.EncodedResource;
  import org.springframework.scripting.ScriptSource;
  import org.springframework.util.Assert;
  import org.springframework.util.FileCopyUtils;
  import org.springframework.util.StringUtils;
  
  /**
   * {@link org.springframework.scripting.ScriptSource} implementation
   * based on Spring's {@link org.springframework.core.io.Resource}
   * abstraction. Loads the script text from the underlying Resource's
   * {@link org.springframework.core.io.Resource#getFile() File} or
   * {@link org.springframework.core.io.Resource#getInputStream() InputStream},
   * and tracks the last-modified timestamp of the file (if possible).
   *
   * @author Rob Harrop
   * @author Juergen Hoeller
   * @since 2.0
   * @see org.springframework.core.io.Resource#getInputStream()
   * @see org.springframework.core.io.Resource#getFile()
   * @see org.springframework.core.io.ResourceLoader
   */
  public class ResourceScriptSource implements ScriptSource {
  
  	/** Logger available to subclasses */
  	protected final Log logger = LogFactory.getLog(getClass());
  
  	private EncodedResource resource;
  
  	private long lastModified = -1;
  
  	private final Object lastModifiedMonitor = new Object();
  
  
  	/**
  	 * Create a new ResourceScriptSource for the given resource.
  	 * @param resource the EncodedResource to load the script from
  	 */
  	public ResourceScriptSource(EncodedResource resource) {
  		Assert.notNull(resource, "Resource must not be null");
  		this.resource = resource;
  	}
  
  	/**
  	 * Create a new ResourceScriptSource for the given resource.
  	 * @param resource the Resource to load the script from (using UTF-8 encoding)
  	 */
  	public ResourceScriptSource(Resource resource) {
  		Assert.notNull(resource, "Resource must not be null");
  		this.resource = new EncodedResource(resource, "UTF-8");
  	}
  
  
  	/**
  	 * Return the {@link org.springframework.core.io.Resource} to load the
  	 * script from.
  	 */
  	public final Resource getResource() {
  		return this.resource.getResource();
  	}
  
  	/**
  	 * Set the encoding used for reading the script resource.
  	 * <p>The default value for regular Resources is "UTF-8".
  	 * A {@code null} value implies the platform default.
  	 */
  	public void setEncoding(String encoding) {
  		this.resource = new EncodedResource(this.resource.getResource(), encoding);
  	}
  
  
  	@Override
  	public String getScriptAsString() throws IOException {
  		synchronized (this.lastModifiedMonitor) {
  			this.lastModified = retrieveLastModifiedTime();
 		}
 		Reader reader = this.resource.getReader();
 		return FileCopyUtils.copyToString(reader);
 	}
 
 	@Override
 	public boolean isModified() {
 		synchronized (this.lastModifiedMonitor) {
 			return (this.lastModified < 0 || retrieveLastModifiedTime() > this.lastModified);
 		}
 	}
 
 	/**
 	 * Retrieve the current last-modified timestamp of the underlying resource.
 	 * @return the current timestamp, or 0 if not determinable
 	 */
 	protected long retrieveLastModifiedTime() {
 		try {
 			return getResource().lastModified();
 		}
 		catch (IOException ex) {
 			if (logger.isDebugEnabled()) {
 				logger.debug(getResource() + " could not be resolved in the file system - " +
 						"current timestamp not available for script modification check", ex);
 			}
 			return 0;
 		}
 	}
 
 	@Override
 	public String suggestedClassName() {
 		return StringUtils.stripFilenameExtension(getResource().getFilename());
 	}
 
 	@Override
 	public String toString() {
 		return this.resource.toString();
 	}
 
 }