// 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.Diagnostics;
using Microsoft.AspNetCore.Razor.PooledObjects;
 
namespace Microsoft.CodeAnalysis.Razor.Telemetry;
 
internal sealed class TelemetryScope : IDisposable
{
    public static readonly TelemetryScope Null = new();
 
    private readonly ITelemetryReporter? _reporter;
    private readonly string _name;
    private readonly Severity _severity;
    private readonly Property[] _properties;
    private readonly Stopwatch _stopwatch;
    private readonly TimeSpan _minTimeToReport;
    private bool _disposed;
 
    private TelemetryScope()
    {
        // This constructor is only called to initialize the Null instance
        // above. Rather than make _name, _properties, and _stopwatch
        // nullable, we use a ! to initialize them to null for this case only.
        _reporter = null;
        _name = null!;
        _properties = null!;
        _stopwatch = null!;
    }
 
    private TelemetryScope(
        ITelemetryReporter reporter,
        string name,
        TimeSpan minTimeToReport,
        Severity severity,
        Property[] properties)
    {
        _reporter = reporter;
        _name = name;
        _severity = severity;
 
        // Note: The builder that is passed in always has its capacity set to at least
        // 1 larger than the number of properties to allow the final "ellapsedms"
        // property to be added in Dispose below.
        _properties = properties;
 
        _stopwatch = StopwatchPool.Default.Get();
        _minTimeToReport = minTimeToReport;
        _stopwatch.Restart();
    }
 
    public void Dispose()
    {
        if (_reporter is null || _disposed)
        {
            return;
        }
 
        _disposed = true;
 
        _stopwatch.Stop();
 
        var elapsed = _stopwatch.Elapsed;
        if (elapsed >= _minTimeToReport)
        {
            // We know that we were created with an array of at least length one.
            _properties[^1] = new("eventscope.ellapsedms", _stopwatch.ElapsedMilliseconds);
 
            _reporter.ReportEvent(_name, _severity, _properties);
        }
 
        StopwatchPool.Default.Return(_stopwatch);
    }
 
    public static TelemetryScope Create(ITelemetryReporter reporter, string name, Severity severity, TimeSpan minTimeToReport)
    {
        var array = new Property[1];
 
        return new(reporter, name, minTimeToReport, severity, array);
    }
 
    public static TelemetryScope Create(ITelemetryReporter reporter, string name, Severity severity, TimeSpan minTimeToReport, Property property)
    {
        var array = new Property[2];
        array[0] = property;
 
        return new(reporter, name, minTimeToReport, severity, array);
    }
 
    public static TelemetryScope Create(ITelemetryReporter reporter, string name, Severity severity, TimeSpan minTimeToReport, Property property1, Property property2)
    {
        var array = new Property[3];
        array[0] = property1;
        array[1] = property2;
 
        return new(reporter, name, minTimeToReport, severity, array);
    }
 
    public static TelemetryScope Create(ITelemetryReporter reporter, string name, Severity severity, TimeSpan minTimeToReport, Property property1, Property property2, Property property3)
    {
        var array = new Property[4];
        array[0] = property1;
        array[1] = property2;
        array[2] = property3;
 
        return new(reporter, name, minTimeToReport, severity, array);
    }
 
    public static TelemetryScope Create(ITelemetryReporter reporter, string name, Severity severity, TimeSpan minTimeToReport, ReadOnlySpan<Property> properties)
    {
        var array = new Property[properties.Length + 1];
        properties.CopyTo(array);
 
        return new(reporter, name, minTimeToReport, severity, array);
    }
}