listener.hh

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// SPDX-FileCopyrightText: 2021-2025 The Ikarus Developers mueller@ibb.uni-stuttgart.de
// SPDX-License-Identifier: LGPL-3.0-or-later
 
#pragma once
#include <memory>
#include <vector>
 
#include <ikarus/utils/functionhelper.hh>
#include <ikarus/utils/traits.hh>
 
namespace Ikarus {
 
struct Listener
{
  using Token = std::shared_ptr<void>;
 
  template <typename Broadcaster, typename F>
  auto subscribe(Broadcaster& broadcaster, F&& f) {
    using Signature = typename traits::FunctionTraits<F>::FreeSignature;
    return subscribe<traits::MaybeDereferencedType<Broadcaster>, Signature>(utils::maybeDeref(broadcaster),
                                                                            std::forward<F>(f));
  }
 
  template <typename Broadcaster, typename Signature, typename F>
  requires(not Concepts::PointerOrSmartPointer<Broadcaster>)
  auto subscribe(Broadcaster& broadcaster, F&& f) {
    t.push_back(broadcaster.template station<Signature>().registerListener(std::forward<F>(f)));
    return t.back();
  }
 
  void unSubscribeAll() { t.clear(); }
 
  void unSubscribeLast() { t.pop_back(); }
 
  void unSubscribe(Token&& ts) {
    t.erase(std::ranges::find(t, ts)); // erase the shared ptr in t
    assert(ts.unique() && "The given token has external references");
    ts.reset();
  }
 
private:
  std::vector<Token> t;
};
 
} // namespace Ikarus