OnRfListenerRemoved

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

namespace Oxide.Plugins
{
    [Info("Rf Channel Monitor", "RustPluginGenerator", "1.0.0")]
    [Description("Tracks how many RF listeners are subscribed per frequency and warns on crowded channels.")]
    public class RfChannelMonitor : RustPlugin
    {
        private const string PermAdmin = "rfchannelmonitor.admin";

        private class PluginConfig
        {
            [JsonProperty("Warn threshold (listeners per channel)")]
            public int WarnThreshold = 8;

            [JsonProperty("Warning check interval (seconds)")]
            public float CheckInterval = 60f;
        }

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

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

        protected override void LoadConfig()
        {
            base.LoadConfig();
            try
            {
                config = Config.ReadObject<PluginConfig>();
                if (config == null) throw new System.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>
            {
                ["Top"] = "Most used RF channels: {0}",
                ["Channel"] = "Channel {0} currently has {1} listener(s).",
                ["Empty"] = "No RF listeners are registered right now.",
                ["NoPerm"] = "You do not have permission to use this command.",
                ["Crowded"] = "RF channel {0} has {1} listeners (threshold {2})."
            }, 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, CheckCrowded);
        }

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

        private void OnRfListenerAdded(IRFObject obj, int frequency)
        {
            if (obj == null) return;
            listeners[frequency] = listeners.TryGetValue(frequency, out int count) ? count + 1 : 1;
        }

        private void OnRfListenerRemoved(IRFObject obj, int frequency)
        {
            if (obj == null) return;
            if (!listeners.TryGetValue(frequency, out int count)) return;
            count--;
            if (count <= 0) listeners.Remove(frequency);
            else listeners[frequency] = count;
        }

        private void CheckCrowded()
        {
            foreach (KeyValuePair<int, int> entry in listeners)
            {
                if (entry.Value < config.WarnThreshold) continue;
                Puts(string.Format(Msg("Crowded"), entry.Key, entry.Value, config.WarnThreshold));
            }
        }

        [ChatCommand("rfmon.top")]
        private void CmdTop(BasePlayer player, string command, string[] args)
        {
            if (player == null || !permission.UserHasPermission(player.UserIDString, PermAdmin))
            {
                SendReply(player, Msg("NoPerm", player.UserIDString));
                return;
            }
            if (listeners.Count == 0)
            {
                SendReply(player, Msg("Empty", player.UserIDString));
                return;
            }
            var ordered = new List<KeyValuePair<int, int>>(listeners);
            ordered.Sort((a, b) => b.Value.CompareTo(a.Value));
            var parts = new List<string>();
            for (int i = 0; i < ordered.Count && i < 5; i++)
                parts.Add($"{ordered[i].Key}={ordered[i].Value}");
            SendReply(player, Msg("Top", player.UserIDString, string.Join(", ", parts)));
        }

        [ChatCommand("rfmon.channel")]
        private void CmdChannel(BasePlayer player, string command, string[] args)
        {
            if (player == null || !permission.UserHasPermission(player.UserIDString, PermAdmin))
            {
                SendReply(player, Msg("NoPerm", player.UserIDString));
                return;
            }
            if (!int.TryParse(args != null && args.Length > 0 ? args[0] : "", out int freq))
            {
                SendReply(player, "Usage: /rfmon.channel <frequency>");
                return;
            }
            listeners.TryGetValue(freq, out int count);
            SendReply(player, Msg("Channel", player.UserIDString, freq, count));
        }
    }
}