NadekoBot/src/NadekoBot/Modules/Administration/Commands/AutoAssignRoleCommands.cs

using Discord;
using Discord.Commands;
using NadekoBot.Attributes;
using NadekoBot.Services;
using NadekoBot.Services.Database.Models;
using NLog;
using System;
using System.Linq;
using System.Threading.Tasks;

namespace NadekoBot.Modules.Administration
{
    public partial class Administration
    {
        [Group]
        public class AutoAssignRoleCommands
        {
            private Logger _log { get; }

            public AutoAssignRoleCommands()
            {
                var _client = NadekoBot.Client;
                this._log = LogManager.GetCurrentClassLogger();
                _client.UserJoined += (user) =>
                {
                    var t = Task.Run(async () =>
                    {
                        try
                        {
                            GuildConfig conf;
                            using (var uow = DbHandler.UnitOfWork())
                            {
                                conf = uow.GuildConfigs.For(user.Guild.Id);
                            }

                            if (conf.AutoAssignRoleId == 0)
                                return;

                            var role = user.Guild.Roles.FirstOrDefault(r => r.Id == conf.AutoAssignRoleId);

                            if (role != null)
                                await user.AddRolesAsync(role);
                        }
                        catch (Exception ex) { _log.Warn(ex); }
                    });
                    return Task.CompletedTask;
                };
            }

            [NadekoCommand, Usage, Description, Aliases]
            [RequireContext(ContextType.Guild)]
            [RequirePermission(GuildPermission.ManageRoles)]
            public async Task AutoAssignRole(IUserMessage umsg, [Remainder] IRole role = null)
            {
                var channel = (ITextChannel)umsg.Channel;

                GuildConfig conf;
                using (var uow = DbHandler.UnitOfWork())
                {
                    conf = uow.GuildConfigs.For(channel.Guild.Id);
                    if (role == null)
                        conf.AutoAssignRoleId = 0;
                    else
                        conf.AutoAssignRoleId = role.Id;

                    uow.GuildConfigs.Update(conf);
                    await uow.CompleteAsync().ConfigureAwait(false);
                }

                if (role == null)
                {
                    await channel.SendMessageAsync("🆗 **Auto assign role** on user join is now **disabled**.").ConfigureAwait(false);
                    return;
                }

                await channel.SendMessageAsync("✅ **Auto assign role** on user join is now **enabled**.").ConfigureAwait(false);
            }
        }
    }
}