[NTP Snippets] Schedule periodic fetching

components/ntp_snippets/ntp_snippets_service.cc

 // Copyright 2015 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/ntp_snippets/ntp_snippets_service.h"
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/json/json_string_value_serializer.h"
 #include "base/location.h"
 #include "base/path_service.h"
 #include "base/task_runner_util.h"
 #include "base/values.h"
 
 namespace ntp_snippets {
 
+namespace {
+
+// TODO(treib): Add a command line param to control this.
+const int kDefaultFetchingIntervalSeconds = 30 * 60;

[Bernhard Bauer, 2016/02/16 16:19:08]

TBH, while we are testing this feature, I would reduce the interval even more,
maybe to 5 minutes, but for production 30 minutes seems very frequently (keep in
mind this unconditionally starts the whole browser process every thirty
minutes).

Longer term, it would be cool to e.g. be more aware of if the browser process is
already running, or to integrate more with history analysis to anticipate times
when the user is likely to actually look at snippets.

[Marc Treib, 2016/02/16 16:54:27]

Eh, IMO the value doesn't really matter yet - I was assuming we'd have the
cmdline flag soon. But sure, reduced to 1 minute for now. (Why not go all the
way :) )
Yup. Something kinda sorta like that is on the roadmap.

+
 std::string ReadFileToString(const base::FilePath& path) {
   std::string data;
   bool success = base::ReadFileToString(path, &data);
   DLOG_IF(ERROR, !success) << "Error reading file " << path.LossyDisplayName();
   return data;
 }
 
+}  // namespace
+
 NTPSnippetsService::NTPSnippetsService(
     scoped_refptr<base::SequencedTaskRunner> file_task_runner,
     const std::string& application_language_code,
+    NTPSnippetsScheduler* scheduler,
     scoped_ptr<NTPSnippetsFetcher> snippets_fetcher)
     : loaded_(false),
       file_task_runner_(file_task_runner),
       application_language_code_(application_language_code),
+      scheduler_(scheduler),
       snippets_fetcher_(std::move(snippets_fetcher)),
       weak_ptr_factory_(this) {
   snippets_fetcher_callback_ = snippets_fetcher_->AddCallback(
       base::Bind(&NTPSnippetsService::OnSnippetsDownloaded,
                  weak_ptr_factory_.GetWeakPtr()));
 }
 
 NTPSnippetsService::~NTPSnippetsService() {}
 
+void NTPSnippetsService::Init(bool enabled) {
+  if (scheduler_) {

[Bernhard Bauer, 2016/02/16 16:19:08]

When would the scheduler be null?

[Marc Treib, 2016/02/16 16:54:27]

I was vaguely thinking of iOS, which has an NTPSnippetsServiceFactory
implementation (that I haven't updated yet) and not much else. Really no point
in that though - removed the null check.

+    if (enabled)
+      scheduler_->Schedule(kDefaultFetchingIntervalSeconds);
+    else
+      scheduler_->Unschedule();
+  }
+}
+
 void NTPSnippetsService::Shutdown() {
   FOR_EACH_OBSERVER(NTPSnippetsServiceObserver, observers_,
                     NTPSnippetsServiceShutdown(this));
   loaded_ = false;
 }
 
 void NTPSnippetsService::FetchSnippets(bool overwrite) {
   snippets_fetcher_->FetchSnippets(overwrite);
 }
 
@@ skipping 53 matching lines @@
 void NTPSnippetsService::OnSnippetsDownloaded(
     const base::FilePath& download_path) {
   base::PostTaskAndReplyWithResult(
       file_task_runner_.get(), FROM_HERE,
       base::Bind(&ReadFileToString, download_path),
       base::Bind(&NTPSnippetsService::OnFileReadDone,
                  weak_ptr_factory_.GetWeakPtr()));
 }
 
 }  // namespace ntp_snippets