How to make a Rust gather bonus plugin (VIP tiers)

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

namespace Oxide.Plugins
{
    [Info("Vip Gather Bonus", "RustPluginGenerator", "1.0.0")]
    [Description("Gives permission-tiered players extra resources when gathering and picking up collectibles.")]
    public class VipGatherBonus : RustPlugin
    {
        private const string PermUse = "vipgatherbonus.use";

        private PluginConfig config;
        private readonly Dictionary<string, float> tierCache = new Dictionary<string, float>();
        private Timer refreshTimer;

        private class Tier
        {
            [JsonProperty("Permission suffix")]
            public string Permission { get; set; } = "vip1";

            [JsonProperty("Multiplier")]
            public float Multiplier { get; set; } = 1.25f;
        }

        private class PluginConfig
        {
            [JsonProperty("Global bonus multiplier")]
            public float GlobalBonus { get; set; } = 1f;

            [JsonProperty("Top multiplier only")]
            public bool TopMultiplierOnly { get; set; } = true;

            [JsonProperty("Tier permissions")]
            public List<Tier> Tiers { get; set; } = new List<Tier>
            {
                new Tier { Permission = "vip1", Multiplier = 1.25f },
                new Tier { Permission = "vip2", Multiplier = 1.5f },
                new Tier { Permission = "vip3", Multiplier = 2f }
            };
        }

        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>
            {
                ["NoBonus"] = "You have no gather bonus. Ask an admin about VIP tiers.",
                ["Bonus"] = "Your gather bonus is x{0} (tier: {1}).",
                ["Global"] = "Your gather bonus is x{0}.",
                ["NoPermission"] = "You do not have permission to use this command."
            }, 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);
            if (config.Tiers != null)
            {
                foreach (var tier in config.Tiers)
                {
                    if (tier == null || string.IsNullOrEmpty(tier.Permission)) continue;
                    permission.RegisterPermission(Prefix + "." + tier.Permission, this);
                }
            }
        }

        private void OnServerInitialized()
        {
            RefreshCache();
            refreshTimer = timer.Every(60f, RefreshCache);
        }

        private void Unload()
        {
            refreshTimer?.Destroy();
            tierCache.Clear();
        }

        private string Prefix => Name.ToLower().Replace(" ", "");

        private void RefreshCache()
        {
            tierCache.Clear();
            foreach (var player in BasePlayer.activePlayerList)
            {
                if (player == null || player.IsNpc) continue;
                tierCache[player.UserIDString] = ResolveMultiplier(player.UserIDString);
            }
        }

        private float ResolveMultiplier(string userId)
        {
            float result = 1f;
            float top = 1f;
            if (config.Tiers != null)
            {
                foreach (var tier in config.Tiers)
                {
                    if (tier == null || tier.Multiplier <= 1f) continue;
                    if (!permission.UserHasPermission(userId, Prefix + "." + tier.Permission)) continue;
                    if (tier.Multiplier > top) top = tier.Multiplier;
                    if (!config.TopMultiplierOnly) result *= tier.Multiplier;
                }
            }
            if (config.TopMultiplierOnly) result = top;
            return result * Math.Max(1f, config.GlobalBonus);
        }

        private float GetMultiplier(BasePlayer player)
        {
            if (player == null) return 1f;
            float cached;
            if (tierCache.TryGetValue(player.UserIDString, out cached)) return cached;
            float value = ResolveMultiplier(player.UserIDString);
            tierCache[player.UserIDString] = value;
            return value;
        }

        private int ScaleAmount(Item item, float multiplier)
        {
            if (item == null || item.info == null) return 0;
            int scaled = (int)Math.Ceiling(item.amount * multiplier);
            if (item.info.stackable > 0 && scaled > item.info.stackable) scaled = item.info.stackable;
            return scaled < item.amount ? item.amount : scaled;
        }

        private object OnDispenserGather(ResourceDispenser resourceDispenser, BasePlayer entity, Item item)
        {
            if (entity == null || entity.IsNpc || item == null) return null;
            float multiplier = GetMultiplier(entity);
            if (multiplier <= 1f) return null;
            item.amount = ScaleAmount(item, multiplier);
            return null;
        }

        private object OnCollectiblePickup(CollectibleEntity collectibleEntity, BasePlayer reciever, bool eat)
        {
            if (reciever == null || reciever.IsNpc || eat) return null;
            float multiplier = GetMultiplier(reciever);
            if (multiplier <= 1f) return null;
            var item = reciever.GetActiveItem();
            if (item == null) return null;
            item.amount = ScaleAmount(item, multiplier);
            return null;
        }

        [ChatCommand("gatherbonus")]
        private void CmdGatherBonus(BasePlayer player, string command, string[] args)
        {
            if (player == null) return;
            if (!permission.UserHasPermission(player.UserIDString, PermUse))
            {
                player.ChatMessage(Msg("NoPermission", player.UserIDString));
                return;
            }
            float multiplier = GetMultiplier(player);
            string tierName = "none";
            if (config.Tiers != null)
            {
                foreach (var tier in config.Tiers)
                {
                    if (tier == null) continue;
                    if (permission.UserHasPermission(player.UserIDString, Prefix + "." + tier.Permission))
                    {
                        tierName = tier.Permission;
                        if (config.TopMultiplierOnly) break;
                    }
                }
            }
            if (multiplier <= 1f) player.ChatMessage(Msg("NoBonus", player.UserIDString));
            else if (tierName == "none") player.ChatMessage(Msg("Global", player.UserIDString, multiplier));
            else player.ChatMessage(Msg("Bonus", player.UserIDString, multiplier, tierName));
        }
    }
}