How to make a Rust scheduled commands plugin (timed console tasks)

using System.Linq;
using UnityEngine;
using System;
using System.Collections.Generic;
using System.Globalization;
using Newtonsoft.Json;
using Oxide.Core;

namespace Oxide.Plugins
{
    [Info("Scheduled Commands", "RustPluginGenerator", "1.0.0")]
    [Description("Runs configured console commands at fixed times of day or on repeating minute intervals.")]
    public class ScheduledCommands : RustPlugin
    {
        private const string PermAdmin = "scheduledcommands.admin";

        private PluginConfig config;
        private Timer tickTimer;
        private readonly List<ScheduledTask> schedule = new List<ScheduledTask>();

        private class PluginConfig
        {
            [JsonProperty("Tasks")]
            public List<TaskEntry> Tasks { get; set; } = new List<TaskEntry>
            {
                new TaskEntry { Command = "server.save", Time = "03:55", Source = TaskSource.Console, Enabled = false },
                new TaskEntry { Command = "say Server will restart in 5 minutes", Time = "03:55", Source = TaskSource.Console, Enabled = false },
                new TaskEntry { Command = "say Welcome to the server", Time = "15", Source = TaskSource.Console, Enabled = false }
            };
        }

        private class TaskEntry
        {
            [JsonProperty("Command")]
            public string Command { get; set; }

            [JsonProperty("Time")]
            public string Time { get; set; }

            [JsonProperty("Source")]
            public TaskSource Source { get; set; } = TaskSource.Console;

            [JsonProperty("PlayerId")]
            public string PlayerId { get; set; } = string.Empty;

            [JsonProperty("Enabled")]
            public bool Enabled { get; set; } = true;

            [JsonProperty("LastRun")]
            public string LastRun { get; set; } = string.Empty;
        }

        private enum TaskSource
        {
            Console,
            Player
        }

        private class ScheduledTask
        {
            public TaskEntry Entry;
            public bool IsInterval;
            public TimeSpan DailyTime;
            public int IntervalMinutes;
        }

        protected override void LoadDefaultConfig() => config = new PluginConfig();

        protected override void LoadConfig()
        {
            base.LoadConfig();
            try
            {
                config = Config.ReadObject<PluginConfig>();
                if (config == null) throw new Exception();
            }
            catch
            {
                PrintWarning("Configuration file is invalid, using defaults");
                LoadDefaultConfig();
            }
            SaveConfig();
        }

        protected override void SaveConfig() => Config.WriteObject(config);

        protected override void LoadDefaultMessages()
        {
            lang.RegisterMessages(new Dictionary<string, string>
            {
                ["NoTasks"] = "No scheduled tasks are configured.",
                ["TaskLine"] = "#{0} [{1}] {2} -> {3} (enabled: {4}, last run: {5})",
                ["OnlyAdmin"] = "You do not have permission to use this command.",
                ["BadIndex"] = "Task index {0} does not exist.",
                ["Reloaded"] = "Schedule reloaded: {0} task(s).",
                ["RunNow"] = "Task #{0} executed."
            }, this);
        }

        private string Msg(string key, string userId = null, params object[] args) =>
            string.Format(lang.GetMessage(key, this, userId), args);

        private void Init()
        {
            permission.RegisterPermission(PermAdmin, this);
        }

        private void OnServerInitialized()
        {
            BuildSchedule();
            tickTimer = timer.Every(60f, Tick);
        }

        private void Unload()
        {
            if (tickTimer != null && !tickTimer.Destroyed)
                tickTimer.Destroy();

            tickTimer = null;
            schedule.Clear();
        }

        private void BuildSchedule()
        {
            schedule.Clear();

            if (config?.Tasks == null) return;

            for (int i = 0; i < config.Tasks.Count; i++)
            {
                var entry = config.Tasks[i];
                if (entry == null || string.IsNullOrEmpty(entry.Command) || string.IsNullOrEmpty(entry.Time))
                    continue;

                var task = new ScheduledTask { Entry = entry };

                if (entry.Time.Contains(":"))
                {
                    if (!TimeSpan.TryParseExact(entry.Time, "hh\\:mm", CultureInfo.InvariantCulture, out task.DailyTime) &&
                        !TimeSpan.TryParse(entry.Time, CultureInfo.InvariantCulture, out task.DailyTime))
                    {
                        PrintWarning($"Task #{i} has invalid time '{entry.Time}', skipped");
                        continue;
                    }
                }
                else
                {
                    int minutes;
                    if (!int.TryParse(entry.Time, out minutes) || minutes <= 0)
                    {
                        PrintWarning($"Task #{i} has invalid interval '{entry.Time}', skipped");
                        continue;
                    }

                    task.IsInterval = true;
                    task.IntervalMinutes = minutes;
                }

                schedule.Add(task);
            }

            Puts($"Loaded {schedule.Count} scheduled task(s)");
        }

        private void Tick()
        {
            if (schedule.Count == 0) return;

            DateTime now = DateTime.Now;
            string stamp = now.ToString("yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture);

            for (int i = 0; i < schedule.Count; i++)
            {
                var task = schedule[i];
                var entry = task.Entry;

                if (!entry.Enabled || string.IsNullOrEmpty(entry.Command))
                    continue;

                if (entry.LastRun == stamp)
                    continue;

                bool due = task.IsInterval
                    ? IsIntervalDue(entry, task.IntervalMinutes, now)
                    : task.DailyTime.Hours == now.Hour && task.DailyTime.Minutes == now.Minute;

                if (!due) continue;

                entry.LastRun = stamp;
                RunTask(entry);
            }

            SaveConfig();
        }

        private bool IsIntervalDue(TaskEntry entry, int intervalMinutes, DateTime now)
        {
            if (string.IsNullOrEmpty(entry.LastRun))
                return true;

            DateTime last;
            if (!DateTime.TryParseExact(entry.LastRun, "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture, DateTimeStyles.None, out last))
                return true;

            return (now - last).TotalMinutes >= intervalMinutes;
        }

        private void RunTask(TaskEntry entry)
        {
            BasePlayer caller = null;

            if (entry.Source == TaskSource.Player && !string.IsNullOrEmpty(entry.PlayerId))
                caller = BasePlayer.FindAwakeOrSleeping(entry.PlayerId);

            if (entry.Source == TaskSource.Player && caller != null)
                caller.SendConsoleCommand(entry.Command);
            else
                ConsoleSystem.Run(ConsoleSystem.Option.Server, entry.Command);

            Puts($"Executed: {entry.Command}");
        }

        [ConsoleCommand("scheduledcommands.list")]
        private void CmdList(ConsoleSystem.Arg arg)
        {
            if (!CheckAccess(arg)) return;

            if (config?.Tasks == null || config.Tasks.Count == 0)
            {
                arg.ReplyWith(Msg("NoTasks"));
                return;
            }

            for (int i = 0; i < config.Tasks.Count; i++)
            {
                var entry = config.Tasks[i];
                if (entry == null) continue;
                arg.ReplyWith(Msg("TaskLine", null, i, entry.Time, entry.Command, entry.Source, entry.Enabled, string.IsNullOrEmpty(entry.LastRun) ? "-" : entry.LastRun));
            }
        }

        [ConsoleCommand("scheduledcommands.run")]
        private void CmdRun(ConsoleSystem.Arg arg)
        {
            if (!CheckAccess(arg)) return;

            int index = arg.GetInt(0, -1);
            if (config?.Tasks == null || index < 0 || index >= config.Tasks.Count || config.Tasks[index] == null)
            {
                arg.ReplyWith(Msg("BadIndex", null, index));
                return;
            }

            RunTask(config.Tasks[index]);
            SaveConfig();
            arg.ReplyWith(Msg("RunNow", null, index));
        }

        [ConsoleCommand("scheduledcommands.reload")]
        private void CmdReload(ConsoleSystem.Arg arg)
        {
            if (!CheckAccess(arg)) return;

            if (tickTimer != null && !tickTimer.Destroyed)
                tickTimer.Destroy();

            LoadConfig();
            BuildSchedule();
            tickTimer = timer.Every(60f, Tick);
            arg.ReplyWith(Msg("Reloaded", null, schedule.Count));
        }

        [ChatCommand("schedule")]
        private void CmdSchedule(BasePlayer player, string command, string[] args)
        {
            if (player == null) return;
            if (!permission.UserHasPermission(player.UserIDString, PermAdmin))
            {
                SendReply(player, Msg("OnlyAdmin", player.UserIDString));
                return;
            }

            if (config?.Tasks == null || config.Tasks.Count == 0)
            {
                SendReply(player, Msg("NoTasks", player.UserIDString));
                return;
            }

            for (int i = 0; i < config.Tasks.Count; i++)
            {
                var entry = config.Tasks[i];
                if (entry == null) continue;
                SendReply(player, Msg("TaskLine", player.UserIDString, i, entry.Time, entry.Command, entry.Source, entry.Enabled, string.IsNullOrEmpty(entry.LastRun) ? "-" : entry.LastRun));
            }
        }

        private bool CheckAccess(ConsoleSystem.Arg arg)
        {
            if (arg == null) return false;
            if (!arg.IsAdmin) return false;
            var player = arg.Player();
            if (player != null && !permission.UserHasPermission(player.UserIDString, PermAdmin))
                return false;
            return true;
        }
    }
}