[NTP Snippets] Implement snippets expiry

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_reader.h"
 #include "base/location.h"
@@ skipping 130 matching lines @@
     if (!value->GetAsDictionary(&dict))
       return false;
 
     const base::DictionaryValue* content = nullptr;
     if (!dict->GetDictionary(kContentInfo, &content))
       return false;
     scoped_ptr<NTPSnippet> snippet = NTPSnippet::CreateFromDictionary(*content);
     if (!snippet)
       return false;
 
+    // If the snippet has no publish/expiry dates, fill in defaults.
+    if (snippet->publish_date().is_null())
+      snippet->set_publish_date(base::Time::Now());
+    if (snippet->expiry_date().is_null()) {
+      snippet->set_expiry_date(
+          snippet->publish_date() +
+          base::TimeDelta::FromSeconds(2 * kDefaultFetchingIntervalSeconds));
+    }
+
     // 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;
 
-  FOR_EACH_OBSERVER(NTPSnippetsServiceObserver, observers_,
-                    NTPSnippetsServiceLoaded(this));
+  // Immediately remove any already-expired snippets. This will also notify our
+  // observers and schedule the expiry timer.
+  RemoveExpiredSnippets();
+
   return true;
 }
 
 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 snippets from prefs";
 }
 
 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(kContentInfo, snippet->ToDictionary());
     list.Append(std::move(dict));
   }
   pref_service_->Set(prefs::kSnippets, list);
 }
 
+void NTPSnippetsService::RemoveExpiredSnippets() {
+  base::Time expiry = base::Time::Now();
+  snippets_.erase(
+      std::remove_if(snippets_.begin(), snippets_.end(),
+                     [&expiry](const scoped_ptr<NTPSnippet>& snippet) {
+                       return snippet->expiry_date() <= expiry;
+                     }),
+      snippets_.end());
+
+  FOR_EACH_OBSERVER(NTPSnippetsServiceObserver, observers_,
+                    NTPSnippetsServiceLoaded(this));
+
+  // If there are any snippets left, schedule a timer for the next expiry.
+  if (snippets_.empty())
+    return;
+
+  base::Time next_expiry = base::Time::Max();
+  for (const auto& snippet : snippets_) {
+    if (snippet->expiry_date() < next_expiry)
+      next_expiry = snippet->expiry_date();
+  }
+  DCHECK_GT(next_expiry, expiry);
+  expiry_timer_.Start(FROM_HERE, next_expiry - expiry,
+                      base::Bind(&NTPSnippetsService::RemoveExpiredSnippets,
+                                 base::Unretained(this)));
+}
+
 }  // namespace ntp_snippets