//===----------------------------------------------------------------------===//
//
//                         BusTub
//
// replacer.h
//
// Identification: src/include/buffer/replacer.h
//
// Copyright (c) 2015-2025, Carnegie Mellon University Database Group
//
//===----------------------------------------------------------------------===//

#pragma once

#include "common/config.h"

namespace bustub {

/**
 * Replacer is an abstract class that tracks page usage.
 */
class Replacer {
 public:
  Replacer() = default;
  virtual ~Replacer() = default;

  /**
   * Remove the victim frame as defined by the replacement policy.
   * @param[out] frame_id id of frame that was removed, nullptr if no victim was found
   * @return true if a victim frame was found, false otherwise
   */
  virtual auto Victim(frame_id_t *frame_id) -> bool = 0;

  /**
   * Pins a frame, indicating that it should not be victimized until it is unpinned.
   * @param frame_id the id of the frame to pin
   */
  virtual void Pin(frame_id_t frame_id) = 0;

  /**
   * Unpins a frame, indicating that it can now be victimized.
   * @param frame_id the id of the frame to unpin
   */
  virtual void Unpin(frame_id_t frame_id) = 0;

  /** @return the number of elements in the replacer that can be victimized */
  virtual auto Size() -> size_t = 0;
};

}  // namespace bustub