OnNetworkGroupLeft

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

namespace Oxide.Plugins
{
    [Info("Network Group Watch", "RustPluginGenerator", "1.0.0")]
    [Description("Counts how often players leave network visibility groups and flags heavy churn")]
    public class NetworkGroupWatch : RustPlugin
    {
        private const string PermAdmin = "networkgroupwatch.admin";

        private PluginConfig config;
        private readonly Dictionary<string, int> counters = new Dictionary<string, int>();
        private Timer checkTimer;

        private class PluginConfig
        {
            [JsonProperty("Check interval in seconds")]
            public float CheckInterval = 60f;

            [JsonProperty("Leaves per interval before warning")]
            public int WarningThreshold = 40;
        }

        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>
            {
                ["Stats"] = "{0} has left {1} visibility groups.",
                ["NoData"] = "No churn recorded for that player.",
                ["NoPermission"] = "You do not have permission to use this command."
            }, 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()
        {
            checkTimer = timer.Every(config.CheckInterval, CheckCounters);
        }

        private void Unload()
        {
            checkTimer?.Destroy();
            counters.Clear();
        }

        private void OnNetworkGroupLeft(BaseNetworkable entity, Network.Visibility.Group group)
        {
            if (!(entity is BasePlayer)) return;
            var player = (BasePlayer)entity;
            if (player == null || player.IsNpc) return;

            string id = player.UserIDString;
            int count;
            counters.TryGetValue(id, out count);
            counters[id] = count + 1;
        }

        private void CheckCounters()
        {
            if (counters.Count == 0) return;

            foreach (var entry in counters)
            {
                if (entry.Value < config.WarningThreshold) continue;

                var player = BasePlayer.FindByID(ulong.Parse(entry.Key));
                string name = player != null ? player.displayName : entry.Key;
                PrintWarning($"{name} ({entry.Key}) left {entry.Value} visibility groups in the last interval");
            }

            counters.Clear();
        }

        [ConsoleCommand("ngw.stats")]
        private void CmdStats(ConsoleSystem.Arg arg)
        {
            var player = arg.Player();
            if (player != null && !permission.UserHasPermission(player.UserIDString, PermAdmin))
            {
                arg.ReplyWith(Msg("NoPermission", player.UserIDString));
                return;
            }

            string target = arg.GetString(0, player != null ? player.UserIDString : "");
            int count;
            if (string.IsNullOrEmpty(target) || !counters.TryGetValue(target, out count))
            {
                arg.ReplyWith(Msg("NoData", player?.UserIDString));
                return;
            }

            var found = BasePlayer.FindAwakeOrSleeping(target);
            string display = found != null ? found.displayName : target;
            arg.ReplyWith(Msg("Stats", player?.UserIDString, display, count));
        }
    }
}