NadekoBot/NadekoBot/Modules/Administration/Commands/RatelimitCommand.cs

using Discord.Commands;
using NadekoBot.Classes;
using NadekoBot.Modules.Permissions.Classes;
using System;
using System.Collections.Concurrent;

namespace NadekoBot.Modules.Administration.Commands
{
    internal class RatelimitCommand : DiscordCommand
    {

        public static ConcurrentDictionary<ulong, ConcurrentDictionary<ulong, DateTime>> RatelimitingChannels = new ConcurrentDictionary<ulong, ConcurrentDictionary<ulong, DateTime>>();

        private static readonly TimeSpan ratelimitTime = new TimeSpan(0, 0, 0, 5);

        public RatelimitCommand(DiscordModule module) : base(module)
        {
            NadekoBot.Client.MessageReceived += async (s, e) =>
            {
                if (e.Channel.IsPrivate || e.User.Id == NadekoBot.Client.CurrentUser.Id)
                    return;
                ConcurrentDictionary<ulong, DateTime> userTimePair;
                if (!RatelimitingChannels.TryGetValue(e.Channel.Id, out userTimePair)) return;
                DateTime lastMessageTime;
                if (userTimePair.TryGetValue(e.User.Id, out lastMessageTime))
                {
                    if (DateTime.Now - lastMessageTime < ratelimitTime)
                    {
                        try
                        {
                            await e.Message.Delete().ConfigureAwait(false);
                        }
                        catch { }
                        return;
                    }
                }
                userTimePair.AddOrUpdate(e.User.Id, id => DateTime.Now, (id, dt) => DateTime.Now);
            };
        }

        internal override void Init(CommandGroupBuilder cgb)
        {
            cgb.CreateCommand(Module.Prefix + "slowmode")
                .Description("Toggles slow mode. When ON, users will be able to send only 1 message every 5 seconds.")
                .AddCheck(SimpleCheckers.ManageMessages())
                .Do(async e =>
                {
                    ConcurrentDictionary<ulong, DateTime> throwaway;
                    if (RatelimitingChannels.TryRemove(e.Channel.Id, out throwaway))
                    {
                        await e.Channel.SendMessage("Slow mode disabled.").ConfigureAwait(false);
                        return;
                    }
                    if (RatelimitingChannels.TryAdd(e.Channel.Id, new ConcurrentDictionary<ulong, DateTime>()))
                    {
                        await e.Channel.SendMessage("Slow mode initiated. " +
                                                    "Users can't send more than 1 message every 5 seconds.")
                                                    .ConfigureAwait(false);
                    }
                });
        }
    }
}