OnTeamLeave

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

namespace Oxide.Plugins
{
    [Info("Team Owner Leave Guard", "RustPluginGenerator", "1.0.0")]
    [Description("Prevents a team leader from leaving while other members are still on the team.")]
    public class TeamOwnerLeaveGuard : RustPlugin
    {
        private const string PermBypass = "teamownerleaveguard.bypass";

        private PluginConfig config;

        private class PluginConfig
        {
            [JsonProperty("Bypass permission name")]
            public string BypassPermission = PermBypass;
        }

        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>
            {
                ["LeaveBlocked"] = "You are the team leader. Kick the remaining members or disband the team before leaving."
            }, this);
        }

        private string Msg(string key, string userId = null) => lang.GetMessage(key, this, userId);

        private void Init()
        {
            permission.RegisterPermission(PermBypass, this);
            if (!string.IsNullOrEmpty(config.BypassPermission) && config.BypassPermission != PermBypass)
                permission.RegisterPermission(config.BypassPermission, this);
        }

        private string ResolvePerm(string userId)
        {
            if (!string.IsNullOrEmpty(config.BypassPermission) && permission.UserHasPermission(userId, config.BypassPermission))
                return config.BypassPermission;
            return permission.UserHasPermission(userId, PermBypass) ? PermBypass : null;
        }

        private object OnTeamLeave(RelationshipManager.PlayerTeam playerTeam, BasePlayer player)
        {
            if (playerTeam == null || player == null) return null;
            if (ResolvePerm(player.UserIDString) != null) return null;

            // Leader may leave only when no other members remain.
            if (playerTeam.teamLeader != player.userID.Get()) return null;
            if (playerTeam.members == null || playerTeam.members.Count <= 1) return null;

            player.ChatMessage(Msg("LeaveBlocked", player.UserIDString));
            return true;
        }
    }
}