/// <summary>
/// Performs a potentially CORS-enabled fetch from the given URI by
/// using an asynchronous GET request. For more information see:
/// http://www.w3.org/TR/html5/infrastructure.html#potentially-cors-enabled-fetch
/// </summary>
/// <param name="loader">The resource loader to use.</param>
/// <param name="cors">The CORS request to issue.</param>
/// <returns>
/// The active download.
/// </returns>
public static IDownload FetchWithCors(this IResourceLoader loader, CorsRequest cors)
{
var request = cors.Request;
var setting = cors.Setting;
var url = request.Target;
if (request.Origin == url.Origin || url.Scheme == ProtocolNames.Data || url.Href == "about:blank")
{
return loader.FetchFromSameOrigin(url, cors);
}
else if (setting == CorsSetting.Anonymous || setting == CorsSetting.UseCredentials)
{
return loader.FetchFromDifferentOrigin(cors);
}
else if (setting == CorsSetting.None)
{
return loader.FetchWithoutCors(request, cors.Behavior);
}
throw new DomException(DomError.Network);
}
private static IDownload FetchFromSameOrigin(this IResourceLoader loader, Url url, CorsRequest cors)
{
var request = cors.Request;
var download = loader.DownloadAsync(new ResourceRequest(request.Source, url)
{
Origin = request.Origin,
IsManualRedirectDesired = true
});
return download.Wrap(response =>
{
if (response.IsRedirected())
{
url.Href = response.Headers.GetOrDefault(HeaderNames.Location, url.Href);
return request.Origin.Is(url.Origin) ?
loader.FetchWithCors(cors.RedirectTo(url)) :
loader.FetchFromSameOrigin(url, cors);
}
return cors.CheckIntegrity(download);
});
}
private static IDownload FetchFromDifferentOrigin(this IResourceLoader loader, CorsRequest cors)
{
var request = cors.Request;
request.IsCredentialOmitted = cors.IsAnonymous();
var download = loader.DownloadAsync(request);
return download.Wrap(response =>
{
if (response?.StatusCode != HttpStatusCode.OK)
{
response?.Dispose();
throw new DomException(DomError.Network);
}
return cors.CheckIntegrity(download);
});
}