CooldownPrecondition.cs

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Beatbox.Enums;
using Discord;
using Discord.Commands;

namespace Beatbox.Preconditions
{
    public class CooldownAttribute : PreconditionAttribute
    {
        private readonly TimeSpan _invokeLimitPeriod;
        private readonly uint _invokeLimit;
        private readonly bool _skipAdmin;
        private readonly Dictionary<ulong, CommandTimeout> _invokeTracker = new Dictionary<ulong, CommandTimeout>();
        
        public CooldownAttribute(double period, Measure measure, uint times, bool skipAdmin = false)
        {
            _invokeLimit = times;
            _skipAdmin = skipAdmin;
            _invokeLimitPeriod = measure switch
            {
                Measure.Days => TimeSpan.FromDays(period),
                Measure.Hours => TimeSpan.FromHours(period),
                Measure.Minutes => TimeSpan.FromMinutes(period),
                Measure.Seconds => TimeSpan.FromSeconds(period),
                _ => _invokeLimitPeriod
            };
        }
        
        public override Task<PreconditionResult> CheckPermissionsAsync(ICommandContext context, CommandInfo command, IServiceProvider services)
        {
            var now = DateTime.UtcNow;
            var key = context.User.Id;
            
            var timeout = _invokeTracker.TryGetValue(key, out var t) && now - t.FirstInvoke < _invokeLimitPeriod ? t : new CommandTimeout(now);
            timeout.TimesInvoked++;
            
            if (timeout.TimesInvoked <= _invokeLimit || _skipAdmin && (context.User as IGuildUser).GuildPermissions.Administrator)
            {
                _invokeTracker[key] = timeout;
                return Task.FromResult(PreconditionResult.FromSuccess());
            }

            return Task.FromResult(PreconditionResult.FromError($"{context.User.Mention} Please wait `{timeout.FirstInvoke - now + _invokeLimitPeriod:hh\\:mm\\:ss}`"));
        }
    }

    public sealed class CommandTimeout
    { 
        public uint TimesInvoked { get; set; }
        public DateTime FirstInvoke { get; }

        public CommandTimeout(DateTime timeStarted)
        {
            FirstInvoke = timeStarted;
        }
    }
    
    public enum Measure
    {
        Days,
        Hours,
        Minutes,
        Seconds
    }
}