/* -*- 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/. */

#ifndef nsHTMLDNSPrefetch_h___

#define nsHTMLDNSPrefetch_h___

#include "nsCOMPtr.h"

#include "nsString.h"

#include "nsIDNSListener.h"

#include "nsIWebProgressListener.h"

#include "nsWeakReference.h"

#include "nsIObserver.h"

class nsIDocument;

class nsITimer;

namespace mozilla {

namespace dom {

class Link;

} // namespace dom

} // namespace mozilla

namespace mozilla {

namespace net {

class NeckoParent;

} // namespace net

} // namespace mozilla

class nsHTMLDNSPrefetch

{

public:

  // The required aDocument parameter is the context requesting the prefetch - under

  // certain circumstances (e.g. headers, or security context) associated with

  // the context the prefetch will not be performed.

  static bool     IsAllowed(nsIDocument *aDocument);

  static nsresult Initialize();

  static nsresult Shutdown();

  // Call one of the Prefetch* methods to start the lookup.

  //

  // The URI versions will defer DNS lookup until pageload is

  // complete, while the string versions submit the lookup to

  // the DNS system immediately. The URI version is somewhat lighter

  // weight, but its request is also more likely to be dropped due to a

  // full queue and it may only be used from the main thread.

  static nsresult PrefetchHigh(mozilla::dom::Link *aElement);

  static nsresult PrefetchMedium(mozilla::dom::Link *aElement);

  static nsresult PrefetchLow(mozilla::dom::Link *aElement);

  static nsresult PrefetchHigh(const nsAString &host, bool isHttps,

                               const mozilla::OriginAttributes &aOriginAttributes);

  static nsresult PrefetchMedium(const nsAString &host, bool isHttps,

                                 const mozilla::OriginAttributes &aOriginAttributes);

  static nsresult PrefetchLow(const nsAString &host, bool isHttps,

                              const mozilla::OriginAttributes &aOriginAttributes);

  static nsresult CancelPrefetchLow(const nsAString &host, bool isHttps,

                                    const mozilla::OriginAttributes &aOriginAttributes,

                                    nsresult aReason);

  static nsresult CancelPrefetchLow(mozilla::dom::Link *aElement,

                                    nsresult aReason);

  static void LinkDestroyed(mozilla::dom::Link* aLink);

private:

  static nsresult Prefetch(const nsAString &host, bool isHttps,

                           const mozilla::OriginAttributes &aOriginAttributes,

                           uint16_t flags);

  static nsresult Prefetch(mozilla::dom::Link *aElement, uint16_t flags);

  static nsresult CancelPrefetch(const nsAString &hostname, bool isHttps,

                                 const mozilla::OriginAttributes &aOriginAttributes,

                                 uint16_t flags,

                                 nsresult aReason);

  static nsresult CancelPrefetch(mozilla::dom::Link *aElement,

                                 uint16_t flags,

                                 nsresult aReason);

public:

  class nsListener final : public nsIDNSListener

  {

    // This class exists to give a safe callback no-op DNSListener

  public:

    NS_DECL_THREADSAFE_ISUPPORTS

    NS_DECL_NSIDNSLISTENER

    nsListener()  {}

  private:

    ~nsListener() {}

  };

  class nsDeferrals final: public nsIWebProgressListener

                         , public nsSupportsWeakReference

                         , public nsIObserver

  {

  public:

    NS_DECL_ISUPPORTS

    NS_DECL_NSIWEBPROGRESSLISTENER

    NS_DECL_NSIOBSERVER

    nsDeferrals();

    void Activate();

    nsresult Add(uint16_t flags, mozilla::dom::Link *aElement);

    void RemoveUnboundLinks();

  private:

    ~nsDeferrals();

    void Flush();

    void SubmitQueue();

    uint16_t                  mHead;

    uint16_t                  mTail;

    uint32_t                  mActiveLoaderCount;

    nsCOMPtr<nsITimer>        mTimer;

    bool                      mTimerArmed;

    static void Tick(nsITimer *aTimer, void *aClosure);

    static const int          sMaxDeferred = 512;  // keep power of 2 for masking

    static const int          sMaxDeferredMask = (sMaxDeferred - 1);

    struct deferred_entry

    {

      uint16_t                         mFlags;

      // Link implementation clears this raw pointer in its destructor.

      mozilla::dom::Link*              mElement;

    } mEntries[sMaxDeferred];

  };

  friend class mozilla::net::NeckoParent;

};

#endif