How to make a Rust command menu plugin (CUI button grid)

using System.Linq;
using System;
using System.Collections.Generic;
using Newtonsoft.Json;
using Oxide.Core;
using Oxide.Game.Rust.Cui;
using UnityEngine;

namespace Oxide.Plugins
{
    [Info("Command Menu", "RustPluginGenerator", "1.0.0")]
    [Description("Opens a configurable CUI grid of buttons that run chat commands for the clicking player")]
    public class CommandMenu : RustPlugin
    {
        private const string PermUse = "commandmenu.use";
        private const string PermAdmin = "commandmenu.admin";
        private const string PanelId = "commandmenu.panel";

        private PluginConfig config;

        private class PluginConfig
        {
            [JsonProperty("Menu title")]
            public string Title = "Server Menu";

            [JsonProperty("Buttons per row")]
            public int ButtonsPerRow = 3;

            [JsonProperty("Button width")]
            public float ButtonWidth = 0.18f;

            [JsonProperty("Button height")]
            public float ButtonHeight = 0.07f;

            [JsonProperty("Buttons")]
            public List<MenuButton> Buttons = new List<MenuButton>
            {
                new MenuButton { Label = "Kits", Command = "kit", Permission = "" },
                new MenuButton { Label = "Shop", Command = "shop", Permission = "" },
                new MenuButton { Label = "Info", Command = "info", Permission = "" },
                new MenuButton { Label = "Close", Command = "commandmenu.close", Permission = "" }
            };
        }

        private class MenuButton
        {
            [JsonProperty("Label")]
            public string Label = "Button";

            [JsonProperty("Command")]
            public string Command = "";

            [JsonProperty("Permission")]
            public string Permission = "";
        }

        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>
            {
                ["NoPermission"] = "You do not have permission to use this menu.",
                ["Reloaded"] = "Menu configuration reloaded."
            }, 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(PermAdmin, this);
        }

        private void Unload()
        {
            foreach (var player in BasePlayer.activePlayerList)
            {
                if (player != null && player.IsConnected)
                    CuiHelper.DestroyUi(player, PanelId);
            }
        }

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

            OpenMenu(player);
        }

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

            LoadConfig();
            SendReply(player, Msg("Reloaded", player.UserIDString));
        }

        [ConsoleCommand("commandmenu.select")]
        private void CcmdSelect(ConsoleSystem.Arg arg)
        {
            var player = arg.Player();
            if (player == null) return;
            if (!permission.UserHasPermission(player.UserIDString, PermUse)) return;

            int index = arg.GetInt(0, -1);
            var visible = GetVisibleButtons(player);
            if (index < 0 || index >= visible.Count) return;

            var button = visible[index];
            if (button == null || string.IsNullOrEmpty(button.Command)) return;
            if (!string.IsNullOrEmpty(button.Permission) && !permission.UserHasPermission(player.UserIDString, button.Permission)) return;

            CuiHelper.DestroyUi(player, PanelId);
            player.SendConsoleCommand(button.Command);
        }

        [ConsoleCommand("commandmenu.close")]
        private void CcmdClose(ConsoleSystem.Arg arg)
        {
            var player = arg.Player();
            if (player == null) return;
            if (!permission.UserHasPermission(player.UserIDString, PermUse)) return;

            CuiHelper.DestroyUi(player, PanelId);
        }

        private List<MenuButton> GetVisibleButtons(BasePlayer player)
        {
            var result = new List<MenuButton>();
            if (config?.Buttons == null) return result;

            foreach (var button in config.Buttons)
            {
                if (button == null || string.IsNullOrEmpty(button.Label)) continue;
                if (!string.IsNullOrEmpty(button.Permission) && !permission.UserHasPermission(player.UserIDString, button.Permission)) continue;
                result.Add(button);
            }
            return result;
        }

        private void OpenMenu(BasePlayer player)
        {
            CuiHelper.DestroyUi(player, PanelId);

            var buttons = GetVisibleButtons(player);
            if (buttons.Count == 0) return;

            int perRow = Mathf.Max(1, config.ButtonsPerRow);
            int rows = Mathf.CeilToInt((float)buttons.Count / perRow);
            float buttonW = Mathf.Clamp(config.ButtonWidth, 0.05f, 0.5f);
            float buttonH = Mathf.Clamp(config.ButtonHeight, 0.03f, 0.2f);
            float gap = 0.01f;

            float gridW = perRow * buttonW + (perRow - 1) * gap;
            float gridH = rows * buttonH + (rows - 1) * gap + 0.08f;
            float minX = 0.5f - gridW / 2f;
            float maxY = 0.5f + gridH / 2f;

            var container = new CuiElementContainer();
            container.Add(new CuiPanel
            {
                Image = { Color = "0.1 0.1 0.1 0.85" },
                RectTransform = { AnchorMin = "0.2 0.2", AnchorMax = "0.8 0.8" },
                CursorEnabled = true
            }, "Overlay", PanelId);

            container.Add(new CuiLabel
            {
                Text = { Text = config.Title, FontSize = 18, Align = TextAnchor.MiddleCenter, Color = "1 1 1 1" },
                RectTransform = { AnchorMin = "0 0.88", AnchorMax = "1 1" }
            }, PanelId);

            for (int i = 0; i < buttons.Count; i++)
            {
                int row = i / perRow;
                int col = i % perRow;

                float x = minX + col * (buttonW + gap);
                float y = maxY - 0.08f - (row + 1) * buttonH - row * gap;

                container.Add(new CuiButton
                {
                    Button = { Command = $"commandmenu.select {i}", Color = "0.25 0.45 0.25 1" },
                    RectTransform =
                    {
                        AnchorMin = $"{x} {y}",
                        AnchorMax = $"{x + buttonW} {y + buttonH}"
                    },
                    Text = { Text = buttons[i].Label, FontSize = 14, Align = TextAnchor.MiddleCenter, Color = "1 1 1 1" }
                }, PanelId);
            }

            CuiHelper.AddUi(player, container);
        }
    }
}