AFieldObservable.h

/*
 * AUI Framework - Declarative UI toolkit for modern C++20
 * Copyright (C) 2020-2025 Alex2772 and Contributors
 *
 * SPDX-License-Identifier: MPL-2.0
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
 
#pragma once
 
#include <list>
#include <utility>
#include "AUI/Common/ASignal.h"
#include "AUI/Traits/concepts.h"
#include "AUI/Util/ADataBinding.h"
 
template<typename T, aui::invocable<const T&> AdapterCallable>
struct AFieldObservableAdapter;

template <typename T>
class AFieldObservable
{
public:
   using Observer = std::function<void()>;
   using ObserverHandle = Observer*;
 
   AFieldObservable(T initial = T()):
       mValue(std::move(initial))
   {
   }
 
   void setValue(T t, ObserverHandle exceptObserver = nullptr) {
       if (mValue != t) {
           mValue = std::move(t);
           notifyObservers(exceptObserver);
       }
   }
 
   void notifyObservers(ObserverHandle exceptObserver = nullptr) {
       for (const auto& v : mObservers) {
           if (&v != exceptObserver) {
               v();
           }
       }
   }
 
   AFieldObservable& operator=(T t)
   {
       setValue(t);
       return *this;
   }
 
   T& operator+=(T t) {
       mValue += t;
       notifyObservers();
       return mValue;
   }
   T& operator-=(T t) {
       mValue -= t;
       notifyObservers();
       return mValue;
   }
   T& operator*=(T t) {
       mValue *= t;
       notifyObservers();
       return mValue;
   }
   T& operator/=(T t) {
       mValue /= t;
       notifyObservers();
       return mValue;
   }
 
   operator const T&() const noexcept
   {
       return mValue;
   }
 
   [[nodiscard]]
   const T& value() const noexcept {
       return mValue;
   }
 
   T* operator->() noexcept {
       return &mValue;
   }
 
   T const * operator->() const noexcept {
       return &mValue;
   }

   template<typename Observer_t>
   ObserverHandle addObserver(Observer_t&& observer) {
       constexpr bool expectsValue = !std::is_invocable_v<Observer_t>;
       if constexpr (expectsValue) {
           observer(mValue);
           mObservers.push_back([this, observer = std::forward<Observer_t>(observer)] {
               observer(mValue);
           });
       } else {
           observer();
           mObservers.push_back(std::forward<Observer_t>(observer));
       }
 
       return &mObservers.back();
   }

   template<typename Observer_t>
   ObserverHandle operator<<(Observer_t observer) {
       return addObserver(std::forward<Observer_t>(observer));
   }

   void operator>>(ObserverHandle h) {
       removeObserver(h);
   }

   void removeObserver(ObserverHandle h) {
       mObservers.erase(std::remove_if(mObservers.begin(), mObservers.end(), [&](const Observer& o) {
           return &o == h;
       }), mObservers.end());
   }
 
   template<aui::invocable<const T&> AdapterCallable>
   AFieldObservableAdapter<T, std::decay_t<AdapterCallable>> operator()(AdapterCallable&& callable) noexcept;
 
private:
   T mValue;
   std::list<Observer> mObservers;
};
 
template<typename T, aui::invocable<const T&> AdapterCallable>
struct AFieldObservableAdapter {
   AFieldObservable<T>& field;
   AdapterCallable callable;
 
   using return_t = decltype(callable(std::declval<T>()));
};
 
template<typename T>
template<aui::invocable<const T&> AdapterCallable>
AFieldObservableAdapter<T, std::decay_t<AdapterCallable>> AFieldObservable<T>::operator()(AdapterCallable&& callable) noexcept {
   return { .field = *this, .callable = std::forward<AdapterCallable>(callable) };
}
 
 
template<typename View, typename Data>
_<View> operator&&(const _<View>& object, AFieldObservable<Data>& observable) {
   using ObserverHandle = typename std::decay_t<decltype(observable)>::ObserverHandle;
   auto observerHandle = _new<ObserverHandle>(nullptr);
   if (ADataBindingDefault<View, Data>::getSetter()) {
       *observerHandle = observable << [weak = object.weak(), observerHandle, observable = &observable](const Data& newValue) {
           auto object = weak.lock();
           if (object == nullptr) {
               observable->removeObserver(*observerHandle);
           }
           (object.get()->*ADataBindingDefault<View, Data>::getSetter())(newValue);
       };
   }
   if (auto getter = ADataBindingDefault<View, Data>::getGetter()) {
       AObject::connect(object.get()->*getter, object, [&observable, observerHandle = *observerHandle](Data newValue) {
           observable.setValue(std::move(newValue), observerHandle);
       });
   }
 
   return object;
}
 
template<typename View, typename ModelData, typename AdapterCallback>
_<View> operator&&(const _<View>& object, AFieldObservableAdapter<ModelData, AdapterCallback> observableAdapter) {
   using Data = typename AFieldObservableAdapter<ModelData, AdapterCallback>::return_t;
   auto& observable = observableAdapter.field;
   using ObserverHandle = typename std::decay_t<decltype(observable)>::ObserverHandle;
   auto observerHandle = _new<ObserverHandle>(nullptr);
   if (ADataBindingDefault<View, Data>::getSetter()) {
       *observerHandle = observable << [weak = object.weak(), observable = &observable, observerHandle, transformer = std::move(observableAdapter.callable)](const ModelData& newValue) {
           auto object = weak.lock();
           if (object == nullptr) {
               observable->removeObserver(*observerHandle);
               return;
           }
           (object.get()->*ADataBindingDefault<View, Data>::getSetter())(transformer(newValue));
       };
   }
 
   return object;
}
 

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