DartWordIterator.java

/*
 * Copyright (c) 2011, the Dart project authors.
 * 
 * Licensed under the Eclipse Public License v1.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 * 
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.dart.tools.ui.internal.text.functions;

import com.ibm.icu.text.BreakIterator;

import org.eclipse.core.runtime.Assert;

import java.text.CharacterIterator;

/**
 * Breaks java text into word starts, also stops at line start and end. No direction dependency.
 */
public class DartWordIterator extends BreakIterator {

  /**
   * The underlying java break iterator. It returns all breaks, including before and after every
   * whitespace.
   */
  private DartBreakIterator fIterator;
  /** The current index for the stateful operations. */
  private int fIndex;

  /**
   * Creates a new word iterator.
   */
  public DartWordIterator() {
    fIterator = new DartBreakIterator();
    first();
  }

  /*
   * @see java.text.BreakIterator#current()
   */
  @Override
  public int current() {
    return fIndex;
  }

  /*
   * @see java.text.BreakIterator#first()
   */
  @Override
  public int first() {
    fIndex = fIterator.first();
    return fIndex;
  }

  /*
   * @see java.text.BreakIterator#following(int)
   */
  @Override
  public int following(int offset) {
    int first = fIterator.following(offset);
    if (eatFollowingWhitespace(offset, first)) {
      int second = fIterator.following(first);
      if (isWhitespace(first, second)) {
        return second;
      }
    }
    return first;
  }

  /*
   * @see java.text.BreakIterator#getText()
   */
  @Override
  public CharacterIterator getText() {
    return fIterator.getText();
  }

  /*
   * @see java.text.BreakIterator#last()
   */
  @Override
  public int last() {
    fIndex = fIterator.last();
    return fIndex;
  }

  /*
   * @see java.text.BreakIterator#next()
   */
  @Override
  public int next() {
    fIndex = following(fIndex);
    return fIndex;
  }

  /*
   * @see java.text.BreakIterator#next(int)
   */
  @Override
  public int next(int n) {
    int next = 0;
    while (--n > 0 && next != DONE) {
      next = next();
    }
    return next;
  }

  /*
   * @see java.text.BreakIterator#preceding(int)
   */
  @Override
  public int preceding(int offset) {
    int first = fIterator.preceding(offset);
    if (isWhitespace(first, offset)) {
      int second = fIterator.preceding(first);
      if (second != DONE && !isDelimiter(second, first)) {
        return second;
      }
    }
    return first;
  }

  /*
   * @see java.text.BreakIterator#previous()
   */
  @Override
  public int previous() {
    fIndex = preceding(fIndex);
    return fIndex;
  }

  /*
   * @see java.text.BreakIterator#setText(java.text.CharacterIterator)
   */
  @Override
  public void setText(CharacterIterator newText) {
    fIterator.setText(newText);
    first();
  }

  /**
   * Sets the text as <code>CharSequence</code>.
   * 
   * @param newText the new text
   */
  public void setText(CharSequence newText) {
    fIterator.setText(newText);
    first();
  }

  /*
   * @see java.text.BreakIterator#setText(java.lang.String)
   */
  @Override
  public void setText(String newText) {
    setText((CharSequence) newText);
  }

  private boolean eatFollowingWhitespace(int offset, int exclusiveEnd) {
    if (exclusiveEnd == DONE || offset == DONE) {
      return false;
    }

    if (isWhitespace(offset, exclusiveEnd)) {
      return false;
    }
    if (isDelimiter(offset, exclusiveEnd)) {
      return false;
    }

    return true;
  }

  /**
   * Returns <code>true</code> if the given sequence into the underlying text represents a
   * delimiter, <code>false</code> otherwise.
   * 
   * @param offset the offset
   * @param exclusiveEnd the end offset
   * @return <code>true</code> if the given range is a delimiter
   */
  private boolean isDelimiter(int offset, int exclusiveEnd) {
    if (exclusiveEnd == DONE || offset == DONE) {
      return false;
    }

    Assert.isTrue(offset >= 0);
    Assert.isTrue(exclusiveEnd <= getText().getEndIndex());
    Assert.isTrue(exclusiveEnd > offset);

    CharSequence seq = fIterator.fText;

    while (offset < exclusiveEnd) {
      char ch = seq.charAt(offset);
      if (ch != '\n' && ch != '\r') {
        return false;
      }
      offset++;
    }

    return true;
  }

  /**
   * Returns <code>true</code> if the given sequence into the underlying text represents whitespace,
   * but not a delimiter, <code>false</code> otherwise.
   * 
   * @param offset the offset
   * @param exclusiveEnd the end offset
   * @return <code>true</code> if the given range is whitespace
   */
  private boolean isWhitespace(int offset, int exclusiveEnd) {
    if (exclusiveEnd == DONE || offset == DONE) {
      return false;
    }

    Assert.isTrue(offset >= 0);
    Assert.isTrue(exclusiveEnd <= getText().getEndIndex());
    Assert.isTrue(exclusiveEnd > offset);

    CharSequence seq = fIterator.fText;

    while (offset < exclusiveEnd) {
      char ch = seq.charAt(offset);
      if (!Character.isWhitespace(ch)) {
        return false;
      }
      if (ch == '\n' || ch == '\r') {
        return false;
      }
      offset++;
    }

    return true;
  }

}