/*
    * 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:
    *
    *   https://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.netty5.handler.ipfilter;
  
  import io.netty5.util.NetUtil;
  import io.netty5.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;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * 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, Comparable<IpSubnetFilterRule> {
  
      private final IpFilterRule filterRule;
      private final String ipAddress;
  
      public IpSubnetFilterRule(String ipAddress, int cidrPrefix, IpFilterRuleType ruleType) {
          try {
              this.ipAddress = ipAddress;
              filterRule = selectFilterRule(SocketUtils.addressByName(ipAddress), cidrPrefix, ruleType);
          } catch (UnknownHostException e) {
              throw new IllegalArgumentException("ipAddress", e);
          }
      }
  
      public IpSubnetFilterRule(InetAddress ipAddress, int cidrPrefix, IpFilterRuleType ruleType) {
          this.ipAddress = ipAddress.getHostAddress();
          filterRule = selectFilterRule(ipAddress, cidrPrefix, ruleType);
      }
  
      private static IpFilterRule selectFilterRule(InetAddress ipAddress, int cidrPrefix, IpFilterRuleType ruleType) {
          requireNonNull(ipAddress, "ipAddress");
          requireNonNull(ruleType, "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();
      }
  
      /**
       * Get IP Address of this rule
       */
      String getIpAddress() {
          return ipAddress;
      }
  
      /**
       * {@link Ip4SubnetFilterRule} or {@link Ip6SubnetFilterRule}
       */
      IpFilterRule getFilterRule() {
          return filterRule;
      }
  
      @Override
      public int compareTo(IpSubnetFilterRule ipSubnetFilterRule) {
          if (filterRule instanceof Ip4SubnetFilterRule) {
              return Integer.compare(((Ip4SubnetFilterRule) filterRule).networkAddress,
                      ((Ip4SubnetFilterRule) ipSubnetFilterRule.filterRule).networkAddress);
          } else {
              return ((Ip6SubnetFilterRule) filterRule).networkAddress
                      .compareTo(((Ip6SubnetFilterRule) ipSubnetFilterRule.filterRule).networkAddress);
          }
      }
 
     /**
      * It'll compare IP address with {@link Ip4SubnetFilterRule#networkAddress} or
      * {@link Ip6SubnetFilterRule#networkAddress}.
      *
      * @param inetSocketAddress {@link InetSocketAddress} to match
      * @return 0 if IP Address match else difference index.
      */
     int compareTo(InetSocketAddress inetSocketAddress) {
         if (filterRule instanceof Ip4SubnetFilterRule) {
             Ip4SubnetFilterRule ip4SubnetFilterRule = (Ip4SubnetFilterRule) filterRule;
             return Integer.compare(ip4SubnetFilterRule.networkAddress, NetUtil.ipv4AddressToInt((Inet4Address)
                     inetSocketAddress.getAddress()) & ip4SubnetFilterRule.subnetMask);
         } else {
             Ip6SubnetFilterRule ip6SubnetFilterRule = (Ip6SubnetFilterRule) filterRule;
             return ip6SubnetFilterRule.networkAddress
                     .compareTo(Ip6SubnetFilterRule.ipToInt((Inet6Address) inetSocketAddress.getAddress())
                             .and(ip6SubnetFilterRule.networkAddress));
         }
     }
 
     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 = NetUtil.ipv4AddressToInt(ipAddress) & subnetMask;
             this.ruleType = ruleType;
         }
 
         @Override
         public boolean matches(InetSocketAddress remoteAddress) {
             final InetAddress inetAddress = remoteAddress.getAddress();
             if (inetAddress instanceof Inet4Address) {
                 int ipAddress = NetUtil.ipv4AddressToInt((Inet4Address) inetAddress);
                 return (ipAddress & subnetMask) == networkAddress;
             }
             return false;
         }
 
         @Override
         public IpFilterRuleType ruleType() {
             return ruleType;
         }
 
         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);
         }
     }
 
     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) {
             final InetAddress inetAddress = remoteAddress.getAddress();
             if (inetAddress instanceof Inet6Address) {
                 BigInteger ipAddress = ipToInt((Inet6Address) inetAddress);
                 return ipAddress.and(subnetMask).equals(subnetMask) || ipAddress.and(subnetMask).equals(networkAddress);
             }
             return false;
         }
 
         @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);
         }
     }
 }