/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */

#include "mozilla/dom/CustomElementRegistry.h"

#include "mozilla/AsyncEventDispatcher.h"
#include "mozilla/CycleCollectedJSContext.h"
#include "mozilla/dom/CustomElementRegistryBinding.h"
#include "mozilla/dom/HTMLElementBinding.h"
#include "mozilla/dom/XULElementBinding.h"
#include "mozilla/dom/Promise.h"
#include "mozilla/dom/WebComponentsBinding.h"
#include "mozilla/dom/DocGroup.h"
#include "mozilla/dom/CustomEvent.h"
#include "mozilla/dom/ShadowRoot.h"
#include "nsHTMLTags.h"
#include "jsapi.h"
#include "xpcprivate.h"
#include "nsGlobalWindow.h"

namespace mozilla {
namespace dom {

//-----------------------------------------------------
// CustomElementUpgradeReaction

class CustomElementUpgradeReaction final : public CustomElementReaction
{
public:
  explicit CustomElementUpgradeReaction(CustomElementDefinition* aDefinition)
    : mDefinition(aDefinition)
  {
    mIsUpgradeReaction = true;
  }

  virtual void Traverse(nsCycleCollectionTraversalCallback& aCb) const override
  {
    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(aCb, "mDefinition");
    aCb.NoteNativeChild(mDefinition,
      NS_CYCLE_COLLECTION_PARTICIPANT(CustomElementDefinition));
  }
private:
  virtual void Invoke(Element* aElement, ErrorResult& aRv) override
  {
    CustomElementRegistry::Upgrade(aElement, mDefinition, aRv);
  }

  RefPtr<CustomElementDefinition> mDefinition;
};

//-----------------------------------------------------
// CustomElementCallbackReaction

class CustomElementCallbackReaction final : public CustomElementReaction
{
  public:
    explicit CustomElementCallbackReaction(UniquePtr<CustomElementCallback> aCustomElementCallback)
      : mCustomElementCallback(std::move(aCustomElementCallback))
    {
    }

    virtual void Traverse(nsCycleCollectionTraversalCallback& aCb) const override
    {
      mCustomElementCallback->Traverse(aCb);
    }

  private:
    virtual void Invoke(Element* aElement, ErrorResult& aRv) override
    {
      mCustomElementCallback->Call();
    }

    UniquePtr<CustomElementCallback> mCustomElementCallback;
};

//-----------------------------------------------------
// CustomElementCallback

void
CustomElementCallback::Call()
{
  switch (mType) {
    case nsIDocument::eConnected:
      static_cast<LifecycleConnectedCallback *>(mCallback.get())->Call(mThisObject);
      break;
    case nsIDocument::eDisconnected:
      static_cast<LifecycleDisconnectedCallback *>(mCallback.get())->Call(mThisObject);
      break;
    case nsIDocument::eAdopted:
      static_cast<LifecycleAdoptedCallback *>(mCallback.get())->Call(mThisObject,
        mAdoptedCallbackArgs.mOldDocument, mAdoptedCallbackArgs.mNewDocument);
      break;
    case nsIDocument::eAttributeChanged:
      static_cast<LifecycleAttributeChangedCallback *>(mCallback.get())->Call(mThisObject,
        mArgs.name, mArgs.oldValue, mArgs.newValue, mArgs.namespaceURI);
      break;
    case nsIDocument::eGetCustomInterface:
      MOZ_ASSERT_UNREACHABLE("Don't call GetCustomInterface through callback");
      break;
  }
}

void
CustomElementCallback::Traverse(nsCycleCollectionTraversalCallback& aCb) const
{
  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(aCb, "mThisObject");
  aCb.NoteXPCOMChild(mThisObject);

  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(aCb, "mCallback");
  aCb.NoteXPCOMChild(mCallback);
}

CustomElementCallback::CustomElementCallback(Element* aThisObject,
                                             nsIDocument::ElementCallbackType aCallbackType,
                                             mozilla::dom::CallbackFunction* aCallback)
  : mThisObject(aThisObject),
    mCallback(aCallback),
    mType(aCallbackType)
{
}
//-----------------------------------------------------
// CustomElementConstructor

already_AddRefed<Element>
CustomElementConstructor::Construct(const char* aExecutionReason,
                                    ErrorResult& aRv)
{
  CallSetup s(this, aRv, aExecutionReason,
              CallbackFunction::eRethrowExceptions);

  JSContext* cx = s.GetContext();
  if (!cx) {
    MOZ_ASSERT(aRv.Failed());
    return nullptr;
  }

  JS::Rooted<JSObject*> result(cx);
  JS::Rooted<JS::Value> constructor(cx, JS::ObjectValue(*mCallback));
  if (!JS::Construct(cx, constructor, JS::HandleValueArray::empty(), &result)) {
    aRv.NoteJSContextException(cx);
    return nullptr;
  }

  RefPtr<Element> element;
  if (NS_FAILED(UNWRAP_OBJECT(Element, &result, element))) {
    return nullptr;
  }

  return element.forget();
}

//-----------------------------------------------------
// CustomElementData

CustomElementData::CustomElementData(nsAtom* aType)
  : CustomElementData(aType, CustomElementData::State::eUndefined)
{
}

CustomElementData::CustomElementData(nsAtom* aType, State aState)
  : mState(aState)
  , mType(aType)
{
}

void
CustomElementData::SetCustomElementDefinition(CustomElementDefinition* aDefinition)
{
  MOZ_ASSERT(mState == State::eCustom);
  MOZ_ASSERT(!mCustomElementDefinition);
  MOZ_ASSERT(aDefinition->mType == mType);

  mCustomElementDefinition = aDefinition;
}

CustomElementDefinition*
CustomElementData::GetCustomElementDefinition()
{
  MOZ_ASSERT(mCustomElementDefinition ? mState == State::eCustom
                                      : mState != State::eCustom);

  return mCustomElementDefinition;
}

nsAtom*
CustomElementData::GetCustomElementType()
{
  return mType;
}

void
CustomElementData::Traverse(nsCycleCollectionTraversalCallback& aCb) const
{
  for (uint32_t i = 0; i < mReactionQueue.Length(); i++) {
    if (mReactionQueue[i]) {
      mReactionQueue[i]->Traverse(aCb);
    }
  }

  if (mCustomElementDefinition) {
    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(aCb, "mCustomElementDefinition");
    aCb.NoteNativeChild(mCustomElementDefinition,
      NS_CYCLE_COLLECTION_PARTICIPANT(CustomElementDefinition));
  }
}

void
CustomElementData::Unlink()
{
  mReactionQueue.Clear();
  mCustomElementDefinition = nullptr;
}

//-----------------------------------------------------
// CustomElementRegistry

namespace {

class MOZ_RAII AutoConstructionStackEntry final
{
public:
  AutoConstructionStackEntry(nsTArray<RefPtr<Element>>& aStack,
                             Element* aElement)
    : mStack(aStack)
  {
    MOZ_ASSERT(aElement->IsHTMLElement() || aElement->IsXULElement());

    mIndex = mStack.Length();
    mStack.AppendElement(aElement);
  }

  ~AutoConstructionStackEntry()
  {
    MOZ_ASSERT(mIndex == mStack.Length() - 1,
               "Removed element should be the last element");
    mStack.RemoveElementAt(mIndex);
  }

private:
  nsTArray<RefPtr<Element>>& mStack;
  uint32_t mIndex;
};

} // namespace anonymous

// Only needed for refcounted objects.
NS_IMPL_CYCLE_COLLECTION_CLASS(CustomElementRegistry)

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(CustomElementRegistry)
  tmp->mConstructors.clear();
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mCustomDefinitions)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mWhenDefinedPromiseMap)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mElementCreationCallbacks)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mWindow)
  NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(CustomElementRegistry)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mCustomDefinitions)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mWhenDefinedPromiseMap)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mElementCreationCallbacks)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mWindow)
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(CustomElementRegistry)
  for (auto iter = tmp->mConstructors.iter(); !iter.done(); iter.next()) {
    aCallbacks.Trace(&iter.get().mutableKey(),
                     "mConstructors key",
                     aClosure);
  }
  NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER
NS_IMPL_CYCLE_COLLECTION_TRACE_END

NS_IMPL_CYCLE_COLLECTING_ADDREF(CustomElementRegistry)
NS_IMPL_CYCLE_COLLECTING_RELEASE(CustomElementRegistry)

NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(CustomElementRegistry)
  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
  NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END

CustomElementRegistry::CustomElementRegistry(nsPIDOMWindowInner* aWindow)
 : mWindow(aWindow)
 , mIsCustomDefinitionRunning(false)
{
  MOZ_ASSERT(aWindow);

  mozilla::HoldJSObjects(this);
}

CustomElementRegistry::~CustomElementRegistry()
{
  mozilla::DropJSObjects(this);
}

bool
CustomElementRegistry::IsCustomElementEnabled(JSContext* aCx, JSObject* aObject)
{
  if (nsContentUtils::IsCustomElementsEnabled()) {
    return true;
  }

  if (!XRE_IsParentProcess()) {
    return false;
  }

  nsIPrincipal* principal =
    nsContentUtils::ObjectPrincipal(js::UncheckedUnwrap(aObject));
  return nsContentUtils::AllowXULXBLForPrincipal(principal);
}

bool
CustomElementRegistry::IsCustomElementEnabled(nsIDocument* aDoc)
{
  if (nsContentUtils::IsCustomElementsEnabled()) {
    return true;
  }

  return XRE_IsParentProcess() && aDoc->AllowXULXBL();
}

NS_IMETHODIMP
CustomElementRegistry::RunCustomElementCreationCallback::Run()
{
  ErrorResult er;
  nsDependentAtomString value(mAtom);
  mCallback->Call(value, er);
  MOZ_ASSERT(NS_SUCCEEDED(er.StealNSResult()),
    "chrome JavaScript error in the callback.");

  CustomElementDefinition* definition =
    mRegistry->mCustomDefinitions.GetWeak(mAtom);
  MOZ_ASSERT(definition, "Callback should define the definition of type.");
  MOZ_ASSERT(!mRegistry->mElementCreationCallbacks.GetWeak(mAtom),
    "Callback should be removed.");

  nsAutoPtr<nsTHashtable<nsRefPtrHashKey<nsIWeakReference>>> elements;
  mRegistry->mElementCreationCallbacksUpgradeCandidatesMap.Remove(mAtom, &elements);
  MOZ_ASSERT(elements, "There should be a list");

  for (auto iter = elements->Iter(); !iter.Done(); iter.Next()) {
    nsCOMPtr<Element> elem = do_QueryReferent(iter.Get()->GetKey());
    if (!elem) {
      continue;
    }

    CustomElementRegistry::Upgrade(elem, definition, er);
    MOZ_ASSERT(NS_SUCCEEDED(er.StealNSResult()),
      "chrome JavaScript error in custom element construction.");
  }

  return NS_OK;
}

CustomElementDefinition*
CustomElementRegistry::LookupCustomElementDefinition(nsAtom* aNameAtom,
                                                     int32_t aNameSpaceID,
                                                     nsAtom* aTypeAtom)
{
  CustomElementDefinition* data = mCustomDefinitions.GetWeak(aTypeAtom);

  if (!data) {
    RefPtr<CustomElementCreationCallback> callback;
    mElementCreationCallbacks.Get(aTypeAtom, getter_AddRefs(callback));
    if (callback) {
      mElementCreationCallbacks.Remove(aTypeAtom);
      mElementCreationCallbacksUpgradeCandidatesMap.LookupOrAdd(aTypeAtom);
      RefPtr<Runnable> runnable =
        new RunCustomElementCreationCallback(this, aTypeAtom, callback);
      nsContentUtils::AddScriptRunner(runnable);
      data = mCustomDefinitions.GetWeak(aTypeAtom);
    }
  }

  if (data && data->mLocalName == aNameAtom && data->mNamespaceID == aNameSpaceID) {
    return data;
  }

  return nullptr;
}

CustomElementDefinition*
CustomElementRegistry::LookupCustomElementDefinition(JSContext* aCx,
                                                     JSObject* aConstructor) const
{
  JS::Rooted<JSObject*> constructor(aCx, js::CheckedUnwrap(aConstructor));

  const auto& ptr = mConstructors.lookup(constructor);
  if (!ptr) {
    return nullptr;
  }

  CustomElementDefinition* definition = mCustomDefinitions.GetWeak(ptr->value());
  MOZ_ASSERT(definition, "Definition must be found in mCustomDefinitions");

  return definition;
}

void
CustomElementRegistry::RegisterUnresolvedElement(Element* aElement, nsAtom* aTypeName)
{
  // We don't have a use-case for a Custom Element inside NAC, and continuing
  // here causes performance issues for NAC + XBL anonymous content.
  if (aElement->IsInNativeAnonymousSubtree()) {
    return;
  }

  mozilla::dom::NodeInfo* info = aElement->NodeInfo();

  // Candidate may be a custom element through extension,
  // in which case the custom element type name will not
  // match the element tag name. e.g. <button is="x-button">.
  RefPtr<nsAtom> typeName = aTypeName;
  if (!typeName) {
    typeName = info->NameAtom();
  }

  if (mCustomDefinitions.GetWeak(typeName)) {
    return;
  }

  nsTHashtable<nsRefPtrHashKey<nsIWeakReference>>* unresolved =
    mCandidatesMap.LookupOrAdd(typeName);
  nsWeakPtr elem = do_GetWeakReference(aElement);
  unresolved->PutEntry(elem);
}

void
CustomElementRegistry::UnregisterUnresolvedElement(Element* aElement,
                                                   nsAtom* aTypeName)
{
  nsIWeakReference* weak = aElement->GetExistingWeakReference();
  if (!weak) {
    return;
  }

#ifdef DEBUG
  {
    nsWeakPtr weakPtr = do_GetWeakReference(aElement);
    MOZ_ASSERT(weak == weakPtr.get(),
               "do_GetWeakReference should reuse the existing nsIWeakReference.");
  }
#endif

  nsTHashtable<nsRefPtrHashKey<nsIWeakReference>>* candidates = nullptr;
  if (mCandidatesMap.Get(aTypeName, &candidates)) {
    MOZ_ASSERT(candidates);
    candidates->RemoveEntry(weak);
  }
}

/* static */ UniquePtr<CustomElementCallback>
CustomElementRegistry::CreateCustomElementCallback(
  nsIDocument::ElementCallbackType aType, Element* aCustomElement,
  LifecycleCallbackArgs* aArgs,
  LifecycleAdoptedCallbackArgs* aAdoptedCallbackArgs,
  CustomElementDefinition* aDefinition)
{
  MOZ_ASSERT(aDefinition, "CustomElementDefinition should not be null");
  MOZ_ASSERT(aCustomElement->GetCustomElementData(),
             "CustomElementData should exist");

  // Let CALLBACK be the callback associated with the key NAME in CALLBACKS.
  CallbackFunction* func = nullptr;
  switch (aType) {
    case nsIDocument::eConnected:
      if (aDefinition->mCallbacks->mConnectedCallback.WasPassed()) {
        func = aDefinition->mCallbacks->mConnectedCallback.Value();
      }
      break;

    case nsIDocument::eDisconnected:
      if (aDefinition->mCallbacks->mDisconnectedCallback.WasPassed()) {
        func = aDefinition->mCallbacks->mDisconnectedCallback.Value();
      }
      break;

    case nsIDocument::eAdopted:
      if (aDefinition->mCallbacks->mAdoptedCallback.WasPassed()) {
        func = aDefinition->mCallbacks->mAdoptedCallback.Value();
      }
      break;

    case nsIDocument::eAttributeChanged:
      if (aDefinition->mCallbacks->mAttributeChangedCallback.WasPassed()) {
        func = aDefinition->mCallbacks->mAttributeChangedCallback.Value();
      }
      break;

    case nsIDocument::eGetCustomInterface:
      MOZ_ASSERT_UNREACHABLE("Don't call GetCustomInterface through callback");
      break;
  }

  // If there is no such callback, stop.
  if (!func) {
    return nullptr;
  }

  // Add CALLBACK to ELEMENT's callback queue.
  auto callback =
    MakeUnique<CustomElementCallback>(aCustomElement, aType, func);

  if (aArgs) {
    callback->SetArgs(*aArgs);
  }

  if (aAdoptedCallbackArgs) {
    callback->SetAdoptedCallbackArgs(*aAdoptedCallbackArgs);
  }
  return callback;
}

/* static */ void
CustomElementRegistry::EnqueueLifecycleCallback(nsIDocument::ElementCallbackType aType,
                                                Element* aCustomElement,
                                                LifecycleCallbackArgs* aArgs,
                                                LifecycleAdoptedCallbackArgs* aAdoptedCallbackArgs,
                                                CustomElementDefinition* aDefinition)
{
  CustomElementDefinition* definition = aDefinition;
  if (!definition) {
    definition = aCustomElement->GetCustomElementDefinition();
    if (!definition ||
        definition->mLocalName != aCustomElement->NodeInfo()->NameAtom()) {
      return;
    }

    if (!definition->mCallbacks) {
      // definition has been unlinked.  Don't try to mess with it.
      return;
    }
  }

  auto callback =
    CreateCustomElementCallback(aType, aCustomElement, aArgs,
                                aAdoptedCallbackArgs, definition);
  if (!callback) {
    return;
  }

  DocGroup* docGroup = aCustomElement->OwnerDoc()->GetDocGroup();
  if (!docGroup) {
    return;
  }

  if (aType == nsIDocument::eAttributeChanged) {
    RefPtr<nsAtom> attrName = NS_Atomize(aArgs->name);
    if (definition->mObservedAttributes.IsEmpty() ||
        !definition->mObservedAttributes.Contains(attrName)) {
      return;
    }
  }

  CustomElementReactionsStack* reactionsStack =
    docGroup->CustomElementReactionsStack();
  reactionsStack->EnqueueCallbackReaction(aCustomElement, std::move(callback));
}

namespace {

class CandidateFinder
{
public:
  CandidateFinder(nsTHashtable<nsRefPtrHashKey<nsIWeakReference>>& aCandidates,
                  nsIDocument* aDoc);
  nsTArray<nsCOMPtr<Element>> OrderedCandidates();

private:
  bool Traverse(Element* aRoot, nsTArray<nsCOMPtr<Element>>& aOrderedElements);

  nsCOMPtr<nsIDocument> mDoc;
  nsInterfaceHashtable<nsPtrHashKey<Element>, Element> mCandidates;
};

CandidateFinder::CandidateFinder(nsTHashtable<nsRefPtrHashKey<nsIWeakReference>>& aCandidates,
                                 nsIDocument* aDoc)
  : mDoc(aDoc)
  , mCandidates(aCandidates.Count())
{
  MOZ_ASSERT(mDoc);
  for (auto iter = aCandidates.Iter(); !iter.Done(); iter.Next()) {
    nsCOMPtr<Element> elem = do_QueryReferent(iter.Get()->GetKey());
    if (!elem) {
      continue;
    }

    Element* key = elem.get();
    mCandidates.Put(key, elem.forget());
  }
}

nsTArray<nsCOMPtr<Element>>
CandidateFinder::OrderedCandidates()
{
  if (mCandidates.Count() == 1) {
    // Fast path for one candidate.
    for (auto iter = mCandidates.Iter(); !iter.Done(); iter.Next()) {
      nsTArray<nsCOMPtr<Element>> rval({ std::move(iter.Data()) });
      iter.Remove();
      return rval;
    }
  }

  nsTArray<nsCOMPtr<Element>> orderedElements(mCandidates.Count());
  for (Element* child = mDoc->GetFirstElementChild(); child; child = child->GetNextElementSibling()) {
    if (!Traverse(child, orderedElements)) {
      break;
    }
  }

  return orderedElements;
}

bool
CandidateFinder::Traverse(Element* aRoot, nsTArray<nsCOMPtr<Element>>& aOrderedElements)
{
  nsCOMPtr<Element> elem;
  if (mCandidates.Remove(aRoot, getter_AddRefs(elem))) {
    aOrderedElements.AppendElement(std::move(elem));
    if (mCandidates.Count() == 0) {
      return false;
    }
  }

  if (ShadowRoot* root = aRoot->GetShadowRoot()) {
    // First iterate the children of the shadow root if aRoot is a shadow host.
    for (Element* child = root->GetFirstElementChild(); child;
         child = child->GetNextElementSibling()) {
      if (!Traverse(child, aOrderedElements)) {
        return false;
      }
    }
  }

  // Iterate the explicit children of aRoot.
  for (Element* child = aRoot->GetFirstElementChild(); child;
       child = child->GetNextElementSibling()) {
    if (!Traverse(child, aOrderedElements)) {
      return false;
    }
  }

  return true;
}

}

void
CustomElementRegistry::UpgradeCandidates(nsAtom* aKey,
                                         CustomElementDefinition* aDefinition,
                                         ErrorResult& aRv)
{
  DocGroup* docGroup = mWindow->GetDocGroup();
  if (!docGroup) {
    aRv.Throw(NS_ERROR_UNEXPECTED);
    return;
  }

  nsAutoPtr<nsTHashtable<nsRefPtrHashKey<nsIWeakReference>>> candidates;
  if (mCandidatesMap.Remove(aKey, &candidates)) {
    MOZ_ASSERT(candidates);
    CustomElementReactionsStack* reactionsStack =
      docGroup->CustomElementReactionsStack();

    CandidateFinder finder(*candidates, mWindow->GetExtantDoc());
    for (auto& elem : finder.OrderedCandidates()) {
      reactionsStack->EnqueueUpgradeReaction(elem, aDefinition);
    }
  }
}

JSObject*
CustomElementRegistry::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
{
  return CustomElementRegistry_Binding::Wrap(aCx, this, aGivenProto);
}

nsISupports* CustomElementRegistry::GetParentObject() const
{
  return mWindow;
}

DocGroup*
CustomElementRegistry::GetDocGroup() const
{
  return mWindow ? mWindow->GetDocGroup() : nullptr;
}

int32_t
CustomElementRegistry::InferNamespace(JSContext* aCx,
                                      JS::Handle<JSObject*> constructor)
{
  JSObject* XULConstructor = XULElement_Binding::GetConstructorObject(aCx);

  JS::Rooted<JSObject*> proto(aCx, constructor);
  while (proto) {
    if (proto == XULConstructor) {
      return kNameSpaceID_XUL;
    }

    JS_GetPrototype(aCx, proto, &proto);
  }

  return kNameSpaceID_XHTML;
}

// https://html.spec.whatwg.org/multipage/scripting.html#element-definition
void
CustomElementRegistry::Define(JSContext* aCx,
                              const nsAString& aName,
                              Function& aFunctionConstructor,
                              const ElementDefinitionOptions& aOptions,
                              ErrorResult& aRv)
{
  // Note: No calls that might run JS or trigger CC before this point, or
  // there's a (vanishingly small) chance of our constructor being nulled
  // before we access it.
  JS::Rooted<JSObject*> constructor(aCx, aFunctionConstructor.CallableOrNull());

  /**
   * 1. If IsConstructor(constructor) is false, then throw a TypeError and abort
   *    these steps.
   */
  // For now, all wrappers are constructable if they are callable. So we need to
  // unwrap constructor to check it is really constructable.
  JS::Rooted<JSObject*> constructorUnwrapped(aCx, js::CheckedUnwrap(constructor));
  if (!constructorUnwrapped) {
    // If the caller's compartment does not have permission to access the
    // unwrapped constructor then throw.
    aRv.Throw(NS_ERROR_DOM_SECURITY_ERR);
    return;
  }

  if (!JS::IsConstructor(constructorUnwrapped)) {
    aRv.ThrowTypeError<MSG_NOT_CONSTRUCTOR>(NS_LITERAL_STRING("Argument 2 of CustomElementRegistry.define"));
    return;
  }

  int32_t nameSpaceID = InferNamespace(aCx, constructor);

  /**
   * 2. If name is not a valid custom element name, then throw a "SyntaxError"
   *    DOMException and abort these steps.
   */
  nsIDocument* doc = mWindow->GetExtantDoc();
  RefPtr<nsAtom> nameAtom(NS_Atomize(aName));
  if (!nsContentUtils::IsCustomElementName(nameAtom, nameSpaceID)) {
    aRv.Throw(NS_ERROR_DOM_SYNTAX_ERR);
    return;
  }

  /**
   * 3. If this CustomElementRegistry contains an entry with name name, then
   *    throw a "NotSupportedError" DOMException and abort these steps.
   */
  if (mCustomDefinitions.GetWeak(nameAtom)) {
    aRv.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
    return;
  }

  /**
   * 4. If this CustomElementRegistry contains an entry with constructor constructor,
   *    then throw a "NotSupportedError" DOMException and abort these steps.
   */
  const auto& ptr = mConstructors.lookup(constructorUnwrapped);
  if (ptr) {
    MOZ_ASSERT(mCustomDefinitions.GetWeak(ptr->value()),
               "Definition must be found in mCustomDefinitions");
    aRv.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
    return;
  }

  /**
   * 5. Let localName be name.
   * 6. Let extends be the value of the extends member of options, or null if
   *    no such member exists.
   * 7. If extends is not null, then:
   *    1. If extends is a valid custom element name, then throw a
   *       "NotSupportedError" DOMException.
   *    2. If the element interface for extends and the HTML namespace is
   *       HTMLUnknownElement (e.g., if extends does not indicate an element
   *       definition in this specification), then throw a "NotSupportedError"
   *       DOMException.
   *    3. Set localName to extends.
   *
   * Special note for XUL elements:
   *
   * For step 7.1, we'll subject XUL to the same rules as HTML, so that a
   * custom built-in element will not be extending from a dashed name.
   * Step 7.2 is disregarded. But, we do check if the name is a dashed name
   * (i.e. step 2) given that there is no reason for a custom built-in element
   * type to take on a non-dashed name.
   * This also ensures the name of the built-in custom element type can never
   * be the same as the built-in element name, so we don't break the assumption
   * elsewhere.
   */
  nsAutoString localName(aName);
  if (aOptions.mExtends.WasPassed()) {
    RefPtr<nsAtom> extendsAtom(NS_Atomize(aOptions.mExtends.Value()));
    if (nsContentUtils::IsCustomElementName(extendsAtom, kNameSpaceID_XHTML)) {
      aRv.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
      return;
    }

    if (nameSpaceID == kNameSpaceID_XHTML) {
      // bgsound and multicol are unknown html element.
      int32_t tag = nsHTMLTags::CaseSensitiveAtomTagToId(extendsAtom);
      if (tag == eHTMLTag_userdefined ||
          tag == eHTMLTag_bgsound ||
          tag == eHTMLTag_multicol) {
        aRv.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
        return;
      }
    } else { // kNameSpaceID_XUL
      // As stated above, ensure the name of the customized built-in element
      // (the one that goes to the |is| attribute) is a dashed name.
      if (!nsContentUtils::IsNameWithDash(nameAtom)) {
        aRv.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
        return;
      }
    }

    localName.Assign(aOptions.mExtends.Value());
  }

  /**
   * 8. If this CustomElementRegistry's element definition is running flag is set,
   *    then throw a "NotSupportedError" DOMException and abort these steps.
   */
  if (mIsCustomDefinitionRunning) {
    aRv.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
    return;
  }

  auto callbacksHolder = MakeUnique<LifecycleCallbacks>();
  nsTArray<RefPtr<nsAtom>> observedAttributes;
  { // Set mIsCustomDefinitionRunning.
    /**
     * 9. Set this CustomElementRegistry's element definition is running flag.
     */
    AutoSetRunningFlag as(this);

    /**
     * 10.1. Let prototype be Get(constructor, "prototype"). Rethrow any exceptions.
     */
    // The .prototype on the constructor passed could be an "expando" of a
    // wrapper. So we should get it from wrapper instead of the underlying
    // object.
    JS::Rooted<JS::Value> prototype(aCx);
    if (!JS_GetProperty(aCx, constructor, "prototype", &prototype)) {
      aRv.NoteJSContextException(aCx);
      return;
    }

    /**
     * 10.2. If Type(prototype) is not Object, then throw a TypeError exception.
     */
    if (!prototype.isObject()) {
      aRv.ThrowTypeError<MSG_NOT_OBJECT>(NS_LITERAL_STRING("constructor.prototype"));
      return;
    }

    /**
     * 10.3. Let lifecycleCallbacks be a map with the four keys
     *       "connectedCallback", "disconnectedCallback", "adoptedCallback", and
     *       "attributeChangedCallback", each of which belongs to an entry whose
     *       value is null. The 'getCustomInterface' callback is also included
     *       for chrome usage.
     * 10.4. For each of the four keys callbackName in lifecycleCallbacks:
     *       1. Let callbackValue be Get(prototype, callbackName). Rethrow any
     *          exceptions.
     *       2. If callbackValue is not undefined, then set the value of the
     *          entry in lifecycleCallbacks with key callbackName to the result
     *          of converting callbackValue to the Web IDL Function callback type.
     *          Rethrow any exceptions from the conversion.
     */
    if (!callbacksHolder->Init(aCx, prototype)) {
      aRv.NoteJSContextException(aCx);
      return;
    }

    /**
     * 10.5. Let observedAttributes be an empty sequence<DOMString>.
     * 10.6. If the value of the entry in lifecycleCallbacks with key
     *       "attributeChangedCallback" is not null, then:
     *       1. Let observedAttributesIterable be Get(constructor,
     *          "observedAttributes"). Rethrow any exceptions.
     *       2. If observedAttributesIterable is not undefined, then set
     *          observedAttributes to the result of converting
     *          observedAttributesIterable to a sequence<DOMString>. Rethrow
     *          any exceptions from the conversion.
     */
    if (callbacksHolder->mAttributeChangedCallback.WasPassed()) {
      JS::Rooted<JS::Value> observedAttributesIterable(aCx);

      if (!JS_GetProperty(aCx, constructor, "observedAttributes",
                          &observedAttributesIterable)) {
        aRv.NoteJSContextException(aCx);
        return;
      }

      if (!observedAttributesIterable.isUndefined()) {
        if (!observedAttributesIterable.isObject()) {
          aRv.ThrowTypeError<MSG_NOT_SEQUENCE>(NS_LITERAL_STRING("observedAttributes"));
          return;
        }

        JS::ForOfIterator iter(aCx);
        if (!iter.init(observedAttributesIterable, JS::ForOfIterator::AllowNonIterable)) {
          aRv.NoteJSContextException(aCx);
          return;
        }

        if (!iter.valueIsIterable()) {
          aRv.ThrowTypeError<MSG_NOT_SEQUENCE>(NS_LITERAL_STRING("observedAttributes"));
          return;
        }

        JS::Rooted<JS::Value> attribute(aCx);
        while (true) {
          bool done;
          if (!iter.next(&attribute, &done)) {
            aRv.NoteJSContextException(aCx);
            return;
          }
          if (done) {
            break;
          }

          nsAutoString attrStr;
          if (!ConvertJSValueToString(aCx, attribute, eStringify, eStringify, attrStr)) {
            aRv.NoteJSContextException(aCx);
            return;
          }

          if (!observedAttributes.AppendElement(NS_Atomize(attrStr))) {
            aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
            return;
          }
        }
      }
    }
  } // Unset mIsCustomDefinitionRunning

  /**
   * 11. Let definition be a new custom element definition with name name,
   *     local name localName, constructor constructor, prototype prototype,
   *     observed attributes observedAttributes, and lifecycle callbacks
   *     lifecycleCallbacks.
   */
  // Associate the definition with the custom element.
  RefPtr<nsAtom> localNameAtom(NS_Atomize(localName));

  /**
   * 12. Add definition to this CustomElementRegistry.
   */
  if (!mConstructors.put(constructorUnwrapped, nameAtom)) {
    aRv.Throw(NS_ERROR_FAILURE);
    return;
  }

  RefPtr<CustomElementDefinition> definition =
    new CustomElementDefinition(nameAtom,
                                localNameAtom,
                                nameSpaceID,
                                &aFunctionConstructor,
                                std::move(observedAttributes),
                                std::move(callbacksHolder));

  CustomElementDefinition* def = definition.get();
  mCustomDefinitions.Put(nameAtom, definition.forget());

  MOZ_ASSERT(mCustomDefinitions.Count() == mConstructors.count(),
             "Number of entries should be the same");

  /**
   * 13. 14. 15. Upgrade candidates
   */
  UpgradeCandidates(nameAtom, def, aRv);

  /**
   * 16. If this CustomElementRegistry's when-defined promise map contains an
   *     entry with key name:
   *     1. Let promise be the value of that entry.
   *     2. Resolve promise with undefined.
   *     3. Delete the entry with key name from this CustomElementRegistry's
   *        when-defined promise map.
   */
  RefPtr<Promise> promise;
  mWhenDefinedPromiseMap.Remove(nameAtom, getter_AddRefs(promise));
  if (promise) {
    promise->MaybeResolveWithUndefined();
  }

  // Dispatch a "customelementdefined" event for DevTools.
  {
    JSString* nameJsStr = JS_NewUCStringCopyN(aCx,
                                              aName.BeginReading(),
                                              aName.Length());

    JS::Rooted<JS::Value> detail(aCx, JS::StringValue(nameJsStr));
    RefPtr<CustomEvent> event = NS_NewDOMCustomEvent(doc, nullptr, nullptr);
    event->InitCustomEvent(aCx,
                           NS_LITERAL_STRING("customelementdefined"),
                           /* CanBubble */ true,
                           /* Cancelable */ true,
                           detail);
    event->SetTrusted(true);

    AsyncEventDispatcher* dispatcher = new AsyncEventDispatcher(doc, event);
    dispatcher->mOnlyChromeDispatch = ChromeOnlyDispatch::eYes;

    dispatcher->PostDOMEvent();
  }

  /**
   * Clean-up mElementCreationCallbacks (if it exists)
   */
  mElementCreationCallbacks.Remove(nameAtom);

}

void
CustomElementRegistry::SetElementCreationCallback(const nsAString& aName,
                                                  CustomElementCreationCallback& aCallback,
                                                  ErrorResult& aRv)
{
  RefPtr<nsAtom> nameAtom(NS_Atomize(aName));
  if (mElementCreationCallbacks.GetWeak(nameAtom) ||
      mCustomDefinitions.GetWeak(nameAtom)) {
    aRv.Throw(NS_ERROR_DOM_NOT_SUPPORTED_ERR);
    return;
  }

  RefPtr<CustomElementCreationCallback> callback = &aCallback;
  mElementCreationCallbacks.Put(nameAtom, callback.forget());
  return;
}

static void
TryUpgrade(nsINode& aNode)
{
  Element* element = aNode.IsElement() ? aNode.AsElement() : nullptr;
  if (element) {
    CustomElementData* ceData = element->GetCustomElementData();
    if (ceData) {
      NodeInfo* nodeInfo = element->NodeInfo();
      nsAtom* typeAtom = ceData->GetCustomElementType();
      CustomElementDefinition* definition =
        nsContentUtils::LookupCustomElementDefinition(nodeInfo->GetDocument(),
                                                      nodeInfo->NameAtom(),
                                                      nodeInfo->NamespaceID(),
                                                      typeAtom);
      if (definition) {
        nsContentUtils::EnqueueUpgradeReaction(element, definition);
      }
    }

    if (ShadowRoot* root = element->GetShadowRoot()) {
      for (Element* child = root->GetFirstElementChild(); child;
           child = child->GetNextElementSibling()) {
        TryUpgrade(*child);
      }
    }
  }

  for (Element* child = aNode.GetFirstElementChild(); child;
       child = child->GetNextElementSibling()) {
    TryUpgrade(*child);
  }
}

void
CustomElementRegistry::Upgrade(nsINode& aRoot)
{
  TryUpgrade(aRoot);
}

void
CustomElementRegistry::Get(JSContext* aCx, const nsAString& aName,
                           JS::MutableHandle<JS::Value> aRetVal)
{
  RefPtr<nsAtom> nameAtom(NS_Atomize(aName));
  CustomElementDefinition* data = mCustomDefinitions.GetWeak(nameAtom);

  if (!data) {
    aRetVal.setUndefined();
    return;
  }

  aRetVal.setObject(*data->mConstructor->Callback(aCx));
}

already_AddRefed<Promise>
CustomElementRegistry::WhenDefined(const nsAString& aName, ErrorResult& aRv)
{
  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(mWindow);
  RefPtr<Promise> promise = Promise::Create(global, aRv);

  if (aRv.Failed()) {
    return nullptr;
  }

  RefPtr<nsAtom> nameAtom(NS_Atomize(aName));
  nsIDocument* doc = mWindow->GetExtantDoc();
  uint32_t nameSpaceID = doc ? doc->GetDefaultNamespaceID() : kNameSpaceID_XHTML;
  if (!nsContentUtils::IsCustomElementName(nameAtom, nameSpaceID)) {
    promise->MaybeReject(NS_ERROR_DOM_SYNTAX_ERR);
    return promise.forget();
  }

  if (mCustomDefinitions.GetWeak(nameAtom)) {
    promise->MaybeResolve(JS::UndefinedHandleValue);
    return promise.forget();
  }

  auto entry = mWhenDefinedPromiseMap.LookupForAdd(nameAtom);
  if (entry) {
    promise = entry.Data();
  } else {
    entry.OrInsert([&promise](){ return promise; });
  }

  return promise.forget();
}

namespace {

static void
DoUpgrade(Element* aElement,
          CustomElementConstructor* aConstructor,
          ErrorResult& aRv)
{
  // Rethrow the exception since it might actually throw the exception from the
  // upgrade steps back out to the caller of document.createElement.
  RefPtr<Element> constructResult =
    aConstructor->Construct("Custom Element Upgrade", aRv);
  if (aRv.Failed()) {
    return;
  }

  if (!constructResult || constructResult.get() != aElement) {
    aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
    return;
  }
}

} // anonymous namespace

// https://html.spec.whatwg.org/multipage/scripting.html#upgrades
/* static */ void
CustomElementRegistry::Upgrade(Element* aElement,
                               CustomElementDefinition* aDefinition,
                               ErrorResult& aRv)
{
  RefPtr<CustomElementData> data = aElement->GetCustomElementData();
  MOZ_ASSERT(data, "CustomElementData should exist");

  // Step 1 and step 2.
  if (data->mState == CustomElementData::State::eCustom ||
      data->mState == CustomElementData::State::eFailed) {
    return;
  }

  // Step 3.
  if (!aDefinition->mObservedAttributes.IsEmpty()) {
    uint32_t count = aElement->GetAttrCount();
    for (uint32_t i = 0; i < count; i++) {
      mozilla::dom::BorrowedAttrInfo info = aElement->GetAttrInfoAt(i);

      const nsAttrName* name = info.mName;
      nsAtom* attrName = name->LocalName();

      if (aDefinition->IsInObservedAttributeList(attrName)) {
        int32_t namespaceID = name->NamespaceID();
        nsAutoString attrValue, namespaceURI;
        info.mValue->ToString(attrValue);
        nsContentUtils::NameSpaceManager()->GetNameSpaceURI(namespaceID,
                                                            namespaceURI);

        LifecycleCallbackArgs args = {
          nsDependentAtomString(attrName),
          VoidString(),
          attrValue,
          (namespaceURI.IsEmpty() ? VoidString() : namespaceURI)
        };
        nsContentUtils::EnqueueLifecycleCallback(nsIDocument::eAttributeChanged,
                                                 aElement,
                                                 &args, nullptr, aDefinition);
      }
    }
  }

  // Step 4.
  if (aElement->IsInComposedDoc()) {
    nsContentUtils::EnqueueLifecycleCallback(nsIDocument::eConnected, aElement,
      nullptr, nullptr, aDefinition);
  }

  // Step 5.
  AutoConstructionStackEntry acs(aDefinition->mConstructionStack, aElement);

  // Step 6 and step 7.
  DoUpgrade(aElement, aDefinition->mConstructor, aRv);
  if (aRv.Failed()) {
    data->mState = CustomElementData::State::eFailed;
    // Empty element's custom element reaction queue.
    data->mReactionQueue.Clear();
    return;
  }

  // Step 8.
  data->mState = CustomElementData::State::eCustom;
  aElement->SetDefined(true);

  // Step 9.
  aElement->SetCustomElementDefinition(aDefinition);
}

already_AddRefed<nsISupports>
CustomElementRegistry::CallGetCustomInterface(Element* aElement,
                                              const nsIID& aIID)
{
  MOZ_ASSERT(aElement);

  if (nsContentUtils::IsChromeDoc(aElement->OwnerDoc())) {
    CustomElementDefinition* definition = aElement->GetCustomElementDefinition();
    if (definition && definition->mCallbacks &&
        definition->mCallbacks->mGetCustomInterfaceCallback.WasPassed() &&
        definition->mLocalName == aElement->NodeInfo()->NameAtom()) {

      LifecycleGetCustomInterfaceCallback* func =
        definition->mCallbacks->mGetCustomInterfaceCallback.Value();
      JS::Rooted<JSObject*> customInterface(RootingCx());

      nsCOMPtr<nsIJSID> iid = nsJSID::NewID(aIID);
      func->Call(aElement, iid, &customInterface);
      JS::Rooted<JSObject*> funcGlobal(RootingCx(), func->CallbackGlobalOrNull());
      if (customInterface && funcGlobal) {
        RefPtr<nsXPCWrappedJS> wrappedJS;
        AutoJSAPI jsapi;
        if (jsapi.Init(funcGlobal)) {
          JSContext* cx = jsapi.cx();
          nsresult rv =
            nsXPCWrappedJS::GetNewOrUsed(cx, customInterface,
                                         NS_GET_IID(nsISupports),
                                         getter_AddRefs(wrappedJS));
          if (NS_SUCCEEDED(rv) && wrappedJS) {
            // Check if the returned object implements the desired interface.
            nsCOMPtr<nsISupports> retval;
            if (NS_SUCCEEDED(wrappedJS->QueryInterface(aIID,
                                                       getter_AddRefs(retval)))) {
              return retval.forget();
            }
          }
        }
      }
    }
  }

  // Otherwise, check if the element supports the interface directly, and just use that.
  nsCOMPtr<nsISupports> supports;
  if (NS_SUCCEEDED(aElement->QueryInterface(aIID, getter_AddRefs(supports)))) {
    return supports.forget();
  }

  return nullptr;
}

//-----------------------------------------------------
// CustomElementReactionsStack

void
CustomElementReactionsStack::CreateAndPushElementQueue()
{
  MOZ_ASSERT(mRecursionDepth);
  MOZ_ASSERT(!mIsElementQueuePushedForCurrentRecursionDepth);

  // Push a new element queue onto the custom element reactions stack.
  mReactionsStack.AppendElement(MakeUnique<ElementQueue>());
  mIsElementQueuePushedForCurrentRecursionDepth = true;
}

void
CustomElementReactionsStack::PopAndInvokeElementQueue()
{
  MOZ_ASSERT(mRecursionDepth);
  MOZ_ASSERT(mIsElementQueuePushedForCurrentRecursionDepth);
  MOZ_ASSERT(!mReactionsStack.IsEmpty(),
             "Reaction stack shouldn't be empty");

  // Pop the element queue from the custom element reactions stack,
  // and invoke custom element reactions in that queue.
  const uint32_t lastIndex = mReactionsStack.Length() - 1;
  ElementQueue* elementQueue = mReactionsStack.ElementAt(lastIndex).get();
  // Check element queue size in order to reduce function call overhead.
  if (!elementQueue->IsEmpty()) {
    // It is still not clear what error reporting will look like in custom
    // element, see https://github.com/w3c/webcomponents/issues/635.
    // We usually report the error to entry global in gecko, so just follow the
    // same behavior here.
    // This may be null if it's called from parser, see the case of
    // attributeChangedCallback in
    // https://html.spec.whatwg.org/multipage/parsing.html#create-an-element-for-the-token
    // In that case, the exception of callback reactions will be automatically
    // reported in CallSetup.
    nsIGlobalObject* global = GetEntryGlobal();
    InvokeReactions(elementQueue, global);
  }

  // InvokeReactions() might create other custom element reactions, but those
  // new reactions should be already consumed and removed at this point.
  MOZ_ASSERT(lastIndex == mReactionsStack.Length() - 1,
             "reactions created by InvokeReactions() should be consumed and removed");

  mReactionsStack.RemoveElementAt(lastIndex);
  mIsElementQueuePushedForCurrentRecursionDepth = false;
}

void
CustomElementReactionsStack::EnqueueUpgradeReaction(Element* aElement,
                                                    CustomElementDefinition* aDefinition)
{
  Enqueue(aElement, new CustomElementUpgradeReaction(aDefinition));
}

void
CustomElementReactionsStack::EnqueueCallbackReaction(Element* aElement,
                                                     UniquePtr<CustomElementCallback> aCustomElementCallback)
{
  Enqueue(aElement, new CustomElementCallbackReaction(std::move(aCustomElementCallback)));
}

void
CustomElementReactionsStack::Enqueue(Element* aElement,
                                     CustomElementReaction* aReaction)
{
  RefPtr<CustomElementData> elementData = aElement->GetCustomElementData();
  MOZ_ASSERT(elementData, "CustomElementData should exist");

  if (mRecursionDepth) {
    // If the element queue is not created for current recursion depth, create
    // and push an element queue to reactions stack first.
    if (!mIsElementQueuePushedForCurrentRecursionDepth) {
      CreateAndPushElementQueue();
    }

    MOZ_ASSERT(!mReactionsStack.IsEmpty());
    // Add element to the current element queue.
    mReactionsStack.LastElement()->AppendElement(aElement);
    elementData->mReactionQueue.AppendElement(aReaction);
    return;
  }

  // If the custom element reactions stack is empty, then:
  // Add element to the backup element queue.
  MOZ_ASSERT(mReactionsStack.IsEmpty(),
             "custom element reactions stack should be empty");
  mBackupQueue.AppendElement(aElement);
  elementData->mReactionQueue.AppendElement(aReaction);

  if (mIsBackupQueueProcessing) {
    return;
  }

  CycleCollectedJSContext* context = CycleCollectedJSContext::Get();
  RefPtr<BackupQueueMicroTask> bqmt = new BackupQueueMicroTask(this);
  context->DispatchToMicroTask(bqmt.forget());
}

void
CustomElementReactionsStack::InvokeBackupQueue()
{
  // Check backup queue size in order to reduce function call overhead.
  if (!mBackupQueue.IsEmpty()) {
    // Upgrade reactions won't be scheduled in backup queue and the exception of
    // callback reactions will be automatically reported in CallSetup.
    // If the reactions are invoked from backup queue (in microtask check point),
    // we don't need to pass global object for error reporting.
    InvokeReactions(&mBackupQueue, nullptr);
  }
  MOZ_ASSERT(mBackupQueue.IsEmpty(),
             "There are still some reactions in BackupQueue not being consumed!?!");
}

void
CustomElementReactionsStack::InvokeReactions(ElementQueue* aElementQueue,
                                             nsIGlobalObject* aGlobal)
{
  // This is used for error reporting.
  Maybe<AutoEntryScript> aes;
  if (aGlobal) {
    aes.emplace(aGlobal, "custom elements reaction invocation");
  }

  // Note: It's possible to re-enter this method.
  for (uint32_t i = 0; i < aElementQueue->Length(); ++i) {
    Element* element = aElementQueue->ElementAt(i);
    // ElementQueue hold a element's strong reference, it should not be a nullptr.
    MOZ_ASSERT(element);

    RefPtr<CustomElementData> elementData = element->GetCustomElementData();
    if (!elementData || !element->GetOwnerGlobal()) {
      // This happens when the document is destroyed and the element is already
      // unlinked, no need to fire the callbacks in this case.
      continue;
    }

    auto& reactions = elementData->mReactionQueue;
    for (uint32_t j = 0; j < reactions.Length(); ++j) {
      // Transfer the ownership of the entry due to reentrant invocation of
      // this function.
      auto reaction(std::move(reactions.ElementAt(j)));
      if (reaction) {
        if (!aGlobal && reaction->IsUpgradeReaction()) {
          nsIGlobalObject* global = element->GetOwnerGlobal();
          MOZ_ASSERT(!aes);
          aes.emplace(global, "custom elements reaction invocation");
        }
        ErrorResult rv;
        reaction->Invoke(element, rv);
        if (aes) {
          JSContext* cx = aes->cx();
          if (rv.MaybeSetPendingException(cx)) {
            aes->ReportException();
          }
          MOZ_ASSERT(!JS_IsExceptionPending(cx));
          if (!aGlobal && reaction->IsUpgradeReaction()) {
            aes.reset();
          }
        }
        MOZ_ASSERT(!rv.Failed());
      }
    }
    reactions.Clear();
  }
  aElementQueue->Clear();
}

//-----------------------------------------------------
// CustomElementDefinition

NS_IMPL_CYCLE_COLLECTION_CLASS(CustomElementDefinition)

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(CustomElementDefinition)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mConstructor)
  tmp->mCallbacks = nullptr;
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(CustomElementDefinition)
  mozilla::dom::LifecycleCallbacks* callbacks = tmp->mCallbacks.get();

  if (callbacks->mAttributeChangedCallback.WasPassed()) {
    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb,
      "mCallbacks->mAttributeChangedCallback");
    cb.NoteXPCOMChild(callbacks->mAttributeChangedCallback.Value());
  }

  if (callbacks->mConnectedCallback.WasPassed()) {
    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mCallbacks->mConnectedCallback");
    cb.NoteXPCOMChild(callbacks->mConnectedCallback.Value());
  }

  if (callbacks->mDisconnectedCallback.WasPassed()) {
    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mCallbacks->mDisconnectedCallback");
    cb.NoteXPCOMChild(callbacks->mDisconnectedCallback.Value());
  }

  if (callbacks->mAdoptedCallback.WasPassed()) {
    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mCallbacks->mAdoptedCallback");
    cb.NoteXPCOMChild(callbacks->mAdoptedCallback.Value());
  }

  if (callbacks->mGetCustomInterfaceCallback.WasPassed()) {
    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mCallbacks->mGetCustomInterfaceCallback");
    cb.NoteXPCOMChild(callbacks->mGetCustomInterfaceCallback.Value());
  }

  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mConstructor");
  cb.NoteXPCOMChild(tmp->mConstructor);
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(CustomElementDefinition)
NS_IMPL_CYCLE_COLLECTION_TRACE_END

NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(CustomElementDefinition, AddRef)
NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(CustomElementDefinition, Release)


CustomElementDefinition::CustomElementDefinition(nsAtom* aType,
                                                 nsAtom* aLocalName,
                                                 int32_t aNamespaceID,
                                                 Function* aConstructor,
                                                 nsTArray<RefPtr<nsAtom>>&& aObservedAttributes,
                                                 UniquePtr<LifecycleCallbacks>&& aCallbacks)
  : mType(aType),
    mLocalName(aLocalName),
    mNamespaceID(aNamespaceID),
    mConstructor(new CustomElementConstructor(aConstructor)),
    mObservedAttributes(std::move(aObservedAttributes)),
    mCallbacks(std::move(aCallbacks))
{
}

} // namespace dom
} // namespace mozilla