// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Net;
using System.Net.Http;
using Microsoft.Extensions.Logging;
 
namespace Microsoft.AspNetCore.Server.IntegrationTesting.IIS;
 
public class RetryHandler : DelegatingHandler
{
    private const int MaxRetries = 5;
    private static readonly TimeSpan RetryDelay = TimeSpan.FromSeconds(1);
 
    private readonly ILogger _logger;
 
    public RetryHandler(HttpMessageHandler innerHandler, ILogger logger)
        : base(innerHandler)
    {
        _logger = logger;
    }
 
    protected override async Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request,
        CancellationToken cancellationToken)
    {
        HttpResponseMessage response = null;
        for (int i = 0; i < MaxRetries; i++)
        {
            response = null;
            try
            {
                response = await base.SendAsync(request, cancellationToken);
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Error sending request");
                if (i == MaxRetries - 1)
                {
                    throw;
                }
            }
 
            // Retry only on 503 that is expected during IIS startup
            if (response != null &&
               (response.IsSuccessStatusCode || response.StatusCode != (HttpStatusCode)503))
            {
                break;
            }
 
            _logger.LogDebug($"Retrying {i + 1}th time after {RetryDelay.Seconds} sec.");
            await Task.Delay(RetryDelay, cancellationToken);
        }
        return response;
    }
}