// SPDX-License-Identifier: GPL-3.0-only
using System;
using System.Collections.Generic;
using System.Reflection;
using System.Runtime.InteropServices;

namespace BlockModLoader
{
    [Flags]
    public enum WhiteListLoader
    {
        None = 0,
        MelonLoader = 1,
        BepInEx = 2,
        UMM = 4,
        All = MelonLoader | BepInEx | UMM
    }

    public static class LoaderGuard
    {
        public static void EnsureAllowed(string modName)
        {
            EnsureAllowed(modName, null);
        }

        public static void EnsureAllowed(string modName, string recommendedLoader)
        {
            EnsureAllowed(modName, WhiteListLoader.None, recommendedLoader);
        }

        public static void EnsureAllowed(string modName, WhiteListLoader whiteListLoader,
            string recommendedLoader = null)
        {
            EnsureAllowed(modName, AppDomain.CurrentDomain.GetAssemblies(), ShowAlert, Environment.FailFast,
                recommendedLoader, whiteListLoader);
        }

        internal static void EnsureAllowed(string modName, IEnumerable<Assembly> assemblies,
            Action<string> showAlert, Action<string> terminate, string recommendedLoader = null,
            WhiteListLoader whiteListLoader = WhiteListLoader.None)
        {
            if ((whiteListLoader & ~WhiteListLoader.All) != 0)
                throw new ArgumentOutOfRangeException(nameof(whiteListLoader));

            foreach (var assembly in assemblies)
            {
                var loader = GetLoader(assembly.GetName().Name);
                if (loader == WhiteListLoader.None || (whiteListLoader & loader) != 0)
                    continue;

                var loaderName = loader == WhiteListLoader.UMM ? "Unity Mod Manager (UMM)" : loader.ToString();
                var message = modName + " cannot run while " + loaderName + " is active.\n\n"
                    + "Remove the unsupported mod loader and follow this mod's installation instructions.\n\n"
                    + (string.IsNullOrWhiteSpace(recommendedLoader)
                        ? string.Empty
                        : "Recommended mod loader: " + recommendedLoader.Trim() + ".\n\n")
                    + "The game will close after this message.";
                // Loader exception handlers can swallow a thrown exception, so termination
                // must happen even if the native dialog fails.
                try { showAlert(message); }
                finally { terminate(message); }
                return;
            }
        }

        private static WhiteListLoader GetLoader(string assemblyName)
        {
            if (string.Equals(assemblyName, "MelonLoader", StringComparison.OrdinalIgnoreCase))
                return WhiteListLoader.MelonLoader;
            if (string.Equals(assemblyName, "BepInEx", StringComparison.OrdinalIgnoreCase)
                || string.Equals(assemblyName, "BepInEx.Core", StringComparison.OrdinalIgnoreCase))
                return WhiteListLoader.BepInEx;
            if (string.Equals(assemblyName, "UnityModManager", StringComparison.OrdinalIgnoreCase))
                return WhiteListLoader.UMM;
            return WhiteListLoader.None;
        }

        private static void ShowAlert(string message)
        {
            Console.Error.WriteLine(message);
            if (Environment.OSVersion.Platform == PlatformID.Win32NT)
                MessageBoxW(IntPtr.Zero, message, "Unsupported mod loader", 0x10 | 0x10000);
        }

        [DllImport("user32.dll", CharSet = CharSet.Unicode, ExactSpelling = true)]
        private static extern int MessageBoxW(IntPtr window, string text, string caption, uint type);
    }
}