// ==++==
// 
//   Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// ==--==
#if FEATURE_WIN32_REGISTRY    

namespace Microsoft.Win32 {
    using System;
    using System.Runtime.InteropServices;
    using System.Runtime.Versioning;

#if !FEATURE_PAL

    /**
     * Registry encapsulation. Contains members representing all top level system
     * keys.
     *
     * @security(checkClassLinking=on)
     */
    //This class contains only static members and does not need to be serializable.
    [ComVisible(true)]
    public static class Registry {
        [System.Security.SecuritySafeCritical]  // auto-generated
        static Registry()
        { 
        }

        /**
         * Current User Key.
         * 
         * This key should be used as the root for all user specific settings.
         */
        [ResourceExposure(ResourceScope.Machine)]
        public static readonly RegistryKey CurrentUser        = RegistryKey.GetBaseKey(RegistryKey.HKEY_CURRENT_USER);
        
        /**
         * Local Machine Key.
         * 
         * This key should be used as the root for all machine specific settings.
         */
        [ResourceExposure(ResourceScope.Machine)]
        public static readonly RegistryKey LocalMachine       = RegistryKey.GetBaseKey(RegistryKey.HKEY_LOCAL_MACHINE);
        
        /**
         * Classes Root Key.
         * 
         * This is the root key of class information.
         */
        [ResourceExposure(ResourceScope.Machine)]
        public static readonly RegistryKey ClassesRoot        = RegistryKey.GetBaseKey(RegistryKey.HKEY_CLASSES_ROOT);
        
        /**
         * Users Root Key.
         * 
         * This is the root of users.
         */
        [ResourceExposure(ResourceScope.Machine)]
        public static readonly RegistryKey Users              = RegistryKey.GetBaseKey(RegistryKey.HKEY_USERS);
        
        /**
         * Performance Root Key.
         * 
         * This is where dynamic performance data is stored on NT.
         */
        [ResourceExposure(ResourceScope.Machine)]
        public static readonly RegistryKey PerformanceData    = RegistryKey.GetBaseKey(RegistryKey.HKEY_PERFORMANCE_DATA);
        
        /**
         * Current Config Root Key.
         * 
         * This is where current configuration information is stored.
         */
        [ResourceExposure(ResourceScope.Machine)]
        public static readonly RegistryKey CurrentConfig      = RegistryKey.GetBaseKey(RegistryKey.HKEY_CURRENT_CONFIG);
        
        /**
         * Dynamic Data Root Key.
         * 
         * LEGACY: This is where dynamic performance data is stored on Win9X.
         * This does not exist on NT.
         */
        [ResourceExposure(ResourceScope.Machine)]
        [Obsolete("The DynData registry key only works on Win9x, which is no longer supported by the CLR.  On NT-based operating systems, use the PerformanceData registry key instead.")]
        public static readonly RegistryKey DynData            = RegistryKey.GetBaseKey(RegistryKey.HKEY_DYN_DATA);

        //
        // Following function will parse a keyName and returns the basekey for it.
        // It will also store the subkey name in the out parameter.
        // If the keyName is not valid, we will throw ArgumentException.
        // The return value shouldn't be null. 
        //
        [System.Security.SecurityCritical]  // auto-generated
        private static RegistryKey GetBaseKeyFromKeyName(string keyName, out string subKeyName) {
            if( keyName == null) {
                throw new ArgumentNullException("keyName");
            }

            string basekeyName;
            int i = keyName.IndexOf('\\');
            if( i != -1) {
                basekeyName = keyName.Substring(0, i).ToUpper(System.Globalization.CultureInfo.InvariantCulture);
            }
            else {
                basekeyName = keyName.ToUpper(System.Globalization.CultureInfo.InvariantCulture);
            }                        
            RegistryKey basekey = null;

            switch(basekeyName) {
                case "HKEY_CURRENT_USER": 
                    basekey = Registry.CurrentUser;
                    break;
                case "HKEY_LOCAL_MACHINE": 
                    basekey = Registry.LocalMachine;
                    break;
                case "HKEY_CLASSES_ROOT": 
                    basekey = Registry.ClassesRoot;
                    break;
                case "HKEY_USERS": 
                    basekey = Registry.Users;
                    break;
                case "HKEY_PERFORMANCE_DATA": 
                    basekey = Registry.PerformanceData;
                    break;
                case "HKEY_CURRENT_CONFIG": 
                    basekey = Registry.CurrentConfig;
                    break;
                case "HKEY_DYN_DATA": 
                    basekey = RegistryKey.GetBaseKey(RegistryKey.HKEY_DYN_DATA);
                    break;                    
                default:
                    throw new ArgumentException(Environment.GetResourceString("Arg_RegInvalidKeyName", "keyName"));
            }            
            if( i == -1 || i == keyName.Length) {
                subKeyName = string.Empty;
            }
            else {
                subKeyName = keyName.Substring(i + 1, keyName.Length - i - 1);
            }
            return basekey;
        }

        [System.Security.SecuritySafeCritical]  // auto-generated
        [ResourceExposure(ResourceScope.Machine)]
        [ResourceConsumption(ResourceScope.Machine)]
        public static object GetValue(string keyName, string valueName, object defaultValue ) {
            string subKeyName;
            RegistryKey basekey = GetBaseKeyFromKeyName(keyName, out subKeyName);
            BCLDebug.Assert(basekey != null, "basekey can't be null.");
            RegistryKey key = basekey.OpenSubKey(subKeyName);
            if(key == null) { // if the key doesn't exist, do nothing
                return null;
            }
            try {
                return key.GetValue(valueName, defaultValue);                
            }            
            finally {
                key.Close();
            }            
        }
        
        [ResourceExposure(ResourceScope.Machine)]
        [ResourceConsumption(ResourceScope.Machine)]
        public static void SetValue(string keyName, string valueName, object value ) {
            SetValue(keyName, valueName, value, RegistryValueKind.Unknown);            
        }
        
        [System.Security.SecuritySafeCritical]  // auto-generated
        [ResourceExposure(ResourceScope.Machine)]
        [ResourceConsumption(ResourceScope.Machine)]
        public static void SetValue(string keyName, string valueName, object value, RegistryValueKind valueKind ) {
            string subKeyName; 
            RegistryKey basekey = GetBaseKeyFromKeyName(keyName, out subKeyName);
            BCLDebug.Assert(basekey != null, "basekey can't be null!");                
            RegistryKey key = basekey.CreateSubKey(subKeyName);
            BCLDebug.Assert(key != null, "An exception should be thrown if failed!");
            try {
                key.SetValue(valueName, value, valueKind);            
            }
            finally {
                key.Close();
            }
        }                
    }

#endif // !FEATURE_PAL
}
#endif // FEATURE_WIN32_REGISTRY