using System;
using System.Linq;
using System.Net;
using System.Net.Sockets;

namespace Unosquare.Swan {
  /// <summary>
  /// Provides various extension methods for networking-related tasks.
  /// </summary>
  public static class NetworkExtensions {
    /// <summary>
    /// Determines whether the IP address is private.
    /// </summary>
    /// <param name="address">The IP address.</param>
    /// <returns>
    /// True if the IP Address is private; otherwise, false.
    /// </returns>
    /// <exception cref="ArgumentNullException">address.</exception>
    public static Boolean IsPrivateAddress(this IPAddress address) {
      if(address == null) {
        throw new ArgumentNullException(nameof(address));
      }

      Byte[] octets = address.ToString().Split(new[] { "." }, StringSplitOptions.RemoveEmptyEntries).Select(Byte.Parse).ToArray();
      Boolean is24Bit = octets[0] == 10;
      Boolean is20Bit = octets[0] == 172 && octets[1] >= 16 && octets[1] <= 31;
      Boolean is16Bit = octets[0] == 192 && octets[1] == 168;

      return is24Bit || is20Bit || is16Bit;
    }

    /// <summary>
    /// Converts an IPv4 Address to its Unsigned, 32-bit integer representation.
    /// </summary>
    /// <param name="address">The address.</param>
    /// <returns>
    /// A 32-bit unsigned integer converted from four bytes at a specified position in a byte array.
    /// </returns>
    /// <exception cref="ArgumentNullException">address.</exception>
    /// <exception cref="ArgumentException">InterNetwork - address.</exception>
    public static UInt32 ToUInt32(this IPAddress address) {
      if(address == null) {
        throw new ArgumentNullException(nameof(address));
      }

      if(address.AddressFamily != AddressFamily.InterNetwork) {
        throw new ArgumentException($"Address has to be of family '{nameof(AddressFamily.InterNetwork)}'", nameof(address));
      }

      Byte[] addressBytes = address.GetAddressBytes();
      if(BitConverter.IsLittleEndian) {
        Array.Reverse(addressBytes);
      }

      return BitConverter.ToUInt32(addressBytes, 0);
    }
  }
}