// Created on: 2013-01-28
// Created by: Kirill GAVRILOV
// Copyright (c) 2013-2014 OPEN CASCADE SAS
//
// This file is part of Open CASCADE Technology software library.
//
// This library is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License version 2.1 as published
// by the Free Software Foundation, with special exception defined in the file
// OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT
// distribution for complete text of the license and disclaimer of any warranty.
//
// Alternatively, this file may be used under the terms of Open CASCADE
// commercial license or contractual agreement.

#ifndef _NCollection_UtfIterator_H__
#define _NCollection_UtfIterator_H__

#include <Standard_TypeDef.hxx>

//! Template class for Unicode strings support.
//! It defines an iterator and provide correct way to read multi-byte text (UTF-8 and UTF-16)
//! and convert it from one to another.
//! The current value of iterator returned as UTF-32 Unicode code.
template<typename Type>
class NCollection_UtfIterator
{

public:

  //! Constructor.
  //! @param theString buffer to iterate
  NCollection_UtfIterator (const Type* theString)
  : myPosition(theString),
    myPosNext(theString),
    myCharIndex(0),
    myCharUtf32(0)
  {
    if (theString != NULL)
    {
      ++(*this);
      myCharIndex = 0;
    }
  }

  //! Initialize iterator within specified NULL-terminated string.
  void Init (const Type* theString)
  {
    myPosition  = theString;
    myPosNext   = theString;
    myCharUtf32 = 0;
    if (theString != NULL)
    {
      ++(*this);
    }
    myCharIndex = 0;
  }

  //! Pre-increment operator. Reads the next unicode character.
  //! Notice - no protection against overrun!
  NCollection_UtfIterator& operator++()
  {
    myPosition = myPosNext;
    ++myCharIndex;
    switch (sizeof(Type))
    {
      case 1: readUTF8();  break;
      case 2: readUTF16(); break;
      case 4: // UTF-32
      default:
        myCharUtf32 = *myPosNext++;
    }
    return *this;
  }

  //! Post-increment operator.
  //! Notice - no protection against overrun!
  NCollection_UtfIterator operator++ (int )
  {
    NCollection_UtfIterator aCopy = *this;
    ++*this;
    return aCopy;
  }

  //! Equality operator.
  bool operator== (const NCollection_UtfIterator& theRight) const
  {
    return myPosition == theRight.myPosition;
  }

  //! Dereference operator.
  //! @return the UTF-32 codepoint of the character currently pointed by iterator.
  Standard_Utf32Char operator*() const
  {
    return myCharUtf32;
  }

  //! Buffer-fetching getter.
  const Type* BufferHere() const { return myPosition; }

  //! Buffer-fetching getter. Dangerous! Iterator should be reinitialized on buffer change.
  Type* ChangeBufferHere() { return (Type* )myPosition; }

  //! Buffer-fetching getter.
  const Type* BufferNext() const { return myPosNext; }

  //! @return the index displacement from iterator intialization
  Standard_Integer Index() const
  {
    return myCharIndex;
  }

  //! @return the advance in bytes to store current symbol in UTF-8.
  //! 0 means an invalid symbol;
  //! 1-4 bytes are valid range.
  Standard_Integer AdvanceBytesUtf8() const;

  //! @return the advance in bytes to store current symbol in UTF-16.
  //! 0 means an invalid symbol;
  //! 2 bytes is a general case;
  //! 4 bytes for surrogate pair.
  Standard_Integer AdvanceBytesUtf16() const;

  //! @return the advance in bytes to store current symbol in UTF-32.
  //! Always 4 bytes (method for consistency).
  Standard_Integer AdvanceBytesUtf32() const
  {
    return Standard_Integer(sizeof(Standard_Utf32Char));
  }

  //! Fill the UTF-8 buffer within current Unicode symbol.
  //! Use method AdvanceUtf8() to allocate buffer with enough size.
  //! @param theBuffer buffer to fill
  //! @return new buffer position (for next char)
  Standard_Utf8Char*  GetUtf8 (Standard_Utf8Char*  theBuffer) const;
  Standard_Utf8UChar* GetUtf8 (Standard_Utf8UChar* theBuffer) const;

  //! Fill the UTF-16 buffer within current Unicode symbol.
  //! Use method AdvanceUtf16() to allocate buffer with enough size.
  //! @param theBuffer buffer to fill
  //! @return new buffer position (for next char)
  Standard_Utf16Char* GetUtf16 (Standard_Utf16Char* theBuffer) const;

  //! Fill the UTF-32 buffer within current Unicode symbol.
  //! Use method AdvanceUtf32() to allocate buffer with enough size.
  //! @param theBuffer buffer to fill
  //! @return new buffer position (for next char)
  Standard_Utf32Char* GetUtf32 (Standard_Utf32Char* theBuffer) const;

  //! @return the advance in TypeWrite chars needed to store current symbol
  template<typename TypeWrite>
  Standard_Integer AdvanceBytesUtf() const;

  //! Fill the UTF-** buffer within current Unicode symbol.
  //! Use method AdvanceUtf**() to allocate buffer with enough size.
  //! @param theBuffer buffer to fill
  //! @return new buffer position (for next char)
  template<typename TypeWrite>
  TypeWrite* GetUtf (TypeWrite* theBuffer) const;

private:

  //! Helper function for reading a single UTF8 character from the string.
  //! Updates internal state appropriately.
  void readUTF8();

  //! Helper function for reading a single UTF16 character from the string.
  //! Updates internal state appropriately.
  void readUTF16();

private: //! @name unicode magic numbers

  static const unsigned char UTF8_BYTES_MINUS_ONE[256];
  static const unsigned long offsetsFromUTF8[6];
  static const unsigned char UTF8_FIRST_BYTE_MARK[7];
  static const unsigned long UTF8_BYTE_MASK;
  static const unsigned long UTF8_BYTE_MARK;
  static const unsigned long UTF16_SURROGATE_HIGH_START;
  static const unsigned long UTF16_SURROGATE_HIGH_END;
  static const unsigned long UTF16_SURROGATE_LOW_START;
  static const unsigned long UTF16_SURROGATE_LOW_END;
  static const unsigned long UTF16_SURROGATE_HIGH_SHIFT;
  static const unsigned long UTF16_SURROGATE_LOW_BASE;
  static const unsigned long UTF16_SURROGATE_LOW_MASK;
  static const unsigned long UTF32_MAX_BMP;
  static const unsigned long UTF32_MAX_LEGAL;

private: //! @name private fields

  const Type*        myPosition;  //!< buffer position of the first element in the current character
  const Type*        myPosNext;   //!< buffer position of the first element in the next character
  Standard_Integer   myCharIndex; //!< index displacement from iterator intialization
  Standard_Utf32Char myCharUtf32; //!< character stored at the current buffer position

};

typedef NCollection_UtfIterator<Standard_Utf8Char>  NCollection_Utf8Iter;
typedef NCollection_UtfIterator<Standard_Utf16Char> NCollection_Utf16Iter;
typedef NCollection_UtfIterator<Standard_Utf32Char> NCollection_Utf32Iter;
typedef NCollection_UtfIterator<Standard_WideChar>  NCollection_UtfWideIter;

// template implementation
#include "NCollection_UtfIterator.lxx"

#endif // _NCollection_UtfIterator_H__