How to make a Rust map grid location plugin (chat /grid command)

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

namespace Oxide.Plugins
{
    [Info("Map Grid Location", "RustPluginGenerator", "1.0.0")]
    [Description("Adds a /grid command that reports the player's map grid cell and shows exact coordinates to admins.")]
    public class MapGridLocation : RustPlugin
    {
        private const string PermUse = "mapgridlocation.use";
        private const string PermCoords = "mapgridlocation.coords";

        private PluginConfig config;
        private float worldSize;
        private float cellSize;
        private readonly List<Timer> timers = new List<Timer>();

        private class PluginConfig
        {
            [JsonProperty("Announce On Connect")]
            public bool AnnounceOnConnect { get; set; } = true;

            [JsonProperty("Grid Cells")]
            public int GridCells { get; set; } = 30;

            [JsonProperty("Show Grid In Reply")]
            public bool ShowGridInReply { get; set; } = true;
        }

        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>
            {
                ["GridReply"] = "You are in grid {0}.",
                ["GridReplyCoords"] = "You are in grid {0} (X: {1}, Z: {2}, Y: {3}).",
                ["GridUnknown"] = "Could not work out your grid position.",
                ["NoPermission"] = "You do not have permission to use this command.",
                ["Announce"] = "You are currently in grid {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(PermUse, this);
            permission.RegisterPermission(PermCoords, this);
        }

        private void OnServerInitialized()
        {
            worldSize = ConVar.Server.worldsize;
            RefreshCellSize();
        }

        private void RefreshCellSize()
        {
            int cells = config.GridCells <= 0 ? 30 : config.GridCells;
            if (worldSize <= 0f) worldSize = ConVar.Server.worldsize;
            if (worldSize <= 0f) worldSize = 3000f;
            cellSize = worldSize / cells;
        }

        private string PositionToGrid(Vector3 pos)
        {
            if (cellSize <= 0f) RefreshCellSize();

            int cells = config.GridCells <= 0 ? 30 : config.GridCells;
            float half = worldSize * 0.5f;
            float shiftedX = (pos.x + half) / cellSize;
            float shiftedZ = (pos.z + half) / cellSize;
            int column = Mathf.FloorToInt(shiftedX);
            int row = Mathf.FloorToInt(shiftedZ);

            if (column < 0) column = 0;
            if (column > cells - 1) column = cells - 1;
            if (row < 0) row = 0;
            if (row > cells - 1) row = cells - 1;

            char letter = (char)('A' + row);
            return letter + (column + 1).ToString();
        }

        private string BuildReply(BasePlayer player, string userId, bool withCoords)
        {
            Vector3 pos = player.transform.position;
            string grid = PositionToGrid(pos);
            string coords = string.Format("{0}, {1}, {2}",
                Mathf.RoundToInt(pos.x), Mathf.RoundToInt(pos.z), Mathf.RoundToInt(pos.y));

            if (!config.ShowGridInReply)
            {
                return withCoords
                    ? string.Format("X: {0}, Z: {1}, Y: {2}", Mathf.RoundToInt(pos.x), Mathf.RoundToInt(pos.z), Mathf.RoundToInt(pos.y))
                    : Msg("GridReply", userId, grid);
            }

            if (withCoords)
                return Msg("GridReplyCoords", userId, grid, Mathf.RoundToInt(pos.x), Mathf.RoundToInt(pos.z), Mathf.RoundToInt(pos.y));

            return Msg("GridReply", userId, grid);
        }

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

            bool withCoords = permission.UserHasPermission(userId, PermCoords) || player.IsAdmin;
            SendReply(player, BuildReply(player, userId, withCoords));
        }

        private void OnPlayerConnected(BasePlayer player)
        {
            if (player == null || !config.AnnounceOnConnect) return;
            if (!permission.UserHasPermission(player.UserIDString, PermUse)) return;

            Timer t = timer.Once(3f, () =>
            {
                if (player == null || !player.IsConnected) return;
                SendReply(player, Msg("Announce", player.UserIDString, PositionToGrid(player.transform.position)));
            });
            timers.Add(t);
        }

        private void Unload()
        {
            foreach (Timer t in timers)
            {
                if (t != null) t.Destroy();
            }
            timers.Clear();
        }
    }
}