MirroredBreakIterator.java

/*
 * Copyright (c) 2007, Oracle and/or its affiliates. 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.
 *
 * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

import java.text.BreakIterator;
import java.text.CharacterIterator;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

public class MirroredBreakIterator extends BreakIterator {
    private final List<Integer> boundaries;
    private int charIndex;
    private int boundaryIndex;

    MirroredBreakIterator(BreakIterator bi) {
        List<Integer> b = new ArrayList<Integer>();
        int i = bi.first();
        charIndex = i;
        for (; i != DONE; i = bi.next()) {
            b.add(i);
        }
        boundaries = Collections.unmodifiableList(b);
    }

    @Override
    public Object clone() {
        try {
            return super.clone();
        } catch (Exception e) {
            throw new RuntimeException("clone failed", e);
        }
    }

    @Override
    public int first() {
        return changeIndices(0);
    }

    @Override
    public int last() {
        return changeIndices(boundaries.size() - 1);
    }

    @Override
    public int next(int n) {
        if (n == 0) {
            return current();
        }
        int newBoundary = boundaryIndex + n;
        if (newBoundary < 0) {
            first();
            return DONE;
        }
        if (newBoundary > lastBoundary()) {
            last();
            return DONE;
        }
        return changeIndices(newBoundary);
    }

    @Override
    public int next() {
        if (boundaryIndex == lastBoundary()) {
            return DONE;
        }
        return changeIndices(boundaryIndex + 1);
    }

    @Override
    public int previous() {
        if (boundaryIndex == 0) {
            return DONE;
        }
        return changeIndices(boundaryIndex - 1);
    }

    @Override
    public int following(int offset) {
        validateOffset(offset);
        for (int b = 0; b <= lastBoundary(); b++) {
            int i = boundaries.get(b);
            if (i > offset) {
                return changeIndices(i, b);
            }
        }
        return DONE;
    }

    @Override
    public int preceding(int offset) {
        validateOffset(offset);
        for (int b = lastBoundary(); b >= 0; b--) {
            int i = boundaries.get(b);
            if (i < offset) {
                return changeIndices(i, b);
            }
        }
        return DONE;
    }

    @Override
    public boolean isBoundary(int offset) {
        // Call the default impelementation in BreakIterator
        return super.isBoundary(offset);
    }

    @Override
    public int current() {
        return charIndex;
    }

    @Override
    public CharacterIterator getText() {
        throw new UnsupportedOperationException();
    }

    @Override
    public void setText(CharacterIterator newText) {
        throw new UnsupportedOperationException();
    }

    private int lastBoundary() {
        return boundaries.size() - 1;
    }

    private int changeIndices(int newCharIndex, int newBoundary) {
        boundaryIndex = newBoundary;
        return charIndex = newCharIndex;
    }

    private int changeIndices(int newBoundary) {
        try {
            return changeIndices(boundaries.get(newBoundary), newBoundary);
        } catch (IndexOutOfBoundsException e) {
            throw new IllegalArgumentException(e);
        }
    }

    private void validateOffset(int offset) {
        if (offset < boundaries.get(0) || offset > boundaries.get(lastBoundary())) {
            throw new IllegalArgumentException();
        }
    }
}