/* (c) 2014 Open Source Geospatial Foundation - all rights reserved
 * (c) 2001 - 2013 OpenPlans
 * This code is licensed under the GPL 2.0 license, available at the root
 * application directory.
 */
package org.geoserver.filters;

import java.io.IOException;
import java.util.List;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.geoserver.platform.ExtensionPriority;
import org.geoserver.platform.GeoServerExtensions;

/**
 * <p>
 * A composite servlet filter that loaders delegate filters from a spring context, rather then from
 * the traditional web.xml. This class allows for servlet filters to be dynamically contributed via 
 * a spring context.
 * </p>
 * <p>It will pick up any filter declared in the Spring context that implements the 
 * {@link GeoServerFilter} interface</p>.
 * Ordering of the filters won't normally be predictable, but as with all other extension points
 * it's possible to force a specific ordering by having filters implement the 
 * {@link ExtensionPriority} interface
 * </p> 
 *
 * @author Justin Deoliveira, OpenGeo
 */
public class SpringDelegatingFilter implements Filter {

    List<GeoServerFilter> filters;
    
    public void init(FilterConfig filterConfig) throws ServletException {
        filters = GeoServerExtensions.extensions(GeoServerFilter.class);
    }
    
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        new Chain(chain).doFilter(request, response);
    }
    
    public void destroy() {
        if (filters != null) {
            for (Filter f : filters) {
                f.destroy();
            }
            filters = null;
        }
    }
    
    class Chain implements FilterChain {

        FilterChain delegate;
        int filter = 0;
        
        public Chain(FilterChain chain) {
            this.delegate = chain;
        }
        
        public void doFilter(ServletRequest request, ServletResponse response) throws IOException,
                ServletException {
            
            if (filter < filters.size()) {
                filters.get(filter++).doFilter(request, response, this);
            }
            else {
                //resume the actual chain
                delegate.doFilter(request, response);
            }
        }
        
    }
}