OnFuelAmountCheck

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

namespace Oxide.Plugins
{
    [Info("Fuel Amount Override", "RustPluginGenerator", "1.0.0")]
    [Description("Reports a virtual fuel amount for whitelisted fuel systems so they keep running.")]
    public class FuelAmountOverride : RustPlugin
    {
        private const string PermAdmin = "fuelamountoverride.admin";

        private PluginConfig config;

        private class PluginConfig
        {
            [JsonProperty("Enable virtual fuel")]
            public bool Enabled = true;

            [JsonProperty("Virtual fuel amount")]
            public int VirtualAmount = 100;

            [JsonProperty("Only matching prefabs")]
            public List<string> Prefabs = new List<string> { "fuelgenerator.static" };
        }

        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>
            {
                ["ToggleOn"] = "Virtual fuel is now enabled.",
                ["ToggleOff"] = "Virtual fuel is now disabled."
            }, this);
        }

        private string Msg(string key, string userId = null) => lang.GetMessage(key, this, userId);

        private void Init()
        {
            permission.RegisterPermission(PermAdmin, this);
        }

        [ChatCommand("fueltoggle")]
        private void CmdFuelToggle(BasePlayer player, string command, string[] args)
        {
            if (player == null || !permission.UserHasPermission(player.UserIDString, PermAdmin)) return;

            config.Enabled = !config.Enabled;
            SaveConfig();
            player.ChatMessage(Msg(config.Enabled ? "ToggleOn" : "ToggleOff", player.UserIDString));
        }

        private object OnFuelAmountCheck(EntityFuelSystem entityFuelSystem, Item fuelItem)
        {
            if (!config.Enabled || entityFuelSystem == null) return null;
            if (fuelItem == null || fuelItem.parent == null) return null;

            BaseEntity owner = fuelItem.parent.entityOwner;
            if (owner == null || owner.IsDestroyed) return null;

            string prefab = owner.ShortPrefabName;
            if (string.IsNullOrEmpty(prefab) || !config.Prefabs.Contains(prefab)) return null;

            int stored = Mathf.Max(fuelItem.amount, 0);
            return stored + config.VirtualAmount;
        }
    }
}