/*

 * Copyright 1996-2006 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

/*

 * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved

 * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved

 *

 * The original version of this source code and documentation

 * is copyrighted and owned by Taligent, Inc., a wholly-owned

 * subsidiary of IBM. These materials are provided under terms

 * of a License Agreement between Taligent and Sun. This technology

 * is protected by multiple US and International patents.

 *

 * This notice and attribution to Taligent may not be removed.

 * Taligent is a registered trademark of Taligent, Inc.

 *

 */

package java.text;

import java.lang.ref.SoftReference;

import java.net.URL;

import java.io.InputStream;

import java.io.IOException;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.text.CharacterIterator;

import java.text.StringCharacterIterator;

import java.text.spi.BreakIteratorProvider;

import java.util.Locale;

import java.util.MissingResourceException;

import java.util.ResourceBundle;

import java.util.spi.LocaleServiceProvider;

import sun.util.LocaleServiceProviderPool;

import sun.util.resources.LocaleData;

/**

 * The <code>BreakIterator</code> class implements methods for finding

 * the location of boundaries in text. Instances of <code>BreakIterator</code>

 * maintain a current position and scan over text

 * returning the index of characters where boundaries occur.

 * Internally, <code>BreakIterator</code> scans text using a

 * <code>CharacterIterator</code>, and is thus able to scan text held

 * by any object implementing that protocol. A <code>StringCharacterIterator</code>

 * is used to scan <code>String</code> objects passed to <code>setText</code>.

 *

 * <p>

 * You use the factory methods provided by this class to create

 * instances of various types of break iterators. In particular,

 * use <code>getWordInstance</code>, <code>getLineInstance</code>,

 * <code>getSentenceInstance</code>, and <code>getCharacterInstance</code>

 * to create <code>BreakIterator</code>s that perform

 * word, line, sentence, and character boundary analysis respectively.

 * A single <code>BreakIterator</code> can work only on one unit

 * (word, line, sentence, and so on). You must use a different iterator

 * for each unit boundary analysis you wish to perform.

 *

 * <p><a name="line"></a>

 * Line boundary analysis determines where a text string can be

 * broken when line-wrapping. The mechanism correctly handles

 * punctuation and hyphenated words. Actual line breaking needs

 * to also consider the available line width and is handled by

 * higher-level software.

 *

 * <p><a name="sentence"></a>

 * Sentence boundary analysis allows selection with correct interpretation

 * of periods within numbers and abbreviations, and trailing punctuation

 * marks such as quotation marks and parentheses.

 *

 * <p><a name="word"></a>

 * Word boundary analysis is used by search and replace functions, as

 * well as within text editing applications that allow the user to

 * select words with a double click. Word selection provides correct

 * interpretation of punctuation marks within and following

 * words. Characters that are not part of a word, such as symbols

 * or punctuation marks, have word-breaks on both sides.

 *

 * <p><a name="character"></a>

 * Character boundary analysis allows users to interact with characters

 * as they expect to, for example, when moving the cursor through a text

 * string. Character boundary analysis provides correct navigation

 * through character strings, regardless of how the character is stored.

 * The boundaries returned may be those of supplementary characters,

 * combining character sequences, or ligature clusters.

 * For example, an accented character might be stored as a base character

 * and a diacritical mark. What users consider to be a character can

 * differ between languages.

 *

 * <p>

 * The <code>BreakIterator</code> instances returned by the factory methods

 * of this class are intended for use with natural languages only, not for

 * programming language text. It is however possible to define subclasses

 * that tokenize a programming language.

 *

 * <P>

 * <strong>Examples</strong>:<P>

 * Creating and using text boundaries:

 * <blockquote>

 * <pre>

 * public static void main(String args[]) {

 *      if (args.length == 1) {

 *          String stringToExamine = args[0];

 *          //print each word in order

 *          BreakIterator boundary = BreakIterator.getWordInstance();

 *          boundary.setText(stringToExamine);

 *          printEachForward(boundary, stringToExamine);

 *          //print each sentence in reverse order

 *          boundary = BreakIterator.getSentenceInstance(Locale.US);

 *          boundary.setText(stringToExamine);

 *          printEachBackward(boundary, stringToExamine);

 *          printFirst(boundary, stringToExamine);

 *          printLast(boundary, stringToExamine);

 *      }

 * }

 * </pre>

 * </blockquote>

 *

 * Print each element in order:

 * <blockquote>

 * <pre>

 * public static void printEachForward(BreakIterator boundary, String source) {

 *     int start = boundary.first();

 *     for (int end = boundary.next();

 *          end != BreakIterator.DONE;

 *          start = end, end = boundary.next()) {

 *          System.out.println(source.substring(start,end));

 *     }

 * }

 * </pre>

 * </blockquote>

 *

 * Print each element in reverse order:

 * <blockquote>

 * <pre>

 * public static void printEachBackward(BreakIterator boundary, String source) {

 *     int end = boundary.last();

 *     for (int start = boundary.previous();

 *          start != BreakIterator.DONE;

 *          end = start, start = boundary.previous()) {

 *         System.out.println(source.substring(start,end));

 *     }

 * }

 * </pre>

 * </blockquote>

 *

 * Print first element:

 * <blockquote>

 * <pre>

 * public static void printFirst(BreakIterator boundary, String source) {

 *     int start = boundary.first();

 *     int end = boundary.next();

 *     System.out.println(source.substring(start,end));

 * }

 * </pre>

 * </blockquote>

 *

 * Print last element:

 * <blockquote>

 * <pre>

 * public static void printLast(BreakIterator boundary, String source) {

 *     int end = boundary.last();

 *     int start = boundary.previous();

 *     System.out.println(source.substring(start,end));

 * }

 * </pre>

 * </blockquote>

 *

 * Print the element at a specified position:

 * <blockquote>

 * <pre>

 * public static void printAt(BreakIterator boundary, int pos, String source) {

 *     int end = boundary.following(pos);

 *     int start = boundary.previous();

 *     System.out.println(source.substring(start,end));

 * }

 * </pre>

 * </blockquote>

 *

 * Find the next word:

 * <blockquote>

 * <pre>

 * public static int nextWordStartAfter(int pos, String text) {

 *     BreakIterator wb = BreakIterator.getWordInstance();

 *     wb.setText(text);

 *     int last = wb.following(pos);

 *     int current = wb.next();

 *     while (current != BreakIterator.DONE) {

 *         for (int p = last; p < current; p++) {

 *             if (Character.isLetter(text.codePointAt(p)))

 *                 return last;

 *         }

 *         last = current;

 *         current = wb.next();

 *     }

 *     return BreakIterator.DONE;

 * }

 * </pre>

 * (The iterator returned by BreakIterator.getWordInstance() is unique in that

 * the break positions it returns don't represent both the start and end of the

 * thing being iterated over.  That is, a sentence-break iterator returns breaks

 * that each represent the end of one sentence and the beginning of the next.

 * With the word-break iterator, the characters between two boundaries might be a

 * word, or they might be the punctuation or whitespace between two words.  The

 * above code uses a simple heuristic to determine which boundary is the beginning

 * of a word: If the characters between this boundary and the next boundary

 * include at least one letter (this can be an alphabetical letter, a CJK ideograph,

 * a Hangul syllable, a Kana character, etc.), then the text between this boundary

 * and the next is a word; otherwise, it's the material between words.)

 * </blockquote>

 *

 * @see CharacterIterator

 *

 */

public abstract class BreakIterator implements Cloneable

{

    /**

     * Constructor. BreakIterator is stateless and has no default behavior.

     */

    protected BreakIterator()

    {

    }

    /**

     * Create a copy of this iterator

     * @return A copy of this

     */

    public Object clone()

    {

        try {

            return super.clone();

        }

        catch (CloneNotSupportedException e) {

            throw new InternalError();

        }

    }

    /**

     * DONE is returned by previous(), next(), next(int), preceding(int)

     * and following(int) when either the first or last text boundary has been

     * reached.

     */

    public static final int DONE = -1;

    /**

     * Returns the first boundary. The iterator's current position is set

     * to the first text boundary.

     * @return The character index of the first text boundary.

     */

    public abstract int first();

    /**

     * Returns the last boundary. The iterator's current position is set

     * to the last text boundary.

     * @return The character index of the last text boundary.

     */

    public abstract int last();

    /**

     * Returns the nth boundary from the current boundary. If either

     * the first or last text boundary has been reached, it returns

     * <code>BreakIterator.DONE</code> and the current position is set to either

     * the first or last text boundary depending on which one is reached. Otherwise,

     * the iterator's current position is set to the new boundary.

     * For example, if the iterator's current position is the mth text boundary

     * and three more boundaries exist from the current boundary to the last text

     * boundary, the next(2) call will return m + 2. The new text position is set

     * to the (m + 2)th text boundary. A next(4) call would return

     * <code>BreakIterator.DONE</code> and the last text boundary would become the

     * new text position.

     * @param n which boundary to return.  A value of 0

     * does nothing.  Negative values move to previous boundaries

     * and positive values move to later boundaries.

     * @return The character index of the nth boundary from the current position

     * or <code>BreakIterator.DONE</code> if either first or last text boundary

     * has been reached.

     */

    public abstract int next(int n);

    /**

     * Returns the boundary following the current boundary. If the current boundary

     * is the last text boundary, it returns <code>BreakIterator.DONE</code> and

     * the iterator's current position is unchanged. Otherwise, the iterator's

     * current position is set to the boundary following the current boundary.

     * @return The character index of the next text boundary or

     * <code>BreakIterator.DONE</code> if the current boundary is the last text

     * boundary.

     * Equivalent to next(1).

     * @see #next(int)

     */

    public abstract int next();

    /**

     * Returns the boundary preceding the current boundary. If the current boundary

     * is the first text boundary, it returns <code>BreakIterator.DONE</code> and

     * the iterator's current position is unchanged. Otherwise, the iterator's

     * current position is set to the boundary preceding the current boundary.

     * @return The character index of the previous text boundary or

     * <code>BreakIterator.DONE</code> if the current boundary is the first text

     * boundary.

     */

    public abstract int previous();

    /**

     * Returns the first boundary following the specified character offset. If the

     * specified offset equals to the last text boundary, it returns

     * <code>BreakIterator.DONE</code> and the iterator's current position is unchanged.

     * Otherwise, the iterator's current position is set to the returned boundary.

     * The value returned is always greater than the offset or the value

     * <code>BreakIterator.DONE</code>.

     * @param offset the character offset to begin scanning.

     * @return The first boundary after the specified offset or

     * <code>BreakIterator.DONE</code> if the last text boundary is passed in

     * as the offset.

     * @exception  IllegalArgumentException if the specified offset is less than

     * the first text boundary or greater than the last text boundary.

     */

    public abstract int following(int offset);

    /**

     * Returns the last boundary preceding the specified character offset. If the

     * specified offset equals to the first text boundary, it returns

     * <code>BreakIterator.DONE</code> and the iterator's current position is unchanged.

     * Otherwise, the iterator's current position is set to the returned boundary.

     * The value returned is always less than the offset or the value

     * <code>BreakIterator.DONE</code>.

     * @param offset the characater offset to begin scanning.

     * @return The last boundary before the specified offset or

     * <code>BreakIterator.DONE</code> if the first text boundary is passed in

     * as the offset.

     * @exception   IllegalArgumentException if the specified offset is less than

     * the first text boundary or greater than the last text boundary.

     * @since 1.2

     */

    public int preceding(int offset) {

        // NOTE:  This implementation is here solely because we can't add new

        // abstract methods to an existing class.  There is almost ALWAYS a

        // better, faster way to do this.

        int pos = following(offset);

        while (pos >= offset && pos != DONE)

            pos = previous();

        return pos;

    }

    /**

     * Returns true if the specified character offset is a text boundary.

     * @param offset the character offset to check.

     * @return <code>true</code> if "offset" is a boundary position,

     * <code>false</code> otherwise.

     * @exception   IllegalArgumentException if the specified offset is less than

     * the first text boundary or greater than the last text boundary.

     * @since 1.2

     */

    public boolean isBoundary(int offset) {

        // NOTE: This implementation probably is wrong for most situations

        // because it fails to take into account the possibility that a

        // CharacterIterator passed to setText() may not have a begin offset

        // of 0.  But since the abstract BreakIterator doesn't have that

        // knowledge, it assumes the begin offset is 0.  If you subclass

        // BreakIterator, copy the SimpleTextBoundary implementation of this

        // function into your subclass.  [This should have been abstract at

        // this level, but it's too late to fix that now.]

        if (offset == 0) {

            return true;

        }

        int boundary = following(offset - 1);

        if (boundary == DONE) {

            throw new IllegalArgumentException();

        }

        return boundary == offset;

    }

    /**

     * Returns character index of the text boundary that was most

     * recently returned by next(), next(int), previous(), first(), last(),

     * following(int) or preceding(int). If any of these methods returns

     * <code>BreakIterator.DONE</code> because either first or last text boundary

     * has been reached, it returns the first or last text boundary depending on

     * which one is reached.

     * @return The text boundary returned from the above methods, first or last

     * text boundary.

     * @see #next()

     * @see #next(int)

     * @see #previous()

     * @see #first()

     * @see #last()

     * @see #following(int)

     * @see #preceding(int)

     */

    public abstract int current();

    /**

     * Get the text being scanned

     * @return the text being scanned

     */

    public abstract CharacterIterator getText();

    /**

     * Set a new text string to be scanned.  The current scan

     * position is reset to first().

     * @param newText new text to scan.

     */

    public void setText(String newText)

    {

        setText(new StringCharacterIterator(newText));

    }

    /**

     * Set a new text for scanning.  The current scan

     * position is reset to first().

     * @param newText new text to scan.

     */

    public abstract void setText(CharacterIterator newText);

    private static final int CHARACTER_INDEX = 0;

    private static final int WORD_INDEX = 1;

    private static final int LINE_INDEX = 2;

    private static final int SENTENCE_INDEX = 3;

    private static final SoftReference[] iterCache = new SoftReference[4];

    /**

     * Returns a new <code>BreakIterator</code> instance

     * for <a href="#word">word breaks</a>

     * for the {@linkplain Locale#getDefault() default locale}.

     * @return A break iterator for word breaks

     */

    public static BreakIterator getWordInstance()

    {

        return getWordInstance(Locale.getDefault());

    }

    /**

     * Returns a new <code>BreakIterator</code> instance

     * for <a href="#word">word breaks</a>

     * for the given locale.

     * @param locale the desired locale

     * @return A break iterator for word breaks

     * @exception NullPointerException if <code>locale</code> is null

     */

    public static BreakIterator getWordInstance(Locale locale)

    {

        return getBreakInstance(locale,

                                WORD_INDEX,

                                "WordData",

                                "WordDictionary");

    }

    /**

     * Returns a new <code>BreakIterator</code> instance

     * for <a href="#line">line breaks</a>

     * for the {@linkplain Locale#getDefault() default locale}.

     * @return A break iterator for line breaks

     */

    public static BreakIterator getLineInstance()

    {

        return getLineInstance(Locale.getDefault());

    }

    /**

     * Returns a new <code>BreakIterator</code> instance

     * for <a href="#line">line breaks</a>

     * for the given locale.

     * @param locale the desired locale

     * @return A break iterator for line breaks

     * @exception NullPointerException if <code>locale</code> is null

     */

    public static BreakIterator getLineInstance(Locale locale)

    {

        return getBreakInstance(locale,

                                LINE_INDEX,

                                "LineData",

                                "LineDictionary");

    }

    /**

     * Returns a new <code>BreakIterator</code> instance

     * for <a href="#character">character breaks</a>

     * for the {@linkplain Locale#getDefault() default locale}.

     * @return A break iterator for character breaks

     */

    public static BreakIterator getCharacterInstance()

    {

        return getCharacterInstance(Locale.getDefault());

    }

    /**

     * Returns a new <code>BreakIterator</code> instance

     * for <a href="#character">character breaks</a>

     * for the given locale.

     * @param locale the desired locale

     * @return A break iterator for character breaks

     * @exception NullPointerException if <code>locale</code> is null

     */

    public static BreakIterator getCharacterInstance(Locale locale)

    {

        return getBreakInstance(locale,

                                CHARACTER_INDEX,

                                "CharacterData",

                                "CharacterDictionary");

    }

    /**

     * Returns a new <code>BreakIterator</code> instance

     * for <a href="#sentence">sentence breaks</a>

     * for the {@linkplain Locale#getDefault() default locale}.

     * @return A break iterator for sentence breaks