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	/*
	* Copyright (c) 2005, 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. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	/*
	*******************************************************************************
	* (C) Copyright IBM Corp. 1996-2005 - All Rights Reserved *
	* *
	* The original version of this source code and documentation is copyrighted *
	* and owned by IBM, These materials are provided under terms of a License *
	* Agreement between IBM and Sun. This technology is protected by multiple *
	* US and International patents. This notice and attribution to IBM may not *
	* to removed. *
	*******************************************************************************
	*/

	/*
	**********************************************************************
	* Author: Alan Liu
	* Created: September 23 2003
	* Since: ICU 2.8
	**********************************************************************
	*/

	package sun.text.normalizer;

	import java.text.ParsePosition;

	/**
	* An iterator that returns 32-bit code points. This class is deliberately
	* <em>not</em> related to any of the JDK or ICU4J character iterator classes
	* in order to minimize complexity.
	* @author Alan Liu
	* @since ICU 2.8
	*/
	public class RuleCharacterIterator {

	// TODO: Ideas for later. (Do not implement if not needed, lest the
	// code coverage numbers go down due to unused methods.)
	// 1. Add a copy constructor, equals() method, clone() method.
	// 2. Rather than return DONE, throw an exception if the end
	// is reached -- this is an alternate usage model, probably not useful.
	// 3. Return isEscaped from next(). If this happens,
	// don't keep an isEscaped member variable.

	/**
	* Text being iterated.
	*/
	private String text;

	/**
	* Position of iterator.
	*/
	private ParsePosition pos;

	/**
	* Symbol table used to parse and dereference variables. May be null.
	*/
	private SymbolTable sym;

	/**
	* Current variable expansion, or null if none.
	*/
	private char[] buf;

	/**
	* Position within buf[]. Meaningless if buf == null.
	*/
	private int bufPos;

	/**
	* Flag indicating whether the last character was parsed from an escape.
	*/
	private boolean isEscaped;

	/**
	* Value returned when there are no more characters to iterate.
	*/
	public static final int DONE = -1;

	/**
	* Bitmask option to enable parsing of variable names. If (options &
	* PARSE_VARIABLES) != 0, then an embedded variable will be expanded to
	* its value. Variables are parsed using the SymbolTable API.
	*/
	public static final int PARSE_VARIABLES = 1;

	/**
	* Bitmask option to enable parsing of escape sequences. If (options &
	* PARSE_ESCAPES) != 0, then an embedded escape sequence will be expanded
	* to its value. Escapes are parsed using Utility.unescapeAt().
	*/
	public static final int PARSE_ESCAPES = 2;

	/**
	* Bitmask option to enable skipping of whitespace. If (options &
	* SKIP_WHITESPACE) != 0, then whitespace characters will be silently
	* skipped, as if they were not present in the input. Whitespace
	* characters are defined by UCharacterProperty.isRuleWhiteSpace().
	*/
	public static final int SKIP_WHITESPACE = 4;

	/**
	* Constructs an iterator over the given text, starting at the given
	* position.
	* @param text the text to be iterated
	* @param sym the symbol table, or null if there is none. If sym is null,
	* then variables will not be deferenced, even if the PARSE_VARIABLES
	* option is set.
	* @param pos upon input, the index of the next character to return. If a
	* variable has been dereferenced, then pos will <em>not</em> increment as
	* characters of the variable value are iterated.
	*/
	public RuleCharacterIterator(String text, SymbolTable sym,
	ParsePosition pos) {
	if (text == null \|\| pos.getIndex() > text.length()) {
	throw new IllegalArgumentException();
	}
	this.text = text;
	this.sym = sym;
	this.pos = pos;
	buf = null;
	}

	/**
	* Returns true if this iterator has no more characters to return.
	*/
	public boolean atEnd() {
	return buf == null && pos.getIndex() == text.length();
	}

	/**
	* Returns the next character using the given options, or DONE if there
	* are no more characters, and advance the position to the next
	* character.
	* @param options one or more of the following options, bitwise-OR-ed
	* together: PARSE_VARIABLES, PARSE_ESCAPES, SKIP_WHITESPACE.
	* @return the current 32-bit code point, or DONE
	*/
	public int next(int options) {
	int c = DONE;
	isEscaped = false;

	for (;;) {
	c = _current();
	_advance(UTF16.getCharCount(c));

	if (c == SymbolTable.SYMBOL_REF && buf == null &&
	(options & PARSE_VARIABLES) != 0 && sym != null) {
	String name = sym.parseReference(text, pos, text.length());
	// If name == null there was an isolated SYMBOL_REF;
	// return it. Caller must be prepared for this.
	if (name == null) {
	break;
	}
	bufPos = 0;
	buf = sym.lookup(name);
	if (buf == null) {
	throw new IllegalArgumentException(
	"Undefined variable: " + name);
	}
	// Handle empty variable value
	if (buf.length == 0) {
	buf = null;
	}
	continue;
	}

	if ((options & SKIP_WHITESPACE) != 0 &&
	UCharacterProperty.isRuleWhiteSpace(c)) {
	continue;
	}

	if (c == '\\' && (options & PARSE_ESCAPES) != 0) {
	int offset[] = new int[] { 0 };
	c = Utility.unescapeAt(lookahead(), offset);
	jumpahead(offset[0]);
	isEscaped = true;
	if (c < 0) {
	throw new IllegalArgumentException("Invalid escape");
	}
	}

	break;
	}

	return c;
	}

	/**
	* Returns true if the last character returned by next() was
	* escaped. This will only be the case if the option passed in to
	* next() included PARSE_ESCAPED and the next character was an
	* escape sequence.
	*/
	public boolean isEscaped() {
	return isEscaped;
	}

	/**
	* Returns true if this iterator is currently within a variable expansion.
	*/
	public boolean inVariable() {
	return buf != null;
	}

	/**
	* Returns an object which, when later passed to setPos(), will
	* restore this iterator's position. Usage idiom:
	*
	* RuleCharacterIterator iterator = ...;
	* Object pos = iterator.getPos(null); // allocate position object
	* for (;;) {
	* pos = iterator.getPos(pos); // reuse position object
	* int c = iterator.next(...);
	* ...
	* }
	* iterator.setPos(pos);
	*
	* @param p a position object previously returned by getPos(),
	* or null. If not null, it will be updated and returned. If
	* null, a new position object will be allocated and returned.
	* @return a position object which may be passed to setPos(),
	* either `p,' or if `p' == null, a newly-allocated object
	*/
	public Object getPos(Object p) {
	if (p == null) {
	return new Object[] {buf, new int[] {pos.getIndex(), bufPos}};
	}
	Object[] a = (Object[]) p;
	a[0] = buf;
	int[] v = (int[]) a[1];
	v[0] = pos.getIndex();
	v[1] = bufPos;
	return p;
	}

	/**
	* Restores this iterator to the position it had when getPos()
	* returned the given object.
	* @param p a position object previously returned by getPos()
	*/
	public void setPos(Object p) {
	Object[] a = (Object[]) p;
	buf = (char[]) a[0];
	int[] v = (int[]) a[1];
	pos.setIndex(v[0]);
	bufPos = v[1];
	}

	/**
	* Skips ahead past any ignored characters, as indicated by the given
	* options. This is useful in conjunction with the lookahead() method.
	*
	* Currently, this only has an effect for SKIP_WHITESPACE.
	* @param options one or more of the following options, bitwise-OR-ed
	* together: PARSE_VARIABLES, PARSE_ESCAPES, SKIP_WHITESPACE.
	*/
	public void skipIgnored(int options) {
	if ((options & SKIP_WHITESPACE) != 0) {
	for (;;) {
	int a = _current();
	if (!UCharacterProperty.isRuleWhiteSpace(a)) break;
	_advance(UTF16.getCharCount(a));
	}
	}
	}

	/**
	* Returns a string containing the remainder of the characters to be
	* returned by this iterator, without any option processing. If the
	* iterator is currently within a variable expansion, this will only
	* extend to the end of the variable expansion. This method is provided
	* so that iterators may interoperate with string-based APIs. The typical
	* sequence of calls is to call skipIgnored(), then call lookahead(), then
	* parse the string returned by lookahead(), then call jumpahead() to
	* resynchronize the iterator.
	* @return a string containing the characters to be returned by future
	* calls to next()
	*/
	public String lookahead() {
	if (buf != null) {
	return new String(buf, bufPos, buf.length - bufPos);
	} else {
	return text.substring(pos.getIndex());
	}
	}

	/**
	* Advances the position by the given number of 16-bit code units.
	* This is useful in conjunction with the lookahead() method.
	* @param count the number of 16-bit code units to jump over
	*/
	public void jumpahead(int count) {
	if (count < 0) {
	throw new IllegalArgumentException();
	}
	if (buf != null) {
	bufPos += count;
	if (bufPos > buf.length) {
	throw new IllegalArgumentException();
	}
	if (bufPos == buf.length) {
	buf = null;
	}
	} else {
	int i = pos.getIndex() + count;
	pos.setIndex(i);
	if (i > text.length()) {
	throw new IllegalArgumentException();
	}
	}
	}

	/**
	* Returns the current 32-bit code point without parsing escapes, parsing
	* variables, or skipping whitespace.
	* @return the current 32-bit code point
	*/
	private int _current() {
	if (buf != null) {
	return UTF16.charAt(buf, 0, buf.length, bufPos);
	} else {
	int i = pos.getIndex();
	return (i < text.length()) ? UTF16.charAt(text, i) : DONE;
	}
	}

	/**
	* Advances the position by the given amount.
	* @param count the number of 16-bit code units to advance past
	*/
	private void _advance(int count) {
	if (buf != null) {
	bufPos += count;
	if (bufPos == buf.length) {
	buf = null;
	}
	} else {
	pos.setIndex(pos.getIndex() + count);
	if (pos.getIndex() > text.length()) {
	pos.setIndex(text.length());
	}
	}
	}
	}

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