[NTP Snippets] Persist the set of snippets in a pref

components/ntp_snippets/ntp_snippets_service.cc

Index: components/ntp_snippets/ntp_snippets_service.cc
diff --git a/components/ntp_snippets/ntp_snippets_service.cc b/components/ntp_snippets/ntp_snippets_service.cc
index c696405d82fc58ec56c79ca21a2d7ced803a2938..88eda32e87db682fcb1d001c74f5f992ff227daa 100644
--- a/components/ntp_snippets/ntp_snippets_service.cc
+++ b/components/ntp_snippets/ntp_snippets_service.cc
@@ -6,11 +6,14 @@
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
-#include "base/json/json_string_value_serializer.h"
+#include "base/json/json_reader.h"
 #include "base/location.h"
 #include "base/path_service.h"
 #include "base/task_runner_util.h"
 #include "base/values.h"
+#include "components/ntp_snippets/pref_names.h"
+#include "components/pref_registry/pref_registry_syncable.h"
+#include "components/prefs/pref_service.h"
 
 namespace {
 
@@ -30,11 +33,13 @@ bool ReadFileToString(const base::FilePath& path, std::string* data) {
 namespace ntp_snippets {
 
 NTPSnippetsService::NTPSnippetsService(
+    PrefService* pref_service,
     scoped_refptr<base::SequencedTaskRunner> file_task_runner,
     const std::string& application_language_code,
     NTPSnippetsScheduler* scheduler,
     scoped_ptr<NTPSnippetsFetcher> snippets_fetcher)
-    : loaded_(false),
+    : pref_service_(pref_service),
+      loaded_(false),
       file_task_runner_(file_task_runner),
       application_language_code_(application_language_code),
       scheduler_(scheduler),
@@ -47,11 +52,21 @@ NTPSnippetsService::NTPSnippetsService(
 
 NTPSnippetsService::~NTPSnippetsService() {}
 
+// static
+void NTPSnippetsService::RegisterProfilePrefs(
+    user_prefs::PrefRegistrySyncable* registry) {
+  registry->RegisterListPref(prefs::kSnippets);
+}
+
 void NTPSnippetsService::Init(bool enabled) {
-  // If enabled, get snippets immediately. If we've downloaded them before,
-  // this will just read from disk.
-  if (enabled)
-    FetchSnippets(false);
+  // If enabled, get any existing snippets immediately from prefs.
+  if (enabled) {
+    LoadFromPrefs();
+
+    // If we don't have any snippets yet, start a fetch.
+    if (snippets_.empty())
+      FetchSnippets(false);
+  }
 
   // The scheduler only exists on Android so far, it's null on other platforms.
   if (!scheduler_)
@@ -83,47 +98,64 @@ void NTPSnippetsService::RemoveObserver(NTPSnippetsServiceObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
+void NTPSnippetsService::OnSnippetsDownloaded(
+    const base::FilePath& download_path) {
+  std::string* downloaded_data = new std::string;
+  base::PostTaskAndReplyWithResult(
+      file_task_runner_.get(), FROM_HERE,
+      base::Bind(&ReadFileToString, download_path, downloaded_data),
+      base::Bind(&NTPSnippetsService::OnFileReadDone,
+                 weak_ptr_factory_.GetWeakPtr(), base::Owned(downloaded_data)));
+}
+
 void NTPSnippetsService::OnFileReadDone(const std::string* json, bool success) {
   if (!success)
     return;
 
   DCHECK(json);
   LoadFromJSONString(*json);
+  StoreToPrefs();
 }
 
 bool NTPSnippetsService::LoadFromJSONString(const std::string& str) {
-  snippets_.clear();
-
-  JSONStringValueDeserializer deserializer(str);
-  int error_code;
-  std::string error_message;
-
-  scoped_ptr<base::Value> deserialized =
-      deserializer.Deserialize(&error_code, &error_message);
+  scoped_ptr<base::Value> deserialized = base::JSONReader::Read(str);
   if (!deserialized)
     return false;
 
-  const base::DictionaryValue* top_dict = NULL;
+  const base::DictionaryValue* top_dict = nullptr;
   if (!deserialized->GetAsDictionary(&top_dict))
     return false;
 
-  const base::ListValue* list = NULL;
+  const base::ListValue* list = nullptr;
   if (!top_dict->GetList("recos", &list))
     return false;
 
-  for (base::Value* const value : *list) {
-    const base::DictionaryValue* dict = NULL;
+  return LoadFromJSONList(*list);
+}
+
+bool NTPSnippetsService::LoadFromJSONList(const base::ListValue& list) {
+  for (const base::Value* const value : list) {
+    const base::DictionaryValue* dict = nullptr;
     if (!value->GetAsDictionary(&dict))
       return false;
 
-    const base::DictionaryValue* content = NULL;
+    const base::DictionaryValue* content = nullptr;
     if (!dict->GetDictionary("contentInfo", &content))
       return false;
-    scoped_ptr<NTPSnippet> snippet =
-        NTPSnippet::NTPSnippetFromDictionary(*content);
+    scoped_ptr<NTPSnippet> snippet = NTPSnippet::CreateFromDictionary(*content);
     if (!snippet)
       return false;
-    snippets_.push_back(std::move(snippet));
+    // Check if we already have a snippet with the same URL. If so, replace it
+    // rather than adding a duplicate.
+    const GURL& url = snippet->url();
+    auto it = std::find_if(snippets_.begin(), snippets_.end(),
+                           [&url](const scoped_ptr<NTPSnippet>& old_snippet) {
+      return old_snippet->url() == url;
+    });
+    if (it != snippets_.end())
+      *it = std::move(snippet);
+    else
+      snippets_.push_back(std::move(snippet));
   }
   loaded_ = true;
 
@@ -132,14 +164,25 @@ bool NTPSnippetsService::LoadFromJSONString(const std::string& str) {
   return true;
 }
 
-void NTPSnippetsService::OnSnippetsDownloaded(
-    const base::FilePath& download_path) {
-  std::string* downloaded_data = new std::string;
-  base::PostTaskAndReplyWithResult(
-      file_task_runner_.get(), FROM_HERE,
-      base::Bind(&ReadFileToString, download_path, downloaded_data),
-      base::Bind(&NTPSnippetsService::OnFileReadDone,
-                 weak_ptr_factory_.GetWeakPtr(), base::Owned(downloaded_data)));
+void NTPSnippetsService::LoadFromPrefs() {
+  // |pref_service_| can be null in tests.
+  if (!pref_service_)
+    return;
+  if (!LoadFromJSONList(*pref_service_->GetList(prefs::kSnippets)))
+    LOG(ERROR) << "Failed to parse " << prefs::kSnippets << " pref";

[Bernhard Bauer, 2016/02/26 17:30:48]

Nit: printing the value of the pref key is not going to be very useful -- just
"Failed to parse snippets from prefs"?

[Marc Treib, 2016/02/29 10:04:42]

Done.

+}
+
+void NTPSnippetsService::StoreToPrefs() {
+  // |pref_service_| can be null in tests.
+  if (!pref_service_)
+    return;
+  base::ListValue list;
+  for (const auto& snippet : snippets_) {
+    scoped_ptr<base::DictionaryValue> dict(new base::DictionaryValue);
+    dict->Set("contentInfo", snippet->ToDictionary());
+    list.Append(std::move(dict));
+  }
+  pref_service_->Set(prefs::kSnippets, list);
 }
 
 }  // namespace ntp_snippets