/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* ***** BEGIN LICENSE BLOCK *****

 * Version: MPL 1.1/GPL 2.0/LGPL 2.1

 *

 * The contents of this file are subject to the Mozilla Public License Version

 * 1.1 (the "License"); you may not use this file except in compliance with

 * the License. You may obtain a copy of the License at

 * http://www.mozilla.org/MPL/

 *

 * Software distributed under the License is distributed on an "AS IS" basis,

 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License

 * for the specific language governing rights and limitations under the

 * License.

 *

 * The Original Code is Mozilla Universal charset detector code.

 *

 * The Initial Developer of the Original Code is

 *          Shy Shalom <shooshX@gmail.com>

 * Portions created by the Initial Developer are Copyright (C) 2005

 * the Initial Developer: All Rights Reserved.

 *

 * Contributor(s):

 *

 * Alternatively, the contents of this file may be used under the terms of

 * either the GNU General Public License Version 2 or later (the "GPL"), or

 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),

 * in which case the provisions of the GPL or the LGPL are applicable instead

 * of those above. If you wish to allow use of your version of this file only

 * under the terms of either the GPL or the LGPL, and not to allow others to

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 * the terms of any one of the MPL, the GPL or the LGPL.

 *

 * ***** END LICENSE BLOCK ***** */

#ifndef nsHebrewProber_h__

#define nsHebrewProber_h__

#include "nsSBCharSetProber.h"

// This prober doesn't actually recognize a language or a charset.

// It is a helper prober for the use of the Hebrew model probers

class nsHebrewProber: public nsCharSetProber

{

public:

  nsHebrewProber(void) :mLogicalProb(0), mVisualProb(0) { Reset(); }

  virtual ~nsHebrewProber(void) {}

  virtual nsProbingState HandleData(const char* aBuf, PRUint32 aLen);

  virtual const char* GetCharSetName();

  virtual void Reset(void);

  virtual nsProbingState GetState(void);

  virtual float     GetConfidence(void) { return (float)0.0; }

  virtual void      SetOpion() {}

  void SetModelProbers(nsCharSetProber *logicalPrb, nsCharSetProber *visualPrb) 

  { mLogicalProb = logicalPrb; mVisualProb = visualPrb; }

#ifdef DEBUG_chardet

  virtual void  DumpStatus();

#endif

protected:

  static PRBool isFinal(char c);

  static PRBool isNonFinal(char c);

  PRInt32 mFinalCharLogicalScore, mFinalCharVisualScore;

  // The two last characters seen in the previous buffer.

  char mPrev, mBeforePrev;

  // These probers are owned by the group prober.

  nsCharSetProber *mLogicalProb, *mVisualProb;

};

/**

 * ** General ideas of the Hebrew charset recognition **

 *

 * Four main charsets exist in Hebrew:

 * "ISO-8859-8" - Visual Hebrew

 * "windows-1255" - Logical Hebrew 

 * "ISO-8859-8-I" - Logical Hebrew

 * "x-mac-hebrew" - ?? Logical Hebrew ??

 *

 * Both "ISO" charsets use a completely identical set of code points, whereas

 * "windows-1255" and "x-mac-hebrew" are two different proper supersets of 

 * these code points. windows-1255 defines additional characters in the range

 * 0x80-0x9F as some misc punctuation marks as well as some Hebrew-specific 

 * diacritics and additional 'Yiddish' ligature letters in the range 0xc0-0xd6.

 * x-mac-hebrew defines similar additional code points but with a different 

 * mapping.

 *

 * As far as an average Hebrew text with no diacritics is concerned, all four 

 * charsets are identical with respect to code points. Meaning that for the 

 * main Hebrew alphabet, all four map the same values to all 27 Hebrew letters 

 * (including final letters).

 *

 * The dominant difference between these charsets is their directionality.

 * "Visual" directionality means that the text is ordered as if the renderer is

 * not aware of a BIDI rendering algorithm. The renderer sees the text and 

 * draws it from left to right. The text itself when ordered naturally is read 

 * backwards. A buffer of Visual Hebrew generally looks like so:

 * "[last word of first line spelled backwards] [whole line ordered backwards

 * and spelled backwards] [first word of first line spelled backwards] 

 * [end of line] [last word of second line] ... etc' "

 * adding punctuation marks, numbers and English text to visual text is

 * naturally also "visual" and from left to right.

 * 

 * "Logical" directionality means the text is ordered "naturally" according to

 * the order it is read. It is the responsibility of the renderer to display 

 * the text from right to left. A BIDI algorithm is used to place general 

 * punctuation marks, numbers and English text in the text.

 *

 * Texts in x-mac-hebrew are almost impossible to find on the Internet. From 

 * what little evidence I could find, it seems that its general directionality

 * is Logical.

 *

 * To sum up all of the above, the Hebrew probing mechanism knows about two

 * charsets:

 * Visual Hebrew - "ISO-8859-8" - backwards text - Words and sentences are

 *    backwards while line order is natural. For charset recognition purposes

 *    the line order is unimportant (In fact, for this implementation, even 

 *    word order is unimportant).

 * Logical Hebrew - "windows-1255" - normal, naturally ordered text.

 *

 * "ISO-8859-8-I" is a subset of windows-1255 and doesn't need to be 

 *    specifically identified.

 * "x-mac-hebrew" is also identified as windows-1255. A text in x-mac-hebrew

 *    that contain special punctuation marks or diacritics is displayed with

 *    some unconverted characters showing as question marks. This problem might

 *    be corrected using another model prober for x-mac-hebrew. Due to the fact

 *    that x-mac-hebrew texts are so rare, writing another model prober isn't 

 *    worth the effort and performance hit.

 *

 * *** The Prober ***

 *

 * The prober is divided between two nsSBCharSetProbers and an nsHebrewProber,

 * all of which are managed, created, fed data, inquired and deleted by the

 * nsSBCSGroupProber. The two nsSBCharSetProbers identify that the text is in

 * fact some kind of Hebrew, Logical or Visual. The final decision about which

 * one is it is made by the nsHebrewProber by combining final-letter scores

 * with the scores of the two nsSBCharSetProbers to produce a final answer.

 *

 * The nsSBCSGroupProber is responsible for stripping the original text of HTML

 * tags, English characters, numbers, low-ASCII punctuation characters, spaces

 * and new lines. It reduces any sequence of such characters to a single space.

 * The buffer fed to each prober in the SBCS group prober is pure text in

 * high-ASCII.

 * The two nsSBCharSetProbers (model probers) share the same language model:

 * Win1255Model.

 * The first nsSBCharSetProber uses the model normally as any other

 * nsSBCharSetProber does, to recognize windows-1255, upon which this model was

 * built. The second nsSBCharSetProber is told to make the pair-of-letter

 * lookup in the language model backwards. This in practice exactly simulates

 * a visual Hebrew model using the windows-1255 logical Hebrew model.

 *

 * The nsHebrewProber is not using any language model. All it does is look for

 * final-letter evidence suggesting the text is either logical Hebrew or visual

 * Hebrew. Disjointed from the model probers, the results of the nsHebrewProber

 * alone are meaningless. nsHebrewProber always returns 0.00 as confidence

 * since it never identifies a charset by itself. Instead, the pointer to the

 * nsHebrewProber is passed to the model probers as a helper "Name Prober".

 * When the Group prober receives a positive identification from any prober,

 * it asks for the name of the charset identified. If the prober queried is a

 * Hebrew model prober, the model prober forwards the call to the

 * nsHebrewProber to make the final decision. In the nsHebrewProber, the

 * decision is made according to the final-letters scores maintained and Both

 * model probers scores. The answer is returned in the form of the name of the

 * charset identified, either "windows-1255" or "ISO-8859-8".

 *

 */

#endif /* nsHebrewProber_h__ */