How to make a Rust daily rewards plugin (Oxide C#)

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

namespace Oxide.Plugins
{
    [Info("Daily Rewards", "RustPluginGenerator", "1.0.0")]
    [Description("Adds a /daily command with a 24 hour cooldown, weighted rewards and a streak bonus")]
    public class DailyRewards : RustPlugin
    {
        private const string PermAdmin = "dailyrewards.admin";
        private const string DataFileName = "DailyRewards";

        private PluginConfig config;
        private Dictionary<string, PlayerData> data = new Dictionary<string, PlayerData>();

        private class PlayerData
        {
            [JsonProperty("Last claim (UTC)")]
            public DateTime LastClaim { get; set; }

            [JsonProperty("Streak")]
            public int Streak { get; set; }
        }

        private class PluginConfig
        {
            [JsonProperty("Cooldown Hours")]
            public double CooldownHours = 24.0;

            [JsonProperty("Streak Reset Hours")]
            public double StreakResetHours = 48.0;

            [JsonProperty("Streak Bonus Shortname")]
            public string StreakBonusShortname = "scrap";

            [JsonProperty("Streak Bonus Base Amount")]
            public int StreakBonusBaseAmount = 10;

            [JsonProperty("Streak Bonus Per Day")]
            public int StreakBonusPerDay = 5;

            [JsonProperty("Rewards")]
            public List<RewardEntry> Rewards = new List<RewardEntry>
            {
                new RewardEntry { Shortname = "scrap", Amount = 150, Weight = 4 },
                new RewardEntry { Shortname = "metal.fragments", Amount = 500, Weight = 3 },
                new RewardEntry { Shortname = "sulfur.ore", Amount = 200, Weight = 2 },
                new RewardEntry { Shortname = "rifle.ak", Amount = 1, Weight = 1, Skin = 0 }
            };
        }

        private class RewardEntry
        {
            [JsonProperty("Shortname")]
            public string Shortname = "scrap";

            [JsonProperty("Amount")]
            public int Amount = 1;

            [JsonProperty("Skin")]
            public ulong Skin = 0;

            [JsonProperty("Weight")]
            public int Weight = 1;
        }

        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>
            {
                ["Claimed"] = "You claimed {0} x{1}. Streak: {2} day(s).{3}",
                ["Bonus"] = " Streak bonus: {0} x{1}.",
                ["Cooldown"] = "You already claimed today. Next reward in {0}.",
                ["NoRewards"] = "The reward list is empty. Tell an admin.",
                ["InvalidTarget"] = "No player found for that name or id.",
                ["ResetDone"] = "Rewards reset for {0}.",
                ["FormatHours"] = "{0}h {1}m"
            }, 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 void OnServerInitialized()
        {
            data = Interface.Oxide.DataFileSystem.ReadObject<Dictionary<string, PlayerData>>(DataFileName)
                   ?? new Dictionary<string, PlayerData>();

            var bad = config.Rewards
                .Where(r => r == null || r.Weight <= 0 || ItemManager.FindItemDefinition(r.Shortname) == null)
                .ToList();
            if (config.Rewards.Count == 0)
                PrintWarning("Reward list is empty; /daily will not pay anything.");
            else if (bad.Count > 0)
                PrintWarning($"{bad.Count} reward entries have an unknown shortname or non-positive weight and will be skipped.");
            if (!string.IsNullOrEmpty(config.StreakBonusShortname) &&
                ItemManager.FindItemDefinition(config.StreakBonusShortname) == null)
                PrintWarning($"Streak bonus shortname '{config.StreakBonusShortname}' is unknown; the bonus will not be granted.");
        }

        private void OnServerSave()
        {
            Interface.Oxide.DataFileSystem.WriteObject(DataFileName, data);
        }

        private void Unload()
        {
            Interface.Oxide.DataFileSystem.WriteObject(DataFileName, data);
        }

        [ChatCommand("daily")]
        private void CmdDaily(BasePlayer player, string command, string[] args)
        {
            if (player == null || !player.IsConnected) return;

            var id = player.UserIDString;
            if (!data.TryGetValue(id, out var record) || record == null)
            {
                record = new PlayerData();
                data[id] = record;
            }

            var now = DateTime.UtcNow;
            var cooldown = TimeSpan.FromHours(Math.Max(0.0, config.CooldownHours));
            var elapsed = now - record.LastClaim;

            if (record.LastClaim != default(DateTime) && elapsed < cooldown)
            {
                var left = cooldown - elapsed;
                player.ChatMessage(Msg("Cooldown", id, Msg("FormatHours", id, (int)left.TotalHours, left.Minutes)));
                return;
            }

            var streakWindow = TimeSpan.FromHours(Math.Max(0.0, config.StreakResetHours));
            record.Streak = (record.LastClaim != default(DateTime) && elapsed <= streakWindow)
                ? record.Streak + 1
                : 1;

            var reward = PickReward();
            string bonusText = string.Empty;

            if (reward != null)
            {
                var item = ItemManager.CreateByName(reward.Shortname, Math.Max(1, reward.Amount), reward.Skin);
                if (item != null)
                {
                    player.GiveItem(item);
                    player.ChatMessage(Msg("Claimed", id, item.info.displayName.english, item.amount, record.Streak,
                        BuildBonusText(player, record.Streak, id)));
                }
                else
                {
                    player.ChatMessage(Msg("NoRewards", id));
                }
            }
            else
            {
                player.ChatMessage(Msg("NoRewards", id));
            }

            record.LastClaim = now;
        }

        private string BuildBonusText(BasePlayer player, int streak, string id)
        {
            if (string.IsNullOrEmpty(config.StreakBonusShortname)) return string.Empty;

            var definition = ItemManager.FindItemDefinition(config.StreakBonusShortname);
            if (definition == null) return string.Empty;

            var amount = config.StreakBonusBaseAmount + config.StreakBonusPerDay * (streak - 1);
            if (amount <= 0) return string.Empty;

            var bonus = ItemManager.CreateByName(config.StreakBonusShortname, amount);
            if (bonus == null) return string.Empty;

            player.GiveItem(bonus);
            return Msg("Bonus", id, definition.displayName.english, amount);
        }

        private RewardEntry PickReward()
        {
            var entries = config.Rewards
                .Where(r => r != null && r.Weight > 0 && ItemManager.FindItemDefinition(r.Shortname) != null)
                .ToList();
            if (entries.Count == 0) return null;

            var total = entries.Sum(r => r.Weight);
            var roll = UnityEngine.Random.Range(0f, (float)total);
            float running = 0f;
            foreach (var entry in entries)
            {
                running += entry.Weight;
                if (roll < running) return entry;
            }
            return entries[entries.Count - 1];
        }

        [ConsoleCommand("daily.reset")]
        private void CcmdReset(ConsoleSystem.Arg arg)
        {
            var caller = arg.Player();
            if (caller != null && !permission.UserHasPermission(caller.UserIDString, PermAdmin))
            {
                arg.ReplyWith("You do not have permission to use this command.");
                return;
            }

            var target = arg.GetString(0, string.Empty);
            if (string.IsNullOrEmpty(target))
            {
                arg.ReplyWith("Usage: daily.reset <steamid|name>");
                return;
            }

            var player = BasePlayer.FindAwakeOrSleeping(target);
            if (player == null)
            {
                arg.ReplyWith(Msg("InvalidTarget"));
                return;
            }

            data.Remove(player.UserIDString);
            Interface.Oxide.DataFileSystem.WriteObject(DataFileName, data);
            arg.ReplyWith(Msg("ResetDone", null, player.displayName));
        }
    }
}