/* -*- 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 nsTreeStyleCache_h__

#define nsTreeStyleCache_h__

#include "mozilla/AtomArray.h"

#include "mozilla/Attributes.h"

#include "nsAutoPtr.h"

#include "nsCOMArray.h"

#include "nsRefPtrHashtable.h"

#include "mozilla/ComputedStyle.h"

class nsTreeStyleCache

{

public:

  nsTreeStyleCache()

    : mNextState(0)

  {

  }

  ~nsTreeStyleCache()

  {

    Clear();

  }

  void Clear()

  {

    mTransitionTable = nullptr;

    mCache = nullptr;

    mNextState = 0;

  }

  mozilla::ComputedStyle* GetComputedStyle(

      nsPresContext* aPresContext,

      nsIContent* aContent,

      mozilla::ComputedStyle* aStyle,

      nsICSSAnonBoxPseudo* aPseudoElement,

      const mozilla::AtomArray& aInputWord);

protected:

  typedef uint32_t DFAState;

  class Transition final

  {

  public:

    Transition(DFAState aState, nsAtom* aSymbol);

    bool operator==(const Transition& aOther) const;

    uint32_t Hash() const;

  private:

    DFAState mState;

    RefPtr<nsAtom> mInputSymbol;

  };

  typedef nsDataHashtable<nsGenericHashKey<Transition>, DFAState> TransitionTable;

  // A transition table for a deterministic finite automaton.  The DFA

  // takes as its input a single pseudoelement and an ordered set of properties.

  // It transitions on an input word that is the concatenation of the pseudoelement supplied

  // with the properties in the array.

  //

  // It transitions from state to state by looking up entries in the transition table (which is

  // a mapping from (S,i)->S', where S is the current state, i is the next

  // property in the input word, and S' is the state to transition to.

  //

  // If S' is not found, it is constructed and entered into the hashtable

  // under the key (S,i).

  //

  // Once the entire word has been consumed, the final state is used

  // to reference the cache table to locate the ComputedStyle.

  nsAutoPtr<TransitionTable> mTransitionTable;

  // The cache of all active ComputedStyles.  This is a hash from

  // a final state in the DFA, Sf, to the resultant ComputedStyle.

  typedef nsRefPtrHashtable<nsUint32HashKey, mozilla::ComputedStyle> ComputedStyleCache;

  nsAutoPtr<ComputedStyleCache> mCache;

  // An integer counter that is used when we need to make new states in the

  // DFA.

  DFAState mNextState;

};

#endif // nsTreeStyleCache_h__