OnShopCompleteTrade

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

namespace Oxide.Plugins
{
    [Info("Shop Owner Online Only", "RustPluginGenerator", "1.0.0")]
    [Description("Cancels vending machine sales when the shop owner is not connected")]
    public class ShopOwnerOnlineOnly : RustPlugin
    {
        private const string PermAdmin = "shopowneronlineonly.admin";

        private PluginConfig config;
        private int blockedCount;

        private class PluginConfig
        {
            [JsonProperty("Notify customer on blocked sale")]
            public bool NotifyCustomer = true;

            [JsonProperty("Allow NPC vendors")]
            public bool AllowNpcVendors = 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>
            {
                ["SaleBlocked"] = "This vending machine is not taking purchases right now.",
                ["Stats"] = "ShopOwnerOnlineOnly has blocked {0} sale(s) this session."
            }, 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(PermAdmin, this);
        }

        private object OnShopCompleteTrade(ShopFront shopFront)
        {
            if (shopFront == null) return null;

            BasePlayer vendor = shopFront.vendorPlayer;
            if (vendor == null) return null;

            if (config.AllowNpcVendors && vendor.IsNpc) return null;
            if (vendor.IsConnected && !vendor.IsSleeping()) return null;

            blockedCount++;

            BasePlayer customer = shopFront.customerPlayer;
            if (config.NotifyCustomer && customer != null && customer.IsConnected)
            {
                customer.ChatMessage(Msg("SaleBlocked", customer.UserIDString));
            }

            return true;
        }

        [ChatCommand("shopblockstats")]
        private void CmdStats(BasePlayer player, string command, string[] args)
        {
            if (player == null || !permission.UserHasPermission(player.UserIDString, PermAdmin)) return;
            player.ChatMessage(Msg("Stats", player.UserIDString, blockedCount));
        }
    }
}