/**
 * Copyright 2007-2016, Kaazing Corporation. All rights reserved.
 *
 * 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.apache.mina.filter.firewall;

import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;

import org.apache.mina.core.filterchain.IoFilter;
import org.apache.mina.core.filterchain.IoFilterAdapter;
import org.apache.mina.core.session.IdleStatus;
import org.apache.mina.core.session.IoSession;
import org.apache.mina.core.write.WriteRequest;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A {@link IoFilter} which blocks connections from blacklisted remote
 * address.
 *
 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
 * @org.apache.xbean.XBean
 */
public class BlacklistFilter extends IoFilterAdapter {
    private final List<Subnet> blacklist = new CopyOnWriteArrayList<>();

    private static final Logger LOGGER = LoggerFactory.getLogger(BlacklistFilter.class);
    /**
     * Sets the addresses to be blacklisted.
     *
     * NOTE: this call will remove any previously blacklisted addresses.
     *
     * @param addresses an array of addresses to be blacklisted.
     */
    public void setBlacklist(InetAddress[] addresses) {
        if (addresses == null) {
            throw new NullPointerException("addresses");
        }
        blacklist.clear();
        for (int i = 0; i < addresses.length; i++) {
            InetAddress addr = addresses[i];
            block(addr);
        }
    }

    /**
     * Sets the subnets to be blacklisted.
     *
     * NOTE: this call will remove any previously blacklisted subnets.
     *
     * @param subnets an array of subnets to be blacklisted.
     */
    public void setSubnetBlacklist(Subnet[] subnets) {
        if (subnets == null) {
            throw new NullPointerException("Subnets must not be null");
        }
        blacklist.clear();
        for (Subnet subnet : subnets) {
            block(subnet);
        }
    }
    
    /**
     * Sets the addresses to be blacklisted.
     *
     * NOTE: this call will remove any previously blacklisted addresses.
     *
     * @param addresses a collection of InetAddress objects representing the
     *        addresses to be blacklisted.
     * @throws IllegalArgumentException if the specified collections contains
     *         non-{@link InetAddress} objects.
     */
    public void setBlacklist(Iterable<InetAddress> addresses) {
        if (addresses == null) {
            throw new NullPointerException("addresses");
        }

        blacklist.clear();
        
        for( InetAddress address : addresses ){
            block(address);
        }
    }

    /**
     * Sets the subnets to be blacklisted.
     *
     * NOTE: this call will remove any previously blacklisted subnets.
     *
     * @param subnets an array of subnets to be blacklisted.
     */
    public void setSubnetBlacklist(Iterable<Subnet> subnets) {
        if (subnets == null) {
            throw new NullPointerException("Subnets must not be null");
        }
        blacklist.clear();
        for (Subnet subnet : subnets) {
            block(subnet);
        }
    }

    /**
     * Blocks the specified endpoint.
     */
    public void block(InetAddress address) {
        if (address == null) {
            throw new NullPointerException("Adress to block can not be null");
        }

        block(new Subnet(address, 32));
    }

    /**
     * Blocks the specified subnet.
     */
    public void block(Subnet subnet) {
        if(subnet == null) {
            throw new NullPointerException("Subnet can not be null");
        }
        
        blacklist.add(subnet);
    }
    
    /**
     * Unblocks the specified endpoint.
     */
    public void unblock(InetAddress address) {
        if (address == null) {
            throw new NullPointerException("Adress to unblock can not be null");
        }
        
        unblock(new Subnet(address, 32));
    }

    /**
     * Unblocks the specified subnet.
     */
    public void unblock(Subnet subnet) {
        if (subnet == null) {
            throw new NullPointerException("Subnet can not be null");
        }
        blacklist.remove(subnet);
    }

    @Override
    public void sessionCreated(NextFilter nextFilter, IoSession session) {
        if (!isBlocked(session)) {
            // forward if not blocked
            nextFilter.sessionCreated(session);
        } else {
            blockSession(session);
        }
    }

    @Override
    public void sessionOpened(NextFilter nextFilter, IoSession session)
            throws Exception {
        if (!isBlocked(session)) {
            // forward if not blocked
            nextFilter.sessionOpened(session);
        } else {
            blockSession(session);
        }
    }

    @Override
    public void sessionClosed(NextFilter nextFilter, IoSession session)
            throws Exception {
        if (!isBlocked(session)) {
            // forward if not blocked
            nextFilter.sessionClosed(session);
        } else {
            blockSession(session);
        }
    }

    @Override
    public void sessionIdle(NextFilter nextFilter, IoSession session,
            IdleStatus status) throws Exception {
        if (!isBlocked(session)) {
            // forward if not blocked
            nextFilter.sessionIdle(session, status);
        } else {
            blockSession(session);
        }
    }

    @Override
    public void messageReceived(NextFilter nextFilter, IoSession session,
            Object message) {
        if (!isBlocked(session)) {
            // forward if not blocked
            nextFilter.messageReceived(session, message);
        } else {
            blockSession(session);
        }
    }

    @Override
    public void messageSent(NextFilter nextFilter, IoSession session,
            WriteRequest writeRequest) throws Exception {
        if (!isBlocked(session)) {
            // forward if not blocked
            nextFilter.messageSent(session, writeRequest);
        } else {
            blockSession(session);
        }
    }

    private void blockSession(IoSession session) {
        LOGGER.warn("Remote address in the blacklist; closing.");
        session.close(true);
    }

    private boolean isBlocked(IoSession session) {
        SocketAddress remoteAddress = session.getRemoteAddress();
        if (remoteAddress instanceof InetSocketAddress) {
            InetAddress address = ((InetSocketAddress) remoteAddress).getAddress(); 
            
            // check all subnets
            for(Subnet subnet : blacklist) {
                if(subnet.inSubnet(address)) {
                    return true;
                }
            }
        }

        return false;
    }
}
