/*
**************************************************************************
* Copyright (C) 1999-2001, 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/utypes.h"
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 style attributes.  In other
 * words, an implicit aspect of the <code>Replaceable</code> API is
 * that during a replace operation, new characters take on the
 * attributes, if any, 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 an initial
 * offset and a limit offset.  The range of characters thus specified
 * includes the characters at offset initial..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>, and
 * <code>extractBetween()</code>.
 *
 * <p>If a subclass supports styles, then typically the behavior is the following:
 * <ul>
 *   <li>Set the styles to the style of the first character replaced</li>
 *   <li>If no characters are replaced, use the style 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), a
 *     default style.<br>
 *   </li>
 * </ul>
 * If this is not the behavior, the subclass should document any differences.
 * @author Alan Liu
 * @stable
 */
class U_COMMON_API Replaceable {

public:
    /**
     * Destructor.
     * @stable
     */
    virtual ~Replaceable();

    /**
     * Return the number of characters in the text.
     * @return number of characters in text
     * @draft ICU 1.8
     */ 
    inline int32_t length() const;

    /**
     * Return the Unicode code unit at the given offset into the text.
     * @param offset an integer between 0 and <code>length()</code>-1
     * inclusive
     * @return code unit of text at given offset
     * @draft ICU 1.8
     */
    inline UChar charAt(int32_t offset) const;

    /**
     * Return the Unicode code point that contains the code unit
     * at the given offset into the text.
     * @param offset an integer between 0 and <code>length()</code>-1
     * inclusive that indicates the text offset of any of the code units
     * that will be assembled into a code point (21-bit value) and returned
     * @return code point of text at given offset
     * @draft ICU 1.8
     */
    inline UChar32 char32At(int32_t offset) const;

    /**
     * Copy the 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>
     * @draft ICU 2.1
     */
    virtual void extractBetween(int32_t start,
                                int32_t limit,
                                UnicodeString& target) const = 0;

    /**
     * Replace a substring of this object with the given text.  If the
     * characters being replaced have attributes, the new characters
     * that replace them should be given the same attributes.
     *
     * <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 out-of-band information such as styles
     * should be unaffected. In addition, subclasses are encourage to
     * check for initial and trailing identical characters, and make a
     * smaller replacement if possible. This will preserve as much
     * style information 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
     */
    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.

    /**
     * Copy a substring of this object, retaining attribute (out-of-band)
     * information.  This method is used to duplicate or reorder substrings.
     * The destination index must not overlap the source range.
     * Implementations that do not care about maintaining out-of-band
     * information or performance during copying may use the naive
     * implementation:
     *
     * <pre> char[] text = new char[limit - start];
     * getChars(start, limit, text, 0);
     * replace(dest, dest, text, 0, limit - start);</pre>
     * 
     * @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 */
    virtual void copy(int32_t start, int32_t limit, int32_t dest) = 0;

protected:

    /**
     * Default constructor.
     */
    Replaceable();

    /**
     * Virtual version of length().
     */ 
    virtual int32_t getLength() const = 0;

    /**
     * Virtual version of charAt().
     */
    virtual UChar getCharAt(int32_t offset) const = 0;

    /**
     * Virtual version of char32At().
     */
    virtual UChar32 getChar32At(int32_t offset) const = 0;
};

inline Replaceable::Replaceable() {}

inline Replaceable::~Replaceable() {}

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);
}

U_NAMESPACE_END

#endif