/*

**************************************************************************

* Copyright (C) 1999-2005, International Business Machines Corporation and

* others. All Rights Reserved.

**************************************************************************

*   Date        Name        Description

*   11/17/99    aliu        Creation.  Ported from java.  Modified to

*                           match current UnicodeString API.  Forced

*                           to use name "handleReplaceBetween" because

*                           of existing methods in UnicodeString.

**************************************************************************

*/

#ifndef REP_H

#define REP_H

#include "unicode/uobject.h"

/**

 * \file 

 * \brief C++ API: Replaceable String

 */

U_NAMESPACE_BEGIN

class UnicodeString;

/**

 * <code>Replaceable</code> is an abstract base class representing a

 * string of characters that supports the replacement of a range of

 * itself with a new string of characters.  It is used by APIs that

 * change a piece of text while retaining metadata.  Metadata is data

 * other than the Unicode characters returned by char32At().  One

 * example of metadata is style attributes; another is an edit

 * history, marking each character with an author and revision number.

 *

 * <p>An implicit aspect of the <code>Replaceable</code> API is that

 * during a replace operation, new characters take on the metadata of

 * the old characters.  For example, if the string "the <b>bold</b>

 * font" has range (4, 8) replaced with "strong", then it becomes "the

 * <b>strong</b> font".

 *

 * <p><code>Replaceable</code> specifies ranges using a start

 * offset and a limit offset.  The range of characters thus specified

 * includes the characters at offset start..limit-1.  That is, the

 * start offset is inclusive, and the limit offset is exclusive.

 *

 * <p><code>Replaceable</code> also includes API to access characters

 * in the string: <code>length()</code>, <code>charAt()</code>,

 * <code>char32At()</code>, and <code>extractBetween()</code>.

 *

 * <p>For a subclass to support metadata, typical behavior of

 * <code>replace()</code> is the following:

 * <ul>

 *   <li>Set the metadata of the new text to the metadata of the first

 *   character replaced</li>

 *   <li>If no characters are replaced, use the metadata of the

 *   previous character</li>

 *   <li>If there is no previous character (i.e. start == 0), use the

 *   following character</li>

 *   <li>If there is no following character (i.e. the replaceable was

 *   empty), use default metadata.<br>

 *   <li>If the code point U+FFFF is seen, it should be interpreted as

 *   a special marker having no metadata<li>

 *   </li>

 * </ul>

 * If this is not the behavior, the subclass should document any differences.

 * @author Alan Liu

 * @stable ICU 2.0

 */

class U_COMMON_API Replaceable : public UObject {

public:

    /**

     * Destructor.

     * @stable ICU 2.0

     */

    virtual ~Replaceable();

    /**

     * Returns the number of 16-bit code units in the text.

     * @return number of 16-bit code units in text

     * @stable ICU 1.8

     */ 

    inline int32_t length() const;

    /**

     * Returns the 16-bit code unit at the given offset into the text.

     * @param offset an integer between 0 and <code>length()</code>-1

     * inclusive

     * @return 16-bit code unit of text at given offset

     * @stable ICU 1.8

     */

    inline UChar charAt(int32_t offset) const;

    /**

     * Returns the 32-bit code point at the given 16-bit offset into

     * the text.  This assumes the text is stored as 16-bit code units

     * with surrogate pairs intermixed.  If the offset of a leading or

     * trailing code unit of a surrogate pair is given, return the

     * code point of the surrogate pair.

     *

     * @param offset an integer between 0 and <code>length()</code>-1

     * inclusive

     * @return 32-bit code point of text at given offset

     * @stable ICU 1.8

     */

    inline UChar32 char32At(int32_t offset) const;

    /**

     * Copies characters in the range [<tt>start</tt>, <tt>limit</tt>) 

     * into the UnicodeString <tt>target</tt>.

     * @param start offset of first character which will be copied

     * @param limit offset immediately following the last character to

     * be copied

     * @param target UnicodeString into which to copy characters.

     * @return A reference to <TT>target</TT>

     * @stable ICU 2.1

     */

    virtual void extractBetween(int32_t start,

                                int32_t limit,

                                UnicodeString& target) const = 0;

    /**

     * Replaces a substring of this object with the given text.  If the

     * characters being replaced have metadata, the new characters

     * that replace them should be given the same metadata.

     *

     * <p>Subclasses must ensure that if the text between start and

     * limit is equal to the replacement text, that replace has no

     * effect. That is, any metadata

     * should be unaffected. In addition, subclasses are encouraged to

     * check for initial and trailing identical characters, and make a

     * smaller replacement if possible. This will preserve as much

     * metadata as possible.

     * @param start the beginning index, inclusive; <code>0 <= start

     * <= limit</code>.

     * @param limit the ending index, exclusive; <code>start <= limit

     * <= length()</code>.

     * @param text the text to replace characters <code>start</code>

     * to <code>limit - 1</code> 

     * @stable ICU 2.0

     */

    virtual void handleReplaceBetween(int32_t start,

                                      int32_t limit,

                                      const UnicodeString& text) = 0;

    // Note: All other methods in this class take the names of

    // existing UnicodeString methods.  This method is the exception.

    // It is named differently because all replace methods of

    // UnicodeString return a UnicodeString&.  The 'between' is

    // required in order to conform to the UnicodeString naming

    // convention; API taking start/length are named <operation>, and

    // those taking start/limit are named <operationBetween>.  The

    // 'handle' is added because 'replaceBetween' and

    // 'doReplaceBetween' are already taken.

    /**

     * Copies a substring of this object, retaining metadata.

     * This method is used to duplicate or reorder substrings.

     * The destination index must not overlap the source range.

     * 

     * @param start the beginning index, inclusive; <code>0 <= start <=

     * limit</code>.

     * @param limit the ending index, exclusive; <code>start <= limit <=

     * length()</code>.

     * @param dest the destination index.  The characters from

     * <code>start..limit-1</code> will be copied to <code>dest</code>.

     * Implementations of this method may assume that <code>dest <= start ||

     * dest >= limit</code>.

     * @stable ICU 2.0

     */

    virtual void copy(int32_t start, int32_t limit, int32_t dest) = 0;

    /**

     * Returns true if this object contains metadata.  If a

     * Replaceable object has metadata, calls to the Replaceable API

     * must be made so as to preserve metadata.  If it does not, calls

     * to the Replaceable API may be optimized to improve performance.

     * The default implementation returns true.

     * @return true if this object contains metadata

     * @stable ICU 2.2

     */

    virtual UBool hasMetaData() const;

    /**

     * Clone this object, an instance of a subclass of Replaceable.

     * Clones can be used concurrently in multiple threads.

     * If a subclass does not implement clone(), or if an error occurs,

     * then NULL is returned.

     * The clone functions in all subclasses return a pointer to a Replaceable

     * because some compilers do not support covariant (same-as-this)

     * return types; cast to the appropriate subclass if necessary.

     * The caller must delete the clone.

     *

     * @return a clone of this object

     *

     * @see getDynamicClassID

     * @stable ICU 2.6

     */

    virtual Replaceable *clone() const;

protected:

    /**

     * Default constructor.

     * @stable ICU 2.4

     */

    Replaceable();

    /*

     * Assignment operator not declared. The compiler will provide one

     * which does nothing since this class does not contain any data members.

     * API/code coverage may show the assignment operator as present and

     * untested - ignore.

     * Subclasses need this assignment operator if they use compiler-provided

     * assignment operators of their own. An alternative to not declaring one

     * here would be to declare and empty-implement a protected or public one.

    Replaceable &Replaceable::operator=(const Replaceable &);

     */

    /**

     * Virtual version of length().

     * @stable ICU 2.4

     */ 

    virtual int32_t getLength() const = 0;

    /**

     * Virtual version of charAt().

     * @stable ICU 2.4

     */

    virtual UChar getCharAt(int32_t offset) const = 0;

    /**

     * Virtual version of char32At().

     * @stable ICU 2.4

     */

    virtual UChar32 getChar32At(int32_t offset) const = 0;

};

inline int32_t

Replaceable::length() const {

    return getLength();

}

inline UChar

Replaceable::charAt(int32_t offset) const {

    return getCharAt(offset);

}

inline UChar32

Replaceable::char32At(int32_t offset) const {

    return getChar32At(offset);

}

// There is no rep.cpp, see unistr.cpp for Replaceable function implementations.

U_NAMESPACE_END

#endif