How to make a Rust team tags in chat plugin (Oxide/Carbon)

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

namespace Oxide.Plugins
{
    [Info("Team Chat Tags", "RustPluginGenerator", "1.0.0")]
    [Description("Lets team leaders set a short tag that is shown before team members' chat messages.")]
    public class TeamChatTags : RustPlugin
    {
        private const string PermUse = "teamchattags.use";
        private const string DataFileName = "TeamChatTags";

        private PluginConfig config;
        private Dictionary<string, string> tags = new Dictionary<string, string>();

        private class PluginConfig
        {
            [JsonProperty("Tag format ({0} tag, {1} name, {2} message)")]
            public string TagFormat { get; set; } = "[{0}] {1}: {2}";

            [JsonProperty("Minimum tag length")]
            public int MinLength { get; set; } = 2;

            [JsonProperty("Maximum tag length")]
            public int MaxLength { get; set; } = 5;
        }

        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>
            {
                ["Set.Success"] = "Team tag set to [{0}].",
                ["Set.Cleared"] = "Your team tag has been removed.",
                ["Set.Invalid"] = "Tags must be {0}-{1} characters, letters and numbers only.",
                ["Set.NotLeader"] = "Only the team leader can change the team tag.",
                ["Set.NoTeam"] = "You are not in a team.",
                ["Set.None"] = "Your team has no tag. Use /tag <TAG> to set one.",
                ["Set.Current"] = "Your team tag is [{0}].",
                ["Set.InUse"] = "That tag is already used by another team.",
                ["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(PermUse, this);
        }

        private void OnServerInitialized()
        {
            tags = Interface.Oxide.DataFileSystem.ReadObject<Dictionary<string, string>>(DataFileName)
                   ?? new Dictionary<string, string>();
        }

        private void Unload()
        {
            Interface.Oxide.DataFileSystem.WriteObject(DataFileName, tags);
        }

        private object OnPlayerChat(BasePlayer player, string message, ConVar.Chat.ChatChannel channel)
        {
            if (player == null || string.IsNullOrEmpty(message)) return null;
            if (player.currentTeam == 0) return null;

            string tag;
            if (!tags.TryGetValue(player.currentTeam.ToString(), out tag) || string.IsNullOrEmpty(tag))
                return null;

            return string.Format(config.TagFormat, tag, player.displayName, message);
        }

        [ChatCommand("tag")]
        private void CmdTag(BasePlayer player, string command, string[] args)
        {
            if (player == null) return;
            if (!permission.UserHasPermission(player.UserIDString, PermUse))
            {
                SendReply(player, Msg("NoPermission", player.UserIDString));
                return;
            }

            if (player.currentTeam == 0)
            {
                SendReply(player, Msg("Set.NoTeam", player.UserIDString));
                return;
            }

            var team = RelationshipManager.ServerInstance.FindTeam(player.currentTeam);
            if (team == null)
            {
                SendReply(player, Msg("Set.NoTeam", player.UserIDString));
                return;
            }

            string teamId = player.currentTeam.ToString();

            if (args == null || args.Length == 0)
            {
                string current;
                SendReply(player, tags.TryGetValue(teamId, out current)
                    ? Msg("Set.Current", player.UserIDString, current)
                    : Msg("Set.None", player.UserIDString));
                return;
            }

            if (team.teamLeader != player.userID.Get())
            {
                SendReply(player, Msg("Set.NotLeader", player.UserIDString));
                return;
            }

            string candidate = args[0].Trim();
            if (!IsValidTag(candidate))
            {
                SendReply(player, Msg("Set.Invalid", player.UserIDString, config.MinLength, config.MaxLength));
                return;
            }

            foreach (var pair in tags)
            {
                if (pair.Key != teamId && pair.Value.Equals(candidate, StringComparison.OrdinalIgnoreCase))
                {
                    SendReply(player, Msg("Set.InUse", player.UserIDString));
                    return;
                }
            }

            tags[teamId] = candidate;
            SendReply(player, Msg("Set.Success", player.UserIDString, candidate));
        }

        [ChatCommand("tagclear")]
        private void CmdTagClear(BasePlayer player, string command, string[] args)
        {
            if (player == null) return;
            if (!permission.UserHasPermission(player.UserIDString, PermUse))
            {
                SendReply(player, Msg("NoPermission", player.UserIDString));
                return;
            }

            if (player.currentTeam == 0)
            {
                SendReply(player, Msg("Set.NoTeam", player.UserIDString));
                return;
            }

            var team = RelationshipManager.ServerInstance.FindTeam(player.currentTeam);
            if (team == null)
            {
                SendReply(player, Msg("Set.NoTeam", player.UserIDString));
                return;
            }

            if (team.teamLeader != player.userID.Get())
            {
                SendReply(player, Msg("Set.NotLeader", player.UserIDString));
                return;
            }

            tags.Remove(player.currentTeam.ToString());
            SendReply(player, Msg("Set.Cleared", player.UserIDString));
        }

        private bool IsValidTag(string tag)
        {
            if (string.IsNullOrEmpty(tag)) return false;
            if (tag.Length < config.MinLength || tag.Length > config.MaxLength) return false;

            for (int i = 0; i < tag.Length; i++)
            {
                char c = tag[i];
                bool ok = (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9');
                if (!ok) return false;
            }

            return true;
        }
    }
}