Download web payment manifests.

components/payments/content/android/payment_manifest_downloader.h

+// 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.
+
+#ifndef COMPONENTS_PAYMENTS_CONTENT_ANDROID_PAYMENT_MANIFEST_DOWNLOADER_H_
+#define COMPONENTS_PAYMENTS_CONTENT_ANDROID_PAYMENT_MANIFEST_DOWNLOADER_H_
+
+#include <memory>
+#include <string>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "url/gurl.h"
+
+namespace net {
+class URLRequestContextGetter;
+}
+
+namespace payments {
+
+// Downloader of the payment method manifest based on the payment method name
+// that is a URL with HTTPS scheme, e.g., https://bobpay.com. The download
+// happens via two consecutive HTTP requests:
+//
+// 1) HEAD request for the payment method name. The HTTP response header is
+//    parsed for Link header that points to the location of the payment method
+//    manifest file. Example of a relative location:
+//
+//      Link: <data/payment-manifest.json>; rel="payment-method-manifest"
+//
+//    (This is relative to the payment method URL.) Example of an absolute
+//    location:
+//
+//      Link: <https://bobpay.com/data/payment-manifest.json>;
+//      rel="payment-method-manifest"
+//
+//    The absolute location must use HTTPS scheme.
+//
+// 2) GET request for the payment method manifest file.
+//
+// The downloader does not follow redirects. A download succeeds only if both
+// HTTP response codes are 200.
+class PaymentManifestDownloader : public net::URLFetcherDelegate {
+ public:
+  // The interface for receiving the result of downloading a manifest.
+  class Delegate {
+   public:
+    // Called when a manifest has been successfully downloaded.
+    virtual void OnManifestDownloadSuccess(const std::string& content) = 0;
+
+    // Called when failed to download the manifest for any reason:
+    //  - HTTP response code is not 200.
+    //  - HTTP response headers are absent.
+    //  - HTTP response headers does not contain Link headers.
+    //  - Link header does not contain rel="payment-method-manifest".
+    //  - Link header does not contain a valid URL.
+    //  - HTTP GET on the manifest URL returns empty content.
+    virtual void OnManifestDownloadFailure() = 0;
+
+   protected:
+    virtual ~Delegate() {}
+  };
+
+  // |delegate| should not be null and must outlive this object. |method_name|
+  // should be a valid URL that starts with "https://".
+  PaymentManifestDownloader(
+      const scoped_refptr<net::URLRequestContextGetter>& context,
+      const GURL& method_name,
+      Delegate* delegate);
+
+  ~PaymentManifestDownloader() override;
+
+  void Download();
+
+ private:
+  void InitiateDownload(const GURL& url,
+                        net::URLFetcher::RequestType request_type);
+
+  // net::URLFetcherDelegate
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  scoped_refptr<net::URLRequestContextGetter> context_;
+  const GURL method_name_;
+
+  // Non-owned. Never null. Outlives this object.
+  Delegate* delegate_;
+
+  bool is_downloading_http_link_header_;
+  std::unique_ptr<net::URLFetcher> fetcher_;
+
+  DISALLOW_COPY_AND_ASSIGN(PaymentManifestDownloader);
+};
+
+}  // namespace payments
+
+#endif  // COMPONENTS_PAYMENTS_CONTENT_ANDROID_PAYMENT_MANIFEST_DOWNLOADER_H_