/*
    * 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.commons.net.util;
  
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * Performs subnet calculations given a network address and a subnet mask.
   *
   * @see "http://www.faqs.org/rfcs/rfc1519.html"
   * @since 2.0
   */
  public class SubnetUtils {
  
      /**
       * Convenience container for subnet summary information.
       */
      public final class SubnetInfo {
  
          /** Mask to convert unsigned int to a long (i.e. keep 32 bits). */
          private static final long UNSIGNED_INT_MASK = 0x0FFFFFFFFL;
  
          private SubnetInfo() {
          }
  
          public int asInteger(final String address) {
              return toInteger(address);
          }
  
          private long broadcastLong() {
              return broadcast & UNSIGNED_INT_MASK;
          }
  
          /**
           * Converts a 4-element array into dotted decimal format.
           */
          private String format(final int[] octets) {
              final int last = octets.length - 1;
              final StringBuilder builder = new StringBuilder();
              for (int i = 0;; i++) {
                  builder.append(octets[i]);
                  if (i == last) {
                      return builder.toString();
                  }
                  builder.append('.');
              }
          }
  
          public String getAddress() {
              return format(toArray(address));
          }
  
          /**
           * Gets the count of available addresses. Will be zero for CIDR/31 and CIDR/32 if the inclusive flag is false.
           *
           * @return the count of addresses, may be zero.
           * @throws RuntimeException if the correct count is greater than {@code Integer.MAX_VALUE}
           * @deprecated (3.4) use {@link #getAddressCountLong()} instead
           */
          @Deprecated
          public int getAddressCount() {
              final long countLong = getAddressCountLong();
              if (countLong > Integer.MAX_VALUE) {
                  throw new IllegalStateException("Count is larger than an integer: " + countLong);
              }
              // Cannot be negative here
              return (int) countLong;
          }
  
          /**
           * Gets the count of available addresses. Will be zero for CIDR/31 and CIDR/32 if the inclusive flag is false.
           *
           * @return the count of addresses, may be zero.
           * @since 3.4
           */
          public long getAddressCountLong() {
              final long b = broadcastLong();
              final long n = networkLong();
              final long count = b - n + (isInclusiveHostCount() ? 1 : -1);
              return count < 0 ? 0 : count;
          }
  
          public String[] getAllAddresses() {
              final int ct = getAddressCount();
             final String[] addresses = new String[ct];
             if (ct == 0) {
                 return addresses;
             }
             for (int add = low(), j = 0; add <= high(); ++add, ++j) {
                 addresses[j] = format(toArray(add));
             }
             return addresses;
         }
 
         public String getBroadcastAddress() {
             return format(toArray(broadcast));
         }
 
         public String getCidrSignature() {
             return format(toArray(address)) + "/" + Integer.bitCount(netmask);
         }
 
         /**
          * Gets the high address as a dotted IP address. Will be zero for CIDR/31 and CIDR/32 if the inclusive flag is false.
          *
          * @return the IP address in dotted format, may be "0.0.0.0" if there is no valid address
          */
         public String getHighAddress() {
             return format(toArray(high()));
         }
 
         /**
          * Gets the low address as a dotted IP address. Will be zero for CIDR/31 and CIDR/32 if the inclusive flag is false.
          *
          * @return the IP address in dotted format, may be "0.0.0.0" if there is no valid address
          */
         public String getLowAddress() {
             return format(toArray(low()));
         }
 
         public String getNetmask() {
             return format(toArray(netmask));
         }
 
         public String getNetworkAddress() {
             return format(toArray(network));
         }
 
         public String getNextAddress() {
             return format(toArray(address + 1));
         }
 
         public String getPreviousAddress() {
             return format(toArray(address - 1));
         }
 
         private int high() {
             return isInclusiveHostCount() ? broadcast : broadcastLong() - networkLong() > 1 ? broadcast - 1 : 0;
         }
 
         /**
          * Tests if the parameter <code>address</code> is in the range of usable endpoint addresses for this subnet. This excludes the network and broadcast
          * addresses by default. Use {@link SubnetUtils#setInclusiveHostCount(boolean)} to change this.
          *
          * @param address the address to check
          * @return true if it is in range
          * @since 3.4 (made public)
          */
         public boolean isInRange(final int address) {
             if (address == 0) { // cannot ever be in range; rejecting now avoids problems with CIDR/31,32
                 return false;
             }
             final long addLong = address & UNSIGNED_INT_MASK;
             final long lowLong = low() & UNSIGNED_INT_MASK;
             final long highLong = high() & UNSIGNED_INT_MASK;
             return addLong >= lowLong && addLong <= highLong;
         }
 
         /**
          * Tests if the parameter <code>address</code> is in the range of usable endpoint addresses for this subnet. This excludes the network and broadcast
          * addresses. Use {@link SubnetUtils#setInclusiveHostCount(boolean)} to change this.
          *
          * @param address A dot-delimited IPv4 address, e.g. "192.168.0.1"
          * @return True if in range, false otherwise
          */
         public boolean isInRange(final String address) {
             return isInRange(toInteger(address));
         }
 
         private int low() {
             return isInclusiveHostCount() ? network : broadcastLong() - networkLong() > 1 ? network + 1 : 0;
         }
 
         /** Long versions of the values (as unsigned int) which are more suitable for range checking. */
         private long networkLong() {
             return network & UNSIGNED_INT_MASK;
         }
 
         /**
          * Converts a packed integer address into a 4-element array
          */
         private int[] toArray(final int val) {
             final int[] ret = new int[4];
             for (int j = 3; j >= 0; --j) {
                 ret[j] |= val >>> 8 * (3 - j) & 0xff;
             }
             return ret;
         }
 
         /**
          * {@inheritDoc}
          *
          * @since 2.2
          */
         @Override
         public String toString() {
             final StringBuilder buf = new StringBuilder();
             // @formatter:off
             buf.append("CIDR Signature:\t[").append(getCidrSignature()).append("]\n")
                 .append("  Netmask: [").append(getNetmask()).append("]\n")
                 .append("  Network: [").append(getNetworkAddress()).append("]\n")
                 .append("  Broadcast: [").append(getBroadcastAddress()).append("]\n")
                 .append("  First address: [").append(getLowAddress()).append("]\n")
                 .append("  Last address: [").append(getHighAddress()).append("]\n")
                 .append("  Address Count: [").append(getAddressCountLong()).append("]\n");
             // @formatter:on
             return buf.toString();
         }
     }
 
     private static final String IP_ADDRESS = "(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})\\.(\\d{1,3})";
     private static final String SLASH_FORMAT = IP_ADDRESS + "/(\\d{1,2})"; // 0 -> 32
     private static final Pattern ADDRESS_PATTERN = Pattern.compile(IP_ADDRESS);
     private static final Pattern CIDR_PATTERN = Pattern.compile(SLASH_FORMAT);
 
     private static final int NBITS = 32;
 
     private static final String PARSE_FAIL = "Could not parse [%s]";
 
     /*
      * Extracts the components of a dotted decimal address and pack into an integer using a regex match
      */
     private static int matchAddress(final Matcher matcher) {
         int addr = 0;
         for (int i = 1; i <= 4; ++i) {
             final int n = rangeCheck(Integer.parseInt(matcher.group(i)), 0, 255);
             addr |= (n & 0xff) << 8 * (4 - i);
         }
         return addr;
     }
 
     /*
      * Checks integer boundaries. Checks if a value x is in the range [begin,end]. Returns x if it is in range, throws an exception otherwise.
      */
     private static int rangeCheck(final int value, final int begin, final int end) {
         if (value >= begin && value <= end) { // (begin,end]
             return value;
         }
         throw new IllegalArgumentException("Value [" + value + "] not in range [" + begin + "," + end + "]");
     }
 
     /*
      * Converts a dotted decimal format address to a packed integer format
      */
     private static int toInteger(final String address) {
         final Matcher matcher = ADDRESS_PATTERN.matcher(address);
         if (matcher.matches()) {
             return matchAddress(matcher);
         }
         throw new IllegalArgumentException(String.format(PARSE_FAIL, address));
     }
 
     private final int netmask;
 
     private final int address;
 
     private final int network;
 
     private final int broadcast;
 
     /** Whether the broadcast/network address are included in host count */
     private boolean inclusiveHostCount;
 
     /**
      * Constructs an instance from a CIDR-notation string, e.g. "192.168.0.1/16"
      *
      * @param cidrNotation A CIDR-notation string, e.g. "192.168.0.1/16"
      * @throws IllegalArgumentException if the parameter is invalid, i.e. does not match n.n.n.n/m where n=1-3 decimal digits, m = 1-2 decimal digits in range
      *                                  0-32
      */
     public SubnetUtils(final String cidrNotation) {
         final Matcher matcher = CIDR_PATTERN.matcher(cidrNotation);
 
         if (!matcher.matches()) {
             throw new IllegalArgumentException(String.format(PARSE_FAIL, cidrNotation));
         }
         this.address = matchAddress(matcher);
 
         // Create a binary netmask from the number of bits specification /x
 
         final int trailingZeroes = NBITS - rangeCheck(Integer.parseInt(matcher.group(5)), 0, NBITS);
 
         //
         // An IPv4 netmask consists of 32 bits, a contiguous sequence
         // of the specified number of ones followed by all zeros.
         // So, it can be obtained by shifting an unsigned integer (32 bits) to the left by
         // the number of trailing zeros which is (32 - the # bits specification).
         // Note that there is no unsigned left shift operator, so we have to use
         // a long to ensure that the left-most bit is shifted out correctly.
         //
         this.netmask = (int) (0x0FFFFFFFFL << trailingZeroes);
 
         // Calculate base network address
         this.network = address & netmask;
 
         // Calculate broadcast address
         this.broadcast = network | ~netmask;
     }
 
     /**
      * Constructs an instance from a dotted decimal address and a dotted decimal mask.
      *
      * @param address An IP address, e.g. "192.168.0.1"
      * @param mask    A dotted decimal netmask e.g. "255.255.0.0"
      * @throws IllegalArgumentException if the address or mask is invalid, i.e. does not match n.n.n.n where n=1-3 decimal digits and the mask is not all zeros
      */
     public SubnetUtils(final String address, final String mask) {
         this.address = toInteger(address);
         this.netmask = toInteger(mask);
 
         if ((this.netmask & -this.netmask) - 1 != ~this.netmask) {
             throw new IllegalArgumentException(String.format(PARSE_FAIL, mask));
         }
 
         // Calculate base network address
         this.network = this.address & this.netmask;
 
         // Calculate broadcast address
         this.broadcast = this.network | ~this.netmask;
     }
 
     /**
      * Gets a {@link SubnetInfo} instance that contains subnet-specific statistics
      *
      * @return new instance
      */
     public final SubnetInfo getInfo() {
         return new SubnetInfo();
     }
 
     public SubnetUtils getNext() {
         return new SubnetUtils(getInfo().getNextAddress(), getInfo().getNetmask());
     }
 
     public SubnetUtils getPrevious() {
         return new SubnetUtils(getInfo().getPreviousAddress(), getInfo().getNetmask());
     }
 
     /**
      * Tests if the return value of {@link SubnetInfo#getAddressCount()} includes the network and broadcast addresses.
      *
      * @since 2.2
      * @return true if the host count includes the network and broadcast addresses
      */
     public boolean isInclusiveHostCount() {
         return inclusiveHostCount;
     }
 
     /**
      * Sets to {@code true} if you want the return value of {@link SubnetInfo#getAddressCount()} to include the network and broadcast addresses. This also
      * applies to {@link SubnetInfo#isInRange(int)}
      *
      * @param inclusiveHostCount true if network and broadcast addresses are to be included
      * @since 2.2
      */
     public void setInclusiveHostCount(final boolean inclusiveHostCount) {
         this.inclusiveHostCount = inclusiveHostCount;
     }
 
     /**
      * Converts this instance to a debug String.
      *
      * @return this instance to a debug String.
      * @since 3.11.0
      */
     @Override
     public String toString() {
         return getInfo().toString();
     }
 }