Clipboard.cpp

/* -*- 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/Clipboard.h"

#include <algorithm>

#include "mozilla/AbstractThread.h"
#include "mozilla/BasePrincipal.h"
#include "mozilla/RefPtr.h"
#include "mozilla/Result.h"
#include "mozilla/ResultVariant.h"
#include "mozilla/dom/BlobBinding.h"
#include "mozilla/dom/ClipboardItem.h"
#include "mozilla/dom/ClipboardBinding.h"
#include "mozilla/dom/ContentChild.h"
#include "mozilla/dom/Promise.h"
#include "mozilla/dom/PromiseNativeHandler.h"
#include "mozilla/dom/DataTransfer.h"
#include "mozilla/dom/DataTransferItemList.h"
#include "mozilla/dom/DataTransferItem.h"
#include "mozilla/dom/Document.h"
#include "mozilla/StaticPrefs_dom.h"
#include "imgIContainer.h"
#include "imgITools.h"
#include "nsArrayUtils.h"
#include "nsComponentManagerUtils.h"
#include "nsContentUtils.h"
#include "nsIClipboard.h"
#include "nsIInputStream.h"
#include "nsIParserUtils.h"
#include "nsISupportsPrimitives.h"
#include "nsITransferable.h"
#include "nsNetUtil.h"
#include "nsServiceManagerUtils.h"
#include "nsStringStream.h"
#include "nsTArray.h"
#include "nsThreadUtils.h"
#include "nsVariant.h"

static mozilla::LazyLogModule gClipboardLog("Clipboard");

namespace mozilla::dom {

Clipboard::Clipboard(nsPIDOMWindowInner* aWindow)
    : DOMEventTargetHelper(aWindow) {}

Clipboard::~Clipboard() = default;

// static
bool Clipboard::IsTestingPrefEnabledOrHasReadPermission(
    nsIPrincipal& aSubjectPrincipal) {
  return IsTestingPrefEnabled() ||
         nsContentUtils::PrincipalHasPermission(aSubjectPrincipal,
                                                nsGkAtoms::clipboardRead);
}

// @return true iff the event was dispatched successfully.
static bool MaybeCreateAndDispatchMozClipboardReadPasteEvent(
    nsPIDOMWindowInner& aOwner) {
  RefPtr<Document> document = aOwner.GetDoc();

  if (!document) {
    // Presumably, this shouldn't happen but to be safe, this case is handled.
    MOZ_LOG(Clipboard::GetClipboardLog(), LogLevel::Debug,
            ("%s: no document.", __FUNCTION__));
    return false;
  }

  // Conceptionally, `ClipboardReadPasteChild` is the target of the event.
  // It ensures to receive the event by declaring the event in
  // <BrowserGlue.sys.mjs>.
  return !NS_WARN_IF(NS_FAILED(nsContentUtils::DispatchChromeEvent(
      document, ToSupports(document), u"MozClipboardReadPaste"_ns,
      CanBubble::eNo, Cancelable::eNo)));
}

void Clipboard::ReadRequest::Answer() {
  RefPtr<Promise> p(std::move(mPromise));
  RefPtr<nsPIDOMWindowInner> owner(std::move(mOwner));

  nsresult rv;
  nsCOMPtr<nsIClipboard> clipboardService(
      do_GetService("@mozilla.org/widget/clipboard;1", &rv));
  if (NS_FAILED(rv)) {
    p->MaybeReject(NS_ERROR_UNEXPECTED);
    return;
  }

  switch (mType) {
    case ReadRequestType::eRead: {
      clipboardService
          ->AsyncHasDataMatchingFlavors(
              // Mandatory data types defined in
              // https://w3c.github.io/clipboard-apis/#mandatory-data-types-x
              AutoTArray<nsCString, 3>{nsDependentCString(kHTMLMime),
                                       nsDependentCString(kTextMime),
                                       nsDependentCString(kPNGImageMime)},
              nsIClipboard::kGlobalClipboard)
          ->Then(
              GetMainThreadSerialEventTarget(), __func__,
              /* resolve */
              [owner, p](nsTArray<nsCString> formats) {
                nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(owner);
                if (NS_WARN_IF(!global)) {
                  p->MaybeReject(NS_ERROR_UNEXPECTED);
                  return;
                }

                AutoTArray<RefPtr<ClipboardItem::ItemEntry>, 3> entries;
                for (const auto& format : formats) {
                  nsCOMPtr<nsITransferable> trans =
                      do_CreateInstance("@mozilla.org/widget/transferable;1");
                  if (NS_WARN_IF(!trans)) {
                    continue;
                  }

                  trans->Init(nullptr);
                  trans->AddDataFlavor(format.get());

                  RefPtr<ClipboardItem::ItemEntry> entry =
                      MakeRefPtr<ClipboardItem::ItemEntry>(
                          NS_ConvertUTF8toUTF16(format));
                  entry->LoadData(*global, *trans);
                  entries.AppendElement(std::move(entry));
                }

                // We currently only support one clipboard item.
                AutoTArray<RefPtr<ClipboardItem>, 1> items;
                items.AppendElement(MakeRefPtr<ClipboardItem>(
                    global, PresentationStyle::Unspecified,
                    std::move(entries)));

                p->MaybeResolve(std::move(items));
              },
              /* reject */
              [p](nsresult rv) { p->MaybeReject(rv); });
      break;
    }
    case ReadRequestType::eReadText: {
      nsCOMPtr<nsITransferable> trans =
          do_CreateInstance("@mozilla.org/widget/transferable;1");
      if (NS_WARN_IF(!trans)) {
        p->MaybeReject(NS_ERROR_UNEXPECTED);
        return;
      }

      trans->Init(nullptr);
      trans->AddDataFlavor(kTextMime);
      clipboardService->AsyncGetData(trans, nsIClipboard::kGlobalClipboard)
          ->Then(
              GetMainThreadSerialEventTarget(), __func__,
              /* resolve */
              [trans, p]() {
                nsCOMPtr<nsISupports> data;
                nsresult rv =
                    trans->GetTransferData(kTextMime, getter_AddRefs(data));

                nsAutoString str;
                if (!NS_WARN_IF(NS_FAILED(rv))) {
                  nsCOMPtr<nsISupportsString> supportsstr =
                      do_QueryInterface(data);
                  MOZ_ASSERT(supportsstr);
                  if (supportsstr) {
                    supportsstr->GetData(str);
                  }
                }

                p->MaybeResolve(str);
              },
              /* reject */
              [p](nsresult rv) { p->MaybeReject(rv); });
      break;
    }
    default: {
      MOZ_ASSERT_UNREACHABLE("Unknown read type");
      break;
    }
  }
}

static bool IsReadTextExposedToContent() {
  return StaticPrefs::dom_events_asyncClipboard_readText_DoNotUseDirectly();
}

void Clipboard::CheckReadPermissionAndHandleRequest(
    Promise& aPromise, nsIPrincipal& aSubjectPrincipal, ReadRequestType aType) {
  if (IsTestingPrefEnabledOrHasReadPermission(aSubjectPrincipal)) {
    MOZ_LOG(GetClipboardLog(), LogLevel::Debug,
            ("%s: testing pref enabled or has read permission", __FUNCTION__));
    nsPIDOMWindowInner* owner = GetOwner();
    if (!owner) {
      aPromise.MaybeRejectWithUndefined();
      return;
    }

    ReadRequest{aPromise, aType, *owner}.Answer();
    return;
  }

  if (aSubjectPrincipal.GetIsAddonOrExpandedAddonPrincipal()) {
    // TODO: enable showing the "Paste" button in this case; see bug 1773681.
    MOZ_LOG(GetClipboardLog(), LogLevel::Debug,
            ("%s: Addon without read permssion.", __FUNCTION__));
    aPromise.MaybeRejectWithUndefined();
    return;
  }

  HandleReadRequestWhichRequiresPasteButton(aPromise, aType);
}

void Clipboard::HandleReadRequestWhichRequiresPasteButton(
    Promise& aPromise, ReadRequestType aType) {
  nsPIDOMWindowInner* owner = GetOwner();
  WindowContext* windowContext = owner ? owner->GetWindowContext() : nullptr;
  if (!windowContext) {
    MOZ_ASSERT_UNREACHABLE("There should be a WindowContext.");
    aPromise.MaybeRejectWithUndefined();
    return;
  }

  // If no transient user activation, reject the promise and return.
  if (!windowContext->HasValidTransientUserGestureActivation()) {
    aPromise.MaybeRejectWithNotAllowedError(
        "Clipboard read request was blocked due to lack of "
        "user activation.");
    return;
  }

  // TODO: when a user activation stems from a contextmenu event
  // (https://developer.mozilla.org/en-US/docs/Web/API/Element/contextmenu_event),
  // forbid pasting (bug 1767941).

  switch (mTransientUserPasteState.RefreshAndGet(*windowContext)) {
    case TransientUserPasteState::Value::Initial: {
      MOZ_ASSERT(mReadRequests.IsEmpty());

      if (MaybeCreateAndDispatchMozClipboardReadPasteEvent(*owner)) {
        mTransientUserPasteState.OnStartWaitingForUserReactionToPasteMenuPopup(
            windowContext->GetUserGestureStart());
        mReadRequests.AppendElement(
            MakeUnique<ReadRequest>(aPromise, aType, *owner));
      } else {
        // This shouldn't happen but let's handle this case.
        aPromise.MaybeRejectWithUndefined();
      }
      break;
    }
    case TransientUserPasteState::Value::
        WaitingForUserReactionToPasteMenuPopup: {
      MOZ_ASSERT(!mReadRequests.IsEmpty());

      mReadRequests.AppendElement(
          MakeUnique<ReadRequest>(aPromise, aType, *owner));
      break;
    }
    case TransientUserPasteState::Value::TransientlyForbiddenByUser: {
      aPromise.MaybeRejectWithNotAllowedError(
          "`Clipboard read request was blocked due to the user "
          "dismissing the 'Paste' button.");
      break;
    }
    case TransientUserPasteState::Value::TransientlyAllowedByUser: {
      ReadRequest{aPromise, aType, *owner}.Answer();
      break;
    }
  }
}

already_AddRefed<Promise> Clipboard::ReadHelper(nsIPrincipal& aSubjectPrincipal,
                                                ReadRequestType aType,
                                                ErrorResult& aRv) {
  // Create a new promise
  RefPtr<Promise> p = dom::Promise::Create(GetOwnerGlobal(), aRv);
  if (aRv.Failed()) {
    return nullptr;
  }

  CheckReadPermissionAndHandleRequest(*p, aSubjectPrincipal, aType);
  return p.forget();
}

auto Clipboard::TransientUserPasteState::RefreshAndGet(
    WindowContext& aWindowContext) -> Value {
  MOZ_ASSERT(aWindowContext.HasValidTransientUserGestureActivation());

  switch (mValue) {
    case Value::Initial: {
      MOZ_ASSERT(mUserGestureStart.IsNull());
      break;
    }
    case Value::WaitingForUserReactionToPasteMenuPopup: {
      MOZ_ASSERT(!mUserGestureStart.IsNull());
      MOZ_ASSERT(
          mUserGestureStart == aWindowContext.GetUserGestureStart(),
          "A new transient user gesture activation should be impossible while "
          "there's no response to the 'Paste' button.");
      // `OnUserReactedToPasteMenuPopup` will handle the reaction.
      break;
    }
    case Value::TransientlyForbiddenByUser: {
      [[fallthrough]];
    }
    case Value::TransientlyAllowedByUser: {
      MOZ_ASSERT(!mUserGestureStart.IsNull());

      if (mUserGestureStart != aWindowContext.GetUserGestureStart()) {
        *this = {};
      }
      break;
    }
  }

  return mValue;
}

void Clipboard::TransientUserPasteState::
    OnStartWaitingForUserReactionToPasteMenuPopup(
        const TimeStamp& aUserGestureStart) {
  MOZ_ASSERT(mValue == Value::Initial);
  MOZ_ASSERT(!aUserGestureStart.IsNull());

  mValue = Value::WaitingForUserReactionToPasteMenuPopup;
  mUserGestureStart = aUserGestureStart;
}

void Clipboard::TransientUserPasteState::OnUserReactedToPasteMenuPopup(
    const bool aAllowed) {
  mValue = aAllowed ? Value::TransientlyAllowedByUser
                    : Value::TransientlyForbiddenByUser;
}

already_AddRefed<Promise> Clipboard::Read(nsIPrincipal& aSubjectPrincipal,
                                          ErrorResult& aRv) {
  return ReadHelper(aSubjectPrincipal, ReadRequestType::eRead, aRv);
}

already_AddRefed<Promise> Clipboard::ReadText(nsIPrincipal& aSubjectPrincipal,
                                              ErrorResult& aRv) {
  return ReadHelper(aSubjectPrincipal, ReadRequestType::eReadText, aRv);
}

namespace {

struct NativeEntry {
  nsString mType;
  nsCOMPtr<nsIVariant> mData;

  NativeEntry(const nsAString& aType, nsIVariant* aData)
      : mType(aType), mData(aData) {}
};
using NativeEntryPromise = MozPromise<NativeEntry, CopyableErrorResult, false>;

class BlobTextHandler final : public PromiseNativeHandler {
 public:
  NS_DECL_THREADSAFE_ISUPPORTS

  explicit BlobTextHandler(const nsAString& aType) : mType(aType) {}

  RefPtr<NativeEntryPromise> Promise() { return mHolder.Ensure(__func__); }

  void Reject() {
    CopyableErrorResult rv;
    rv.ThrowUnknownError("Unable to read blob for '"_ns +
                         NS_ConvertUTF16toUTF8(mType) + "' as text."_ns);
    mHolder.Reject(rv, __func__);
  }

  void ResolvedCallback(JSContext* aCx, JS::Handle<JS::Value> aValue,
                        ErrorResult& aRv) override {
    AssertIsOnMainThread();

    nsString text;
    if (!ConvertJSValueToUSVString(aCx, aValue, "ClipboardItem text", text)) {
      Reject();
      return;
    }

    RefPtr<nsVariantCC> variant = new nsVariantCC();
    variant->SetAsAString(text);

    NativeEntry native(mType, variant);
    mHolder.Resolve(std::move(native), __func__);
  }

  void RejectedCallback(JSContext* aCx, JS::Handle<JS::Value> aValue,
                        ErrorResult& aRv) override {
    Reject();
  }

 private:
  ~BlobTextHandler() = default;

  nsString mType;
  MozPromiseHolder<NativeEntryPromise> mHolder;
};

NS_IMPL_ISUPPORTS0(BlobTextHandler)

RefPtr<NativeEntryPromise> GetStringNativeEntry(
    const nsAString& aType, const OwningStringOrBlob& aData) {
  if (aData.IsString()) {
    RefPtr<nsVariantCC> variant = new nsVariantCC();
    variant->SetAsAString(aData.GetAsString());
    NativeEntry native(aType, variant);
    return NativeEntryPromise::CreateAndResolve(native, __func__);
  }

  RefPtr<BlobTextHandler> handler = new BlobTextHandler(aType);
  IgnoredErrorResult ignored;
  RefPtr<Promise> promise = aData.GetAsBlob()->Text(ignored);
  if (ignored.Failed()) {
    CopyableErrorResult rv;
    rv.ThrowUnknownError("Unable to read blob for '"_ns +
                         NS_ConvertUTF16toUTF8(aType) + "' as text."_ns);
    return NativeEntryPromise::CreateAndReject(rv, __func__);
  }
  promise->AppendNativeHandler(handler);
  return handler->Promise();
}

class ImageDecodeCallback final : public imgIContainerCallback {
 public:
  NS_DECL_ISUPPORTS

  explicit ImageDecodeCallback(const nsAString& aType) : mType(aType) {}

  RefPtr<NativeEntryPromise> Promise() { return mHolder.Ensure(__func__); }

  NS_IMETHOD OnImageReady(imgIContainer* aImage, nsresult aStatus) override {
    // Request the image's width to force decoding the image header.
    int32_t ignored;
    if (NS_FAILED(aStatus) || NS_FAILED(aImage->GetWidth(&ignored))) {
      CopyableErrorResult rv;
      rv.ThrowDataError("Unable to decode blob for '"_ns +
                        NS_ConvertUTF16toUTF8(mType) + "' as image."_ns);
      mHolder.Reject(rv, __func__);
      return NS_OK;
    }

    RefPtr<nsVariantCC> variant = new nsVariantCC();
    variant->SetAsISupports(aImage);

    // Note: We always put the image as "native" on the clipboard.
    NativeEntry native(NS_LITERAL_STRING_FROM_CSTRING(kNativeImageMime),
                       variant);
    mHolder.Resolve(std::move(native), __func__);
    return NS_OK;
  };

 private:
  ~ImageDecodeCallback() = default;

  nsString mType;
  MozPromiseHolder<NativeEntryPromise> mHolder;
};

NS_IMPL_ISUPPORTS(ImageDecodeCallback, imgIContainerCallback)

RefPtr<NativeEntryPromise> GetImageNativeEntry(
    const nsAString& aType, const OwningStringOrBlob& aData) {
  if (aData.IsString()) {
    CopyableErrorResult rv;
    rv.ThrowTypeError("DOMString not supported for '"_ns +
                      NS_ConvertUTF16toUTF8(aType) + "' as image data."_ns);
    return NativeEntryPromise::CreateAndReject(rv, __func__);
  }

  IgnoredErrorResult ignored;
  nsCOMPtr<nsIInputStream> stream;
  aData.GetAsBlob()->CreateInputStream(getter_AddRefs(stream), ignored);
  if (ignored.Failed()) {
    CopyableErrorResult rv;
    rv.ThrowUnknownError("Unable to read blob for '"_ns +
                         NS_ConvertUTF16toUTF8(aType) + "' as image."_ns);
    return NativeEntryPromise::CreateAndReject(rv, __func__);
  }

  RefPtr<ImageDecodeCallback> callback = new ImageDecodeCallback(aType);
  nsCOMPtr<imgITools> imgtool = do_CreateInstance("@mozilla.org/image/tools;1");
  imgtool->DecodeImageAsync(stream, NS_ConvertUTF16toUTF8(aType), callback,
                            GetMainThreadSerialEventTarget());
  return callback->Promise();
}

Result<NativeEntry, ErrorResult> SanitizeNativeEntry(
    const NativeEntry& aEntry) {
  MOZ_ASSERT(aEntry.mType.EqualsLiteral(kHTMLMime));

  nsAutoString string;
  aEntry.mData->GetAsAString(string);

  nsCOMPtr<nsIParserUtils> parserUtils =
      do_GetService(NS_PARSERUTILS_CONTRACTID);
  if (!parserUtils) {
    ErrorResult rv;
    rv.ThrowUnknownError("Error while processing '"_ns +
                         NS_ConvertUTF16toUTF8(aEntry.mType) + "'."_ns);
    return Err(std::move(rv));
  }

  uint32_t flags = nsIParserUtils::SanitizerAllowStyle |
                   nsIParserUtils::SanitizerAllowComments;
  nsAutoString sanitized;
  if (NS_FAILED(parserUtils->Sanitize(string, flags, sanitized))) {
    ErrorResult rv;
    rv.ThrowUnknownError("Error while processing '"_ns +
                         NS_ConvertUTF16toUTF8(aEntry.mType) + "'."_ns);
    return Err(std::move(rv));
  }

  RefPtr<nsVariantCC> variant = new nsVariantCC();
  variant->SetAsAString(sanitized);
  return NativeEntry(aEntry.mType, variant);
}

// Restrict to types allowed by Chrome
// SVG is still disabled by default in Chrome.
static bool IsValidType(const nsAString& aType) {
  return aType.EqualsLiteral(kPNGImageMime) || aType.EqualsLiteral(kTextMime) ||
         aType.EqualsLiteral(kHTMLMime);
}

using NativeItemPromise = NativeEntryPromise::AllPromiseType;

RefPtr<NativeItemPromise> GetClipboardNativeItem(const ClipboardItem& aItem) {
  nsTArray<RefPtr<NativeEntryPromise>> promises;
  for (const auto& entry : aItem.Entries()) {
    const nsAString& type = entry->Type();
    if (!IsValidType(type)) {
      CopyableErrorResult rv;
      rv.ThrowNotAllowedError("Type '"_ns + NS_ConvertUTF16toUTF8(type) +
                              "' not supported for write"_ns);
      return NativeItemPromise::CreateAndReject(rv, __func__);
    }

    const OwningStringOrBlob& data = entry->Data();
    if (type.EqualsLiteral(kPNGImageMime)) {
      promises.AppendElement(GetImageNativeEntry(type, data));
    } else {
      RefPtr<NativeEntryPromise> promise = GetStringNativeEntry(type, data);
      if (type.EqualsLiteral(kHTMLMime)) {
        promise = promise->Then(
            GetMainThreadSerialEventTarget(), __func__,
            [](const NativeEntryPromise::ResolveOrRejectValue& aValue)
                -> RefPtr<NativeEntryPromise> {
              if (aValue.IsReject()) {
                return NativeEntryPromise::CreateAndReject(aValue.RejectValue(),
                                                           __func__);
              }

              auto sanitized = SanitizeNativeEntry(aValue.ResolveValue());
              if (sanitized.isErr()) {
                return NativeEntryPromise::CreateAndReject(
                    CopyableErrorResult(sanitized.unwrapErr()), __func__);
              }
              return NativeEntryPromise::CreateAndResolve(sanitized.unwrap(),
                                                          __func__);
            });
      }
      promises.AppendElement(promise);
    }
  }
  return NativeEntryPromise::All(GetCurrentSerialEventTarget(), promises);
}

}  // namespace

already_AddRefed<Promise> Clipboard::Write(
    const Sequence<OwningNonNull<ClipboardItem>>& aData,
    nsIPrincipal& aSubjectPrincipal, ErrorResult& aRv) {
  // Create a promise
  RefPtr<Promise> p = dom::Promise::Create(GetOwnerGlobal(), aRv);
  if (aRv.Failed()) {
    return nullptr;
  }

  RefPtr<nsPIDOMWindowInner> owner = GetOwner();
  Document* doc = owner ? owner->GetDoc() : nullptr;
  if (!doc) {
    p->MaybeRejectWithUndefined();
    return p.forget();
  }

  // We want to disable security check for automated tests that have the pref
  //  dom.events.testing.asyncClipboard set to true
  if (!IsTestingPrefEnabled() &&
      !nsContentUtils::IsCutCopyAllowed(doc, aSubjectPrincipal)) {
    MOZ_LOG(GetClipboardLog(), LogLevel::Debug,
            ("Clipboard, Write, Not allowed to write to clipboard\n"));
    p->MaybeRejectWithNotAllowedError(
        "Clipboard write was blocked due to lack of user activation.");
    return p.forget();
  }

  // Get the clipboard service
  nsCOMPtr<nsIClipboard> clipboard(
      do_GetService("@mozilla.org/widget/clipboard;1"));
  if (!clipboard) {
    p->MaybeRejectWithUndefined();
    return p.forget();
  }

  nsCOMPtr<nsILoadContext> context = doc->GetLoadContext();
  if (!context) {
    p->MaybeRejectWithUndefined();
    return p.forget();
  }

  if (aData.Length() > 1) {
    p->MaybeRejectWithNotAllowedError(
        "Clipboard write is only supported with one ClipboardItem at the "
        "moment");
    return p.forget();
  }

  if (aData.Length() == 0) {
    // Nothing needs to be written to the clipboard.
    p->MaybeResolveWithUndefined();
    return p.forget();
  }

  GetClipboardNativeItem(aData[0])->Then(
      GetMainThreadSerialEventTarget(), __func__,
      [owner, p, clipboard, context, principal = RefPtr{&aSubjectPrincipal}](
          const nsTArray<NativeEntry>& aEntries) {
        RefPtr<DataTransfer> dataTransfer =
            new DataTransfer(owner, eCopy,
                             /* is external */ true,
                             /* clipboard type */ -1);

        for (const auto& entry : aEntries) {
          nsresult rv = dataTransfer->SetDataWithPrincipal(
              entry.mType, entry.mData, 0, principal);

          if (NS_FAILED(rv)) {
            p->MaybeRejectWithUndefined();
            return;
          }
        }

        // Get the transferable
        RefPtr<nsITransferable> transferable =
            dataTransfer->GetTransferable(0, context);
        if (!transferable) {
          p->MaybeRejectWithUndefined();
          return;
        }

        // Finally write data to clipboard
        nsresult rv =
            clipboard->SetData(transferable,
                               /* owner of the transferable */ nullptr,
                               nsIClipboard::kGlobalClipboard);
        if (NS_FAILED(rv)) {
          p->MaybeRejectWithUndefined();
          return;
        }

        p->MaybeResolveWithUndefined();
      },
      [p](const CopyableErrorResult& aErrorResult) {
        p->MaybeReject(CopyableErrorResult(aErrorResult));
      });

  return p.forget();
}

already_AddRefed<Promise> Clipboard::WriteText(const nsAString& aData,
                                               nsIPrincipal& aSubjectPrincipal,
                                               ErrorResult& aRv) {
  // Create a single-element Sequence to reuse Clipboard::Write.
  OwningStringOrBlob data;
  data.SetAsString() = aData;

  nsTArray<RefPtr<ClipboardItem::ItemEntry>> items;
  items.AppendElement(MakeRefPtr<ClipboardItem::ItemEntry>(
      NS_LITERAL_STRING_FROM_CSTRING(kTextMime), std::move(data)));

  nsTArray<OwningNonNull<ClipboardItem>> sequence;
  RefPtr<ClipboardItem> item = MakeRefPtr<ClipboardItem>(
      GetOwner(), PresentationStyle::Unspecified, std::move(items));
  sequence.AppendElement(*item);

  return Write(std::move(sequence), aSubjectPrincipal, aRv);
}

void Clipboard::ReadRequest::MaybeRejectWithNotAllowedError(
    const nsACString& aMessage) {
  mPromise->MaybeRejectWithNotAllowedError(aMessage);
}

void Clipboard::OnUserReactedToPasteMenuPopup(const bool aAllowed) {
  MOZ_LOG(GetClipboardLog(), LogLevel::Debug, ("%s", __FUNCTION__));

  mTransientUserPasteState.OnUserReactedToPasteMenuPopup(aAllowed);

  MOZ_ASSERT(!mReadRequests.IsEmpty());

  for (UniquePtr<ReadRequest>& request : mReadRequests) {
    if (aAllowed) {
      request->Answer();
    } else {
      request->MaybeRejectWithNotAllowedError(
          "The user dismissed the 'Paste' button."_ns);
    }
  }

  mReadRequests.Clear();
}

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

/* static */
LogModule* Clipboard::GetClipboardLog() { return gClipboardLog; }

/* static */
bool Clipboard::ReadTextEnabled(JSContext* aCx, JSObject* aGlobal) {
  nsIPrincipal* prin = nsContentUtils::SubjectPrincipal(aCx);
  return IsReadTextExposedToContent() ||
         prin->GetIsAddonOrExpandedAddonPrincipal() ||
         prin->IsSystemPrincipal();
}

/* static */
bool Clipboard::IsTestingPrefEnabled() {
  bool clipboardTestingEnabled =
      StaticPrefs::dom_events_testing_asyncClipboard_DoNotUseDirectly();
  MOZ_LOG(GetClipboardLog(), LogLevel::Debug,
          ("Clipboard, Is testing enabled? %d\n", clipboardTestingEnabled));
  return clipboardTestingEnabled;
}

NS_IMPL_CYCLE_COLLECTION_CLASS(Clipboard)

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(Clipboard,
                                                  DOMEventTargetHelper)
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(Clipboard, DOMEventTargetHelper)
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Clipboard)
NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)

NS_IMPL_ADDREF_INHERITED(Clipboard, DOMEventTargetHelper)
NS_IMPL_RELEASE_INHERITED(Clipboard, DOMEventTargetHelper)

}  // namespace mozilla::dom