/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.catalina.valves;


import java.io.IOException;
import java.util.ArrayList;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletResponse;

import org.apache.catalina.Lifecycle;
import org.apache.catalina.LifecycleException;
import org.apache.catalina.LifecycleListener;
import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
import org.apache.catalina.util.LifecycleSupport;
import org.apache.catalina.util.StringManager;

/**
 * Implementation of a Valve that performs filtering based on comparing the
 * appropriate request property (selected based on which subclass you choose
 * to configure into your Container's pipeline) against a set of regular
 * expressions configured for this Valve.
 * <p>
 * This valve is configured by setting the <code>allow</code> and/or
 * <code>deny</code> properties to a comma-delimited list of regular
 * expressions (in the syntax supported by the jakarta-regexp library) to
 * which the appropriate request property will be compared.  Evaluation
 * proceeds as follows:
 * <ul>
 * <li>The subclass extracts the request property to be filtered, and
 *     calls the common <code>process()</code> method.
 * <li>If there are any deny expressions configured, the property will
 *     be compared to each such expression.  If a match is found, this
 *     request will be rejected with a "Forbidden" HTTP response.</li>
 * <li>If there are any allow expressions configured, the property will
 *     be compared to each such expression.  If a match is found, this
 *     request will be allowed to pass through to the next Valve in the
 *     current pipeline.</li>
 * <li>If one or more deny expressions was specified but no allow expressions,
 *     allow this request to pass through (because none of the deny
 *     expressions matched it).
 * <li>The request will be rejected with a "Forbidden" HTTP response.</li>
 * </ul>
 * <p>
 * This Valve may be attached to any Container, depending on the granularity
 * of the filtering you wish to perform.
 *
 * @author Craig R. McClanahan
 *
 */

public abstract class RequestFilterValve
    extends ValveBase implements Lifecycle {


    // ----------------------------------------------------- Class Variables


    /**
     * The descriptive information related to this implementation.
     */
    private static final String info =
        "org.apache.catalina.valves.RequestFilterValve/1.0";


    /**
     * The StringManager for this package.
     */
    protected static StringManager sm =
        StringManager.getManager(Constants.Package);


    // ----------------------------------------------------- Instance Variables


    /**
     * The comma-delimited set of <code>allow</code> expressions.
     */
    protected volatile String allow = null;

    /**
     * Helper variable to catch configuration errors.
     * It is <code>true</code> by default, but becomes <code>false</code>
     * if there was an attempt to assign an invalid value to the
     * <code>allow</code> pattern.
     */
    protected volatile boolean allowValid = true;


    /**
     * The set of <code>allow</code> regular expressions we will evaluate.
     */
    protected volatile Pattern allows[] = new Pattern[0];


    /**
     * The set of <code>deny</code> regular expressions we will evaluate.
     */
    protected volatile Pattern denies[] = new Pattern[0];


    /**
     * The comma-delimited set of <code>deny</code> expressions.
     */
    protected volatile String deny = null;

    /**
     * Helper variable to catch configuration errors.
     * It is <code>true</code> by default, but becomes <code>false</code>
     * if there was an attempt to assign an invalid value to the
     * <code>deny</code> pattern.
     */
    protected volatile boolean denyValid = true;

    /**
     * The HTTP response status code that is used when rejecting denied
     * request. It is 403 by default, but may be changed to be 404.
     */
    protected int denyStatus = HttpServletResponse.SC_FORBIDDEN;

    /**
     * The lifecycle event support for this component.
     */
    protected LifecycleSupport lifecycle = new LifecycleSupport(this);

    /**
     * Has this component been started yet?
     */
    protected boolean started = false;

    // ------------------------------------------------------------- Properties


    /**
     * Return a comma-delimited set of the <code>allow</code> expressions
     * configured for this Valve, if any; otherwise, return <code>null</code>.
     */
    public String getAllow() {

        return (this.allow);

    }


    /**
     * Set the comma-delimited set of the <code>allow</code> expressions
     * configured for this Valve, if any.
     *
     * @param allow The new set of allow expressions
     */
    public void setAllow(String allow) {
        boolean success = false;
        try {
            this.allow = allow;
            allows = precalculate(allow);
            success = true;
        } finally {
            allowValid = success;
        }
    }


    /**
     * Return a comma-delimited set of the <code>deny</code> expressions
     * configured for this Valve, if any; otherwise, return <code>null</code>.
     */
    public String getDeny() {

        return (this.deny);

    }


    /**
     * Set the comma-delimited set of the <code>deny</code> expressions
     * configured for this Valve, if any.
     *
     * @param deny The new set of deny expressions
     */
    public void setDeny(String deny) {
        boolean success = false;
        try {
            this.deny = deny;
            denies = precalculate(deny);
            success = true;
        } finally {
            denyValid = success;
        }
    }


    /**
     * Returns <code>false</code> if the last change to the
     * <code>allow</code> pattern did not apply successfully. E.g.
     * if the pattern is syntactically invalid.
     */
    public final boolean isAllowValid() {
        return allowValid;
    }


    /**
     * Returns <code>false</code> if the last change to the
     * <code>deny</code> pattern did not apply successfully. E.g.
     * if the pattern is syntactically invalid.
     */
    public final boolean isDenyValid() {
        return denyValid;
    }


    /**
     * Return response status code that is used to reject denied request.
     */
    public int getDenyStatus() {
        return denyStatus;
    }


    /**
     * Set response status code that is used to reject denied request.
     */
    public void setDenyStatus(int denyStatus) {
        this.denyStatus = denyStatus;
    }


    /**
     * Return descriptive information about this Valve implementation.
     */
    public String getInfo() {

        return (info);

    }


    // --------------------------------------------------------- Public Methods


    /**
     * Extract the desired request property, and pass it (along with the
     * specified request and response objects) to the protected
     * <code>process()</code> method to perform the actual filtering.
     * This method must be implemented by a concrete subclass.
     *
     * @param request The servlet request to be processed
     * @param response The servlet response to be created
     *
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet error occurs
     */
    public abstract void invoke(Request request, Response response)
        throws IOException, ServletException;


    // ------------------------------------------------------ Protected Methods


    /**
     * Return an array of regular expression objects initialized from the
     * specified argument, which must be <code>null</code> or a comma-delimited
     * list of regular expression patterns.
     *
     * @param list The comma-separated list of patterns
     *
     * @exception IllegalArgumentException if one of the patterns has
     *  invalid syntax
     */
    protected Pattern[] precalculate(String list) {

        if (list == null)
            return (new Pattern[0]);
        list = list.trim();
        if (list.length() < 1)
            return (new Pattern[0]);
        list += ",";

        ArrayList reList = new ArrayList();
        while (list.length() > 0) {
            int comma = list.indexOf(',');
            if (comma < 0)
                break;
            String pattern = list.substring(0, comma).trim();
            try {
                reList.add(Pattern.compile(pattern));
            } catch (PatternSyntaxException e) {
                IllegalArgumentException iae = new IllegalArgumentException
                    (sm.getString("requestFilterValve.syntax", pattern));
                iae.initCause(e);
                throw iae;
            }
            list = list.substring(comma + 1);
        }

        Pattern reArray[] = new Pattern[reList.size()];
        return ((Pattern[]) reList.toArray(reArray));

    }


    /**
     * Perform the filtering that has been configured for this Valve, matching
     * against the specified request property.
     *
     * @param property The request property on which to filter
     * @param request The servlet request to be processed
     * @param response The servlet response to be processed
     *
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet error occurs
     */
    protected void process(String property,
                           Request request, Response response)
        throws IOException, ServletException {

        if (isAllowed(property)) {
            getNext().invoke(request, response);
            return;
        }

        // Deny this request
        denyRequest(request, response);

    }


    /**
     * Reject the request that was denied by this valve.
     *
     * @param request The servlet request to be processed
     * @param response The servlet response to be processed
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet error occurs
     */
    protected void denyRequest(Request request, Response response)
            throws IOException, ServletException {
        response.sendError(denyStatus);
    }


    /**
     * Perform the test implemented by this Valve, matching against the
     * specified request property value. This method is public so that it can be
     * called through JMX, e.g. to test whether certain IP address is allowed or
     * denied by the valve configuration.
     *
     * @param property
     *            The request property value on which to filter
     */
    public boolean isAllowed(String property) {
        // Use local copies for thread safety
        Pattern[] denies = this.denies;
        Pattern[] allows = this.allows;

        // Check the deny patterns, if any
        for (int i = 0; i < denies.length; i++) {
            if (denies[i].matcher(property).matches()) {
                return false;
            }
        }

        // Check the allow patterns, if any
        for (int i = 0; i < allows.length; i++) {
            if (allows[i].matcher(property).matches()) {
                return true;
            }
        }

        // Allow if denies specified but not allows
        if ((denies.length > 0) && (allows.length == 0)) {
            return true;
        }

        // Deny this request
        return false;
    }


    // ------------------------------------------------------ Lifecycle Methods


    /**
     * Add a lifecycle event listener to this component.
     *
     * @param listener The listener to add
     */
    public void addLifecycleListener(LifecycleListener listener) {
        lifecycle.addLifecycleListener(listener);
    }


    /**
     * Get the lifecycle listeners associated with this lifecycle. If this
     * Lifecycle has no listeners registered, a zero-length array is returned.
     */
    public LifecycleListener[] findLifecycleListeners() {
        return lifecycle.findLifecycleListeners();
    }


    /**
     * Remove a lifecycle event listener from this component.
     *
     * @param listener The listener to add
     */
    public void removeLifecycleListener(LifecycleListener listener) {
        lifecycle.removeLifecycleListener(listener);
    }


    /**
     * Prepare for the beginning of active use of the public methods of this
     * component.  This method should be called after <code>configure()</code>,
     * and before any of the public methods of the component are utilized.
     *
     * @exception LifecycleException if this component detects a fatal error
     *  that prevents this component from being used
     */
    public void start() throws LifecycleException {

        // Validate and update our current component state
        if (started) {
            throw new LifecycleException(
                    sm.getString("requestFilterValve.alreadyStarted"));
        }
        if (!allowValid || !denyValid) {
            throw new LifecycleException(
                    sm.getString("requestFilterValve.configInvalid"));
        }
        lifecycle.fireLifecycleEvent(START_EVENT, null);
        started = true;
    }

    /**
     * Gracefully terminate the active use of the public methods of this
     * component.  This method should be the last one called on a given
     * instance of this component.
     *
     * @exception LifecycleException if this component detects a fatal error
     *  that needs to be reported
     */
    public void stop() throws LifecycleException {
        // Validate and update our current component state
        if (!started) {
            return;
        }
        lifecycle.fireLifecycleEvent(STOP_EVENT, null);
        started = false;
    }

}
