chrome/browser/performance_manager/policies/page_discarding_helper.h

// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CHROME_BROWSER_PERFORMANCE_MANAGER_POLICIES_PAGE_DISCARDING_HELPER_H_
#define CHROME_BROWSER_PERFORMANCE_MANAGER_POLICIES_PAGE_DISCARDING_HELPER_H_

#include "base/containers/flat_map.h"
#include "base/functional/callback_forward.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/weak_ptr.h"
#include "base/time/time.h"
#include "components/performance_manager/public/decorators/page_live_state_decorator.h"
#include "components/performance_manager/public/features.h"
#include "components/performance_manager/public/graph/graph.h"
#include "components/performance_manager/public/graph/graph_registered.h"
#include "components/performance_manager/public/graph/node_data_describer.h"
#include "components/performance_manager/public/graph/page_node.h"
#include "third_party/abseil-cpp/absl/types/optional.h"

namespace url_matcher {
class URLMatcher;
}  // namespace url_matcher

namespace performance_manager {

namespace mechanism {
class PageDiscarder;
}  // namespace mechanism

namespace policies {

// Caches page node properties to facilitate sorting.
class PageNodeSortProxy {
 public:
  PageNodeSortProxy(const PageNode* page_node,
                    bool is_marked,
                    bool is_protected,
                    base::TimeDelta last_visible)
      : page_node_(page_node),
        is_marked_(is_marked),
        is_protected_(is_protected),
        last_visible_(last_visible) {}
  const PageNode* page_node() const { return page_node_; }

  // Returns true if the rhs is more important.
  bool operator<(const PageNodeSortProxy& rhs) const {
    if (is_marked_ && !rhs.is_marked_)
      return false;
    if (!is_marked_ && rhs.is_marked_)
      return true;
    if (is_protected_ && !rhs.is_protected_)
      return false;
    if (!is_protected_ && rhs.is_protected_)
      return true;
    return last_visible_ > rhs.last_visible_;
  }

 private:
  raw_ptr<const PageNode> page_node_;
  bool is_marked_;
  bool is_protected_;
  // Delta between current time and last visibility change time.
  base::TimeDelta last_visible_;
};

// Helper class to be used by the policies that want to discard tabs.
//
// This is a GraphRegistered object and should be accessed via
// PageDiscardingHelper::GetFromGraph(graph()).
class PageDiscardingHelper : public GraphOwned,
                             public PageNode::ObserverDefaultImpl,
                             public GraphRegisteredImpl<PageDiscardingHelper>,
                             public NodeDataDescriberDefaultImpl {
 public:
  enum class CanUrgentlyDiscardResult {
    // Discarding eligible nodes is hard to notice for user.
    kEligible,
    // Discarding protected nodes is noticeable to user.
    kProtected,
    // Marked nodes can never be discarded.
    kMarked,
  };

  PageDiscardingHelper();
  ~PageDiscardingHelper() override;
  PageDiscardingHelper(const PageDiscardingHelper& other) = delete;
  PageDiscardingHelper& operator=(const PageDiscardingHelper&) = delete;

  // Selects a tab to discard and posts to the UI thread to discard it. This
  // will try to discard a tab until there's been a successful discard or until
  // there's no more discard candidate.
  void UrgentlyDiscardAPage(base::OnceCallback<void(bool)> post_discard_cb);

  // Discards multiple tabs to meet the reclaim target based and posts to the UI
  // thread to discard these tabs. Retries discarding if all discardings in the
  // UI thread fail. If |reclaim_target_kb| is nullopt, only discard one tab. If
  // |discard_protected_tabs| is true, protected tab (CanUrgentlyDiscard()
  // returns kProtected) can also be discarded.
  void UrgentlyDiscardMultiplePages(
      absl::optional<uint64_t> reclaim_target_kb,
      bool discard_protected_tabs,
      base::OnceCallback<void(bool)> post_discard_cb);

  void ImmediatelyDiscardSpecificPage(const PageNode* page_node);

  // PageNodeObserver:
  void OnBeforePageNodeRemoved(const PageNode* page_node) override;
  void OnIsAudibleChanged(const PageNode* page_node) override;

  void SetNoDiscardPatternsForProfile(const std::string& browser_context_id,
                                      const std::vector<std::string>& patterns);
  void ClearNoDiscardPatternsForProfile(const std::string& browser_context_id);

  void SetMockDiscarderForTesting(
      std::unique_ptr<mechanism::PageDiscarder> discarder);
  bool CanUrgentlyDiscardForTesting(
      const PageNode* page_node,
      bool consider_minimum_protection_time = true) const {
    return CanUrgentlyDiscard(page_node, consider_minimum_protection_time) ==
           CanUrgentlyDiscardResult::kEligible;
  }
  // Indicates if a PageNode can be urgently discarded. If
  // `consider_minimum_protection_time` is false, the check that ensures the
  // page hasn't been visible recently is ignored. This is to support cases
  // where the time before a tab is discarded is known and shorter than the
  // grace period.
  CanUrgentlyDiscardResult CanUrgentlyDiscard(
      const PageNode* page_node,
      bool consider_minimum_protection_time = true) const;

  void SetGraphForTesting(Graph* graph) { graph_ = graph; }
  static void AddDiscardAttemptMarkerForTesting(PageNode* page_node);
  static void RemovesDiscardAttemptMarkerForTesting(PageNode* page_node);

 protected:
  void OnPassedToGraph(Graph* graph) override;
  void OnTakenFromGraph(Graph* graph) override;

  // Returns the PageLiveStateDecorator::Data associated with a PageNode.
  // Exposed and made virtual to allowed injecting some fake data in tests.
  virtual const PageLiveStateDecorator::Data* GetPageNodeLiveStateData(
      const PageNode* page_node) const;

 private:
  bool IsPageOptedOutOfDiscarding(const std::string& browser_context_id,
                                  const GURL& url) const;

  // NodeDataDescriber implementation:
  base::Value::Dict DescribePageNodeData(const PageNode* node) const override;

  // Called after each discard attempt. |success| will indicate whether or not
  // the attempt has been successful. |post_discard_cb| will be called once
  // there's been at least one successful discard or if there's no more discard
  // candidates.
  void PostDiscardAttemptCallback(
      absl::optional<uint64_t> reclaim_target_kb,
      bool discard_protected_tabs,
      base::OnceCallback<void(bool)> post_discard_cb,
      bool success);

  // Map that associates a PageNode with the last time it became non audible.
  // PageNodes that have never been audible are not present in this map.
  base::flat_map<const PageNode*, base::TimeTicks>
      last_change_to_non_audible_time_;

  // The mechanism used to do the actual discarding.
  std::unique_ptr<performance_manager::mechanism::PageDiscarder>
      page_discarder_;

  std::map<std::string, std::unique_ptr<url_matcher::URLMatcher>>
      profiles_no_discard_patterns_;

  raw_ptr<Graph> graph_ = nullptr;

  SEQUENCE_CHECKER(sequence_checker_);

  base::WeakPtrFactory<PageDiscardingHelper> weak_factory_{this};
};

}  // namespace policies

}  // namespace performance_manager

#endif  // CHROME_BROWSER_PERFORMANCE_MANAGER_POLICIES_PAGE_DISCARDING_HELPER_H_