Version Enforcement

using HarmonyLib;
using SteamworksNative;

namespace YourNamespace
{
    internal static class RequiredMod
    {
        private const string ModIdentifier = "YourModIdentifier"; // Must change! ex. $"lammas123.{MyPluginInfo.PLUGIN_GUID}";
        private const string ModVersion = MyPluginInfo.PLUGIN_VERSION; // If you're certain there won't be incompatibilities between versions, you may just set this to "1"; to accept anyone with the mod

        private static Harmony _harmony;

        // Call this once in your mod's Load method
        internal static void Init()
        {
            _harmony = new(ModIdentifier);
            _harmony.PatchAll(typeof(RequiredMod));
        }

        // Logic to allow or prevent a client from joining
        // clientModVersion will be string.Empty when the client doesn't have the mod, SteamMatchmaking.GetLobbyMemberData doesn't return null
        private static bool MayClientJoin(string clientModVersion)
        {
            // Some may want to improve this, say, let everyone playing on 1.1.X join, but not those on other major/minor versions (SemVer)
            return clientModVersion == ModVersion;
        }


        // Tell the host you have the mod via lobby member data
        [HarmonyPatch(typeof(SteamManager), nameof(SteamManager.Method_Private_Void_LobbyEnter_t_PDM_1))]
        [HarmonyPostfix]
        internal static void PostSteamManagerLobbyEnter()
            => SteamMatchmaking.SetLobbyMemberData(SteamManager.Instance.currentLobby, ModIdentifier, ModVersion);

        // Kick clients that may not join when they request to
        [HarmonyPatch(typeof(ServerHandle), nameof(ServerHandle.LoadMapRequest))]
        [HarmonyPrefix]
        internal static bool PreServerHandleLoadMapRequest(ulong param_0)
        {
            bool mayJoin = MayClientJoin(SteamMatchmaking.GetLobbyMemberData(SteamManager.Instance.currentLobby, new(param_0), ModIdentifier));

            if (mayJoin)
                return true;

            LobbyManager.Instance.KickPlayer(param_0);
            return false;
        }
    }
}