How to make a Rust chat mentions plugin (@name pings)

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

namespace Oxide.Plugins
{
    [Info("Chat Mentions", "RustPluginGenerator", "1.0.0")]
    [Description("Notifies players when someone mentions their name with @ in chat.")]
    public class ChatMentions : RustPlugin
    {
        private PluginConfig config;
        private readonly Dictionary<ulong, float> lastMention = new Dictionary<ulong, float>();

        private class PluginConfig
        {
            [JsonProperty("Cooldown Seconds")]
            public float CooldownSeconds = 10f;

            [JsonProperty("Notify sender about unknown mentions")]
            public bool NotifyUnknown = true;

            [JsonProperty("Sound at ear height")]
            public bool SoundAtEars = true;

            [JsonProperty("Sound prefab")]
            public string SoundPrefab = "assets/bundled/prefabs/fx/notice/item.select.fx.prefab";

            [JsonProperty("Notice prefix")]
            public string NoticePrefix = "@";

            [JsonProperty("Max message length")]
            public int MaxMessageLength = 200;
        }

        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>
            {
                ["Mention Notice"] = "{0} mentioned you in chat: {1}",
                ["Mention Delivered"] = "You mentioned {0}.",
                ["Mention Cooldown"] = "You are mentioning people too often, wait a moment.",
                ["Unknown Player"] = "No online player matches @{0}."
            }, this);
        }

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

        private object OnPlayerChat(BasePlayer player, string message, ConVar.Chat.ChatChannel channel)
        {
            if (player == null || player.IsNpc || !player.IsConnected) return null;
            if (string.IsNullOrEmpty(message) || message.IndexOf('@') < 0) return null;

            float now = UnityEngine.Time.realtimeSinceStartup;
            float last;
            if (config.CooldownSeconds > 0f && lastMention.TryGetValue(player.userID, out last) && now - last < config.CooldownSeconds)
            {
                SendReply(player, Msg("Mention Cooldown", player.UserIDString));
                return null;
            }

            var tokens = message.Split(' ');
            var seen = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
            bool anyDelivered = false;

            foreach (var raw in tokens)
            {
                if (raw.Length < 2 || raw[0] != '@') continue;
                string name = raw.Substring(1).TrimEnd('!', '?', ',', '.', ':', ';');
                if (name.Length == 0 || !seen.Add(name)) continue;

                BasePlayer target = Resolve(name);
                if (target == null || target == player)
                {
                    if (config.NotifyUnknown && target == null)
                    {
                        SendReply(player, Msg("Unknown Player", player.UserIDString, name));
                    }
                    continue;
                }

                string snippet = message.Length > config.MaxMessageLength ? message.Substring(0, config.MaxMessageLength) + "..." : message;
                SendReply(target, string.Format("{0} {1}", config.NoticePrefix, Msg("Mention Notice", target.UserIDString, player.displayName, snippet)));

                if (!string.IsNullOrEmpty(config.SoundPrefab))
                {
                    Vector3 pos = config.SoundAtEars && target.eyes != null ? target.eyes.position : target.transform.position;
                    Effect.server.Run(config.SoundPrefab, pos);
                }

                SendReply(player, Msg("Mention Delivered", player.UserIDString, target.displayName));
                anyDelivered = true;
            }

            if (anyDelivered) lastMention[player.userID] = now;
            return null;
        }

        private BasePlayer Resolve(string name)
        {
            BasePlayer exact = BasePlayer.Find(name);
            if (exact != null && exact.IsConnected) return exact;

            BasePlayer found = null;
            foreach (var candidate in BasePlayer.activePlayerList)
            {
                if (candidate == null || !candidate.IsConnected) continue;
                if (!candidate.displayName.StartsWith(name, StringComparison.OrdinalIgnoreCase)) continue;
                if (found != null && found != candidate) return null;
                found = candidate;
            }
            return found;
        }

        private void OnPlayerDisconnected(BasePlayer player, string reason)
        {
            if (player != null) lastMention.Remove(player.userID);
        }

        private void Unload()
        {
            lastMention.Clear();
        }
    }
}