CanUseFuel

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

namespace Oxide.Plugins
{
    [Info("Fuel Efficiency", "RustPluginGenerator", "1.0.0")]
    [Description("Applies a configurable fuel efficiency multiplier to appliances using the CanUseFuel hook.")]
    public class FuelEfficiency : RustPlugin
    {
        private const string PermManage = "fuelefficiency.manage";

        private PluginConfig config;

        private class PluginConfig
        {
            [JsonProperty("Fuel efficiency multiplier (lower uses less fuel)")]
            public float Efficiency { get; set; } = 0.5f;
        }

        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();
            }
            ClampEfficiency();
            SaveConfig();
        }

        protected override void SaveConfig() => Config.WriteObject(config);

        protected override void LoadDefaultMessages()
        {
            lang.RegisterMessages(new Dictionary<string, string>
            {
                ["Usage"] = "Usage: /fuel [multiplier]",
                ["Set"] = "Fuel efficiency set to {0}.",
                ["Denied"] = "You do not have permission to change fuel efficiency."
            }, 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(PermManage, this);
        }

        private object CanUseFuel(EntityFuelSystem entityFuelSystem, StorageContainer fuelContainer, float seconds, float fuelUsedPerSecond)
        {
            if (entityFuelSystem == null || fuelContainer == null) return null;
            if (config.Efficiency >= 1f) return null;

            int requested = Mathf.CeilToInt(seconds * fuelUsedPerSecond);
            if (requested <= 0) return null;

            int reduced = Mathf.CeilToInt(requested * config.Efficiency);
            if (reduced < 0) reduced = 0;
            return reduced;
        }

        [ChatCommand("fuel")]
        private void CmdFuel(BasePlayer player, string command, string[] args)
        {
            if (player == null) return;
            if (!permission.UserHasPermission(player.UserIDString, PermManage))
            {
                player.ChatMessage(Msg("Denied", player.UserIDString));
                return;
            }

            if (args.Length != 1)
            {
                player.ChatMessage(Msg("Usage", player.UserIDString));
                return;
            }

            if (!float.TryParse(args[0], out float value))
            {
                player.ChatMessage(Msg("Usage", player.UserIDString));
                return;
            }

            config.Efficiency = Mathf.Clamp(value, 0.05f, 5f);
            SaveConfig();
            player.ChatMessage(Msg("Set", player.UserIDString, config.Efficiency));
        }

        private void ClampEfficiency()
        {
            config.Efficiency = Mathf.Clamp(config.Efficiency, 0.05f, 5f);
        }
    }
}