OnLootItem

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

namespace Oxide.Plugins
{
    [Info("First Loot Reward", "RustPluginGenerator", "1.0.0")]
    [Description("Grants a one-time scrap reward the first time a player loots a configured container item.")]
    public class FirstLootReward : RustPlugin
    {
        private const string PermUse = "firstlootreward.use";

        private PluginConfig config;
        private StoredData data;

        private class PluginConfig
        {
            [JsonProperty("Reward amount")]
            public int RewardAmount = 50;

            [JsonProperty("Reward item shortname")]
            public string RewardShortname = "scrap";

            [JsonProperty("Tracked container shortnames")]
            public List<string> TrackedShortnames = new List<string> { "backpack" };
        }

        private class StoredData
        {
            public HashSet<string> Rewarded = new HashSet<string>();
        }

        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>
            {
                ["Reward"] = "First loot bonus: you received {0}x {1}.",
                ["NoPermission"] = "You do not have permission to receive loot bonuses."
            }, this);
        }

        private void Init()
        {
            permission.RegisterPermission(PermUse, this);
            data = Interface.Oxide.DataFileSystem.ReadObject<StoredData>("FirstLootReward") ?? new StoredData();
        }

        private void OnLootItem(BasePlayer player, Item item)
        {
            if (player == null || item == null || item.info == null) return;
            if (!permission.UserHasPermission(player.UserIDString, PermUse)) return;
            if (!config.TrackedShortnames.Contains(item.info.shortname)) return;

            string key = player.UserIDString + ":" + item.info.shortname;
            if (data.Rewarded.Contains(key)) return;

            data.Rewarded.Add(key);
            Interface.Oxide.DataFileSystem.WriteObject("FirstLootReward", data);

            Item reward = ItemManager.CreateByName(config.RewardShortname, config.RewardAmount);
            if (reward == null) return;

            player.GiveItem(reward);
            player.ChatMessage(string.Format(lang.GetMessage("Reward", this, player.UserIDString), config.RewardAmount, item.info.displayName.english));
        }

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