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

namespace AMWD.Common.Utilities
{
	/// <summary>
	/// Provides some network utils.
	/// </summary>
	public static class NetworkHelper
	{
		/// <summary>
		/// Tries to resolve a <paramref name="hostname"/> into an <see cref="IPAddress"/> to connect to.
		/// </summary>
		/// <param name="hostname">The hostname to resolve.</param>
		/// <param name="addressFamily">An address family to use (available: <see cref="AddressFamily.InterNetwork"/> and <see cref="AddressFamily.InterNetworkV6"/>).</param>
		/// <param name="fallback">The fallback ip address when resolving failed.</param>
		/// <returns>The resolved <see cref="IPAddress"/> to connect to or <paramref name="fallback"/> value.</returns>
		public static IPAddress ResolveHost(string hostname, AddressFamily addressFamily = AddressFamily.Unspecified, IPAddress fallback = null)
		{
			if (IPAddress.TryParse(hostname, out var ipAddress))
			{
				if (ipAddress.AddressFamily != AddressFamily.InterNetwork && ipAddress.AddressFamily != AddressFamily.InterNetworkV6)
					return fallback;

				if (addressFamily != AddressFamily.Unspecified && ipAddress.AddressFamily != addressFamily)
					return fallback;

				return ipAddress;
			}

			return Dns.GetHostAddresses(hostname)
				.Where(a => a.AddressFamily == AddressFamily.InterNetwork || a.AddressFamily == AddressFamily.InterNetworkV6)
				.Where(a => addressFamily == AddressFamily.Unspecified || a.AddressFamily == addressFamily)
				.OrderBy(a => a.AddressFamily)
				.FirstOrDefault() ?? fallback;
		}

		/// <summary>
		/// Tries to resolve a <paramref name="iface"/> into an <see cref="IPAddress"/> to bind (listen) on.
		/// </summary>
		/// <param name="iface">The interface name to resolve.</param>
		/// <param name="addressFamily">An address family to use (available: <see cref="AddressFamily.InterNetwork"/> and <see cref="AddressFamily.InterNetworkV6"/>).</param>
		/// <param name="fallback">The fallback ip address when resolving failed.</param>
		/// <returns>The resolved <see cref="IPAddress"/> to bind on or <paramref name="fallback"/> value.</returns>
		public static IPAddress ResolveInterface(string iface, AddressFamily addressFamily = AddressFamily.Unspecified, IPAddress fallback = null)
		{
			if (IPAddress.TryParse(iface, out var ipAddress))
			{
				if (ipAddress.AddressFamily != AddressFamily.InterNetwork && ipAddress.AddressFamily != AddressFamily.InterNetworkV6)
					return fallback;

				if (addressFamily != AddressFamily.Unspecified && ipAddress.AddressFamily != addressFamily)
					return fallback;

				return ipAddress;
			}

			try
			{
				return Dns.GetHostAddresses(iface)
					.Where(a => a.AddressFamily == AddressFamily.InterNetwork || a.AddressFamily == AddressFamily.InterNetworkV6)
					.Where(a => addressFamily == AddressFamily.Unspecified || a.AddressFamily == addressFamily)
					.OrderBy(a => a.AddressFamily)
					.FirstOrDefault() ?? fallback;
			}
			catch (SocketException)
			{
				return NetworkInterface.GetAllNetworkInterfaces()
					.Where(nic => nic.Name.Equals(iface, StringComparison.OrdinalIgnoreCase))
					.SelectMany(nic => nic.GetIPProperties().UnicastAddresses.Select(ai => ai.Address))
					.Where(a => a.AddressFamily == AddressFamily.InterNetwork || a.AddressFamily == AddressFamily.InterNetworkV6)
					.Where(a => addressFamily == AddressFamily.Unspecified || a.AddressFamily == addressFamily)
					.OrderBy(a => a.AddressFamily)
					.FirstOrDefault() ?? fallback;
			}
		}
	}
}