OnClanMemberLeft

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

namespace Oxide.Plugins
{
    [Info("Clan Leave Notifier", "RustPluginGenerator", "1.0.0")]
    [Description("Announces to online clan members when someone leaves their clan.")]
    public class ClanLeaveNotifier : RustPlugin
    {
        private class PluginConfig
        {
            [JsonProperty("Announce departures in chat")]
            public bool Announce { get; set; } = true;
        }

        private PluginConfig config;

        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>
            {
                ["Left"] = "{0} has left the clan.",
                ["Unknown"] = "A clan member has left the clan."
            }, this);
        }

        private string Msg(string key, string userId = null, params object[] args)
            => string.Format(lang.GetMessage(key, this, userId), args);

        private void OnClanMemberLeft(ulong clanId, ulong steamId)
        {
            if (!config.Announce) return;

            string leaverId = steamId.ToString();
            BasePlayer leaver = BasePlayer.FindByID(steamId);
            string text = leaver != null && !string.IsNullOrEmpty(leaver.displayName)
                ? Msg("Left", leaverId, leaver.displayName)
                : Msg("Unknown", leaverId);

            object clan = Interface.CallHook("GetClan", clanId);
            if (clan == null) return;

            var membersObj = clan.GetType().GetProperty("Members")?.GetValue(clan, null) as System.Collections.IEnumerable;
            if (membersObj == null) return;

            foreach (var member in membersObj)
            {
                if (member == null) continue;

                var steamIdProp = member.GetType().GetProperty("SteamId");
                if (steamIdProp == null) continue;
                if (!(steamIdProp.GetValue(member, null) is ulong memberId)) continue;
                if (memberId == steamId) continue;

                BasePlayer player = BasePlayer.FindByID(memberId);
                if (player == null || !player.IsConnected || player.IsSleeping()) continue;

                player.ChatMessage(text);
            }
        }
    }
}