Introduce a Doodle Fetcher for NTP

components/doodle/doodle_fetcher.cc

+// 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/doodle/doodle_fetcher.h"
+
+#include <utility>
+
+#include "base/strings/string_number_conversions.h"
+#include "base/time/time.h"
+#include "base/values.h"
+#include "components/safe_json/safe_json_parser.h"
+#include "net/base/load_flags.h"
+#include "net/http/http_status_code.h"
+#include "net/url_request/url_fetcher.h"
+#include "url/gurl.h"
+
+using net::URLFetcher;
+
+namespace doodle {
+
+const char kDoodleConfigUrl[] =
+    "https://www.google.com/async/ddljson?ogdeb=ct~2000000007";
+
+namespace {
+
+void ParseJson(
+    const std::string& json,
+    const base::Callback<void(std::unique_ptr<base::Value>)>& success_callback,
+    const base::Callback<void(const std::string&)>& error_callback) {
+  // The response may start with )]}'. Ignore this.
+  const char kResponsePreamble[] = ")]}'";
+
+  base::StringPiece json_sp(json);
+  if (json_sp.starts_with(kResponsePreamble)) {
+    json_sp.remove_prefix(strlen(kResponsePreamble));
+  }
+
+  safe_json::SafeJsonParser::Parse(json_sp.as_string(), success_callback,

[Marc Treib, 2017/01/31 09:46:34]

This is okay for now, but eventually it'll have to be injected, because iOS
doesn't have SafeJsonParser :-/

[fhorschig, 2017/01/31 13:59:18]

Now,there is a constructor that allows injecting a Callback.

+                                   error_callback);
+}
+
+}  // namespace
+
+DoodleConfig::DoodleConfig() : state(DoodleState::UNKNOWN) {}
+DoodleConfig::DoodleConfig(DoodleState doodle_state) : state(doodle_state) {}
+DoodleConfig::~DoodleConfig() = default;
+DoodleConfig::DoodleConfig(const DoodleConfig& config) = default;
+
+DoodleFetcher::DoodleFetcher(net::URLRequestContextGetter* download_context,
+                             GURL base_url)
+    : download_context_(download_context),
+      base_url_(base_url),
+      weak_ptr_factory_(this) {}
+
+DoodleFetcher::~DoodleFetcher() {}
+
+void DoodleFetcher::FetchDoodle(const FinishedCallback& callback) {
+  DCHECK(!callback_);
+  callback_ = callback;
+  // TODO(fhorschig): Store multiple callbacks.
+  // TODO(fhorschig): Cache responses?
+  fetcher_ = URLFetcher::Create(GURL(kDoodleConfigUrl), URLFetcher::GET, this);

[Marc Treib, 2017/01/31 09:46:34]

This should use the passed-in base_url too

[fhorschig, 2017/01/31 13:59:18]

Done.

+  fetcher_->SetRequestContext(download_context_);
+  fetcher_->SetLoadFlags(net::LOAD_DO_NOT_SEND_COOKIES |
+                         net::LOAD_DO_NOT_SAVE_COOKIES);
+  fetcher_->SetAutomaticallyRetryOnNetworkChanges(1);
+  fetcher_->Start();
+}
+
+// net::URLFetcherDelegate implementation.
+void DoodleFetcher::OnURLFetchComplete(const net::URLFetcher* source) {
+  DCHECK_EQ(fetcher_.get(), source);
+  std::unique_ptr<net::URLFetcher> free_fetcher = std::move(fetcher_);
+
+  std::string json_string;
+  if (!(source->GetStatus().is_success() &&
+        source->GetResponseCode() == net::HTTP_OK &&
+        source->GetResponseAsString(&json_string))) {
+    callback_.Run(DoodleConfig(DoodleState::DOWNLOAD_ERROR));
+    return;
+  }
+
+  ParseJson(json_string, base::Bind(&DoodleFetcher::OnJsonParsed,
+                                    weak_ptr_factory_.GetWeakPtr()),
+            base::Bind(&DoodleFetcher::OnJsonParseFailed,
+                       weak_ptr_factory_.GetWeakPtr()));
+}
+
+// ParseJSONCallback Success callback
+void DoodleFetcher::OnJsonParsed(std::unique_ptr<base::Value> json) {
+  std::unique_ptr<base::DictionaryValue> dict =
+      base::DictionaryValue::From(std::move(json));
+  if (!dict.get()) {
+    LOG(ERROR) << "Doodle JSON is not valid";
+    callback_.Run(DoodleConfig(DoodleState::PARSING_ERROR));
+    return;
+  }
+
+  ParseDoodle(std::move(dict));
+}
+
+// ParseJSONCallback Failure callback
+void DoodleFetcher::OnJsonParseFailed(const std::string& error_message) {
+  LOG(ERROR) << "JSON parsing failed: " << error_message;
+  callback_.Run(DoodleConfig(DoodleState::PARSING_ERROR));
+}
+
+void DoodleFetcher::ParseDoodle(std::unique_ptr<base::DictionaryValue> config) {
+  const base::DictionaryValue* ddljson = nullptr;
+  if (!config->GetDictionary("ddljson", &ddljson)) {
+    LOG(ERROR) << "Doodle JSON reponse did not contain 'ddljson' key.";
+    callback_.Run(DoodleConfig(DoodleState::PARSING_ERROR));
+    return;
+  }
+  const base::DictionaryValue* image = nullptr;
+  if (!ddljson->GetDictionary("large_image", &image)) {
+    callback_.Run(DoodleConfig(DoodleState::NO_DOODLE));
+    return;
+  }
+  std::string temp;
+  DoodleConfig result(DoodleState::AVAILABLE);
+  ddljson->GetString("search_url", &temp);

[Marc Treib, 2017/01/31 09:46:34]

What if this (or any of the other url fields) is empty?

[fhorschig, 2017/01/31 13:59:18]

I now return an empty GURL, so is_valid() will fail.
Tests exist.

+  result.search_url = base_url_.Resolve(temp);
+  ddljson->GetString("doodle_type", &result.doodle_type);
+  double timediff;
+  ddljson->GetDouble("time_to_live_ms", &timediff);

[Marc Treib, 2017/01/31 09:46:34]

nit: Add a comment on why double

[fhorschig, 2017/01/31 13:59:18]

Done.

+  result.time_to_live_ms =
+      base::Time::Now() + base::TimeDelta::FromMillisecondsD(timediff);
+  ddljson->GetString("fullpage_interactive_url", &temp);
+  result.fullpage_interactive_url = base_url_.Resolve(temp);
+  image->GetString("url", &temp);
+  result.large_image.url = base_url_.Resolve(temp);
+  image->GetString("background_color", &result.large_image.background_color);
+  image->GetInteger("height", &result.large_image.height);
+  image->GetInteger("width", &result.large_image.width);
+
+  callback_.Run(std::move(result));
+}
+
+}  // namespace doodle