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#pragma once
#include "platform/location.hpp"
#include "base/exception.hpp"
#include "base/macros.hpp"
#include "std/fstream.hpp"
#include "std/function.hpp"
#include "std/limits.hpp"
#include "std/string.hpp"
class GpsTrackStorage final
{
public:
DECLARE_EXCEPTION(OpenException, RootException);
DECLARE_EXCEPTION(WriteException, RootException);
DECLARE_EXCEPTION(ReadException, RootException);
using TItem = location::GpsInfo;
/// Opens storage with track data.
/// @param filePath - path to the file on disk
/// @param maxItemCount - max number of items in recycling file
/// @exception OpenException if seek fails.
GpsTrackStorage(string const & filePath, size_t maxItemCount);
/// Appends new point to the storage
/// @param items - collection of gps track points.
/// @exceptions WriteException if write fails or ReadException if read fails.
void Append(vector<TItem> const & items);
/// Removes all data from the storage
/// @exceptions WriteException if write fails.
void Clear();
/// Reads the storage and calls functor for each item
/// @param fn - callable function, return true to stop ForEach
/// @exceptions ReadException if read fails.
void ForEach(std::function<bool(TItem const & item)> const & fn);
private:
DISALLOW_COPY_AND_MOVE(GpsTrackStorage);
void TruncFile();
size_t GetFirstItemIndex() const;
string const m_filePath;
size_t const m_maxItemCount;
fstream m_stream;
size_t m_itemCount; // current number of items in file, read note
// NOTE
// New items append to the end of file, when file become too big, it is truncated.
// Here 'silly window sindrome' is possible: for example max file size is 100k items,
// and 99k items are filled, when 2k items is coming, then 98k items is copying to the tmp file
// which replaces origin file, and 2k added to the new file. Next time, when 1k items
// is comming, then again file truncated. That means that trunc will happens every time.
// Similar problem in TCP called 'silly window sindrome'.
// To prevent that problem, max file size can be 2 x m_maxItemCount items, when current number of items m_itemCount
// exceed 2 x m_maxItemCount, then second half of file - m_maxItemCount items is copying to the tmp file,
// which replaces origin file. That means that trunc will happens only then new m_maxItemCount items will be
// added but not every time.
};
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