FilterPipe.java

/*
 * This file is part of "SnipSnap Radeox Rendering Engine".
 *
 * Copyright (c) 2002 Stephan J. Schmidt, Matthias L. Jugel
 * All Rights Reserved.
 *
 * Please visit http://radeox.org/ for updates and contact.
 *
 * --LICENSE NOTICE--
 * 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.
 * --LICENSE NOTICE--
 */

package org.radeox.filter;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.radeox.api.engine.context.InitialRenderContext;
import org.radeox.api.engine.context.RenderContext;
import org.radeox.engine.context.BaseInitialRenderContext;
import org.radeox.filter.context.FilterContext;

/*
 * FilterPipe is a collection of Filters which are applied one by one to an
 * input to generate output @author stephan @team sonicteam
 * 
 * @version $Id: FilterPipe.java 7756 2006-04-13 12:25:49Z ian@caret.cam.ac.uk $
 */

public class FilterPipe
{
	private static Log log = LogFactory.getLog(FilterPipe.class);

	public final static String FIRST_IN_PIPE = "all";

	public final static String LAST_IN_PIPE = "none";

	public final static String[] EMPTY_BEFORE = new String[] {};

	public final static String[] NO_REPLACES = new String[] {};

	public final static String[] FIRST_BEFORE = new String[] { FIRST_IN_PIPE };

	private InitialRenderContext initialContext;

	private List filterList = null;

	private static Object[] noArguments = new Object[] {};

	public FilterPipe()
	{
		this(new BaseInitialRenderContext());
	}

	public FilterPipe(InitialRenderContext context)
	{
		filterList = new ArrayList();
		initialContext = context;
	}

	public void init()
	{
		Iterator iterator = new ArrayList(filterList).iterator();
		while (iterator.hasNext())
		{
			Filter filter = (Filter) iterator.next();
			String[] replaces = filter.replaces();
			for (int i = 0; i < replaces.length; i++)
			{
				String replace = replaces[i];
				removeFilter(replace);
			}
		}
	}

	public void removeFilter(String filterClass)
	{
		Iterator iterator = filterList.iterator();
		while (iterator.hasNext())
		{
			Filter filter = (Filter) iterator.next();
			if (filter.getClass().getName().equals(filterClass))
			{
				iterator.remove();
			}
		}
	}

	/**
	 * Add a filter to the pipe
	 * 
	 * @param filter
	 *        Filter to add
	 */
	public void addFilter(Filter filter)
	{
		filter.setInitialContext(initialContext);

		int minIndex = Integer.MAX_VALUE;
		String[] before = filter.before();
		for (int i = 0; i < before.length; i++)
		{
			String s = before[i];
			int index = index(filterList, s);
			if (index < minIndex)
			{
				minIndex = index;
			}
		}
		if (minIndex == Integer.MAX_VALUE)
		{
			// -1 is more usable for not-found than MAX_VALUE
			minIndex = -1;
		}

		if (contains(filter.before(), FIRST_IN_PIPE))
		{
			filterList.add(0, filter);
		}
		else if (minIndex != -1)
		{
			filterList.add(minIndex, filter);
			// } else if (contains(filter.before(), LAST_IN_PIPE)) {
			// filterList.add(-1, filter);
		}
		else
		{
			filterList.add(filter);
		}
	}

	public int index(String filterName)
	{
		return FilterPipe.index(filterList, filterName);
	}

	public static int index(List list, final String filterName)
	{
		for (int i = 0; i < list.size(); i++)
		{
			if (filterName.equals(list.get(i).getClass().getName())) return i;
		}
		return -1;
	}

	public static boolean contains(Object[] array, Object value)
	{
		return (Arrays.binarySearch(array, value) != -1);
	}

	/**
	 * Filter some input and generate ouput. FilterPipe pipes the string input
	 * through every filter in the pipe and returns the resulting string.
	 * 
	 * @param input
	 *        Input string which should be transformed
	 * @param context
	 *        FilterContext with information about the enviroment
	 * @return result Filtered output
	 */
	public String filter(String input, FilterContext context)
	{
		// Logger.debug("FilterPipe.filter: context = "+context);
		String output = input;
		Iterator filterIterator = filterList.iterator();
		RenderContext renderContext = context.getRenderContext();

		// Apply every filter in filterList to input string
		while (filterIterator.hasNext())
		{
			Filter f = (Filter) filterIterator.next();
			try
			{
				// assume all filters non cacheable
				if (f instanceof CacheFilter)
				{
					renderContext.setCacheable(true);
				}
				else
				{
					renderContext.setCacheable(false);
				}
				String tmp = f.filter(output, context);
				if (output.equals(tmp))
				{
					renderContext.setCacheable(true);
				}
				if (null == tmp)
				{
					log.warn("FilterPipe.filter: error while filtering: " + f);
				}
				else
				{
					output = tmp;
				}
				renderContext.commitCache();
			}
			catch (Exception e)
			{
				log.warn("Filtering exception: " + f, e);
			}
		}
		return output;
	}

	public Filter getFilter(int index)
	{
		return (Filter) filterList.get(index);
	}
}