sharp-chat/SharpChat/Commands/WhoisCommand.cs

using SharpChat.Packet;
using System.Linq;
using System.Net;

namespace SharpChat.Commands {
    public class WhoisCommand : IUserCommand {
        public bool IsMatch(UserCommandContext ctx) {
            return ctx.NameEquals("ip")
                || ctx.NameEquals("whois");
        }

        public void Dispatch(UserCommandContext ctx) {
            if(!ctx.User.Permissions.HasFlag(UserPermissions.SeeIPAddress)) {
                ctx.Chat.SendTo(ctx.User, new CommandNotAllowedErrorPacket(ctx.Name));
                return;
            }

            string ipUserStr = ctx.Args.FirstOrDefault() ?? string.Empty;
            UserInfo? ipUser;

            if(string.IsNullOrWhiteSpace(ipUserStr) || (ipUser = ctx.Chat.Users.Values.FirstOrDefault(u => u.NameEquals(ipUserStr))) == null) {
                ctx.Chat.SendTo(ctx.User, new UserNotFoundErrorPacket(ipUserStr));
                return;
            }

            foreach(IPAddress ip in ctx.Chat.GetRemoteAddresses(ipUser))
                ctx.Chat.SendTo(ctx.User, new WhoisResponsePacket(ipUser.UserName, ip.ToString()));
        }
    }
}