/*

* Reference arithmetic coding

*

* Copyright (c) Project Nayuki

* MIT License. See readme file.

* https://www.nayuki.io/page/reference-arithmetic-coding

*/

#pragma once

#include <cstdint>

#include <memory>

#include <vector>

#include "FrequencyTable.hpp"

class PpmModel final {

/*---- Helper structure ----*/

public: class Context final {

public: SimpleFrequencyTable frequencies;

public: std::vector<std::unique_ptr<Context> > subcontexts;

public: explicit Context(std::uint32_t symbols, bool hasSubctx);

};

/*---- Fields ----*/

public: int modelOrder;

private: std::uint32_t symbolLimit;

private: std::uint32_t escapeSymbol;

public: std::unique_ptr<Context> rootContext;

public: SimpleFrequencyTable orderMinus1Freqs;

/*---- Constructor ----*/

public: explicit PpmModel(int order, std::uint32_t symLimit, std::uint32_t escapeSym);

/*---- Methods ----*/

public: void incrementContexts(const std::vector<std::uint32_t> &history, std::uint32_t symbol);

private: static std::vector<std::uint32_t> makeEmpty(std::uint32_t len);

};