DeukBot4/DeukBot4/Database/ReminderHandler.cs

using System;
using System.Threading.Tasks;
using Discord;
using StackExchange.Redis;

namespace DeukBot4.Database
{
    public class ReminderHandler
    {
        public static ReminderHandler Main = new ReminderHandler();
        public static ConnectionMultiplexer Redis = ConnectionMultiplexer.Connect("localhost:6379");


        public async Task AddReminder(TimeSpan time, string message, ulong channel, ulong author, ulong recipient)
        {
            try
            {
                var db = Redis.GetDatabase();
                var id = Guid.NewGuid().ToString();
                var expectedTime = DateTime.UtcNow.Add(time);
                db.SortedSetAddAsync("deukbot_reminders", (RedisValue)id, expectedTime.ToBinary());
                db.HashSetAsync((RedisKey) id, new[]
                {
                    new HashEntry("channel", channel.ToString("D")),
                    new HashEntry("message", message),
                    new HashEntry("author", author.ToString("D")),
                    new HashEntry("recipient", recipient.ToString("D")),
                });
            }
            catch (Exception e)
            {
                Logger.Main.LogError(e);
            }
        }

        public async Task CheckReminders()
        {
            var checkTime = TimeSpan.FromSeconds(70);
            try
            {
                var startTime       = DateTime.UtcNow;
                var desiredTopScore = (startTime + checkTime).ToBinary();
                var db              = Redis.GetDatabase();
                var reminders = db.SortedSetRangeByScoreWithScores("deukbot_reminders", start: Double.MinValue,
                    stop: desiredTopScore);
                foreach (var sortedSetEntry in reminders)
                {
                    var    val       = sortedSetEntry.Element.ToString();
                    var    timeLong  = sortedSetEntry.Score;
                    var    time      = DateTime.FromBinary((long) timeLong);
                    var    data      = db.HashGetAll(val);
                    ulong  channel   = 0;
                    ulong  author    = 0;
                    ulong  recipient = 0;
                    string message   = null;
                    foreach (var hashEntry in data)
                    {
                        if (hashEntry.Name      == "channel") channel     = ulong.Parse(hashEntry.Value);
                        else if (hashEntry.Name == "message") message     = hashEntry.Value;
                        else if (hashEntry.Name == "author") author       = ulong.Parse(hashEntry.Value);
                        else if (hashEntry.Name == "recipient") recipient = ulong.Parse(hashEntry.Value);
                    }

                    var diff = time - DateTime.UtcNow;
                    FireReminderAtTime((int) diff.TotalSeconds, channel, message, author, recipient);
                    db.KeyDelete(val);
                }

                db.SortedSetRemoveRangeByScoreAsync("deukbot_reminders", Double.MinValue, desiredTopScore);
            }
            catch (Exception e)
            {
                Logger.Main.LogError(e);
            }
            await Task.Delay(checkTime);
            await CheckReminders();
        }

        private async Task FireReminderAtTime(int seconds, ulong channelId, string message, ulong author, ulong recipient)
        {
            if (seconds > 0)
                await Task.Delay(TimeSpan.FromSeconds(seconds));
            await FireReminder(channelId, message, author, recipient);
        }

        private async Task FireReminder(ulong channelId, string message, ulong author, ulong recipient)
        {
            if (Program.Client.GetChannel(channelId) is ITextChannel channel)
            {
                if (author == recipient)
                {
                    channel.SendMessageAsync($"Hey <@{recipient}>, don't forget to {message}.");
                }
                else
                {
                    channel.SendMessageAsync($"Hey <@{recipient}>, <@{author}> asked me to remind you to {message}.");
                }
            }
        }
    }
}