How to make a Rust car spawn plugin (Oxide/Carbon)

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

namespace Oxide.Plugins
{
    [Info("Car Spawn", "RustPluginGenerator", "1.0.0")]
    [Description("Adds a /car command that spawns a modular car in front of the player with a cooldown and a one-car limit.")]
    public class CarSpawn : RustPlugin
    {
        private const string PermUse = "carspawn.use";

        private class PluginConfig
        {
            [JsonProperty("Chassis prefab")]
            public string ChassisPrefab = "assets/content/vehicles/modularcar/2module_car_spawned.entity.prefab";

            [JsonProperty("Modules")]
            public List<string> Modules = new List<string>
            {
                "assets/content/vehicles/modularcar/models/components/engine.entity.prefab",
                "assets/content/vehicles/modularcar/models/components/seat.entity.prefab"
            };

            [JsonProperty("Spawn distance")]
            public float SpawnDistance = 4f;

            [JsonProperty("Cooldown seconds")]
            public float CooldownSeconds = 300f;

            [JsonProperty("Allow spawning while building blocked")]
            public bool AllowBuildingBlocked = false;
        }

        private class StoredData
        {
            [JsonProperty("Spawned cars")]
            public Dictionary<ulong, ulong> Cars = new Dictionary<ulong, ulong>();

            [JsonProperty("Cooldowns")]
            public Dictionary<ulong, DateTime> Cooldowns = new Dictionary<ulong, DateTime>();
        }

        private PluginConfig config;
        private StoredData data;

        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 command.",
                ["Cooldown"] = "You must wait {0} more seconds before spawning another car.",
                ["AlreadyHaveCar"] = "You already have a spawned car. Destroy it first.",
                ["BuildingBlocked"] = "You cannot spawn a car while building is blocked.",
                ["SpawnFailed"] = "The car could not be spawned. Check the server configuration.",
                ["Spawned"] = "Your car has been spawned in front of you."
            }, 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 Loaded()
        {
            data = Interface.Oxide.DataFileSystem.ReadObject<StoredData>(Name) ?? new StoredData();
        }

        private void Unload()
        {
            if (data != null)
                Interface.Oxide.DataFileSystem.WriteObject(Name, data);
        }

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

            if (!config.AllowBuildingBlocked && player.IsBuildingBlocked())
            {
                player.ChatMessage(Msg("BuildingBlocked", player.UserIDString));
                return;
            }

            DateTime last;
            if (data.Cooldowns.TryGetValue(player.userID, out last))
            {
                var remaining = config.CooldownSeconds - (float)(DateTime.UtcNow - last).TotalSeconds;
                if (remaining > 0f)
                {
                    player.ChatMessage(Msg("Cooldown", player.UserIDString, Mathf.CeilToInt(remaining)));
                    return;
                }
            }

            if (HasActiveCar(player.userID))
            {
                player.ChatMessage(Msg("AlreadyHaveCar", player.UserIDString));
                return;
            }

            var car = SpawnCar(player);
            if (car == null)
            {
                player.ChatMessage(Msg("SpawnFailed", player.UserIDString));
                return;
            }

            data.Cars[player.userID] = car.net.ID.Value;
            data.Cooldowns[player.userID] = DateTime.UtcNow;
            Interface.Oxide.DataFileSystem.WriteObject(Name, data);
            player.ChatMessage(Msg("Spawned", player.UserIDString));
        }

        private bool HasActiveCar(ulong userId)
        {
            ulong carId;
            if (!data.Cars.TryGetValue(userId, out carId)) return false;

            var entity = BaseNetworkable.serverEntities.Find(new NetworkableId(carId)) as ModularCar;
            if (entity == null || entity.IsDestroyed)
            {
                data.Cars.Remove(userId);
                return false;
            }
            return true;
        }

        private ModularCar SpawnCar(BasePlayer player)
        {
            var position = player.eyes.position + player.eyes.HeadForward() * config.SpawnDistance;
            var ground = TerrainMeta.HeightMap.GetHeight(position);
            if (position.y < ground) position.y = ground + 0.5f;

            var entity = GameManager.server.CreateEntity(config.ChassisPrefab, position, Quaternion.identity);
            if (entity == null) return null;

            var car = entity as ModularCar;
            if (car == null)
            {
                entity.Kill();
                return null;
            }

            car.OwnerID = player.userID;
            car.Spawn();
            return car;
        }

        private object OnEntityKill(BaseNetworkable entity)
        {
            if (entity == null || data == null || data.Cars.Count == 0) return null;

            var id = entity.net.ID.Value;
            ulong owner = 0;
            bool found = false;

            foreach (var entry in data.Cars)
            {
                if (entry.Value == id)
                {
                    owner = entry.Key;
                    found = true;
                    break;
                }
            }

            if (found)
            {
                data.Cars.Remove(owner);
                Interface.Oxide.DataFileSystem.WriteObject(Name, data);
            }

            return null;
        }
    }
}