/*******************************************************************************
 *
 * Copyright (c) 2004-2009 Oracle Corporation.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * 
 *    Kohsuke Kawaguchi, Tom Huybrechts
 *
 *
 *******************************************************************************/ 

package hudson.util;

import hudson.ExtensionPoint;
import hudson.security.SecurityRealm;

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

/**
 * Servlet {@link Filter} that chains multiple {@link Filter}s, provided by
 * plugins
 *
 * <p> While this class by itself is not an extension point, I'm marking this
 * class as an extension point so that this class will be more discoverable.
 *
 * <p> {@link SecurityRealm} that wants to contribute {@link Filter}s should
 * first check if {@link SecurityRealm#createFilter(FilterConfig)} is more
 * appropriate.
 *
 * @see SecurityRealm
 */
public class PluginServletFilter implements Filter, ExtensionPoint {

    private static final List<Filter> LIST = new Vector<Filter>();
    private static FilterConfig filterConfig;

    public PluginServletFilter() {
    }

    public void init(FilterConfig filterConfig) throws ServletException {
        PluginServletFilter.filterConfig = filterConfig;
        synchronized (LIST) {
            for (Filter f : LIST) {
                f.init(filterConfig);
            }
        }
    }

    public static void addFilter(Filter filter) throws ServletException {
        synchronized (LIST) {
            if (filterConfig != null) {
                filter.init(filterConfig);
            }
            LIST.add(filter);
        }
    }

    public static void removeFilter(Filter filter) throws ServletException {
        synchronized (LIST) {
            LIST.remove(filter);
        }
    }

    /**
     * All the clearing of filters between test, was causing a leakage
     * breaking all subsequent tests.
     */
    public static void clearFilters() throws ServletException {
        synchronized (LIST) {
            LIST.clear();
        }
    }

    public void doFilter(ServletRequest request, ServletResponse response, final FilterChain chain) throws IOException, ServletException {
        new FilterChain() {
            private int position = 0;
            // capture the array for thread-safety
            private final Filter[] filters = LIST.toArray(new Filter[LIST.size()]);

            public void doFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException {
                if (position == filters.length) {
                    // reached to the end
                    chain.doFilter(request, response);
                } else {
                    // call next
                    filters[position++].doFilter(request, response, this);
                }
            }
        }.doFilter(request, response);
    }

    public void destroy() {
        synchronized (LIST) {
            for (Filter f : LIST) {
                f.destroy();
            }
        }
    }
}