Cursor.h

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#ifndef LINTEL_CURSOR_H
#define LINTEL_CURSOR_H
 
#include <cstddef>
#include <memory>
#include <string>
#include <vector>
 
#include "lintel/core/persistence/Arguments.h"
#include "lintel/core/persistence/Connection.h"
#include "lintel/core/persistence/postgresql/Cursor.h"
#include "lintel/core/persistence/sqlite3/Cursor.h"
 
namespace lintel {
namespace db {
  class Cursor
  {
  private:
    std::shared_ptr<postgresql::Cursor> m_cursor = nullptr;
    std::shared_ptr<sqlite::Cursor> m_cursorSQLite = nullptr;
 
    std::vector<db::Arguments> m_batch;
    std::size_t m_pos = 0;
    bool m_started = false;
    bool m_exhausted = false;
 
    static constexpr std::size_t kDefaultFetchSize = 100;
    std::size_t m_fetchSize = kDefaultFetchSize;
    std::string m_cursorName;
    bool m_noScroll = true;
 
    bool m_needsInit = false;
    std::string m_query;
    std::vector<std::string> m_params;
    std::shared_ptr<postgresql::Connection> m_pgConn;
    std::shared_ptr<sqlite::Connection> m_sqliteConn;
 
    void start();
 
    void initBackendCursor();
 
    void fillBatch();
 
    [[nodiscard]] bool hasCurrent() const;
 
    [[nodiscard]] const db::Arguments &currentOf() const;
 
    void advance();
 
  public:
    class Iterator
    {
    private:
      Cursor &m_cursor;
      bool m_end;
 
      [[nodiscard]] bool reachedEnd() const;
 
    public:
      using iterator_category = std::input_iterator_tag;
      using value_type = Arguments;
      using difference_type = std::ptrdiff_t;
      using pointer = const Arguments *;
      using reference = const Arguments &;
 
      explicit Iterator(Cursor &cursor, bool end = false);
 
      Iterator &operator++();
 
      const Iterator operator++(int);
 
      bool operator==(const Iterator &other) const;
 
      bool operator!=(const Iterator &other) const;
 
      reference operator*() const;
    };
 
    Cursor() = default;
 
    Cursor &setFetchSize(std::size_t rows);
 
    Cursor &setCursorName(const std::string &name);
 
    Cursor &setNoScroll(bool enable);
 
    std::vector<db::Arguments> fetchNext(std::size_t maxRows);
 
    Iterator begin();
 
    Iterator end();
 
  private:
    friend class Statement;
 
    Cursor(std::shared_ptr<postgresql::Cursor> cursor, std::shared_ptr<sqlite::Cursor> cursorSQLite);
  };
}// namespace db
 
}// namespace lintel
#endif// LINTEL_CURSOR_H