// Copyright (c) Ben A Adams. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System.Threading;

namespace DTLib.Ben.Demystifier.Internal;

/// <summary>
///     A helper class that contains utilities methods for dealing with reflection.
/// </summary>
public static class ReflectionHelper
{
    private static PropertyInfo? transformerNamesLazyPropertyInfo;

    /// <summary>
    ///     Returns true if the <paramref name="type" /> is a value tuple type.
    /// </summary>
    public static bool IsValueTuple(this Type type)
    {
        return type.Namespace == "System" && type.Name.Contains("ValueTuple`");
    }

    /// <summary>
    ///     Returns true if the given <paramref name="attribute" /> is of type <code>TupleElementNameAttribute</code>.
    /// </summary>
    /// <remarks>
    ///     To avoid compile-time dependency hell with System.ValueTuple, this method uses reflection and not checks statically
    ///     that
    ///     the given <paramref name="attribute" /> is <code>TupleElementNameAttribute</code>.
    /// </remarks>
    public static bool IsTupleElementNameAttribute(this Attribute attribute)
    {
        var attributeType = attribute.GetType();
        return attributeType.Namespace == "System.Runtime.CompilerServices" &&
               attributeType.Name == "TupleElementNamesAttribute";
    }

    /// <summary>
    ///     Returns 'TransformNames' property value from a given <paramref name="attribute" />.
    /// </summary>
    /// <remarks>
    ///     To avoid compile-time dependency hell with System.ValueTuple, this method uses reflection
    ///     instead of casting the attribute to a specific type.
    /// </remarks>
    public static IList<string>? GetTransformerNames(this Attribute attribute)
    {
        Debug.Assert(attribute.IsTupleElementNameAttribute());

        var propertyInfo = GetTransformNamesPropertyInfo(attribute.GetType())!;
        return propertyInfo.GetValue(attribute) as IList<string>;
    }

    private static PropertyInfo GetTransformNamesPropertyInfo(Type attributeType)
    {
#pragma warning disable 8634
        return LazyInitializer.EnsureInitialized(ref transformerNamesLazyPropertyInfo,
#pragma warning restore 8634
            () => attributeType.GetProperty("TransformNames", BindingFlags.Instance | BindingFlags.Public)!)!;
    }
}