// 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.
 
#nullable disable
 
using System;
using System.Diagnostics.Tracing;
using System.Threading;
using Microsoft.CodeAnalysis.Options;
 
namespace Microsoft.CodeAnalysis.Internal.Log
{
    /// <summary>
    /// A logger that publishes events to ETW using an EventSource.
    /// </summary>
    internal sealed class EtwLogger : ILogger
    {
        private readonly Func<FunctionId, bool> _isEnabledPredicate;
 
        // Due to ETW specifics, RoslynEventSource.Instance needs to be initialized during EtwLogger construction 
        // so that we can enable the listeners synchronously before any events are logged.
        private readonly RoslynEventSource _source = RoslynEventSource.Instance;
 
        public EtwLogger(Func<FunctionId, bool> isEnabledPredicate)
            => _isEnabledPredicate = isEnabledPredicate;
 
        public bool IsEnabled(FunctionId functionId)
            => _source.IsEnabled() && _isEnabledPredicate(functionId);
 
        public void Log(FunctionId functionId, LogMessage logMessage)
            => _source.Log(GetMessage(logMessage), functionId);
 
        public void LogBlockStart(FunctionId functionId, LogMessage logMessage, int uniquePairId, CancellationToken cancellationToken)
            => _source.BlockStart(GetMessage(logMessage), functionId, uniquePairId);
 
        public void LogBlockEnd(FunctionId functionId, LogMessage logMessage, int uniquePairId, int delta, CancellationToken cancellationToken)
        {
            if (cancellationToken.IsCancellationRequested)
            {
                _source.BlockCanceled(functionId, delta, uniquePairId);
            }
            else
            {
                _source.BlockStop(functionId, delta, uniquePairId);
            }
        }
 
        private bool IsVerbose()
        {
            // "-1" makes this to work with any keyword
            return _source.IsEnabled(EventLevel.Verbose, (EventKeywords)(-1));
        }
 
        private string GetMessage(LogMessage logMessage)
            => IsVerbose() ? logMessage.GetMessage() : string.Empty;
    }
}