[NTP::Push] Add the classes for sending a breaking news subscription request

components/ntp_snippets/breaking_news/subscription_json_request.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_NTP_SNIPPETS_BREAKING_NEWS_SUBSCRIPTION_JSON_REQUEST_H_
+#define COMPONENTS_NTP_SNIPPETS_BREAKING_NEWS_SUBSCRIPTION_JSON_REQUEST_H_
+
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "base/callback.h"
+#include "base/memory/weak_ptr.h"
+#include "base/optional.h"
+#include "base/time/time.h"
+#include "components/ntp_snippets/breaking_news/subscription_request_params.h"
+#include "components/ntp_snippets/status.h"
+#include "components/translate/core/browser/language_model.h"
+#include "google_apis/gaia/oauth2_token_service.h"
+#include "net/http/http_request_headers.h"
+
+namespace base {
+class Value;
+}  // namespace base
+
+namespace ntp_snippets {
+
+namespace internal {
+
+// A single request to subscribe for breaking news via GCM,
+class SubscriptionJsonRequest : public net::URLFetcherDelegate {
+ public:
+  // A client can expect error_details only, if there was any error during the
+  // subscription or parsing. In successful cases, it will be an empty string.
+  using CompletedCallback =
+      base::OnceCallback<void(std::unique_ptr<base::Value> result,
+                              const std::string& error_details)>;
+
+  // Builds authenticated and non-authenticated SubscriptionJsonRequests.
+  class Builder {
+   public:
+    Builder();
+    Builder(Builder&&);
+    ~Builder();
+
+    // Builds a Request object that contains all data to fetch new snippets.
+    std::unique_ptr<SubscriptionJsonRequest> Build() const;
+
+    Builder& SetParams(const SubscriptionRequestParams& params);
+    Builder& SetUrl(const GURL& url);
+    Builder& SetUrlRequestContextGetter(
+        const scoped_refptr<net::URLRequestContextGetter>& context_getter);
+    Builder& SetParseJsonCallback(ParseJSONCallback callback);
+
+   private:
+    std::string BuildHeaders() const;
+    std::string BuildBody() const;
+    std::unique_ptr<net::URLFetcher> BuildURLFetcher(
+        net::URLFetcherDelegate* request,
+        const std::string& headers,
+        const std::string& body) const;
+
+    // Only required, if the request needs to be sent.
+    std::string auth_header_;
+    SubscriptionRequestParams params_;
+    ParseJSONCallback parse_json_callback_;
+    GURL url_;
+    scoped_refptr<net::URLRequestContextGetter> url_request_context_getter_;
+
+    // Optional properties.
+    std::string obfuscated_gaia_id_;
+
+    DISALLOW_COPY_AND_ASSIGN(Builder);
+  };
+
+  SubscriptionJsonRequest(const ParseJSONCallback& callback);

[Bernhard Bauer, 2017/05/31 13:12:45]

How is a client supposed to construct an object of this class -- via this
constructor or via the builder?

[mamir, 2017/05/31 14:25:03]

Via the builder.  Making the constructor private.

+  SubscriptionJsonRequest(SubscriptionJsonRequest&&);
+  ~SubscriptionJsonRequest() override;
+
+  void Start(CompletedCallback callback);
+
+  std::string GetResponseString() const;
+
+ private:
+  // URLFetcherDelegate implementation.
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  // The fetcher for subscrbing. Only non-null if a subscription process is

[Bernhard Bauer, 2017/05/31 13:12:45]

"subscribing"

[mamir, 2017/05/31 14:25:03]

Done.

+  // currently ongoing.
+  std::unique_ptr<net::URLFetcher> url_fetcher_;
+
+  // This callback is called to parse a json string. It contains callbacks for
+  // error and success cases.
+  ParseJSONCallback parse_json_callback_;
+
+  // The callback to notify when URLFetcher finished and results are available.
+  CompletedCallback request_completed_callback_;
+
+  base::WeakPtrFactory<SubscriptionJsonRequest> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(SubscriptionJsonRequest);
+};
+
+}  // namespace internal
+
+}  // namespace ntp_snippets
+
+#endif  // COMPONENTS_NTP_SNIPPETS_BREAKING_NEWS_SUBSCRIPTION_JSON_REQUEST_H_