// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Collections.Generic;
using System.Runtime.Versioning;
using Microsoft.Win32;

namespace Microsoft.Build.Shared;

/// <summary>
/// Helper methods that simplify registry access.
/// </summary>
[SupportedOSPlatform("windows")]
internal static class RegistryHelper
{
    /// <summary>
    /// Given a baseKey and a subKey, get all of the subkeys names.
    /// </summary>
    /// <param name="baseKey">The base registry key.</param>
    /// <param name="subkey">The subkey</param>
    /// <returns>An enumeration of strings.</returns>
    internal static IEnumerable<string>? GetSubKeyNames(RegistryKey baseKey, string subkey)
    {
        IEnumerable<string>? subKeys = null;

        using (RegistryKey? subKey = baseKey.OpenSubKey(subkey))
        {
            if (subKey != null)
            {
                subKeys = subKey.GetSubKeyNames();
            }
        }

        return subKeys;
    }

    /// <summary>
    /// Given a baseKey and subKey, get the default value of the subKey.
    /// </summary>
    /// <param name="baseKey">The base registry key.</param>
    /// <param name="subkey">The subkey</param>
    /// <returns>A string containing the default value.</returns>
    internal static string? GetDefaultValue(RegistryKey baseKey, string subkey)
    {
        string? value = null;

        using (RegistryKey? key = baseKey.OpenSubKey(subkey))
        {
            if (key?.ValueCount > 0)
            {
                value = (string?)key.GetValue("");
            }
        }

        return value;
    }

    /// <summary>
    /// Given a hive and a hive view open the base key
    ///      RegistryKey baseKey = RegistryKey.OpenBaseKey(hive, view);
    /// </summary>
    /// <param name="hive">The hive.</param>
    /// <param name="view">The hive view</param>
    /// <returns>A registry Key for the given baseKey and view</returns>
    internal static RegistryKey OpenBaseKey(RegistryHive hive, RegistryView view)
    {
        RegistryKey key = RegistryKey.OpenBaseKey(hive, view);
        return key;
    }
}