/* -*- 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 nsSHistory_h

#define nsSHistory_h

#include "nsCOMPtr.h"

#include "nsExpirationTracker.h"

#include "nsISHistory.h"

#include "nsSHEntryShared.h"

#include "nsSimpleEnumerator.h"

#include "nsTObserverArray.h"

#include "nsWeakReference.h"

#include "mozilla/LinkedList.h"

#include "mozilla/UniquePtr.h"

class nsIDocShell;

class nsDocShell;

class nsSHistoryObserver;

class nsISHEntry;

class nsSHistory final : public mozilla::LinkedListElement<nsSHistory>,

                         public nsISHistory,

                         public nsSupportsWeakReference

{

public:

  // The timer based history tracker is used to evict bfcache on expiration.

  class HistoryTracker final : public nsExpirationTracker<nsSHEntryShared, 3>

  {

  public:

    explicit HistoryTracker(nsSHistory* aSHistory,

                            uint32_t aTimeout,

                            nsIEventTarget* aEventTarget)

      : nsExpirationTracker(1000 * aTimeout / 2, "HistoryTracker", aEventTarget)

    {

      MOZ_ASSERT(aSHistory);

      mSHistory = aSHistory;

    }

  protected:

    virtual void NotifyExpired(nsSHEntryShared* aObj) override

    {

      RemoveObject(aObj);

      mSHistory->EvictExpiredContentViewerForEntry(aObj);

    }

  private:

    // HistoryTracker is owned by nsSHistory; it always outlives HistoryTracker

    // so it's safe to use raw pointer here.

    nsSHistory* mSHistory;

  };

  // Structure used in SetChildHistoryEntry

  struct SwapEntriesData

  {

    nsDocShell* ignoreShell;     // constant; the shell to ignore

    nsISHEntry* destTreeRoot;    // constant; the root of the dest tree

    nsISHEntry* destTreeParent;  // constant; the node under destTreeRoot

                                 // whose children will correspond to aEntry

  };

  nsSHistory();

  NS_DECL_ISUPPORTS

  NS_DECL_NSISHISTORY

  nsresult Reload(uint32_t aReloadFlags);

  nsresult GetCurrentURI(nsIURI** aResultURI);

  // One time initialization method called upon docshell module construction

  static nsresult Startup();

  static void Shutdown();

  static void UpdatePrefs();

  // Max number of total cached content viewers.  If the pref

  // browser.sessionhistory.max_total_viewers is negative, then

  // this value is calculated based on the total amount of memory.

  // Otherwise, it comes straight from the pref.

  static uint32_t GetMaxTotalViewers() { return sHistoryMaxTotalViewers; }

  // Get the root SHEntry from a given entry.

  static nsISHEntry* GetRootSHEntry(nsISHEntry* aEntry);

  // Callback prototype for WalkHistoryEntries.

  // aEntry is the child history entry, aShell is its corresponding docshell,

  // aChildIndex is the child's index in its parent entry, and aData is

  // the opaque pointer passed to WalkHistoryEntries.

  typedef nsresult(*WalkHistoryEntriesFunc)(nsISHEntry* aEntry,

                                            nsDocShell* aShell,

                                            int32_t aChildIndex,

                                            void* aData);

  // Clone a session history tree for subframe navigation.

  // The tree rooted at |aSrcEntry| will be cloned into |aDestEntry|, except

  // for the entry with id |aCloneID|, which will be replaced with

  // |aReplaceEntry|. |aSrcShell| is a (possibly null) docshell which

  // corresponds to |aSrcEntry| via its mLSHE or mOHE pointers, and will

  // have that pointer updated to point to the cloned history entry.

  // If aCloneChildren is true then the children of the entry with id

  // |aCloneID| will be cloned into |aReplaceEntry|.

  static nsresult CloneAndReplace(nsISHEntry* aSrcEntry,

                                  nsDocShell* aSrcShell,

                                  uint32_t aCloneID,

                                  nsISHEntry* aReplaceEntry,

                                  bool aCloneChildren,

                                  nsISHEntry** aDestEntry);

  // Child-walking callback for CloneAndReplace

  static nsresult CloneAndReplaceChild(nsISHEntry* aEntry, nsDocShell* aShell,

                                       int32_t aChildIndex, void* aData);

  // Child-walking callback for SetHistoryEntry

  static nsresult SetChildHistoryEntry(nsISHEntry* aEntry, nsDocShell* aShell,

                                       int32_t aEntryIndex, void* aData);

  // For each child of aRootEntry, find the corresponding docshell which is

  // a child of aRootShell, and call aCallback. The opaque pointer aData

  // is passed to the callback.

  static nsresult WalkHistoryEntries(nsISHEntry* aRootEntry,

                                     nsDocShell* aRootShell,

                                     WalkHistoryEntriesFunc aCallback,

                                     void* aData);

private:

  virtual ~nsSHistory();

  friend class nsSHistoryObserver;

  // The size of the window of SHEntries which can have alive viewers in the

  // bfcache around the currently active SHEntry.

  //

  // We try to keep viewers for SHEntries between index - VIEWER_WINDOW and

  // index + VIEWER_WINDOW alive.

  static const int32_t VIEWER_WINDOW = 3;

  nsresult LoadDifferingEntries(nsISHEntry* aPrevEntry, nsISHEntry* aNextEntry,

                                nsIDocShell* aRootDocShell, long aLoadType,

                                bool& aDifferenceFound);

  nsresult InitiateLoad(nsISHEntry* aFrameEntry, nsIDocShell* aFrameDS,

                        long aLoadType);

  nsresult LoadEntry(int32_t aIndex, long aLoadType, uint32_t aHistCmd);

#ifdef DEBUG

  nsresult PrintHistory();

#endif

  // Find the history entry for a given bfcache entry. It only looks up between

  // the range where alive viewers may exist (i.e nsSHistory::VIEWER_WINDOW).

  nsresult FindEntryForBFCache(nsIBFCacheEntry* aBFEntry,

                               nsISHEntry** aResult,

                               int32_t* aResultIndex);

  // Evict content viewers in this window which don't lie in the "safe" range

  // around aIndex.

  void EvictOutOfRangeWindowContentViewers(int32_t aIndex);

  void EvictContentViewerForEntry(nsISHEntry* aEntry);

  static void GloballyEvictContentViewers();

  static void GloballyEvictAllContentViewers();

  // Calculates a max number of total

  // content viewers to cache, based on amount of total memory

  static uint32_t CalcMaxTotalViewers();

  nsresult LoadNextPossibleEntry(int32_t aNewIndex, long aLoadType,

                                 uint32_t aHistCmd);

  // aIndex is the index of the entry which may be removed.

  // If aKeepNext is true, aIndex is compared to aIndex + 1,

  // otherwise comparison is done to aIndex - 1.

  bool RemoveDuplicate(int32_t aIndex, bool aKeepNext);

  // Track all bfcache entries and evict on expiration.

  mozilla::UniquePtr<HistoryTracker> mHistoryTracker;

  nsTArray<nsCOMPtr<nsISHEntry>> mEntries; // entries are never null

  int32_t mIndex;           // -1 means "no index"

  int32_t mRequestedIndex;  // -1 means "no requested index"

  void WindowIndices(int32_t aIndex, int32_t* aOutStartIndex,

                     int32_t* aOutEndIndex);

  // Length of mEntries.

  int32_t Length() { return int32_t(mEntries.Length()); }

  // Session History listeners

  nsAutoTObserverArray<nsWeakPtr, 2> mListeners;

  // Weak reference. Do not refcount this.

  nsIDocShell* mRootDocShell;

  // Max viewers allowed total, across all SHistory objects

  static int32_t sHistoryMaxTotalViewers;

};

inline nsISupports*

ToSupports(nsSHistory* aObj)

{

  return static_cast<nsISHistory*>(aObj);

}

#endif /* nsSHistory */