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

using System.Collections;
using System.Diagnostics.Tracing;
using System.Text;

namespace ZymonicServices;

/// <summary>
/// Logging helper for tests.
/// Logs event source events into test output.
/// Example usage:
///   // Put the following line into your test method:
///   using var listener = new ZymonicEventListener(logger, ZymonicEventListener.NetworkingEvents);
/// </summary>
public sealed class ZymonicEventListener : EventListener
{
    public static string[] NetworkingEvents => new[]
    {
        "System.Net.Http",
        "System.Net.NameResolution",
        "System.Net.Sockets",
        "System.Net.Security",
        "System.Net.TestLogging",
        "Private.InternalDiagnostics.System.Net.Http",
        "Private.InternalDiagnostics.System.Net.NameResolution",
        "Private.InternalDiagnostics.System.Net.Sockets",
        "Private.InternalDiagnostics.System.Net.Security",
        "Private.InternalDiagnostics.System.Net.Quic",
        "Private.InternalDiagnostics.System.Net.Http.WinHttpHandler",
        "Private.InternalDiagnostics.System.Net.HttpListener",
        "Private.InternalDiagnostics.System.Net.Mail",
        "Private.InternalDiagnostics.System.Net.NetworkInformation",
        "Private.InternalDiagnostics.System.Net.Primitives",
        "Private.InternalDiagnostics.System.Net.Requests",
    };

    	private IZymonicLogger _logger;

    private readonly HashSet<string> _sourceNames;

    // Until https://github.com/dotnet/runtime/issues/63979 is solved.
    private List<EventSource> _eventSources = new List<EventSource>();

    public ZymonicEventListener(IZymonicLogger logger, params string[] sourceNames)
    {
        List<EventSource> eventSources = _eventSources;

        lock (this)
        {
            _logger = logger;
            _sourceNames = new HashSet<string>(sourceNames);
            // Commented out line below as it generates a warning
            //_eventSources = null;
        }

        // eventSources were populated in the base ctor and are now owned by this thread, enable them now.
        foreach (EventSource eventSource in eventSources)
        {
            if (_sourceNames.Contains(eventSource.Name))
            {
                EnableEvents(eventSource, EventLevel.LogAlways);
            }
        }
    }

    protected override void OnEventSourceCreated(EventSource eventSource)
    {
        // We're likely called from base ctor, if so, just save the event source for later initialization.
        if (_sourceNames is null)
        {
            lock (this)
            {
                if (_sourceNames is null)
                {
                    _eventSources.Add(eventSource);
                    return;
                }
            }
        }

        // Second pass called after our ctor, allow logging for specified source names.
        if (_sourceNames.Contains(eventSource.Name))
        {
            EnableEvents(eventSource, EventLevel.LogAlways);
        }
    }

    protected override void OnEventWritten(EventWrittenEventArgs eventData)
    {
        ArrayList paramObjs = new ArrayList();
        StringBuilder sb = new StringBuilder().
#if NET || NETSTANDARD2_1_OR_GREATER
            Append("{TimeStamp}[{EventName}] ");
            paramObjs.Add(eventData.TimeStamp);
            paramObjs.Add(eventData.EventName);
#else
            Append("[{EventName}] ");
            paramObjs.Add(eventData.EventName);
#endif
        for (int i = 0; i < eventData.Payload?.Count; i++)
        {
            if (i > 0)
                sb.Append(", ");
            sb.Append(eventData.PayloadNames?[i]).Append(": {").Append(eventData.PayloadNames?[i]).Append("}");
            paramObjs.Add(eventData.Payload[i]);
        }
        try
        {
            _logger.LogTrace(sb.ToString(), paramObjs.ToArray()!);
        }
        catch { }
    }
}