/*
 * Copyright (C) 2011-2024 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#include <wtf/Compiler.h>

WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN

#include <JavaScriptCore/Handle.h>
#include <JavaScriptCore/HandleSet.h>
#include <JavaScriptCore/Heap.h>
#include <JavaScriptCore/JSLock.h>
#include <JavaScriptCore/StrongForward.h>
#include <wtf/HashFunctions.h>
#include <wtf/RefTrackerMixin.h>

namespace JSC {

class VM;

REFTRACKER_DECL(StrongRefTracker);

// A strongly referenced handle that prevents the object it points to from being garbage collected.
template <typename T, ShouldStrongDestructorGrabLock shouldStrongDestructorGrabLock> class Strong final : public Handle<T> {
    using Handle<T>::slot;
    using Handle<T>::setSlot;
    template <typename U, ShouldStrongDestructorGrabLock> friend class Strong;

public:
    using ExternalType = typename Handle<T>::ExternalType;
    using ValueType = std::remove_pointer_t<ExternalType>;
    using PtrType = ExternalType;

    Strong()
        : Handle<T>()
    {
    }

    inline Strong(VM&, ExternalType = ExternalType());

    inline Strong(VM&, Handle<T>);

    Strong(const Strong& other)
        : Handle<T>()
    {
        if (!other.slot())
            return;
        setSlot(HandleSet::heapFor(other.slot())->allocate());
        set(other.get());
    }

    template <typename U> Strong(const Strong<U>& other)
        : Handle<T>()
    {
        if (!other.slot())
            return;
        setSlot(HandleSet::heapFor(other.slot())->allocate());
        set(other.get());
    }

    enum HashTableDeletedValueTag { HashTableDeletedValue };
    bool isHashTableDeletedValue() const { return slot() == hashTableDeletedValue(); }

    Strong(HashTableDeletedValueTag)
        : Handle<T>(hashTableDeletedValue())
    {
    }

    enum HashTableEmptyValueTag { HashTableEmptyValue };
    bool isHashTableEmptyValue() const { return slot() == hashTableEmptyValue(); }

    Strong(HashTableEmptyValueTag)
        : Handle<T>(hashTableEmptyValue())
    {
    }

    ~Strong() override
    {
        clear();
    }

    bool operator!() const { return !slot() || !*slot(); }

    explicit operator bool() const { return !!*this; }

    void swap(Strong& other)
    {
        Handle<T>::swap(other);
    }

    ExternalType get() const { return HandleTypes<T>::getFromSlot(this->slot()); }

    inline void set(VM&, ExternalType); // Defined in StrongInlines.h
    template <typename U> inline Strong& operator=(const Strong<U>& other); // Defined in StrongInlines.h
    Strong& operator=(const Strong& other); // Defined in StrongInlines.h

    void clear()
    {
        if (!slot())
            return;

        auto* heap = HandleSet::heapFor(slot());
        if (shouldStrongDestructorGrabLock == ShouldStrongDestructorGrabLock::Yes) {
            JSLockHolder holder(heap->vm());
            heap->deallocate(slot());
            setSlot(nullptr);
        } else {
            heap->deallocate(slot());
            setSlot(nullptr);
        }
    }

private:
    static HandleSlot hashTableDeletedValue() { return reinterpret_cast<HandleSlot>(-1); }
    static HandleSlot hashTableEmptyValue() { return reinterpret_cast<HandleSlot>(0); }

    void set(ExternalType externalType)
    {
        ASSERT(slot());
        JSValue value = HandleTypes<T>::toJSValue(externalType);
        HandleSet::heapFor(slot())->template writeBarrier<std::is_base_of_v<JSCell, T>>(slot(), value);
        *slot() = value;
    }

    REFTRACKER_MEMBERS(StrongRefTracker);
};

template<class T> inline void swap(Strong<T>& a, Strong<T>& b)
{
    a.swap(b);
}

} // namespace JSC

namespace WTF {

template<typename T> struct VectorTraits<JSC::Strong<T>> : SimpleClassVectorTraits {
    static constexpr bool canCompareWithMemcmp = false;
#if ENABLE(REFTRACKER)
    static constexpr bool canInitializeWithMemset = false;
    static constexpr bool canMoveWithMemcpy = false;
#endif
};

template <typename P>
struct IsSmartPtr<JSC::Strong<P>> {
    static constexpr bool value = true;
    static constexpr bool isNullable = true;
};

template<typename> struct DefaultHash;
template<typename P> struct DefaultHash<JSC::Strong<P>> : PtrHash<JSC::Strong<P>> { };

template<typename P> struct HashTraits<JSC::Strong<P>> : SimpleClassHashTraits<JSC::Strong<P>> {
#if ENABLE(REFTRACKER)
    using S = JSC::Strong<P>;
    static constexpr bool emptyValueIsZero = false;
    static S emptyValue() { return S::HashTableEmptyValue; }

    template <typename>
    static void constructEmptyValue(S& slot)
    {
        new (NotNull, std::addressof(slot)) S(S::HashTableEmptyValue);
    }

    static constexpr bool hasIsEmptyValueFunction = true;
    static bool isEmptyValue(const S& value) { return value.isHashTableEmptyValue(); }

    static void constructDeletedValue(S& slot) { new (NotNull, &slot) S(S::HashTableDeletedValue); }
    static bool isDeletedValue(const S& value) { return value.isHashTableDeletedValue(); }

#endif
};

} // namespace WTF

WTF_ALLOW_UNSAFE_BUFFER_USAGE_END