/********************************************************************************

#ifndef IFCSPFSTREAM_H

#define IFCSPFSTREAM_H

#include "ifc_parse_api.h"

#include <cstddef>

#include <memory>

#include <optional>

#include <string>

#include <variant>

#include <stdexcept>

#include <vector>

namespace IfcParse {

class IFC_PARSE_API FileReader {

struct Page { std::vector<char> data; };

/// \brief Tag to choose memory-mapped backend via boost::iostreams::mapped_file_source.

struct mmap_tag {};

/// \brief Tag to choose user-pushed sequential pages.

struct caller_fed_tag {};

/// \brief Construct a FileReader.

/// \param fn File path.

/// \param maybe_mmaped_or_chunked

/// - std::nullopt: full-buffer mode (entire file loaded into memory)

/// - size_t: paged mode with this page size in bytes (e.g., 4096)

/// - mmap_tag: memory-mapped mode using boost::iostreams::mapped_file_source

/// \param page_cache_capacity Number of pages to keep in the LRU when in paged mode.

FileReader(const std::string& fn);

FileReader(const std::string& fn, const mmap_tag&);

FileReader(const caller_fed_tag&);

FileReader(const std::string& content, const caller_fed_tag&);

FileReader(const std::string& fn, size_t page_size, size_t page_capacity);

/// \brief Copy-construct a new reader sharing the underlying storage but with its own cursor.

FileReader clone() const;

/// \brief Seek to an absolute byte position.

/// \throws std::out_of_range if pos > size().

void seek(size_t pos);

/// \brief Return the current cursor position.

size_t tell() const;

/// \brief Total file size in bytes.

size_t size() const;

/// \brief Peek the byte at the current cursor.

/// \throws std::out_of_range at EOF.

char peek() const;

/// \brief Advance the cursor by n bytes (default 1).

/// \throws std::out_of_range if advancing crosses EOF.

void increment(size_t n = 1);

/// \brief Push the next sequential page (pushed backend only).

/// \param data Contents of the page.

/// \throws std::logic_error if the current backend is not in pushed mode

void pushNextPage(const std::string& data);

/// \brief Drops pages up to cursor position or provided offset. Does nothing when current backend is not in pushed mode

/// \param up_to_pos Pages with an end offset before up_to_pos are dropped from memory

void dropPages();

void dropPages(size_t up_to_pos);

/// \brief Returns true if the cursor is at or beyond the end of available data.

/// For the pushed backend, EOF means all pushed bytes have been consumed.

bool eof() const;

/// \brief Equivalent of peek() followed by increment(1)

char read();

/// \brief Equivalent of peek() followed by increment(1)

char get(size_t offset) const;

struct Impl {

};

std::shared_ptr<Impl> impl_;

size_t cursor_ = 0;

};

} // namespace IfcParse

#endif