// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.EmbeddedLanguages.Common
{
    internal readonly struct EmbeddedSyntaxNodeOrToken<TSyntaxKind, TSyntaxNode>
        where TSyntaxKind : struct
        where TSyntaxNode : EmbeddedSyntaxNode<TSyntaxKind, TSyntaxNode>
    {
        private readonly EmbeddedSyntaxToken<TSyntaxKind> _token;

        public readonly TSyntaxNode? Node;

        private EmbeddedSyntaxNodeOrToken(TSyntaxNode? node) : this()
        {
            Node = node;
        }

        private EmbeddedSyntaxNodeOrToken(EmbeddedSyntaxToken<TSyntaxKind> token) : this()
        {
            Debug.Assert((int)(object)token.Kind != 0);
            _token = token;
        }

        public readonly EmbeddedSyntaxToken<TSyntaxKind> Token
        {
            get
            {
                Debug.Assert(Node == null);
                return _token;
            }
        }
        public TSyntaxKind Kind => Node?.Kind ?? Token.Kind;

        [MemberNotNullWhen(true, nameof(Node))]
        public bool IsNode => Node != null;

        public TextSpan? GetFullSpan()
            => IsNode ? Node.GetFullSpan() : _token.GetFullSpan();

        public static implicit operator EmbeddedSyntaxNodeOrToken<TSyntaxKind, TSyntaxNode>(TSyntaxNode? node)
            => new(node);

        public static implicit operator EmbeddedSyntaxNodeOrToken<TSyntaxKind, TSyntaxNode>(EmbeddedSyntaxToken<TSyntaxKind> token)
            => new(token);
    }
}
