// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
namespace Microsoft.AspNetCore.Mvc.ViewFeatures;
 
internal sealed class MemberExpressionCacheKeyComparer : IEqualityComparer<MemberExpressionCacheKey>
{
    public static readonly MemberExpressionCacheKeyComparer Instance = new MemberExpressionCacheKeyComparer();
 
    public bool Equals(MemberExpressionCacheKey x, MemberExpressionCacheKey y)
    {
        if (x.ModelType != y.ModelType)
        {
            return false;
        }
 
        var xEnumerator = x.GetEnumerator();
        var yEnumerator = y.GetEnumerator();
 
        while (xEnumerator.MoveNext())
        {
            if (!yEnumerator.MoveNext())
            {
                return false;
            }
 
            // Current is a MemberInfo instance which has a good comparer.
            if (xEnumerator.Current != yEnumerator.Current)
            {
                return false;
            }
        }
 
        return !yEnumerator.MoveNext();
    }
 
    public int GetHashCode(MemberExpressionCacheKey obj)
    {
        var hashCode = new HashCode();
        hashCode.Add(obj.ModelType);
 
        foreach (var member in obj)
        {
            hashCode.Add(member);
        }
 
        return hashCode.ToHashCode();
    }
}