#pragma once

#include <functional>

#include <string>

class JsonObserver {

public:

virtual ~JsonObserver() = default;

virtual void onObjectStart() = 0;

virtual void onObjectEnd() = 0;

virtual void onArrayStart() = 0;

virtual void onArrayEnd() = 0;

virtual void onNumber(int value) = 0;

virtual void onNumber(double value) = 0;

virtual void onBool(bool value) = 0;

virtual void onNull() = 0;

virtual void onString(const std::string& value) = 0;

virtual void onObjectKey(const std::string& key) = 0;

virtual void onObjectValueStart() = 0;

virtual void onObjectValueEnd() = 0;

};

class JsonVisitor {

public:

using NextChar = std::function<int()>;

bool parse(const std::string& input, JsonObserver& observer);

template <typename Stream>

bool parse(Stream& stream, JsonObserver& observer) {

auto nextChar = [&stream]() -> int {

return stream.read();

};

return parseImpl(nextChar, observer);

}

private:

bool parseImpl(NextChar nextChar, JsonObserver& observer);

};