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/*
* Copyright (c) 2021, Kyle Pereira <hey@xylepereira.me>
* Copyright (c) 2022, kleines Filmröllchen <filmroellchen@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <LibCore/EventLoop.h>
#include <LibCore/Object.h>
namespace Core {
template<typename Result>
class Promise : public Object {
C_OBJECT(Promise);
public:
Function<ErrorOr<void>(Result&)> on_resolved;
ErrorOr<void> resolve(Result&& result)
{
m_pending_or_error = move(result);
if (on_resolved)
return on_resolved(m_pending_or_error->value());
return {};
}
void cancel(Error error)
{
m_pending_or_error = move(error);
}
bool is_canceled()
{
return m_pending_or_error.has_value() && m_pending_or_error->is_error();
}
bool is_resolved() const
{
return m_pending_or_error.has_value() && !m_pending_or_error->is_error();
}
ErrorOr<Result> await()
{
while (!m_pending_or_error.has_value())
Core::EventLoop::current().pump();
return m_pending_or_error.release_value();
}
// Converts a Promise<A> to a Promise<B> using a function func: A -> B
template<typename T>
RefPtr<Promise<T>> map(T func(Result&))
{
RefPtr<Promise<T>> new_promise = Promise<T>::construct();
on_resolved = [new_promise, func](Result& result) {
auto t = func(result);
return new_promise->resolve(move(t));
};
return new_promise;
}
private:
Promise() = default;
Promise(Object* parent)
: Object(parent)
{
}
Optional<ErrorOr<Result>> m_pending_or_error;
};
}
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