package com.ibm.text;

/**
 * <code>ReplaceableString</code> is an adapter class that implements the
 * <code>Replaceable</code> API around an ordinary <code>StringBuffer</code>.
 *
 * <p><em>Note:</em> This class does not support attributes and is not
 * intended for general use.  Most clients will need to implement
 * {@link Replaceable} in their text representation class.
 *
 * <p>Copyright &copy; IBM Corporation 1999.  All rights reserved.
 *
 * @see Replaceable
 * @author Alan Liu
 * @version $RCSfile: ReplaceableString.java,v $ $Revision: 1.1 $ $Date: 1999/12/20 18:29:21 $
 */
public class ReplaceableString implements Replaceable {
    private StringBuffer buf;

    private static final String COPYRIGHT =
        "\u00A9 IBM Corporation 1999. All rights reserved.";

    /**
     * Construct a new object with the given initial contents.
     * @param str initial contents
     */
    public ReplaceableString(String str) {
        buf = new StringBuffer(str);
    }

    /**
     * Construct a new object using <code>buf</code> for internal
     * storage.  The contents of <code>buf</code> at the time of
     * construction are used as the initial contents.  <em>Note!
     * Modifications to <code>buf</code> will modify this object, and
     * vice versa.</em>
     * @param buf object to be used as internal storage
     */
    public ReplaceableString(StringBuffer buf) {
        this.buf = buf;
    }

    /**
     * Construct a new empty object.
     */
    public ReplaceableString() {
        buf = new StringBuffer();
    }

    /**
     * Return the contents of this object as a <code>String</code>.
     * @return string contents of this object
     */
    public String toString() {
        return buf.toString();
    }

    /**
     * Return the internal storage of this object.  <em>Note!  Any
     * changes made to the returned object affect this object's
     * contents, and vice versa.</em>
     * @return internal buffer used by this object
     */
    public StringBuffer getStringBuffer() {
        return buf;
    }

    /**
     * Return the number of characters contained in this object.
     * <code>Replaceable</code> API.
     */ 
    public int length() {
        return buf.length();
    }

    /**
     * Return the character at the given position in this object.
     * <code>Replaceable</code> API.
     * @param offset offset into the contents, from 0 to
     * <code>length()</code> - 1
     */
    public char charAt(int offset) {
        return buf.charAt(offset);
    }

    /**
     * Copies characters from this object into the destination
     * character array.  The first character to be copied is at index
     * <code>srcStart</code>; the last character to be copied is at
     * index <code>srcLimit-1</code> (thus the total number of
     * characters to be copied is <code>srcLimit-srcStart</code>). The
     * characters are copied into the subarray of <code>dst</code>
     * starting at index <code>dstStart</code> and ending at index
     * <code>dstStart + (srcLimit-srcStart) - 1</code>.
     *
     * @param srcStart the beginning index to copy, inclusive; <code>0
     * <= start <= limit</code>.
     * @param srcLimit the ending index to copy, exclusive;
     * <code>start <= limit <= length()</code>.
     * @param dst the destination array.
     * @param dstStart the start offset in the destination array.
     */
    public void getChars(int srcStart, int srcLimit, char dst[], int dstStart) {
        buf.getChars(srcStart, srcLimit, dst, dstStart);
    }

    /**
     * Replace zero or more characters with new characters.
     * <code>Replaceable</code> API.
     * @param start the beginning index, inclusive; <code>0 <= start
     * <= limit</code>.
     * @param limit the ending index, exclusive; <code>start <= limit
     * <= length()</code>.
     * @param text new text to replace characters <code>start</code> to
     * <code>limit - 1</code>
     */
    public void replace(int start, int limit, String text) {
        if (start == limit) {
            buf.insert(start, text);
        } else {
            char[] tail = null;
            if (limit < buf.length()) {
                tail = new char[buf.length() - limit];
                buf.getChars(limit, buf.length(), tail, 0);
            }
            buf.setLength(start);
            buf.append(text);
            if (tail != null) {
                buf.append(tail);
            }
        }
    }

    /**
     * Replace a substring of this object with the given text.
     * @param start the beginning index, inclusive; <code>0 <= start
     * <= limit</code>.
     * @param limit the ending index, exclusive; <code>start <= limit
     * <= length()</code>.
     * @param chars the text to replace characters <code>start</code>
     * to <code>limit - 1</code>
     * @param charsStart the beginning index into <code>chars</code>,
     * inclusive; <code>0 <= start <= limit</code>.
     * @param charsLen the number of characters of <code>chars</code>.
     */
    public void replace(int start, int limit, char[] chars,
                        int charsStart, int charsLen) {
        char[] tail = null;
        if (limit < buf.length()) {
            tail = new char[buf.length() - limit];
            buf.getChars(limit, buf.length(), tail, 0);
        }
        buf.setLength(start);
        buf.append(chars, charsStart, charsLen);
        if (tail != null) {
            buf.append(tail);
        }
    }
}