NTP: Extract JSON requests from Fetcher.

components/ntp_snippets/remote/ntp_snippets_json_request.h

+// Copyright 2016 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_REMOTE_NTP_SNIPPETS_JSON_REQUEST_H_
+#define COMPONENTS_NTP_SNIPPETS_REMOTE_NTP_SNIPPETS_JSON_REQUEST_H_
+
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "base/callback.h"
+#include "base/memory/weak_ptr.h"
+#include "base/optional.h"
+#include "components/ntp_snippets/remote/ntp_snippets_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;
+class TickClock;
+}  // namespace base
+
+class FetchAPI;
+class Personalization;
+
+namespace ntp_snippets {
+class UserClassifier;
+
+namespace internal {
+
+// Enumeration listing all possible variants of dealing with personalization.
+enum class Personalization { kPersonal, kNonPersonal, kBoth };
+
+// Enumeration listing all possible outcomes for fetch attempts. Used for UMA
+// histograms, so do not change existing values. Insert new values at the end,
+// and update the histogram definition.
+enum class FetchResult {
+  SUCCESS,
+  DEPRECATED_EMPTY_HOSTS,
+  URL_REQUEST_STATUS_ERROR,
+  HTTP_ERROR,
+  JSON_PARSE_ERROR,
+  INVALID_SNIPPET_CONTENT_ERROR,
+  OAUTH_TOKEN_ERROR,
+  INTERACTIVE_QUOTA_ERROR,
+  NON_INTERACTIVE_QUOTA_ERROR,
+  RESULT_MAX
+};
+
+enum FetchAPI {
+  CHROME_READER_API,
+  CHROME_CONTENT_SUGGESTIONS_API,
+};
+
+// A single request to query snippets.
+class NTPSnippetsJsonRequest : public net::URLFetcherDelegate {
+ public:
+  // Callbacks for JSON parsing, needed because the parsing is platform-
+  // dependent.
+  using SuccessCallback =
+      base::Callback<void(std::unique_ptr<base::Value> result)>;
+  using ErrorCallback = base::Callback<void(const std::string& error)>;
+  using ParseJSONCallback =
+      base::Callback<void(const std::string& raw_json_string,
+                          const SuccessCallback& success_callback,
+                          const ErrorCallback& error_callback)>;
+
+  // A client can expect error_details only, if there was any error during the
+  // fetching or parsing. In successful cases, it will be an empty string.
+  using CompletedCallback =
+      base::OnceCallback<void(std::unique_ptr<base::Value> result,
+                              FetchResult result_code,
+                              const std::string& error_details)>;
+
+  // Builds authenticated and non-authenticated NTPSnippetsJsonRequests.
+  class Builder {
+   public:
+    Builder();
+    Builder(Builder&&);
+    ~Builder();
+
+    // Builds a Request object that contains all data to fetch new snippets.
+    std::unique_ptr<NTPSnippetsJsonRequest> Build() const;
+
+    Builder& SetAuthentication(const std::string& account_id,
+                               const std::string& auth_header);
+    Builder& SetCreationTime(base::TimeTicks creation_time);
+    Builder& SetFetchAPI(FetchAPI fetch_api);
+    // The language_model borrowed from the fetcher needs to stay alive until
+    // the request body is built.
+    Builder& SetLanguageModel(const translate::LanguageModel* language_model);
+    Builder& SetParams(const NTPSnippetsRequestParams& params);
+    Builder& SetParseJsonCallback(ParseJSONCallback callback);
+    Builder& SetPersonalization(Personalization personalization);
+    // The tick_clock borrowed from the fetcher will be injected into the
+    // request. It will be used at build time and after the fetch returned.
+    // It has to be alive until the request is destroyed.
+    Builder& SetTickClock(base::TickClock* tick_clock);
+    Builder& SetUrl(const GURL& url);
+    Builder& SetUrlRequestContextGetter(
+        const scoped_refptr<net::URLRequestContextGetter>& context_getter);
+    Builder& SetUserClassifier(const UserClassifier& user_classifier);
+
+    // These preview methods allow to inspect the Request without exposing it
+    // publicly.
+    // TODO(fhorschig): Remove these when moving the Builder to
+    // snippets::internal and trigger the request to intercept the request.
+    std::string PreviewRequestBodyForTesting() { return BuildBody(); }
+    std::string PreviewRequestHeadersForTesting() { return BuildHeaders(); }
+    Builder& SetUserClassForTesting(const std::string& user_class) {
+      user_class_ = user_class;
+      return *this;
+    }
+
+   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;
+
+    bool ReturnOnlyPersonalizedResults() const {
+      return !obfuscated_gaia_id_.empty() &&
+             personalization_ == Personalization::kPersonal;
+    }
+
+    void PrepareLanguages(
+        translate::LanguageModel::LanguageInfo* ui_language,
+        translate::LanguageModel::LanguageInfo* other_top_language) const;
+
+    // Only required, if the request needs to be sent.
+    std::string auth_header_;
+    base::TickClock* tick_clock_;
+    FetchAPI fetch_api_;
+    NTPSnippetsRequestParams params_;
+    NTPSnippetsJsonRequest::ParseJSONCallback parse_json_callback_;
+    Personalization personalization_;
+    GURL url_;
+    scoped_refptr<net::URLRequestContextGetter> url_request_context_getter_;
+
+    // Optional properties.
+    std::string obfuscated_gaia_id_;
+    std::string user_class_;
+    const translate::LanguageModel* language_model_;
+
+    DISALLOW_COPY_AND_ASSIGN(Builder);
+  };
+
+  NTPSnippetsJsonRequest(base::Optional<Category> exclusive_category,
+                         base::TickClock* tick_clock,
+                         const ParseJSONCallback& callback);
+  NTPSnippetsJsonRequest(NTPSnippetsJsonRequest&&);
+  ~NTPSnippetsJsonRequest() override;
+
+  void Start(CompletedCallback callback);
+
+  const base::Optional<Category>& exclusive_category() const {
+    return exclusive_category_;
+  }
+
+  base::TimeDelta GetFetchDuration() const;
+  std::string GetResponseString() const;
+
+ private:
+  friend class Builder;
+
+  // URLFetcherDelegate implementation.
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  void ParseJsonResponse();
+  void OnJsonParsed(std::unique_ptr<base::Value> result);
+  void OnJsonError(const std::string& error);
+
+  // The fetcher for downloading the snippets. Only non-null if a fetch is
+  // currently ongoing.
+  std::unique_ptr<net::URLFetcher> url_fetcher_;
+
+  // If set, only return results for this category.
+  base::Optional<Category> exclusive_category_;
+
+  // Use the TickClock from the Fetcher to measure the fetch time. It will be
+  // used on creation and after the fetch returned. It has to be alive until the
+  // request is destroyed.
+  base::TickClock* tick_clock_;
+  base::TimeTicks creation_time_;
+
+  // 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<NTPSnippetsJsonRequest> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(NTPSnippetsJsonRequest);
+};
+
+}  // namespace internal
+
+}  // namespace ntp_snippets
+
+#endif  // COMPONENTS_NTP_SNIPPETS_REMOTE_NTP_SNIPPETS_JSON_REQUEST_H_