[Offline Pages] Adding more expiration logic.

components/offline_pages/offline_page_storage_manager.cc

 // 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.
 
 #include "components/offline_pages/offline_page_storage_manager.h"
 
+#include <algorithm>
+
 #include "base/bind.h"
+#include "base/time/clock.h"
+#include "base/time/default_clock.h"
+#include "base/time/time.h"
 #include "components/offline_pages/client_policy_controller.h"
 #include "components/offline_pages/offline_page_client_policy.h"
 #include "components/offline_pages/offline_page_item.h"
 #include "components/offline_pages/offline_page_types.h"
 
 namespace offline_pages {
 
 OfflinePageStorageManager::OfflinePageStorageManager(
     Client* client,
     ClientPolicyController* policy_controller)
     : client_(client),
       policy_controller_(policy_controller),
       in_progress_(false),
+      clock_(new base::DefaultClock()),
       weak_ptr_factory_(this) {}
 
 OfflinePageStorageManager::~OfflinePageStorageManager() {}
 
 void OfflinePageStorageManager::ClearPagesIfNeeded(
     const ClearPageCallback& callback) {
   if (!ShouldClearPages())
     return;
   in_progress_ = true;
   client_->GetAllPages(base::Bind(&OfflinePageStorageManager::ClearExpiredPages,
                                   weak_ptr_factory_.GetWeakPtr(), callback));
 }
 
 void OfflinePageStorageManager::ClearExpiredPages(
     const ClearPageCallback& callback,
     const MultipleOfflinePageItemResult& pages) {
   DCHECK(in_progress_);
   std::vector<int64_t> offline_ids;
   GetExpiredPageIds(pages, offline_ids);
   client_->DeletePagesByOfflineId(
       offline_ids,
       base::Bind(&OfflinePageStorageManager::OnExpiredPagesDeleted,
                  weak_ptr_factory_.GetWeakPtr(), callback, offline_ids.size()));
 }
 
+void OfflinePageStorageManager::SetClockForTesting(
+    std::unique_ptr<base::Clock> clock) {
+  clock_ = std::move(clock);
+}
+
 void OfflinePageStorageManager::GetExpiredPageIds(
     const MultipleOfflinePageItemResult& pages,
     std::vector<int64_t>& offline_ids) {
-  for (const auto& page : pages) {
-    if (IsPageExpired(page))
-      offline_ids.push_back(page.offline_id);
+  base::Time now = clock_->Now();
+
+  // Creating a map from namespace to a vector of page items.
+  // Sort each vector based on last accessed time and all pages after index
+  // min{size(), page_limit} should be expired. And then start iterating
+  // backwards to expire pages.
+  std::map<std::string, std::vector<OfflinePageItem>> pages_map;
+
+  for (const auto& page : pages)
+    pages_map[page.client_id.name_space].push_back(page);
+
+  for (auto& iter : pages_map) {
+    std::string name_space = iter.first;
+    std::vector<OfflinePageItem>& page_list = iter.second;
+
+    LifetimePolicy policy =
+        policy_controller_->GetPolicy(name_space).lifetime_policy;
+
+    std::sort(page_list.begin(), page_list.end(),
+              [](const OfflinePageItem& a, const OfflinePageItem& b) -> bool {
+                return a.last_access_time > b.last_access_time;
+              });
+
+    int page_list_size = page_list.size();
+    int pos = 0;
+    while (pos < page_list_size &&
+           (policy.page_limit == kUnlimitedPages || pos < policy.page_limit) &&
+           !ShouldBeExpired(now, page_list.at(pos))) {
+      pos++;
+    }
+
+    for (int i = pos; i < page_list_size; i++)
+      offline_ids.push_back(page_list.at(i).offline_id);
   }
 }
 
 void OfflinePageStorageManager::OnExpiredPagesDeleted(
     const ClearPageCallback& callback,
     int pages_cleared,
     DeletePageResult result) {
   in_progress_ = false;
   callback.Run(pages_cleared, result);
 }
 
 bool OfflinePageStorageManager::ShouldClearPages() {
   return !in_progress_;
 }
 
-bool OfflinePageStorageManager::IsPageExpired(const OfflinePageItem& page) {
-  base::Time now = base::Time::Now();
+bool OfflinePageStorageManager::ShouldBeExpired(const base::Time& now,
+                                                const OfflinePageItem& page) {
   const LifetimePolicy& policy =
       policy_controller_->GetPolicy(page.client_id.name_space).lifetime_policy;
   return now - page.last_access_time > policy.expiration_period;
 }
 
 }  // namespace offline_pages