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/*
 *******************************************************************************
 * Copyright (C) 1996-2014, International Business Machines Corporation and    *
 * others. All Rights Reserved.                                                *
 *******************************************************************************
 */

package jdk_internal.icu.text;

import jdk_internal.bidi.CharacterIterator;
import jdk_internal.icu.impl.CharacterIteratorWrapper;
import jdk_internal.icu.impl.ReplaceableUCharacterIterator;
import jdk_internal.icu.impl.UCharacterProperty;

/**
 * Abstract class that defines an API for iteration on text objects.This is an
 * interface for forward and backward iteration and random access into a text
 * object. Forward iteration is done with post-increment and backward iteration
 * is done with pre-decrement semantics, while the
 * <code>java.text.CharacterIterator</code> interface methods provided forward
 * iteration with "pre-increment" and backward iteration with pre-decrement
 * semantics. This API is more efficient for forward iteration over code points.
 * The other major difference is that this API can do both code unit and code
 * point iteration, <code>java.text.CharacterIterator</code> can only iterate
 * over code units and is limited to BMP (0 - 0xFFFF)
 * 
 * @author Ram
 * @stable ICU 2.4
 */
public abstract class UCharacterIterator implements Cloneable {

	/**
	 * Protected default constructor for the subclasses
	 * 
	 * @stable ICU 2.4
	 */
	protected UCharacterIterator() {
	}

	/**
	 * Indicator that we have reached the ends of the UTF16 text. Moved from
	 * UForwardCharacterIterator.java
	 * 
	 * @stable ICU 2.4
	 */
	public static final int DONE = -1;

	// static final methods ----------------------------------------------------

	/**
	 * Returns a <code>UCharacterIterator</code> object given a source string.
	 * 
	 * @param source a string
	 * @return UCharacterIterator object
	 * @exception IllegalArgumentException if the argument is null
	 * @stable ICU 2.4
	 */
	public static final UCharacterIterator getInstance(String source) {
		return new ReplaceableUCharacterIterator(source);
	}

	/**
	 * Returns a <code>UCharacterIterator</code> object given a source StringBuffer.
	 * 
	 * @param source an string buffer of UTF-16 code units
	 * @return UCharacterIterator object
	 * @exception IllegalArgumentException if the argument is null
	 * @stable ICU 2.4
	 */
	public static final UCharacterIterator getInstance(StringBuffer source) {
		return new ReplaceableUCharacterIterator(source);
	}

	/**
	 * Returns a <code>UCharacterIterator</code> object given a CharacterIterator.
	 * 
	 * @param source a valid CharacterIterator object.
	 * @return UCharacterIterator object
	 * @exception IllegalArgumentException if the argument is null
	 * @stable ICU 2.4
	 */
	public static final UCharacterIterator getInstance(CharacterIterator source) {
		return new CharacterIteratorWrapper(source);
	}

	// public methods ----------------------------------------------------------

	/**
	 * Returns the length of the text
	 * 
	 * @return length of the text
	 * @stable ICU 2.4
	 */
	public abstract int getLength();

	/**
	 * Gets the current index in text.
	 * 
	 * @return current index in text.
	 * @stable ICU 2.4
	 */
	public abstract int getIndex();

	/**
	 * Returns the UTF16 code unit at index, and increments to the next code unit
	 * (post-increment semantics). If index is out of range, DONE is returned, and
	 * the iterator is reset to the limit of the text.
	 * 
	 * @return the next UTF16 code unit, or DONE if the index is at the limit of the
	 *         text.
	 * @stable ICU 2.4
	 */
	public abstract int next();

	/**
	 * Returns the code point at index, and increments to the next code point
	 * (post-increment semantics). If index does not point to a valid surrogate
	 * pair, the behavior is the same as <code>next()</code>. Otherwise the iterator
	 * is incremented past the surrogate pair, and the code point represented by the
	 * pair is returned.
	 * 
	 * @return the next codepoint in text, or DONE if the index is at the limit of
	 *         the text.
	 * @stable ICU 2.4
	 */
	public int nextCodePoint() {
		int ch1 = next();
		if (UTF16.isLeadSurrogate((char) ch1)) {
			int ch2 = next();
			if (UTF16.isTrailSurrogate((char) ch2)) {
				return UCharacterProperty.getRawSupplementary((char) ch1, (char) ch2);
			} else if (ch2 != DONE) {
				// unmatched surrogate so back out
				previous();
			}
		}
		return ch1;
	}

	/**
	 * Decrement to the position of the previous code unit in the text, and return
	 * it (pre-decrement semantics). If the resulting index is less than 0, the
	 * index is reset to 0 and DONE is returned.
	 * 
	 * @return the previous code unit in the text, or DONE if the new index is
	 *         before the start of the text.
	 * @stable ICU 2.4
	 */
	public abstract int previous();

	/**
	 * Retreat to the start of the previous code point in the text, and return it
	 * (pre-decrement semantics). If the index is not preceeded by a valid surrogate
	 * pair, the behavior is the same as <code>previous()</code>. Otherwise the
	 * iterator is decremented to the start of the surrogate pair, and the code
	 * point represented by the pair is returned.
	 * 
	 * @return the previous code point in the text, or DONE if the new index is
	 *         before the start of the text.
	 * @stable ICU 2.4
	 */
	public int previousCodePoint() {
		int ch1 = previous();
		if (UTF16.isTrailSurrogate((char) ch1)) {
			int ch2 = previous();
			if (UTF16.isLeadSurrogate((char) ch2)) {
				return UCharacterProperty.getRawSupplementary((char) ch2, (char) ch1);
			} else if (ch2 != DONE) {
				// unmatched trail surrogate so back out
				next();
			}
		}
		return ch1;
	}

	/**
	 * Sets the index to the specified index in the text.
	 * 
	 * @param index the index within the text.
	 * @exception IndexOutOfBoundsException is thrown if an invalid index is
	 *                                      supplied
	 * @stable ICU 2.4
	 */
	public abstract void setIndex(int index);

	/**
	 * Sets the current index to the start.
	 * 
	 * @stable ICU 2.4
	 */
	public void setToStart() {
		setIndex(0);
	}

	/**
	 * Fills the buffer with the underlying text storage of the iterator If the
	 * buffer capacity is not enough a exception is thrown. The capacity of the fill
	 * in buffer should at least be equal to length of text in the iterator obtained
	 * by calling <code>getLength()</code>. <b>Usage:</b>
	 *
	 * <pre>{@code
	 *         UChacterIterator iter = new UCharacterIterator.getInstance(text);
	 *         char[] buf = new char[iter.getLength()];
	 *         iter.getText(buf);
	 *
	 *         OR
	 *         char[] buf= new char[1];
	 *         int len = 0;
	 *         for(;;){
	 *             try{
	 *                 len = iter.getText(buf);
	 *                 break;
	 *             }catch(IndexOutOfBoundsException e){
	 *                 buf = new char[iter.getLength()];
	 *             }
	 *         }
	 * }</pre>
	 *
	 * @param fillIn an array of chars to fill with the underlying UTF-16 code
	 *               units.
	 * @param offset the position within the array to start putting the data.
	 * @return the number of code units added to fillIn, as a convenience
	 * @exception IndexOutOfBoundsException exception if there is not enough room
	 *                                      after offset in the array, or if offset
	 *                                      < 0.
	 * @stable ICU 2.4
	 */
	public abstract int getText(char[] fillIn, int offset);

	/**
	 * Convenience override for <code>getText(char[], int)</code> that provides an
	 * offset of 0.
	 * 
	 * @param fillIn an array of chars to fill with the underlying UTF-16 code
	 *               units.
	 * @return the number of code units added to fillIn, as a convenience
	 * @exception IndexOutOfBoundsException exception if there is not enough room in
	 *                                      the array.
	 * @stable ICU 2.4
	 */
	public final int getText(char[] fillIn) {
		return getText(fillIn, 0);
	}

	/**
	 * Convenience method for returning the underlying text storage as a string
	 * 
	 * @return the underlying text storage in the iterator as a string
	 * @stable ICU 2.4
	 */
	public String getText() {
		char[] text = new char[getLength()];
		getText(text);
		return new String(text);
	}

	/**
	 * Moves the current position by the number of code points specified, either
	 * forward or backward depending on the sign of delta (positive or negative
	 * respectively). If the current index is at a trail surrogate then the first
	 * adjustment is by code unit, and the remaining adjustments are by code points.
	 * If the resulting index would be less than zero, the index is set to zero, and
	 * if the resulting index would be greater than limit, the index is set to
	 * limit.
	 * 
	 * @param delta the number of code units to move the current index.
	 * @return the new index
	 * @exception IndexOutOfBoundsException is thrown if an invalid delta is
	 *                                      supplied
	 * @stable ICU 2.4
	 *
	 */
	public int moveCodePointIndex(int delta) {
		if (delta > 0) {
			while (delta > 0 && nextCodePoint() != DONE) {
				delta--;
			}
		} else {
			while (delta < 0 && previousCodePoint() != DONE) {
				delta++;
			}
		}
		if (delta != 0) {
			throw new IndexOutOfBoundsException();
		}

		return getIndex();
	}

	/**
	 * Creates a copy of this iterator, independent from other iterators. If it is
	 * not possible to clone the iterator, returns null.
	 * 
	 * @return copy of this iterator
	 * @stable ICU 2.4
	 */
	public Object clone() throws CloneNotSupportedException {
		return super.clone();
	}

}