/*
    * Copyright 2014 The Netty Project
    *
    * The Netty Project 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 io.netty.handler.ipfilter;
  
  import io.netty.util.internal.SocketUtils;
  
  import java.math.BigInteger;
  import java.net.Inet4Address;
  import java.net.Inet6Address;
  import java.net.InetAddress;
  import java.net.InetSocketAddress;
  import java.net.UnknownHostException;
  
  /**
   * Use this class to create rules for {@link RuleBasedIpFilter} that group IP addresses into subnets.
   * Supports both, IPv4 and IPv6.
   */
  public final class IpSubnetFilterRule implements IpFilterRule {
  
      private final IpFilterRule filterRule;
  
      public IpSubnetFilterRule(String ipAddress, int cidrPrefix, IpFilterRuleType ruleType) {
          try {
              filterRule = selectFilterRule(SocketUtils.addressByName(ipAddress), cidrPrefix, ruleType);
          } catch (UnknownHostException e) {
              throw new IllegalArgumentException("ipAddress", e);
          }
      }
  
      public IpSubnetFilterRule(InetAddress ipAddress, int cidrPrefix, IpFilterRuleType ruleType) {
          filterRule = selectFilterRule(ipAddress, cidrPrefix, ruleType);
      }
  
      private static IpFilterRule selectFilterRule(InetAddress ipAddress, int cidrPrefix, IpFilterRuleType ruleType) {
          if (ipAddress == null) {
              throw new NullPointerException("ipAddress");
          }
  
          if (ruleType == null) {
              throw new NullPointerException("ruleType");
          }
  
          if (ipAddress instanceof Inet4Address) {
              return new Ip4SubnetFilterRule((Inet4Address) ipAddress, cidrPrefix, ruleType);
          } else if (ipAddress instanceof Inet6Address) {
              return new Ip6SubnetFilterRule((Inet6Address) ipAddress, cidrPrefix, ruleType);
          } else {
              throw new IllegalArgumentException("Only IPv4 and IPv6 addresses are supported");
          }
      }
  
      @Override
      public boolean matches(InetSocketAddress remoteAddress) {
          return filterRule.matches(remoteAddress);
      }
  
      @Override
      public IpFilterRuleType ruleType() {
          return filterRule.ruleType();
      }
  
      private static final class Ip4SubnetFilterRule implements IpFilterRule {
  
          private final int networkAddress;
          private final int subnetMask;
          private final IpFilterRuleType ruleType;
  
          private Ip4SubnetFilterRule(Inet4Address ipAddress, int cidrPrefix, IpFilterRuleType ruleType) {
              if (cidrPrefix < 0 || cidrPrefix > 32) {
                  throw new IllegalArgumentException(String.format("IPv4 requires the subnet prefix to be in range of " +
                                                                      "[0,32]. The prefix was: %d", cidrPrefix));
              }
  
              subnetMask = prefixToSubnetMask(cidrPrefix);
              networkAddress = ipToInt(ipAddress) & subnetMask;
              this.ruleType = ruleType;
          }
  
          @Override
          public boolean matches(InetSocketAddress remoteAddress) {
              int ipAddress = ipToInt((Inet4Address) remoteAddress.getAddress());
  
              return (ipAddress & subnetMask) == networkAddress;
          }
  
          @Override
         public IpFilterRuleType ruleType() {
             return ruleType;
         }
 
         private static int ipToInt(Inet4Address ipAddress) {
             byte[] octets = ipAddress.getAddress();
             assert octets.length == 4;
 
             return (octets[0] & 0xff) << 24 |
                    (octets[1] & 0xff) << 16 |
                    (octets[2] & 0xff) << 8 |
                     octets[3] & 0xff;
         }
 
         private static int prefixToSubnetMask(int cidrPrefix) {
             /**
              * Perform the shift on a long and downcast it to int afterwards.
              * This is necessary to handle a cidrPrefix of zero correctly.
              * The left shift operator on an int only uses the five least
              * significant bits of the right-hand operand. Thus -1 << 32 evaluates
              * to -1 instead of 0. The left shift operator applied on a long
              * uses the six least significant bits.
              *
              * Also see https://github.com/netty/netty/issues/2767
              */
             return (int) ((-1L << 32 - cidrPrefix) & 0xffffffff);
         }
     }
 
     private static final class Ip6SubnetFilterRule implements IpFilterRule {
 
         private static final BigInteger MINUS_ONE = BigInteger.valueOf(-1);
 
         private final BigInteger networkAddress;
         private final BigInteger subnetMask;
         private final IpFilterRuleType ruleType;
 
         private Ip6SubnetFilterRule(Inet6Address ipAddress, int cidrPrefix, IpFilterRuleType ruleType) {
             if (cidrPrefix < 0 || cidrPrefix > 128) {
                 throw new IllegalArgumentException(String.format("IPv6 requires the subnet prefix to be in range of " +
                                                                     "[0,128]. The prefix was: %d", cidrPrefix));
             }
 
             subnetMask = prefixToSubnetMask(cidrPrefix);
             networkAddress = ipToInt(ipAddress).and(subnetMask);
             this.ruleType = ruleType;
         }
 
         @Override
         public boolean matches(InetSocketAddress remoteAddress) {
             BigInteger ipAddress = ipToInt((Inet6Address) remoteAddress.getAddress());
 
             return ipAddress.and(subnetMask).equals(networkAddress);
         }
 
         @Override
         public IpFilterRuleType ruleType() {
             return ruleType;
         }
 
         private static BigInteger ipToInt(Inet6Address ipAddress) {
             byte[] octets = ipAddress.getAddress();
             assert octets.length == 16;
 
             return new BigInteger(octets);
         }
 
         private static BigInteger prefixToSubnetMask(int cidrPrefix) {
             return MINUS_ONE.shiftLeft(128 - cidrPrefix);
         }
     }
 }