Download web payment manifests.

components/payments/payment_manifest_downloader.cc

Index: components/payments/payment_manifest_downloader.cc
diff --git a/components/payments/payment_manifest_downloader.cc b/components/payments/payment_manifest_downloader.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6847bcbbb396211afc871065c9c7189efdab6ac8
--- /dev/null
+++ b/components/payments/payment_manifest_downloader.cc
@@ -0,0 +1,110 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/payments/payment_manifest_downloader.h"
+
+#include <unordered_map>

[xunjieli, 2017/02/24 18:18:30]

nit: not used.

[please use gerrit instead, 2017/03/03 03:11:17]

Used on line 83:
std::unordered_map<std::string, base::Optional<std::string>> params;

+#include <utility>
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "components/data_use_measurement/core/data_use_user_data.h"
+#include "components/link_header_util/link_header_util.h"
+#include "net/base/load_flags.h"
+#include "net/http/http_response_headers.h"
+#include "net/url_request/url_request_context_getter.h"
+#include "url/url_constants.h"
+
+namespace payments {
+namespace {
+
+bool IsValidManifestUrl(const GURL& url) {
+  return url.is_valid() && url.SchemeIs(url::kHttpsScheme);
+}
+
+}  // namespace
+
+PaymentManifestDownloader::PaymentManifestDownloader(
+    const scoped_refptr<net::URLRequestContextGetter>& context,
+    const GURL& method_name,
+    Delegate* delegate)
+    : context_(context),
+      method_name_(method_name),
+      delegate_(delegate),
+      is_downloading_http_link_header_(true) {
+  DCHECK(IsValidManifestUrl(method_name_));
+}
+
+PaymentManifestDownloader::~PaymentManifestDownloader() {}
+
+void PaymentManifestDownloader::Download() {
+  InitiateDownload(method_name_, net::URLFetcher::HEAD);
+}
+
+void PaymentManifestDownloader::InitiateDownload(
+    const GURL& url,
+    net::URLFetcher::RequestType request_type) {
+  if (!IsValidManifestUrl(url)) {
+    delegate_->OnManifestDownloadFailure();
+    return;
+  }
+
+  fetcher_ = net::URLFetcher::Create(0 /* id */, url, request_type, this);
+  data_use_measurement::DataUseUserData::AttachToFetcher(
+      fetcher_.get(), data_use_measurement::DataUseUserData::PAYMENTS);
+  fetcher_->SetLoadFlags(net::LOAD_DO_NOT_SEND_COOKIES |
+                         net::LOAD_DO_NOT_SAVE_COOKIES);
+  fetcher_->SetStopOnRedirect(true);
+  fetcher_->SetRequestContext(context_.get());
+  fetcher_->Start();
+}
+
+void PaymentManifestDownloader::OnURLFetchComplete(
+    const net::URLFetcher* source) {
+  if (source->GetResponseCode() != 200) {

[xunjieli, 2017/02/24 18:18:30]

nit: net::HTTP_OK

[please use gerrit instead, 2017/03/03 03:11:17]

Done.

+    delegate_->OnManifestDownloadFailure();
+    return;
+  }
+
+  if (is_downloading_http_link_header_) {
+    is_downloading_http_link_header_ = false;
+
+    net::HttpResponseHeaders* headers = source->GetResponseHeaders();
+    if (headers == nullptr) {
+      delegate_->OnManifestDownloadFailure();
+      return;
+    }
+
+    std::string link_header;
+    headers->GetNormalizedHeader("link", &link_header);
+    if (!link_header.empty()) {
+      std::string manifest_url;
+      std::unordered_map<std::string, base::Optional<std::string>> params;
+      for (const auto& value : link_header_util::SplitLinkHeader(link_header)) {
+        if (!link_header_util::ParseLinkHeaderValue(value.first, value.second,
+                                                    &manifest_url, &params)) {
+          break;

[Marijn Kruisselbrink, 2017/02/23 20:55:22]

Should this be continue rather than break? For example should one invalid link
header cause all later link headers to be ignored?

[please use gerrit instead, 2017/03/03 03:11:17]

Done.

+        }
+
+        auto rel = params.find("rel");
+        if (rel != params.end() &&
+            rel->second.value_or("") == "payment-method-manifest") {

[Marijn Kruisselbrink, 2017/02/23 20:55:21]

This doesn't seem entirely spec compliant.
https://tools.ietf.org/html/rfc5988#section-5 defines the value of the rel param
as possibly multiple space seperated relation types, so you probably want to
pass the value of the rel param through something like
base::SplitStringPiece(rel, HTTP_LWS, base::TRIM_WHITESPACE,
base::SPLIT_WANT_NON_EMPTY)

(it's of course unlikely to be useful to use the same URL both as
payment-method-manifest and some other link relation type, but still better to
be spec compliant).

[please use gerrit instead, 2017/03/03 03:11:17]

Done.

+          InitiateDownload(method_name_.Resolve(manifest_url),
+                           net::URLFetcher::GET);
+          return;
+        }
+      }
+    }
+  } else {
+    std::string content;
+    if (source->GetResponseAsString(&content) && !content.empty()) {
+      delegate_->OnManifestDownloadSuccess(content);
+      return;
+    }
+  }
+
+  delegate_->OnManifestDownloadFailure();
+}
+
+}  // namespace payments