cursor.hpp

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#pragma once
 
/// @file userver/storages/mongo/cursor.hpp
/// @brief @copybrief storages::mongo::Cursor
 
#include <iterator>
#include <memory>
 
#include <userver/formats/bson/document.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace storages::mongo {
namespace impl {
class CursorImpl;
}  // namespace impl
 
/// Interface for MongoDB query cursors
class Cursor {
 public:
  explicit Cursor(std::unique_ptr<impl::CursorImpl>&&);
  ~Cursor();
 
  Cursor(Cursor&&) noexcept;
  Cursor& operator=(Cursor&&) noexcept;
 
  class Iterator {
   public:
    using iterator_category = std::input_iterator_tag;
    using difference_type = ptrdiff_t;
    using value_type = formats::bson::Document;
    using reference = const value_type&;
    using pointer = const value_type*;
 
    explicit Iterator(Cursor*);
 
    class DocHolder {
     public:
      explicit DocHolder(value_type doc) : doc_(std::move(doc)) {}
 
      value_type& operator*() { return doc_; }
 
     private:
      value_type doc_;
    };
    DocHolder operator++(int);
    Iterator& operator++();
    reference operator*() const;
    pointer operator->() const;
 
    bool operator==(const Iterator&) const;
    bool operator!=(const Iterator&) const;
 
   private:
    Cursor* cursor_;
  };
 
  bool HasMore() const;
  explicit operator bool() const { return HasMore(); }
 
  Iterator begin();
  Iterator end();
 
 private:
  std::unique_ptr<impl::CursorImpl> impl_;
};
 
}  // namespace storages::mongo
 
USERVER_NAMESPACE_END