//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2018
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#pragma once

#include "td/utils/common.h"
#include "td/utils/Status.h"

namespace td {

/*** PartsManager***/
struct Part {
  int id;
  int64 offset;
  size_t size;
};

class PartsManager {
 public:
  Status init(int64 size, int64 expected_size, bool is_size_final, size_t part_size,
              const std::vector<int> &ready_parts, bool use_part_count_limit) TD_WARN_UNUSED_RESULT;
  bool ready();
  bool unchecked_ready();
  Status finish() TD_WARN_UNUSED_RESULT;

  // returns empty part if nothing to return
  Result<Part> start_part() TD_WARN_UNUSED_RESULT;
  Status on_part_ok(int32 id, size_t part_size, size_t actual_size) TD_WARN_UNUSED_RESULT;
  void on_part_failed(int32 id);
  Status set_known_prefix(size_t size, bool is_ready);
  void set_need_check();
  void set_checked_prefix_size(int64 size);

  int64 get_checked_prefix_size() const;
  int64 get_unchecked_ready_prefix_size();
  int64 get_size() const;
  int64 get_size_or_zero() const;
  int64 get_expected_size() const;
  int64 get_ready_size() const;
  size_t get_part_size() const;
  int32 get_part_count() const;
  int32 get_ready_prefix_count();

 private:
  static constexpr int MAX_PART_COUNT = 3000;
  static constexpr int MAX_PART_SIZE = 512 * (1 << 10);
  static constexpr int64 MAX_FILE_SIZE = MAX_PART_SIZE * MAX_PART_COUNT;

  enum class PartStatus { Empty, Pending, Ready };

  bool need_check_{false};
  int64 checked_prefix_size_{0};

  bool known_prefix_flag_{false};
  int64 known_prefix_size_;

  int64 size_;
  int64 expected_size_;
  int64 min_size_;
  int64 max_size_;
  bool unknown_size_flag_;
  int64 ready_size_;

  size_t part_size_;
  int part_count_;
  int pending_count_;
  int first_empty_part_;
  int first_not_ready_part_;
  vector<PartStatus> part_status_;
  bool use_part_count_limit_;

  void init_common(const vector<int> &ready_parts);
  Status init_known_prefix(int64 known_prefix, size_t part_size,
                           const std::vector<int> &ready_parts) TD_WARN_UNUSED_RESULT;
  Status init_no_size(size_t part_size, const std::vector<int> &ready_parts) TD_WARN_UNUSED_RESULT;

  Part get_part(int id);
  Part get_empty_part();
  void on_part_start(int32 id);
  void update_first_empty_part();
  void update_first_not_ready_part();
};

}  // namespace td