aocpp/lib/include/intcode/Interpreter.hpp

#ifndef INTCODE_INTERPRETER_HPP_
#define INTCODE_INTERPRETER_HPP_

#include <variant>
#include <concepts>

#include <intcode/Machine.hpp>
#include <Overload.hpp>
namespace intcode {

struct Input {
ValueType &input;
};

struct Output {
ValueType output;
};

struct Halt {};

auto StepInput(Machine & m, ValueType input) -> void;

auto StepOutput(Machine & m) -> ValueType;

auto Step(Machine & m) -> std::variant<Input, Output, Halt>;

struct BadInstruction : public std::runtime_error {
  explicit BadInstruction(char const* what);
};

template <std::invocable<ValueType&> Fin, std::invocable<ValueType> Fout, std::invocable<> Fhalt>
auto Advance(Machine & machine, Fin input, Fout output, Fhalt halt) {
  return std::visit(overloaded{
    [&](Halt) { return halt(); },
    [&](Input i) { return input(i.input); },
    [&](Output o) { return output(o.output); },
    }, Step(machine));
}

template <std::invocable<> Fin, std::invocable<ValueType> Fout>
auto Run(Machine & machine, Fin input, Fout output) -> void {
  while (Advance(machine,
    [&](ValueType &i) { i = input(); return true; },
    [&](ValueType o) { output(o); return true; },
    []() { return false; }
    )) {}
}

} // namespace

#endif