OnNetworkGroupEntered

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

namespace Oxide.Plugins
{
    [Info("Group Entered Crate Announcer", "RustPluginGenerator", "1.0.0")]
    [Description("Broadcasts a message when a hackable locked crate enters a network visibility group")]
    public class GroupEnteredCrateAnnouncer : RustPlugin
    {
        private const string PermView = "groupenteredcrateannouncer.view";

        private PluginConfig config;
        private readonly Dictionary<ulong, float> recentCrates = new Dictionary<ulong, float>();
        private Timer cleanupTimer;

        private class PluginConfig
        {
            [JsonProperty("Announce crate in chat")]
            public bool Announce { get; set; } = true;

            [JsonProperty("Repeat cooldown per crate (seconds)")]
            public float Cooldown { get; set; } = 30f;
        }

        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>
            {
                ["Announce"] = "A hackable crate became network-visible in group {0}"
            }, 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(PermView, this);
        }

        private void OnServerInitialized()
        {
            cleanupTimer = timer.Every(60f, Cleanup);
        }

        private void OnNetworkGroupEntered(BaseNetworkable entity, Network.Visibility.Group group)
        {
            if (entity == null || entity.IsDestroyed) return;
            if (!(entity is HackableLockedCrate crate)) return;
            if (crate.OwnerID != 0) return;

            float now = UnityEngine.Time.realtimeSinceStartup;
            float last;
            if (recentCrates.TryGetValue(crate.net.ID.Value, out last) && now - last < config.Cooldown) return;
            recentCrates[crate.net.ID.Value] = now;

            if (!config.Announce) return;

            Puts(Msg("Announce", null, group.ID));
            foreach (BasePlayer player in BasePlayer.activePlayerList)
            {
                if (player == null || !player.IsConnected) continue;
                if (!permission.UserHasPermission(player.UserIDString, PermView)) continue;
                player.ChatMessage(Msg("Announce", player.UserIDString, group.ID));
            }
        }

        private void Cleanup()
        {
            float now = UnityEngine.Time.realtimeSinceStartup;
            List<ulong> stale = new List<ulong>();
            foreach (KeyValuePair<ulong, float> pair in recentCrates)
            {
                if (now - pair.Value > config.Cooldown * 2f) stale.Add(pair.Key);
            }
            foreach (ulong id in stale) recentCrates.Remove(id);
        }

        private void Unload()
        {
            if (cleanupTimer != null)
            {
                cleanupTimer.Destroy();
                cleanupTimer = null;
            }
            recentCrates.Clear();
        }
    }
}