gecko-dev/dom/html/HTMLLinkElement.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/HTMLLinkElement.h"

#include "mozilla/AsyncEventDispatcher.h"
#include "mozilla/Attributes.h"
#include "mozilla/Components.h"
#include "mozilla/EventDispatcher.h"
#include "mozilla/EventStates.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/Preferences.h"
#include "mozilla/StaticPrefs_network.h"
#include "mozilla/dom/BindContext.h"
#include "mozilla/dom/DocumentInlines.h"
#include "mozilla/dom/HTMLLinkElementBinding.h"
#include "nsContentUtils.h"
#include "nsDOMTokenList.h"
#include "nsGenericHTMLElement.h"
#include "nsGkAtoms.h"
#include "nsHTMLDNSPrefetch.h"
#include "nsIContentInlines.h"
#include "mozilla/dom/Document.h"
#include "nsINode.h"
#include "nsIPrefetchService.h"
#include "nsPIDOMWindow.h"
#include "nsReadableUtils.h"
#include "nsStyleConsts.h"
#include "nsUnicharUtils.h"
#include "nsWindowSizes.h"
#include "nsIContentPolicy.h"
#include "nsMimeTypes.h"
#include "imgLoader.h"
#include "MediaContainerType.h"
#include "DecoderDoctorDiagnostics.h"
#include "DecoderTraits.h"
#include "MediaList.h"
#include "nsAttrValueInlines.h"

#define LINK_ELEMENT_FLAG_BIT(n_) \
  NODE_FLAG_BIT(ELEMENT_TYPE_SPECIFIC_BITS_OFFSET + (n_))

// Link element specific bits
enum {
  // Indicates that a DNS Prefetch has been requested from this Link element.
  HTML_LINK_DNS_PREFETCH_REQUESTED = LINK_ELEMENT_FLAG_BIT(0),

  // Indicates that a DNS Prefetch was added to the deferral queue
  HTML_LINK_DNS_PREFETCH_DEFERRED = LINK_ELEMENT_FLAG_BIT(1)
};

#undef LINK_ELEMENT_FLAG_BIT

ASSERT_NODE_FLAGS_SPACE(ELEMENT_TYPE_SPECIFIC_BITS_OFFSET + 2);

NS_IMPL_NS_NEW_HTML_ELEMENT(Link)

namespace mozilla {
namespace dom {

HTMLLinkElement::HTMLLinkElement(
    already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo)
    : nsGenericHTMLElement(std::move(aNodeInfo)), Link(this) {}

HTMLLinkElement::~HTMLLinkElement() = default;

NS_IMPL_CYCLE_COLLECTION_CLASS(HTMLLinkElement)

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(HTMLLinkElement,
                                                  nsGenericHTMLElement)
  tmp->LinkStyle::Traverse(cb);
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mRelList)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSizes)
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(HTMLLinkElement,
                                                nsGenericHTMLElement)
  tmp->LinkStyle::Unlink();
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mRelList)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mSizes)
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

NS_IMPL_ISUPPORTS_CYCLE_COLLECTION_INHERITED(HTMLLinkElement,
                                             nsGenericHTMLElement, Link)

NS_IMPL_ELEMENT_CLONE(HTMLLinkElement)

bool HTMLLinkElement::Disabled() const {
  return GetBoolAttr(nsGkAtoms::disabled);
}

void HTMLLinkElement::SetDisabled(bool aDisabled, ErrorResult& aRv) {
  return SetHTMLBoolAttr(nsGkAtoms::disabled, aDisabled, aRv);
}

void HTMLLinkElement::OnDNSPrefetchRequested() {
  UnsetFlags(HTML_LINK_DNS_PREFETCH_DEFERRED);
  SetFlags(HTML_LINK_DNS_PREFETCH_REQUESTED);
}

void HTMLLinkElement::OnDNSPrefetchDeferred() {
  UnsetFlags(HTML_LINK_DNS_PREFETCH_REQUESTED);
  SetFlags(HTML_LINK_DNS_PREFETCH_DEFERRED);
}

bool HTMLLinkElement::HasDeferredDNSPrefetchRequest() {
  return HasFlag(HTML_LINK_DNS_PREFETCH_DEFERRED);
}

nsresult HTMLLinkElement::BindToTree(BindContext& aContext, nsINode& aParent) {
  Link::ResetLinkState(false, Link::ElementHasHref());

  nsresult rv = nsGenericHTMLElement::BindToTree(aContext, aParent);
  NS_ENSURE_SUCCESS(rv, rv);

  if (IsInComposedDoc()) {
    TryDNSPrefetchOrPreconnectOrPrefetchOrPreloadOrPrerender();
  }

  void (HTMLLinkElement::*update)() =
      &HTMLLinkElement::UpdateStyleSheetInternal;
  nsContentUtils::AddScriptRunner(
      NewRunnableMethod("dom::HTMLLinkElement::BindToTree", this, update));

  if (IsInUncomposedDoc() &&
      AttrValueIs(kNameSpaceID_None, nsGkAtoms::rel, nsGkAtoms::localization,
                  eIgnoreCase)) {
    aContext.OwnerDoc().LocalizationLinkAdded(this);
  }

  LinkAdded();

  return rv;
}

void HTMLLinkElement::LinkAdded() {
  CreateAndDispatchEvent(OwnerDoc(), u"DOMLinkAdded"_ns);
}

void HTMLLinkElement::LinkRemoved() {
  CreateAndDispatchEvent(OwnerDoc(), u"DOMLinkRemoved"_ns);
}

void HTMLLinkElement::UnbindFromTree(bool aNullParent) {
  // Cancel any DNS prefetches
  // Note: Must come before ResetLinkState.  If called after, it will recreate
  // mCachedURI based on data that is invalid - due to a call to GetHostname.
  CancelDNSPrefetch(HTML_LINK_DNS_PREFETCH_DEFERRED,
                    HTML_LINK_DNS_PREFETCH_REQUESTED);
  CancelPrefetchOrPreload();

  // Without removing the link state we risk a dangling pointer
  // in the mStyledLinks hashtable
  Link::ResetLinkState(false, Link::ElementHasHref());

  // If this is reinserted back into the document it will not be
  // from the parser.
  Document* oldDoc = GetUncomposedDoc();
  ShadowRoot* oldShadowRoot = GetContainingShadow();

  // We want to update the localization but only if the link is removed from a
  // DOM change, and not because the document is going away.
  bool ignore;
  if (oldDoc && oldDoc->GetScriptHandlingObject(ignore) &&
      AttrValueIs(kNameSpaceID_None, nsGkAtoms::rel, nsGkAtoms::localization,
                  eIgnoreCase)) {
    oldDoc->LocalizationLinkRemoved(this);
  }

  CreateAndDispatchEvent(oldDoc, u"DOMLinkRemoved"_ns);
  nsGenericHTMLElement::UnbindFromTree(aNullParent);

  Unused << UpdateStyleSheetInternal(oldDoc, oldShadowRoot);
}

bool HTMLLinkElement::ParseAttribute(int32_t aNamespaceID, nsAtom* aAttribute,
                                     const nsAString& aValue,
                                     nsIPrincipal* aMaybeScriptedPrincipal,
                                     nsAttrValue& aResult) {
  if (aNamespaceID == kNameSpaceID_None) {
    if (aAttribute == nsGkAtoms::crossorigin) {
      ParseCORSValue(aValue, aResult);
      return true;
    }

    if (aAttribute == nsGkAtoms::as) {
      ParseAsValue(aValue, aResult);
      return true;
    }

    if (aAttribute == nsGkAtoms::sizes) {
      aResult.ParseAtomArray(aValue);
      return true;
    }

    if (aAttribute == nsGkAtoms::integrity) {
      aResult.ParseStringOrAtom(aValue);
      return true;
    }
  }

  return nsGenericHTMLElement::ParseAttribute(aNamespaceID, aAttribute, aValue,
                                              aMaybeScriptedPrincipal, aResult);
}

void HTMLLinkElement::CreateAndDispatchEvent(Document* aDoc,
                                             const nsAString& aEventName) {
  if (!aDoc) return;

  // In the unlikely case that both rev is specified *and* rel=stylesheet,
  // this code will cause the event to fire, on the principle that maybe the
  // page really does want to specify that its author is a stylesheet. Since
  // this should never actually happen and the performance hit is minimal,
  // doing the "right" thing costs virtually nothing here, even if it doesn't
  // make much sense.
  static Element::AttrValuesArray strings[] = {nsGkAtoms::_empty,
                                               nsGkAtoms::stylesheet, nullptr};

  if (!nsContentUtils::HasNonEmptyAttr(this, kNameSpaceID_None,
                                       nsGkAtoms::rev) &&
      FindAttrValueIn(kNameSpaceID_None, nsGkAtoms::rel, strings,
                      eIgnoreCase) != ATTR_VALUE_NO_MATCH)
    return;

  RefPtr<AsyncEventDispatcher> asyncDispatcher = new AsyncEventDispatcher(
      this, aEventName, CanBubble::eYes, ChromeOnlyDispatch::eYes);
  // Always run async in order to avoid running script when the content
  // sink isn't expecting it.
  asyncDispatcher->PostDOMEvent();
}

nsresult HTMLLinkElement::BeforeSetAttr(int32_t aNameSpaceID, nsAtom* aName,
                                        const nsAttrValueOrString* aValue,
                                        bool aNotify) {
  if (aNameSpaceID == kNameSpaceID_None &&
      (aName == nsGkAtoms::href || aName == nsGkAtoms::rel)) {
    CancelDNSPrefetch(HTML_LINK_DNS_PREFETCH_DEFERRED,
                      HTML_LINK_DNS_PREFETCH_REQUESTED);
    CancelPrefetchOrPreload();
  }

  return nsGenericHTMLElement::BeforeSetAttr(aNameSpaceID, aName, aValue,
                                             aNotify);
}

nsresult HTMLLinkElement::AfterSetAttr(int32_t aNameSpaceID, nsAtom* aName,
                                       const nsAttrValue* aValue,
                                       const nsAttrValue* aOldValue,
                                       nsIPrincipal* aSubjectPrincipal,
                                       bool aNotify) {
  // It's safe to call ResetLinkState here because our new attr value has
  // already been set or unset.  ResetLinkState needs the updated attribute
  // value because notifying the document that content states have changed will
  // call IntrinsicState, which will try to get updated information about the
  // visitedness from Link.
  if (aName == nsGkAtoms::href && kNameSpaceID_None == aNameSpaceID) {
    bool hasHref = aValue;
    Link::ResetLinkState(!!aNotify, hasHref);
    if (IsInUncomposedDoc()) {
      CreateAndDispatchEvent(OwnerDoc(), u"DOMLinkChanged"_ns);
    }
  }

  if (aNameSpaceID == kNameSpaceID_None && aName == nsGkAtoms::href) {
    mTriggeringPrincipal = nsContentUtils::GetAttrTriggeringPrincipal(
        this, aValue ? aValue->GetStringValue() : EmptyString(),
        aSubjectPrincipal);
  }

  // If a link's `rel` attribute was changed from or to `localization`,
  // update the list of localization links.
  if (aNameSpaceID == kNameSpaceID_None && aName == nsGkAtoms::rel) {
    if (Document* doc = GetUncomposedDoc()) {
      if ((aValue && aValue->Equals(nsGkAtoms::localization, eIgnoreCase)) &&
          (!aOldValue ||
           !aOldValue->Equals(nsGkAtoms::localization, eIgnoreCase))) {
        doc->LocalizationLinkAdded(this);
      } else if ((aOldValue &&
                  aOldValue->Equals(nsGkAtoms::localization, eIgnoreCase)) &&
                 (!aValue ||
                  !aValue->Equals(nsGkAtoms::localization, eIgnoreCase))) {
        doc->LocalizationLinkRemoved(this);
      }
    }
  }

  // If the link has `rel=localization` and its `href` attribute is changed,
  // update the list of localization links.
  if (aNameSpaceID == kNameSpaceID_None && aName == nsGkAtoms::href &&
      AttrValueIs(kNameSpaceID_None, nsGkAtoms::rel, nsGkAtoms::localization,
                  eIgnoreCase)) {
    if (Document* doc = GetUncomposedDoc()) {
      if (aOldValue) {
        doc->LocalizationLinkRemoved(this);
      }
      if (aValue) {
        doc->LocalizationLinkAdded(this);
      }
    }
  }

  if (aValue) {
    if (aNameSpaceID == kNameSpaceID_None &&
        (aName == nsGkAtoms::href || aName == nsGkAtoms::rel ||
         aName == nsGkAtoms::title || aName == nsGkAtoms::media ||
         aName == nsGkAtoms::type || aName == nsGkAtoms::as ||
         aName == nsGkAtoms::crossorigin || aName == nsGkAtoms::disabled)) {
      bool dropSheet = false;
      if (aName == nsGkAtoms::rel) {
        nsAutoString value;
        aValue->ToString(value);
        uint32_t linkTypes = ParseLinkTypes(value);
        if (GetSheet()) {
          dropSheet = !(linkTypes & eSTYLESHEET);
        }
      }

      if ((aName == nsGkAtoms::rel || aName == nsGkAtoms::href) &&
          IsInComposedDoc()) {
        TryDNSPrefetchOrPreconnectOrPrefetchOrPreloadOrPrerender();
      }

      if ((aName == nsGkAtoms::as || aName == nsGkAtoms::type ||
           aName == nsGkAtoms::crossorigin || aName == nsGkAtoms::media) &&
          IsInComposedDoc()) {
        UpdatePreload(aName, aValue, aOldValue);
      }

      const bool forceUpdate =
          dropSheet || aName == nsGkAtoms::title || aName == nsGkAtoms::media ||
          aName == nsGkAtoms::type || aName == nsGkAtoms::disabled;

      Unused << UpdateStyleSheetInternal(
          nullptr, nullptr, forceUpdate ? ForceUpdate::Yes : ForceUpdate::No);
    }
  } else {
    if (aNameSpaceID == kNameSpaceID_None) {
      if (aName == nsGkAtoms::disabled) {
        mExplicitlyEnabled = true;
      }
      // Since removing href or rel makes us no longer link to a stylesheet,
      // force updates for those too.
      if (aName == nsGkAtoms::href || aName == nsGkAtoms::rel ||
          aName == nsGkAtoms::title || aName == nsGkAtoms::media ||
          aName == nsGkAtoms::type || aName == nsGkAtoms::disabled) {
        Unused << UpdateStyleSheetInternal(nullptr, nullptr, ForceUpdate::Yes);
      }
      if ((aName == nsGkAtoms::as || aName == nsGkAtoms::type ||
           aName == nsGkAtoms::crossorigin || aName == nsGkAtoms::media) &&
          IsInComposedDoc()) {
        UpdatePreload(aName, aValue, aOldValue);
      }
    }
  }

  return nsGenericHTMLElement::AfterSetAttr(
      aNameSpaceID, aName, aValue, aOldValue, aSubjectPrincipal, aNotify);
}

void HTMLLinkElement::GetEventTargetParent(EventChainPreVisitor& aVisitor) {
  GetEventTargetParentForAnchors(aVisitor);
}

nsresult HTMLLinkElement::PostHandleEvent(EventChainPostVisitor& aVisitor) {
  return PostHandleEventForAnchors(aVisitor);
}

bool HTMLLinkElement::IsLink(nsIURI** aURI) const { return IsHTMLLink(aURI); }

void HTMLLinkElement::GetLinkTarget(nsAString& aTarget) {
  GetAttr(kNameSpaceID_None, nsGkAtoms::target, aTarget);
  if (aTarget.IsEmpty()) {
    GetBaseTarget(aTarget);
  }
}

static const DOMTokenListSupportedToken sSupportedRelValues[] = {
    // Keep this and the one below in sync with ToLinkMask in
    // LinkStyle.cpp.
    // "preload" must come first because it can be disabled.
    "preload",   "prefetch",   "dns-prefetch", "stylesheet", "next",
    "alternate", "preconnect", "icon",         "search",     nullptr};

static const DOMTokenListSupportedToken sSupportedRelValuesWithManifest[] = {
    // Keep this in sync with ToLinkMask in LinkStyle.cpp.
    // "preload" and "manifest" must come first because they can be disabled.
    "preload",   "manifest",   "prefetch", "dns-prefetch", "stylesheet", "next",
    "alternate", "preconnect", "icon",     "search",       nullptr};

nsDOMTokenList* HTMLLinkElement::RelList() {
  if (!mRelList) {
    auto preload = StaticPrefs::network_preload();
    auto manifest = StaticPrefs::dom_manifest_enabled();
    if (manifest && preload) {
      mRelList = new nsDOMTokenList(this, nsGkAtoms::rel,
                                    sSupportedRelValuesWithManifest);
    } else if (manifest && !preload) {
      mRelList = new nsDOMTokenList(this, nsGkAtoms::rel,
                                    &sSupportedRelValuesWithManifest[1]);
    } else if (!manifest && preload) {
      mRelList = new nsDOMTokenList(this, nsGkAtoms::rel, sSupportedRelValues);
    } else {  // both false...drop preload
      mRelList =
          new nsDOMTokenList(this, nsGkAtoms::rel, &sSupportedRelValues[1]);
    }
  }
  return mRelList;
}

already_AddRefed<nsIURI> HTMLLinkElement::GetHrefURI() const {
  return GetHrefURIForAnchors();
}

Maybe<LinkStyle::SheetInfo> HTMLLinkElement::GetStyleSheetInfo() {
  nsAutoString rel;
  GetAttr(kNameSpaceID_None, nsGkAtoms::rel, rel);
  uint32_t linkTypes = ParseLinkTypes(rel);
  if (!(linkTypes & eSTYLESHEET)) {
    return Nothing();
  }

  if (!IsCSSMimeTypeAttributeForLinkElement(*this)) {
    return Nothing();
  }

  if (Disabled()) {
    return Nothing();
  }

  nsAutoString title;
  nsAutoString media;
  GetTitleAndMediaForElement(*this, title, media);

  bool alternate = linkTypes & eALTERNATE;
  if (alternate && title.IsEmpty()) {
    // alternates must have title.
    return Nothing();
  }

  nsAutoString href;
  GetAttr(kNameSpaceID_None, nsGkAtoms::href, href);
  if (href.IsEmpty()) {
    return Nothing();
  }

  nsAutoString integrity;
  GetAttr(kNameSpaceID_None, nsGkAtoms::integrity, integrity);

  nsCOMPtr<nsIURI> uri = Link::GetURI();
  nsCOMPtr<nsIPrincipal> prin = mTriggeringPrincipal;

  nsAutoString nonce;
  nsString* cspNonce = static_cast<nsString*>(GetProperty(nsGkAtoms::nonce));
  if (cspNonce) {
    nonce = *cspNonce;
  }

  return Some(SheetInfo{
      *OwnerDoc(),
      this,
      uri.forget(),
      prin.forget(),
      MakeAndAddRef<ReferrerInfo>(*this),
      GetCORSMode(),
      title,
      media,
      integrity,
      nonce,
      alternate ? HasAlternateRel::Yes : HasAlternateRel::No,
      IsInline::No,
      mExplicitlyEnabled ? IsExplicitlyEnabled::Yes : IsExplicitlyEnabled::No,
  });
}

EventStates HTMLLinkElement::IntrinsicState() const {
  return Link::LinkState() | nsGenericHTMLElement::IntrinsicState();
}

void HTMLLinkElement::AddSizeOfExcludingThis(nsWindowSizes& aSizes,
                                             size_t* aNodeSize) const {
  nsGenericHTMLElement::AddSizeOfExcludingThis(aSizes, aNodeSize);
  *aNodeSize += Link::SizeOfExcludingThis(aSizes.mState);
}

JSObject* HTMLLinkElement::WrapNode(JSContext* aCx,
                                    JS::Handle<JSObject*> aGivenProto) {
  return HTMLLinkElement_Binding::Wrap(aCx, this, aGivenProto);
}

void HTMLLinkElement::GetAs(nsAString& aResult) {
  GetEnumAttr(nsGkAtoms::as, "", aResult);
}

static const nsAttrValue::EnumTable kAsAttributeTable[] = {
    {"", DESTINATION_INVALID},      {"audio", DESTINATION_AUDIO},
    {"font", DESTINATION_FONT},     {"image", DESTINATION_IMAGE},
    {"script", DESTINATION_SCRIPT}, {"style", DESTINATION_STYLE},
    {"track", DESTINATION_TRACK},   {"video", DESTINATION_VIDEO},
    {"fetch", DESTINATION_FETCH},   {nullptr, 0}};

/* static */
void HTMLLinkElement::ParseAsValue(const nsAString& aValue,
                                   nsAttrValue& aResult) {
  DebugOnly<bool> success =
      aResult.ParseEnumValue(aValue, kAsAttributeTable, false,
                             // default value is a empty string
                             // if aValue is not a value we
                             // understand
                             &kAsAttributeTable[0]);
  MOZ_ASSERT(success);
}

/* static */
nsContentPolicyType HTMLLinkElement::AsValueToContentPolicy(
    const nsAttrValue& aValue) {
  switch (aValue.GetEnumValue()) {
    case DESTINATION_INVALID:
      return nsIContentPolicy::TYPE_INVALID;
    case DESTINATION_AUDIO:
      return nsIContentPolicy::TYPE_INTERNAL_AUDIO;
    case DESTINATION_TRACK:
      return nsIContentPolicy::TYPE_INTERNAL_TRACK;
    case DESTINATION_VIDEO:
      return nsIContentPolicy::TYPE_INTERNAL_VIDEO;
    case DESTINATION_FONT:
      return nsIContentPolicy::TYPE_FONT;
    case DESTINATION_IMAGE:
      return nsIContentPolicy::TYPE_IMAGE;
    case DESTINATION_SCRIPT:
      return nsIContentPolicy::TYPE_SCRIPT;
    case DESTINATION_STYLE:
      return nsIContentPolicy::TYPE_STYLESHEET;
    case DESTINATION_FETCH:
      return nsIContentPolicy::TYPE_INTERNAL_FETCH_PRELOAD;
  }
  return nsIContentPolicy::TYPE_INVALID;
}

void HTMLLinkElement::GetContentPolicyMimeTypeMedia(
    nsAttrValue& aAsAttr, nsContentPolicyType& aPolicyType, nsString& aMimeType,
    nsAString& aMedia) {
  nsAutoString as;
  GetAttr(kNameSpaceID_None, nsGkAtoms::as, as);
  ParseAsValue(as, aAsAttr);
  aPolicyType = AsValueToContentPolicy(aAsAttr);

  nsAutoString type;
  GetAttr(kNameSpaceID_None, nsGkAtoms::type, type);
  nsAutoString notUsed;
  nsContentUtils::SplitMimeType(type, aMimeType, notUsed);

  GetAttr(kNameSpaceID_None, nsGkAtoms::media, aMedia);
}

void HTMLLinkElement::
    TryDNSPrefetchOrPreconnectOrPrefetchOrPreloadOrPrerender() {
  MOZ_ASSERT(IsInComposedDoc());
  if (!ElementHasHref()) {
    return;
  }

  nsAutoString rel;
  if (!GetAttr(kNameSpaceID_None, nsGkAtoms::rel, rel)) {
    return;
  }

  if (!nsContentUtils::PrefetchPreloadEnabled(OwnerDoc()->GetDocShell())) {
    return;
  }

  uint32_t linkTypes = ParseLinkTypes(rel);

  if ((linkTypes & ePREFETCH) || (linkTypes & eNEXT)) {
    nsCOMPtr<nsIPrefetchService> prefetchService(
        components::Prefetch::Service());
    if (prefetchService) {
      nsCOMPtr<nsIURI> uri(GetURI());
      if (uri) {
        auto referrerInfo = MakeRefPtr<ReferrerInfo>(*this);
        prefetchService->PrefetchURI(uri, referrerInfo, this,
                                     linkTypes & ePREFETCH);
        return;
      }
    }
  }

  if (linkTypes & ePRELOAD) {
    nsCOMPtr<nsIURI> uri(GetURI());
    if (uri) {
      nsContentPolicyType policyType;

      nsAttrValue asAttr;
      nsAutoString mimeType;
      nsAutoString media;
      GetContentPolicyMimeTypeMedia(asAttr, policyType, mimeType, media);

      if (policyType == nsIContentPolicy::TYPE_INVALID) {
        // Ignore preload with a wrong or empty as attribute.
        return;
      }

      if (!CheckPreloadAttrs(asAttr, mimeType, media, OwnerDoc())) {
        policyType = nsIContentPolicy::TYPE_INVALID;
      }

      StartPreload(policyType);
      return;
    }
  }

  if (linkTypes & ePRECONNECT) {
    if (nsCOMPtr<nsIURI> uri = GetURI()) {
      OwnerDoc()->MaybePreconnect(
          uri, AttrValueToCORSMode(GetParsedAttr(nsGkAtoms::crossorigin)));
      return;
    }
  }

  if (linkTypes & eDNS_PREFETCH) {
    if (nsHTMLDNSPrefetch::IsAllowed(OwnerDoc())) {
      nsHTMLDNSPrefetch::PrefetchLow(this);
    }
  }
}

void HTMLLinkElement::UpdatePreload(nsAtom* aName, const nsAttrValue* aValue,
                                    const nsAttrValue* aOldValue) {
  MOZ_ASSERT(IsInComposedDoc());

  if (!ElementHasHref()) {
    return;
  }

  nsAutoString rel;
  if (!GetAttr(kNameSpaceID_None, nsGkAtoms::rel, rel)) {
    return;
  }

  if (!nsContentUtils::PrefetchPreloadEnabled(OwnerDoc()->GetDocShell())) {
    return;
  }

  uint32_t linkTypes = ParseLinkTypes(rel);

  if (!(linkTypes & ePRELOAD)) {
    return;
  }

  nsCOMPtr<nsIURI> uri(GetURI());
  if (!uri) {
    return;
  }

  nsAttrValue asAttr;
  nsContentPolicyType asPolicyType;
  nsAutoString mimeType;
  nsAutoString media;
  GetContentPolicyMimeTypeMedia(asAttr, asPolicyType, mimeType, media);

  if (asPolicyType == nsIContentPolicy::TYPE_INVALID) {
    // Ignore preload with a wrong or empty as attribute, but be sure to cancel
    // the old one.
    CancelPrefetchOrPreload();
    return;
  }

  nsContentPolicyType policyType = asPolicyType;
  if (!CheckPreloadAttrs(asAttr, mimeType, media, OwnerDoc())) {
    policyType = nsIContentPolicy::TYPE_INVALID;
  }

  if (aName == nsGkAtoms::crossorigin) {
    CORSMode corsMode = AttrValueToCORSMode(aValue);
    CORSMode oldCorsMode = AttrValueToCORSMode(aOldValue);
    if (corsMode != oldCorsMode) {
      CancelPrefetchOrPreload();
      StartPreload(policyType);
    }
    return;
  }

  nsContentPolicyType oldPolicyType;

  if (aName == nsGkAtoms::as) {
    if (aOldValue) {
      oldPolicyType = AsValueToContentPolicy(*aOldValue);
      if (!CheckPreloadAttrs(*aOldValue, mimeType, media, OwnerDoc())) {
        oldPolicyType = nsIContentPolicy::TYPE_INVALID;
      }
    } else {
      oldPolicyType = nsIContentPolicy::TYPE_INVALID;
    }
  } else if (aName == nsGkAtoms::type) {
    nsAutoString oldType;
    nsAutoString notUsed;
    if (aOldValue) {
      aOldValue->ToString(oldType);
    }
    nsAutoString oldMimeType;
    nsContentUtils::SplitMimeType(oldType, oldMimeType, notUsed);
    if (CheckPreloadAttrs(asAttr, oldMimeType, media, OwnerDoc())) {
      oldPolicyType = asPolicyType;
    } else {
      oldPolicyType = nsIContentPolicy::TYPE_INVALID;
    }
  } else {
    MOZ_ASSERT(aName == nsGkAtoms::media);
    nsAutoString oldMedia;
    if (aOldValue) {
      aOldValue->ToString(oldMedia);
    }
    if (CheckPreloadAttrs(asAttr, mimeType, oldMedia, OwnerDoc())) {
      oldPolicyType = asPolicyType;
    } else {
      oldPolicyType = nsIContentPolicy::TYPE_INVALID;
    }
  }

  if ((policyType != oldPolicyType) &&
      (oldPolicyType != nsIContentPolicy::TYPE_INVALID)) {
    CancelPrefetchOrPreload();
  }

  // Trigger a new preload if the policy type has changed.
  // Also trigger load if the new policy type is invalid, this will only
  // trigger an error event.
  if ((policyType != oldPolicyType) ||
      (policyType == nsIContentPolicy::TYPE_INVALID)) {
    StartPreload(policyType);
  }
}

void HTMLLinkElement::CancelPrefetchOrPreload() {
  CancelPreload();

  nsCOMPtr<nsIPrefetchService> prefetchService(components::Prefetch::Service());
  if (prefetchService) {
    if (nsCOMPtr<nsIURI> uri = GetURI()) {
      prefetchService->CancelPrefetchPreloadURI(uri, this);
    }
  }
}

void HTMLLinkElement::StartPreload(nsContentPolicyType policyType) {
  MOZ_ASSERT(!mPreload, "Forgot to cancel the running preload");

  auto referrerInfo = MakeRefPtr<ReferrerInfo>(*this);
  RefPtr<PreloaderBase> preload =
      OwnerDoc()->Preloads().PreloadLinkElement(this, policyType, referrerInfo);
  mPreload = preload.get();
}

void HTMLLinkElement::CancelPreload() {
  if (mPreload) {
    // This will cancel the loading channel if this was the last referred node
    // and the preload is not used up until now to satisfy a regular tag load
    // request.
    mPreload->RemoveLinkPreloadNode(this);
    mPreload = nullptr;
  }
}

// We will use official mime-types from:
// https://www.iana.org/assignments/media-types/media-types.xhtml#font
// We do not support old deprecated mime-types for preload feature.
// (We currectly do not support font/collection)
static uint32_t StyleLinkElementFontMimeTypesNum = 5;
static const char* StyleLinkElementFontMimeTypes[] = {
    "font/otf", "font/sfnt", "font/ttf", "font/woff", "font/woff2"};

bool IsFontMimeType(const nsAString& aType) {
  if (aType.IsEmpty()) {
    return true;
  }
  for (uint32_t i = 0; i < StyleLinkElementFontMimeTypesNum; i++) {
    if (aType.EqualsASCII(StyleLinkElementFontMimeTypes[i])) {
      return true;
    }
  }
  return false;
}

bool HTMLLinkElement::CheckPreloadAttrs(const nsAttrValue& aAs,
                                        const nsAString& aType,
                                        const nsAString& aMedia,
                                        Document* aDocument) {
  nsContentPolicyType policyType = AsValueToContentPolicy(aAs);
  if (policyType == nsIContentPolicy::TYPE_INVALID) {
    return false;
  }

  // Check if media attribute is valid.
  if (!aMedia.IsEmpty()) {
    RefPtr<MediaList> mediaList = MediaList::Create(aMedia);
    if (!mediaList->Matches(*aDocument)) {
      return false;
    }
  }

  if (aType.IsEmpty()) {
    return true;
  }

  nsString type = nsString(aType);
  ToLowerCase(type);

  if (policyType == nsIContentPolicy::TYPE_INTERNAL_FETCH_PRELOAD) {
    return true;
  }
  if (policyType == nsIContentPolicy::TYPE_MEDIA) {
    if (aAs.GetEnumValue() == DESTINATION_TRACK) {
      return type.EqualsASCII("text/vtt");
    }
    Maybe<MediaContainerType> mimeType = MakeMediaContainerType(aType);
    if (!mimeType) {
      return false;
    }
    DecoderDoctorDiagnostics diagnostics;
    CanPlayStatus status =
        DecoderTraits::CanHandleContainerType(*mimeType, &diagnostics);
    // Preload if this return CANPLAY_YES and CANPLAY_MAYBE.
    return status != CANPLAY_NO;
  }
  if (policyType == nsIContentPolicy::TYPE_FONT) {
    return IsFontMimeType(type);
  }
  if (policyType == nsIContentPolicy::TYPE_IMAGE) {
    return imgLoader::SupportImageWithMimeType(
        NS_ConvertUTF16toUTF8(type).get(),
        AcceptedMimeTypes::IMAGES_AND_DOCUMENTS);
  }
  if (policyType == nsIContentPolicy::TYPE_SCRIPT) {
    return nsContentUtils::IsJavascriptMIMEType(type);
  }
  if (policyType == nsIContentPolicy::TYPE_STYLESHEET) {
    return type.EqualsASCII("text/css");
  }
  return false;
}

bool HTMLLinkElement::IsCSSMimeTypeAttributeForLinkElement(
    const Element& aSelf) {
  // Processing the type attribute per
  // https://html.spec.whatwg.org/multipage/semantics.html#processing-the-type-attribute
  // for HTML link elements.
  nsAutoString type;
  nsAutoString mimeType;
  nsAutoString notUsed;
  aSelf.GetAttr(kNameSpaceID_None, nsGkAtoms::type, type);
  nsContentUtils::SplitMimeType(type, mimeType, notUsed);
  return mimeType.IsEmpty() || mimeType.LowerCaseEqualsLiteral("text/css");
}

}  // namespace dom
}  // namespace mozilla