using System;

namespace ADOFAIRenderer.Util
{
    public static class RegistryUtil
    {
        private static readonly Type? RegistryKeyType;
        private static readonly Type? RegistryHiveType;
        private static readonly Type? RegistryViewType;
        private static readonly System.Reflection.MethodInfo? OpenBaseKeyMethod;
        private static readonly System.Reflection.MethodInfo? OpenSubKeyMethod;
        private static readonly System.Reflection.MethodInfo? GetSubKeyNamesMethod;
        private static readonly System.Reflection.MethodInfo? GetValueMethod;

        static RegistryUtil()
        {
            try
            {
                RegistryKeyType = Type.GetType("Microsoft.Win32.RegistryKey");
                RegistryHiveType = Type.GetType("Microsoft.Win32.RegistryHive");
                RegistryViewType = Type.GetType("Microsoft.Win32.RegistryView");

                if (RegistryKeyType == null || RegistryHiveType == null || RegistryViewType == null)
                {
                    var mscorlib = typeof(object).Assembly;
                    RegistryKeyType = mscorlib.GetType("Microsoft.Win32.RegistryKey");
                    RegistryHiveType = mscorlib.GetType("Microsoft.Win32.RegistryHive");
                    RegistryViewType = mscorlib.GetType("Microsoft.Win32.RegistryView");
                }

                if (RegistryKeyType != null)
                {
                    OpenBaseKeyMethod = RegistryKeyType.GetMethod("OpenBaseKey", new[] { RegistryHiveType!, RegistryViewType! });
                    OpenSubKeyMethod = RegistryKeyType.GetMethod("OpenSubKey", new[] { typeof(string) });
                    GetSubKeyNamesMethod = RegistryKeyType.GetMethod("GetSubKeyNames");
                    GetValueMethod = RegistryKeyType.GetMethod("GetValue", new[] { typeof(string) });
                }
            }
            catch
            {
                // ignored
            }
        }

        private static void CloseKey(object? key)
        {
            if (key == null || RegistryKeyType == null) return;
            try
            {
                if (key is IDisposable disposable)
                {
                    disposable.Dispose();
                }
                else
                {
                    var closeMethod = RegistryKeyType.GetMethod("Close");
                    closeMethod?.Invoke(key, null);
                }
            }
            catch
            {
                // ignored
            }
        }

        public static string[]? GetHKLMSubKeyNames(string parentKeyPath)
        {
            if (RegistryKeyType == null || OpenBaseKeyMethod == null || OpenSubKeyMethod == null || GetSubKeyNamesMethod == null)
                return null;

            try
            {
                object hiveLocalMachine = Enum.ToObject(RegistryHiveType!, 0x80000002);
                object viewRegistry64 = Enum.ToObject(RegistryViewType!, 256);

                object? baseKey = OpenBaseKeyMethod.Invoke(null, new[] { hiveLocalMachine, viewRegistry64 });
                if (baseKey == null) return null;

                object? key = OpenSubKeyMethod.Invoke(baseKey, new object[] { parentKeyPath });
                if (key == null)
                {
                    CloseKey(baseKey);
                    return null;
                }

                string[]? subkeyNames = GetSubKeyNamesMethod.Invoke(key, null) as string[];
                CloseKey(key);
                CloseKey(baseKey);
                return subkeyNames;
            }
            catch
            {
                return null;
            }
        }

        public static string? GetHKLMValue(string keyPath, string valueName)
        {
            if (RegistryKeyType == null || OpenBaseKeyMethod == null || OpenSubKeyMethod == null || GetValueMethod == null)
                return null;

            try
            {
                object hiveLocalMachine = Enum.ToObject(RegistryHiveType!, 0x80000002);
                object viewRegistry64 = Enum.ToObject(RegistryViewType!, 256);

                object? baseKey = OpenBaseKeyMethod.Invoke(null, new[] { hiveLocalMachine, viewRegistry64 });
                if (baseKey == null) return null;

                object? key = OpenSubKeyMethod.Invoke(baseKey, new object[] { keyPath });
                if (key == null)
                {
                    CloseKey(baseKey);
                    return null;
                }

                string? value = GetValueMethod.Invoke(key, new object[] { valueName }) as string;
                CloseKey(key);
                CloseKey(baseKey);
                return value;
            }
            catch
            {
                return null;
            }
        }
    }
}