content/browser/quota/quota_change_dispatcher.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 CONTENT_BROWSER_QUOTA_QUOTA_CHANGE_DISPATCHER_H_
#define CONTENT_BROWSER_QUOTA_QUOTA_CHANGE_DISPATCHER_H_

#include <map>

#include "base/memory/ref_counted_delete_on_sequence.h"
#include "base/memory/scoped_refptr.h"
#include "base/memory/weak_ptr.h"
#include "base/sequence_checker.h"
#include "base/task/sequenced_task_runner.h"
#include "base/time/time.h"
#include "content/common/content_export.h"
#include "mojo/public/cpp/bindings/remote_set.h"
#include "third_party/blink/public/common/storage_key/storage_key.h"
#include "third_party/blink/public/mojom/quota/quota_manager_host.mojom.h"

namespace content {

// Dispatches a storage pressure event to listeners across multiple storage
// keys.
//
// This class handles dispatching the event with randomized delays,
// to avoid creating a cross-storage-key user identifier.
//
// There is one instance per QuotaContext instance. All methods must
// be called on the same sequence.
class CONTENT_EXPORT QuotaChangeDispatcher
    : public base::RefCountedDeleteOnSequence<QuotaChangeDispatcher> {
 public:
  explicit QuotaChangeDispatcher(
      scoped_refptr<base::SequencedTaskRunner> io_thread);

  QuotaChangeDispatcher(const QuotaChangeDispatcher&) = delete;
  QuotaChangeDispatcher& operator=(const QuotaChangeDispatcher&) = delete;

  // Dispatch OnQuotaChange for every storage key and its corresponding
  // listeners.
  void MaybeDispatchEvents();
  void DispatchEventsForStorageKey(const blink::StorageKey& storage_key);
  void AddChangeListener(
      const blink::StorageKey& storage_key,
      mojo::PendingRemote<blink::mojom::QuotaChangeListener> mojo_listener);
  void OnRemoteDisconnect(const blink::StorageKey& storage_key,
                          mojo::RemoteSetElementId id);

 private:
  friend class QuotaChangeDispatcherTest;
  friend class QuotaContext;
  friend class base::RefCountedDeleteOnSequence<QuotaChangeDispatcher>;
  friend class base::DeleteHelper<QuotaChangeDispatcher>;

  ~QuotaChangeDispatcher();
  const base::TimeDelta GetQuotaChangeEventInterval();

  struct DelayedStorageKeyListener {
    DelayedStorageKeyListener();
    ~DelayedStorageKeyListener();
    // This delay is used to introduce noise to the event, to prevent
    // bad actors from using the event to determine cross-storage-key
    // resource size or to correlate and identify users across storage
    // key/profiles.
    base::TimeDelta delay;
    mojo::RemoteSet<blink::mojom::QuotaChangeListener> listeners;
  };
  // Stores all of the listeners associated with a unique storage key
  // corresponding to a randomized delay for that storage key.
  std::map<blink::StorageKey, DelayedStorageKeyListener>
      listeners_by_storage_key_;

  // Keeps track of last time events were dispatched for debouncing events.
  base::TimeTicks last_event_dispatched_at_;

  // Cache the event interval to avoid checking command line switches
  // each time the interval is checked. See kDefaultQuotaChangeIntervalSeconds
  // for the default value. See switches::kQuotaChangeEventInterval for a
  // command-line override.
  base::TimeDelta quota_change_event_interval_;
  bool is_quota_change_interval_cached_ = false;

  SEQUENCE_CHECKER(sequence_checker_);
  base::WeakPtrFactory<QuotaChangeDispatcher> weak_ptr_factory_{this};
};

}  // namespace content

#endif  // CONTENT_BROWSER_QUOTA_QUOTA_CHANGE_DISPATCHER_H_