// Copyright 2018 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_RESOURCE_COORDINATOR_LIFECYCLE_UNIT_BASE_H_
#define CHROME_BROWSER_RESOURCE_COORDINATOR_LIFECYCLE_UNIT_BASE_H_

#include "base/memory/raw_ptr.h"
#include "base/observer_list.h"
#include "base/time/time.h"
#include "chrome/browser/resource_coordinator/lifecycle_unit.h"
#include "chrome/browser/resource_coordinator/lifecycle_unit_state.mojom-shared.h"
#include "chrome/browser/resource_coordinator/time.h"

namespace resource_coordinator {

class LifecycleUnitSourceBase;

using ::mojom::LifecycleUnitState;

// Base class for a LifecycleUnit.
class LifecycleUnitBase : public LifecycleUnit {
 public:
  explicit LifecycleUnitBase(LifecycleUnitSourceBase* source);

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

  ~LifecycleUnitBase() override;

  // LifecycleUnit:
  LifecycleUnitSource* GetSource() const override;
  int32_t GetID() const override;
  LifecycleUnitState GetState() const override;
  base::TimeTicks GetStateChangeTime() const override;
  base::Time GetStateChangeWallTime() const override;
  size_t GetDiscardCount() const override;
  void AddObserver(LifecycleUnitObserver* observer) override;
  void RemoveObserver(LifecycleUnitObserver* observer) override;

  void SetDiscardCountForTesting(size_t discard_count);

 protected:
  // TODO(chrisha|fdoray): Clean up the virtual methods below and make them
  // pure virtual.

  // Sets the state of this LifecycleUnit to |state| and notifies observers.
  void SetState(LifecycleUnitState state);

  // Notifies observers that the LifecycleUnit is being destroyed. This is
  // invoked by derived classes rather than by the base class to avoid notifying
  // observers when the LifecycleUnit has been partially destroyed. This also
  // forwards the notification to the lifecycle unit source via
  // LifecycleUnitSourceBase.
  void OnLifecycleUnitDestroyed();

 private:
  static int32_t next_id_;

  // A unique id representing this LifecycleUnit.
  const int32_t id_ = ++next_id_;

  // The source that owns this lifecycle unit. This can be nullptr.
  raw_ptr<LifecycleUnitSourceBase> source_;

  // Current state of this LifecycleUnit.
  LifecycleUnitState state_ = LifecycleUnitState::ACTIVE;

  // Time at which the state changed, stamped together in both the monotonic
  // and wall-clock domains.
  base::TimeTicks state_change_time_ = NowTicks();
  base::Time state_change_wall_time_ = Now();

  // The number of times that this lifecycle unit has been discarded.
  int discard_count_ = 0;

  base::ObserverList<LifecycleUnitObserver>::Unchecked observers_;
};

}  // namespace resource_coordinator

#endif  // CHROME_BROWSER_RESOURCE_COORDINATOR_LIFECYCLE_UNIT_BASE_H_