// 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.Threading;
 
namespace Microsoft.CodeAnalysis.CSharp
{
    internal abstract class LazyDiagnosticInfo : DiagnosticInfo
    {
        private DiagnosticInfo? _lazyInfo;
 
        protected LazyDiagnosticInfo()
            : base(CSharp.MessageProvider.Instance, (int)ErrorCode.Unknown)
        {
        }
 
        internal sealed override DiagnosticInfo GetResolvedInfo()
        {
            if (_lazyInfo == null)
            {
                Interlocked.CompareExchange(ref _lazyInfo, ResolveInfo() ?? CSDiagnosticInfo.VoidDiagnosticInfo, null);
            }
 
            return _lazyInfo;
        }
 
        protected LazyDiagnosticInfo(LazyDiagnosticInfo original, DiagnosticSeverity severity) : base(original, severity)
        {
            _lazyInfo = original._lazyInfo;
        }
 
        protected abstract override DiagnosticInfo GetInstanceWithSeverityCore(DiagnosticSeverity severity);
 
        protected abstract DiagnosticInfo? ResolveInfo();
    }
}