[assembly: FunctionsStartup(typeof(DotNetThoughts.Demo.Startup))]
namespace DotNetThoughts.Demo
{
    public class Startup : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            builder.Services.AddHttpClient();
        }
    }
}

private readonly TelemetryClient _telemetryClient;
private readonly string instrumentationKey = Environment.GetEnvironmentVariable("APPINSIGHTS_INSTRUMENTATIONKEY");
private readonly string webJobAuthenticationToken = Environment.GetEnvironmentVariable("WEBJOB_AUTHORIZATION");
private readonly string webJobRESTEndpoint = Environment.GetEnvironmentVariable("WEBJOB_RESTENDPOINT");
private const string EndpointAddress = "https://dc.services.visualstudio.com/v2/track";
private readonly IHttpClientFactory _httpClientFactory;
public WebJobAvailability(IHttpClientFactory httpClientFactory)
{
    _httpClientFactory = httpClientFactory;
    _telemetryClient = new TelemetryClient(
            new TelemetryConfiguration(instrumentationKey, 
            new InMemoryChannel { EndpointAddress = EndpointAddress }));
}

[FunctionName("WebJobAvailability")]
public async Task Run([TimerTrigger("0 */1 * * * *")] TimerInfo myTimer, ILogger log)
{
    string testName = "WebJobStatusTest";
    string location = Environment.GetEnvironmentVariable("REGION_NAME");
    string operationId = Guid.NewGuid().ToString("N");
    var availabilityTelemetry = new AvailabilityTelemetry
    {
        Id = operationId,
        Name = testName,
        RunLocation = location,
        Success = false
    };

    try
    {
        await ExecuteTestAsync(log);
        availabilityTelemetry.Success = true;
    }
    catch (Exception ex)
    {
        availabilityTelemetry.Message = ex.Message;

        var exceptionTelemetry = new ExceptionTelemetry(ex);
        exceptionTelemetry.Context.Operation.Id = operationId;
        exceptionTelemetry.Properties.Add("TestName", testName);
        exceptionTelemetry.Properties.Add("TestLocation", location);
        _telemetryClient.TrackException(exceptionTelemetry);
    }
    finally
    {
        _telemetryClient.TrackAvailability(availabilityTelemetry);
        _telemetryClient.Flush();
    }
}

public async Task ExecuteTestAsync(ILogger log)
{
    log.LogInformation("RunAvailabilityTestAsync - Started.");
    var httpClient = _httpClientFactory.CreateClient();
    httpClient.DefaultRequestHeaders.Authorization =
        new AuthenticationHeaderValue("Basic", webJobAuthenticationToken);
    var webJobResponseJson = await httpClient.GetStringAsync(webJobRESTEndpoint);
    var webJobResponse = JsonSerializer.Deserialize<WebJobResponse>(webJobResponseJson);
    if (!webJobResponse.LatestRun.Status.Equals("Success", StringComparison.OrdinalIgnoreCase))
    {
        throw new Exception("Latest Run status is not success.");
    }
}