/*

 * Copyright (c) 2021-2022, Idan Horowitz <idan.horowitz@serenityos.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#include <LibJS/Runtime/WeakRef.h>

namespace JS {

JS_DEFINE_ALLOCATOR(WeakRef);

NonnullGCPtr<WeakRef> WeakRef::create(Realm& realm, Object& value)

{

    return realm.heap().allocate<WeakRef>(realm, value, realm.intrinsics().weak_ref_prototype());

}

NonnullGCPtr<WeakRef> WeakRef::create(Realm& realm, Symbol& value)

{

    return realm.heap().allocate<WeakRef>(realm, value, realm.intrinsics().weak_ref_prototype());

}

WeakRef::WeakRef(Object& value, Object& prototype)

    : Object(ConstructWithPrototypeTag::Tag, prototype)

    , WeakContainer(heap())

    , m_value(&value)

    , m_last_execution_generation(vm().execution_generation())

{

}

WeakRef::WeakRef(Symbol& value, Object& prototype)

    : Object(ConstructWithPrototypeTag::Tag, prototype)

    , WeakContainer(heap())

    , m_value(&value)

    , m_last_execution_generation(vm().execution_generation())

{

}

void WeakRef::remove_dead_cells(Badge<Heap>)

{

    if (m_value.visit([](Cell* cell) -> bool { return cell->state() == Cell::State::Live; }, [](Empty) -> bool { VERIFY_NOT_REACHED(); }))

        return;

    m_value = Empty {};

    // This is an optimization, we deregister from the garbage collector early (even if we were not garbage collected ourself yet)

    // to reduce the garbage collection overhead, which we can do because a cleared weak ref cannot be reused.

    WeakContainer::deregister();

}

void WeakRef::visit_edges(Visitor& visitor)

{

    Base::visit_edges(visitor);

    if (vm().execution_generation() == m_last_execution_generation) {

        auto* cell = m_value.visit([](Cell* cell) -> Cell* { return cell; }, [](Empty) -> Cell* { return nullptr; });

        visitor.visit(cell);

    }

}

}