How to make a Rust top players command plugin (stat leaderboard)

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

namespace Oxide.Plugins
{
    [Info("Top Players Command", "RustPluginGenerator", "1.0.0")]
    [Description("Tracks kills, deaths and playtime and prints a top 10 leaderboard through /top.")]
    public class TopPlayersCommand : RustPlugin
    {
        private const string PermReset = "topplayerscommand.reset";

        private PluginConfig config;
        private StoredData data;
        private Timer playtimeTimer;
        private Timer saveTimer;

        private class PlayerStats
        {
            public string Name;
            public int Kills;
            public int Deaths;
            public long Seconds;
        }

        private class StoredData
        {
            public Dictionary<ulong, PlayerStats> Players = new Dictionary<ulong, PlayerStats>();
        }

        private class PluginConfig
        {
            [JsonProperty("Players shown in leaderboard")]
            public int DisplayCount = 10;

            [JsonProperty("Save interval (seconds)")]
            public int SaveIntervalSeconds = 300;
        }

        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>
            {
                ["TopHeader"] = "Top {0} (page 1):",
                ["TopRow"] = "{0}. {1} - {2}",
                ["Empty"] = "No players tracked yet for {0}.",
                ["Usage"] = "Usage: /top kills | /top deaths | /top playtime",
                ["ResetDone"] = "All tracked stats have been cleared."
            }, 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(PermReset, this);
        }

        private void OnServerInitialized()
        {
            data = Interface.Oxide.DataFileSystem.ReadObject<StoredData>("TopPlayersCommand") ?? new StoredData();
            if (data.Players == null) data.Players = new Dictionary<ulong, PlayerStats>();

            playtimeTimer = timer.Every(60f, TrackPlaytime);
            saveTimer = timer.Every(Mathf.Max(60, config.SaveIntervalSeconds), SaveData);
        }

        private void Unload()
        {
            if (playtimeTimer != null) playtimeTimer.Destroy();
            if (saveTimer != null) saveTimer.Destroy();
            SaveData();
            data = null;
        }

        private void SaveData()
        {
            if (data == null) return;
            Interface.Oxide.DataFileSystem.WriteObject("TopPlayersCommand", data);
        }

        private PlayerStats GetOrCreate(ulong userId, string name)
        {
            PlayerStats stats;
            if (!data.Players.TryGetValue(userId, out stats))
            {
                stats = new PlayerStats { Name = name ?? "Unknown" };
                data.Players[userId] = stats;
            }
            else if (!string.IsNullOrEmpty(name))
            {
                stats.Name = name;
            }
            return stats;
        }

        private void OnEntityDeath(BaseCombatEntity entity, HitInfo info)
        {
            var victim = entity as BasePlayer;
            if (victim == null || victim.IsNpc || info == null) return;

            var attacker = info.InitiatorPlayer;
            if (attacker == null || attacker.IsNpc) return;

            var victimId = victim.userID.Get();
            var attackerId = attacker.userID.Get();

            GetOrCreate(victimId, victim.displayName).Deaths++;

            if (attackerId != victimId)
            {
                GetOrCreate(attackerId, attacker.displayName).Kills++;
            }
        }

        private void OnPlayerDisconnected(BasePlayer player, string reason)
        {
            if (player == null || data == null) return;
            PlayerStats stats;
            if (data.Players.TryGetValue(player.userID.Get(), out stats))
            {
                stats.Name = player.displayName;
            }
        }

        private void TrackPlaytime()
        {
            if (data == null) return;
            foreach (var player in BasePlayer.activePlayerList)
            {
                if (player == null || player.IsNpc || !player.IsConnected) continue;
                GetOrCreate(player.userID.Get(), player.displayName).Seconds += 60;
            }
        }

        [ChatCommand("top")]
        private void CmdTop(BasePlayer player, string command, string[] args)
        {
            if (player == null) return;
            if (args == null || args.Length == 0)
            {
                SendReply(player, Msg("Usage", player.UserIDString));
                return;
            }

            var key = args[0].ToLowerInvariant();
            Func<PlayerStats, long> selector;
            string label;

            switch (key)
            {
                case "kills":
                    selector = s => s.Kills;
                    label = "Kills";
                    break;
                case "deaths":
                    selector = s => s.Deaths;
                    label = "Deaths";
                    break;
                case "playtime":
                    selector = s => s.Seconds;
                    label = "Playtime";
                    break;
                default:
                    SendReply(player, Msg("Usage", player.UserIDString));
                    return;
            }

            var top = data.Players.Values
                .OrderByDescending(selector)
                .ThenBy(s => s.Name)
                .Take(Mathf.Max(1, config.DisplayCount))
                .ToList();

            if (top.Count == 0 || selector(top[0]) <= 0)
            {
                SendReply(player, Msg("Empty", player.UserIDString, label));
                return;
            }

            SendReply(player, Msg("TopHeader", player.UserIDString, label));

            for (int i = 0; i < top.Count; i++)
            {
                var entry = top[i];
                var value = key == "playtime" ? FormatTime(entry.Seconds) : selector(entry).ToString();
                SendReply(player, Msg("TopRow", player.UserIDString, i + 1, entry.Name, value));
            }
        }

        [ConsoleCommand("topplayers.reset")]
        private void CcmdReset(ConsoleSystem.Arg arg)
        {
            var player = arg.Player();
            if (player != null && !permission.UserHasPermission(player.UserIDString, PermReset))
            {
                arg.ReplyWith("You do not have permission to use this command.");
                return;
            }

            if (arg.GetString(0, "") != "confirm")
            {
                arg.ReplyWith("Run topplayers.reset confirm to clear all stored stats.");
                return;
            }

            data.Players.Clear();
            SaveData();
            arg.ReplyWith(Msg("ResetDone"));
        }

        private static string FormatTime(long seconds)
        {
            var span = TimeSpan.FromSeconds(seconds);
            return string.Format("{0}h {1}m", (int)span.TotalHours, span.Minutes);
        }
    }
}