// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_BLOCKLIST_OPT_OUT_BLOCKLIST_OPT_OUT_BLOCKLIST_ITEM_H_
#define COMPONENTS_BLOCKLIST_OPT_OUT_BLOCKLIST_OPT_OUT_BLOCKLIST_ITEM_H_

#include <stdint.h>

#include <memory>
#include <optional>
#include <queue>

#include "base/time/time.h"

namespace blocklist {

// Stores the recent block list history for a single host. Stores
// |stored_history_length| of the most recent actions. To determine action
// eligibility fewer than |opt_out_block_list_threshold| out of the past
// |stored_history_length| navigations must be opt outs. |block_list_duration|
// is the amount of time that elapses until the host is no longer on the block
// list.
class OptOutBlocklistItem {
 public:
  OptOutBlocklistItem(size_t stored_history_length,
                      int opt_out_block_list_threshold,
                      base::TimeDelta block_list_duration);

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

  ~OptOutBlocklistItem();

  // Adds a new navigation at the specified |entry_time|.
  void AddEntry(bool opt_out, base::Time entry_time);

  // Whether the action corresponding to |this| should be disallowed.
  bool IsBlockListed(base::Time now) const;

  std::optional<base::Time> most_recent_opt_out_time() const {
    return most_recent_opt_out_time_;
  }

  size_t OptOutRecordsSizeForTesting() const;

 private:
  // An action to |this| is represented by time and whether the action was an
  // opt out.
  class OptOutRecord {
   public:
    OptOutRecord(base::Time entry_time, bool opt_out);

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

    ~OptOutRecord();
    OptOutRecord(OptOutRecord&&) noexcept;
    OptOutRecord& operator=(OptOutRecord&&) noexcept;

    // Used to determine eviction priority.
    bool operator<(const OptOutRecord& other) const;

    // The time that the opt out state was determined.
    base::Time entry_time() const { return entry_time_; }

    // Whether the user opted out of the action.
    bool opt_out() const { return opt_out_; }

   private:
    // The time that the opt out state was determined.
    base::Time entry_time_;
    // Whether the user opted out of the action.
    bool opt_out_;
  };

  // The number of entries to store to determine action eligibility.
  const size_t max_stored_history_length_;
  // The number opt outs in recent history that will trigger blocklisting.
  const int opt_out_block_list_threshold_;
  // The amount of time to block list a domain after the most recent opt out.
  const base::TimeDelta max_block_list_duration_;

  // The |max_stored_history_length_| most recent action. Is maintained as a
  // priority queue that has high priority for items that should be evicted
  // (i.e., they are old).
  std::priority_queue<OptOutRecord> opt_out_records_;

  // Time of the most recent opt out.
  std::optional<base::Time> most_recent_opt_out_time_;

  // The total number of opt outs currently in |opt_out_records_|.
  int total_opt_out_;
};

}  // namespace blocklist

#endif  // COMPONENTS_BLOCKLIST_OPT_OUT_BLOCKLIST_OPT_OUT_BLOCKLIST_ITEM_H_