OnPlayerOfflineChat

using System;
using System.Collections.Generic;
using Newtonsoft.Json;
using Oxide.Core;
using Oxide.Core.Libraries.Covalence;
using UnityEngine;
using Rust;

namespace Oxide.Plugins
{
    [Info("Offline Chat Relay", "RustPluginGenerator", "1.0.0")]
    [Description("Relays team-channel chat sent from the Rust+ app to online teammates.")]
    public class OfflineChatRelay : RustPlugin
    {
        private const string PermUse = "offlinechatrelay.use";

        private PluginConfig config;

        private class PluginConfig
        {
            [JsonProperty("Prefix with sender name")]
            public bool ShowSenderName = true;

            [JsonProperty("Only relay if sender has permission")]
            public bool RequirePermission = false;
        }

        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>
            {
                ["Relay"] = "[Rust+] {0}: {1}",
                ["RelayAnon"] = "[Rust+] {0}"
            }, 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);
        }

        private object OnPlayerOfflineChat(ulong playerid, string playerName, string message, ConVar.Chat.ChatChannel channel)
        {
            if (channel != ConVar.Chat.ChatChannel.Team) return null;
            if (string.IsNullOrEmpty(message)) return null;
            if (config.RequirePermission && !permission.UserHasPermission(playerid.ToString(), PermUse)) return null;

            var player = BasePlayer.FindByID(playerid);
            if (player == null || player.currentTeam == 0) return null;

            var team = RelationshipManager.ServerInstance.FindTeam(player.currentTeam);
            if (team == null || team.members == null) return null;

            foreach (var memberId in team.members)
            {
                if (memberId == playerid) continue;

                var member = BasePlayer.FindByID(memberId);
                if (member == null || !member.IsConnected) continue;

                member.ChatMessage(config.ShowSenderName
                    ? Msg("Relay", member.UserIDString, playerName, message)
                    : Msg("RelayAnon", member.UserIDString, message));
            }

            return null;
        }
    }
}