OnPlayerWantsMount

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

namespace Oxide.Plugins
{
    [Info("Mount Guard", "RustPluginGenerator", "1.0.0")]
    [Description("Restricts mounting of vehicles to owners, authorised players and permission holders")]
    public class MountGuard : RustPlugin
    {
        private const string PermBypass = "mountguard.bypass";

        private PluginConfig config;

        private class PluginConfig
        {
            [JsonProperty("Protect cars and boats only")]
            public bool VehiclesOnly { get; set; } = true;

            [JsonProperty("Block when owner is offline")]
            public bool RequireOwnerOnline { get; set; } = false;
        }

        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>
            {
                ["NotOwner"] = "This vehicle does not belong to you.",
                ["OwnerOffline"] = "The owner must be online to use this vehicle."
            }, 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(PermBypass, this);
        }

        private object OnPlayerWantsMount(BasePlayer player, BaseMountable mountable)
        {
            if (player == null || mountable == null) return null;
            if (player.IsAdmin) return null;

            var vehicle = mountable.GetParentEntity() ?? mountable;
            if (vehicle == null || vehicle.OwnerID == 0) return null;

            if (config.VehiclesOnly && !(vehicle is ModularCar) && !(vehicle is BaseBoat) && !(vehicle is BaseHelicopter))
                return null;

            ulong ownerId = vehicle.OwnerID;
            if (player.userID.Get() == ownerId) return null;
            if (permission.UserHasPermission(player.UserIDString, PermBypass)) return null;

            if (vehicle is BuildingPrivlidge == false)
            {
                var auth = vehicle.GetBuildingPrivilege();
                if (auth != null && auth.IsAuthed(player)) return null;
            }

            if (config.RequireOwnerOnline && !IsOwnerOnline(ownerId))
            {
                player.ChatMessage(Msg("OwnerOffline", player.UserIDString));
                return true;
            }

            player.ChatMessage(Msg("NotOwner", player.UserIDString));
            return true;
        }

        private bool IsOwnerOnline(ulong ownerId)
        {
            var player = BasePlayer.FindByID(ownerId);
            return player != null && player.IsConnected;
        }
    }
}