manager-service/ManagerService.Tests/Infrastructure/FakeHttpClientFactory.cs

using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;

namespace ManagerService.Tests.Infrastructure
{
    /// <summary>
    /// Fabrique d'HttpClient sans réseau, pour les chemins qui sondent le poids d'un blob
    /// par HEAD (<c>ResourceSizeProbe</c>). Les tailles sont données par URL ; une URL
    /// absente de la table répond sans <c>Content-Length</c>, ce qui est exactement le cas
    /// « blob introuvable » que le backfill doit inventorier au lieu de le compter pour zéro.
    /// </summary>
    public class FakeHttpClientFactory : IHttpClientFactory
    {
        private readonly IDictionary<string, long> _sizesByUrl;
        private readonly ISet<string> _throwingUrls;

        public FakeHttpClientFactory(IDictionary<string, long> sizesByUrl = null, ISet<string> throwingUrls = null)
        {
            _sizesByUrl = sizesByUrl ?? new Dictionary<string, long>();
            _throwingUrls = throwingUrls ?? new HashSet<string>();
        }

        public HttpClient CreateClient(string name = "") =>
            new HttpClient(new StubHandler(_sizesByUrl, _throwingUrls));

        private class StubHandler : HttpMessageHandler
        {
            private readonly IDictionary<string, long> _sizesByUrl;
            private readonly ISet<string> _throwingUrls;

            public StubHandler(IDictionary<string, long> sizesByUrl, ISet<string> throwingUrls)
            {
                _sizesByUrl = sizesByUrl;
                _throwingUrls = throwingUrls;
            }

            protected override Task<HttpResponseMessage> SendAsync(
                HttpRequestMessage request, CancellationToken cancellationToken)
            {
                var url = request.RequestUri!.ToString();

                if (_throwingUrls.Contains(url))
                    throw new HttpRequestException("hôte injoignable");

                var response = new HttpResponseMessage(HttpStatusCode.OK);
                if (_sizesByUrl.TryGetValue(url, out var size))
                {
                    // Content-Length ne se pose que sur un contenu : un HEAD réel renvoie
                    // l'en-tête sans le corps, ce que StringContent + la longueur imite
                    // suffisamment pour la sonde, qui ne lit que l'en-tête.
                    response.Content = new ByteArrayContent(Array.Empty<byte>());
                    response.Content.Headers.ContentLength = size;
                }
                else
                {
                    response.StatusCode = HttpStatusCode.NotFound;
                    response.Content = new ByteArrayContent(Array.Empty<byte>());
                    response.Content.Headers.ContentLength = null;
                }

                return Task.FromResult(response);
            }
        }
    }
}