How to make a Rust PvP toggle plugin (Oxide/Carbon)

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

namespace Oxide.Plugins
{
    [Info("PvpToggle", "RustPluginGenerator", "1.0.0")]
    [Description("Lets players opt in or out of PvP damage with a cooldown and persists their choice.")]
    public class PvpToggle : RustPlugin
    {
        private const string PermUse = "pvptoggle.use";
        private const string PermAdmin = "pvptoggle.admin";
        private const string PermNoCooldown = "pvptoggle.nocooldown";

        private PluginConfig config;
        private StoredData data;

        public class PluginConfig
        {
            [JsonProperty("Default PvP Mode")]
            public bool DefaultPvpMode = true;

            [JsonProperty("Toggle Cooldown (seconds)")]
            public float ToggleCooldown = 300f;

            [JsonProperty("Block Damage Message")]
            public bool BlockDamageMessage = true;
        }

        public class StoredData
        {
            [JsonProperty("Players")]
            public Dictionary<ulong, PlayerState> Players = new Dictionary<ulong, PlayerState>();
        }

        public class PlayerState
        {
            [JsonProperty("PvP Enabled")]
            public bool PvpEnabled;

            [JsonProperty("Last Toggle (UTC)")]
            public DateTime LastToggle = DateTime.MinValue;
        }

        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>
            {
                ["Toggle.Enabled"] = "PvP mode is now <color=#ff4444>ON</color>. Other players can hurt you and you can hurt them.",
                ["Toggle.Disabled"] = "PvP mode is now <color=#44ff44>OFF</color>. You are protected from player damage and deal none.",
                ["Toggle.Cooldown"] = "You must wait {0} more seconds before changing your PvP mode.",
                ["Status.On"] = "Your PvP mode is currently ON.",
                ["Status.Off"] = "Your PvP mode is currently OFF.",
                ["NoPermission"] = "You do not have permission to use this command.",
                ["BlockedDamage"] = "Damage blocked: you or your attacker has PvP mode disabled.",
                ["Admin.Toggled"] = "PvP mode for {0} is now {1}.",
                ["Admin.NotFound"] = "No player found matching that name or ID."
            }, 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);
            permission.RegisterPermission(PermAdmin, this);
            permission.RegisterPermission(PermNoCooldown, this);
        }

        private void OnServerInitialized()
        {
            data = Interface.Oxide.DataFileSystem.ReadObject<StoredData>(Name) ?? new StoredData();
        }

        private void OnServerSave()
        {
            if (data != null) Interface.Oxide.DataFileSystem.WriteObject(Name, data);
        }

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

        private bool IsPvpOn(ulong userId)
        {
            PlayerState state;
            if (data != null && data.Players.TryGetValue(userId, out state))
                return state.PvpEnabled;
            return config.DefaultPvpMode;
        }

        private PlayerState GetOrCreateState(ulong userId)
        {
            PlayerState state;
            if (!data.Players.TryGetValue(userId, out state))
            {
                state = new PlayerState { PvpEnabled = config.DefaultPvpMode, LastToggle = DateTime.MinValue };
                data.Players[userId] = state;
            }
            return state;
        }

        [ChatCommand("pvp")]
        private void CmdPvp(BasePlayer player, string command, string[] args)
        {
            if (player == null || !player.IsConnected) return;
            if (!permission.UserHasPermission(player.UserIDString, PermUse))
            {
                player.ChatMessage(Msg("NoPermission", player.UserIDString));
                return;
            }

            if (args != null && args.Length > 0 && args[0].Equals("status", StringComparison.OrdinalIgnoreCase))
            {
                player.ChatMessage(Msg(IsPvpOn(player.userID.Get()) ? "Status.On" : "Status.Off", player.UserIDString));
                return;
            }

            var state = GetOrCreateState(player.userID.Get());

            if (!permission.UserHasPermission(player.UserIDString, PermNoCooldown) && config.ToggleCooldown > 0f)
            {
                double elapsed = (DateTime.UtcNow - state.LastToggle).TotalSeconds;
                if (elapsed < config.ToggleCooldown)
                {
                    player.ChatMessage(Msg("Toggle.Cooldown", player.UserIDString, Math.Ceiling(config.ToggleCooldown - elapsed)));
                    return;
                }
            }

            state.PvpEnabled = !state.PvpEnabled;
            state.LastToggle = DateTime.UtcNow;
            player.ChatMessage(Msg(state.PvpEnabled ? "Toggle.Enabled" : "Toggle.Disabled", player.UserIDString));
            Interface.Oxide.DataFileSystem.WriteObject(Name, data);
        }

        [ConsoleCommand("pvp.toggle")]
        private void CcmdPvpToggle(ConsoleSystem.Arg arg)
        {
            var caller = arg.Player();
            if (caller != null && !permission.UserHasPermission(caller.UserIDString, PermAdmin))
            {
                arg.ReplyWith(Msg("NoPermission", caller.UserIDString));
                return;
            }

            string target = arg.GetString(0, string.Empty);
            if (string.IsNullOrEmpty(target))
            {
                arg.ReplyWith("Usage: pvp.toggle <name or steamid>");
                return;
            }

            var player = BasePlayer.FindAwakeOrSleeping(target);
            if (player == null)
            {
                arg.ReplyWith(Msg("Admin.NotFound", caller == null ? null : caller.UserIDString));
                return;
            }

            var state = GetOrCreateState(player.userID.Get());
            state.PvpEnabled = !state.PvpEnabled;
            state.LastToggle = DateTime.UtcNow;
            Interface.Oxide.DataFileSystem.WriteObject(Name, data);

            arg.ReplyWith(Msg("Admin.Toggled", caller == null ? null : caller.UserIDString, player.displayName, state.PvpEnabled ? "ON" : "OFF"));
            player.ChatMessage(Msg(state.PvpEnabled ? "Toggle.Enabled" : "Toggle.Disabled", player.UserIDString));
        }

        private object OnEntityTakeDamage(BasePlayer player, HitInfo hitInfo)
        {
            if (player == null || hitInfo == null) return null;

            var attacker = hitInfo.InitiatorPlayer;
            if (attacker == null || attacker == player || attacker.IsNpc) return null;

            if (IsPvpOn(player.userID.Get()) && IsPvpOn(attacker.userID.Get())) return null;

            hitInfo.damageTypes.ScaleAll(0f);

            if (config.BlockDamageMessage)
                player.ChatMessage(Msg("BlockedDamage", player.UserIDString));

            return true;
        }
    }
}