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

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Extensions.Internal;

namespace Microsoft.AspNetCore.Razor.Language
{
	internal class DirectiveDescriptorComparer : IEqualityComparer<DirectiveDescriptor>
	{
		public static readonly DirectiveDescriptorComparer Default = new DirectiveDescriptorComparer();

		protected DirectiveDescriptorComparer()
		{
		}

		public bool Equals( DirectiveDescriptor descriptorX, DirectiveDescriptor descriptorY )
		{
			if ( descriptorX == descriptorY )
			{
				return true;
			}

			return descriptorX != null &&
				string.Equals( descriptorX.Directive, descriptorY.Directive, StringComparison.Ordinal ) &&
				descriptorX.Kind == descriptorY.Kind &&
				Enumerable.SequenceEqual(
					descriptorX.Tokens,
					descriptorY.Tokens,
					DirectiveTokenDescriptorComparer.Default );
		}

		public int GetHashCode( DirectiveDescriptor descriptor )
		{
			if ( descriptor == null )
			{
				throw new ArgumentNullException( nameof( descriptor ) );
			}

			var hash = HashCodeCombiner.Start();
			hash.Add( descriptor.Directive, StringComparer.Ordinal );
			hash.Add( descriptor.Kind );

			if ( descriptor.Tokens != null )
			{
				for ( var i = 0; i < descriptor.Tokens.Count; i++ )
				{
					hash.Add( descriptor.Tokens[i] );
				}
			}

			return hash.CombinedHash;
		}
	}
}
