/*
 * @(#)CollationElementIterator.java	1.30 00/01/19
 *
 * Copyright 1996-2000 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */

/*
 * (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.Character;
import java.util.Vector;

/**
 * The <code>CollationElementIterator</code> class is used as an iterator
 * to walk through each character of an international string. Use the iterator
 * to return the ordering priority of the positioned character. The ordering
 * priority of a character, which we refer to as a key, defines how a character
 * is collated in the given collation object.
 *
 * <p>
 * For example, consider the following in Spanish:
 * <blockquote>
 * <pre>
 * "ca" -> the first key is key('c') and second key is key('a').
 * "cha" -> the first key is key('ch') and second key is key('a').
 * </pre>
 * </blockquote>
 * And in German,
 * <blockquote>
 * <pre>
 * "\u00e4b"-> the first key is key('a'), the second key is key('e'), and
 * the third key is key('b').
 * </pre>
 * </blockquote>
 * The key of a character is an integer composed of primary order(short),
 * secondary order(byte), and tertiary order(byte). Java strictly defines
 * the size and signedness of its primitive data types. Therefore, the static
 * functions <code>primaryOrder</code>, <code>secondaryOrder</code>, and
 * <code>tertiaryOrder</code> return <code>int</code>, <code>short</code>,
 * and <code>short</code> respectively to ensure the correctness of the key
 * value.
 *
 * <p>
 * Example of the iterator usage,
 * <blockquote>
 * <pre>
 * // get the first key of the string
 * String str = "This is a test";
 * CollationElementIterator c =
 *     new CollationElementIterator(str, 0, str.length(),
 *                                  Collator.getInstance());
 * int primaryOrder = CollationElementIterator.primaryOrder(c->next());
 * </pre>
 * </blockquote>
 *
 * <p>
 * <code>CollationElementIterator.next</code> returns the collation order
 * of the next character. A collation order consists of primary order,
 * secondary order and tertiary order. The data type of the collation
 * order is <strong>int</strong>. The first 16 bits of a collation order
 * is its primary order; the next 8 bits is the secondary order and the
 * last 8 bits is the tertiary order.
 *
 * @see                Collator
 * @see                RuleBasedCollator
 * @version            1.24 07/27/98
 * @author             Helena Shih, Laura Werner, Richard Gillam
 */
public final class CollationElementIterator
{
    /**
     * Null order which indicates the end of string is reached by the
     * cursor.
     */
    public final static int NULLORDER = 0xffffffff;

    /**
     * CollationElementIterator constructor.  This takes the source string and
     * the collation object.  The cursor will walk thru the source string based
     * on the predefined collation rules.  If the source string is empty,
     * NULLORDER will be returned on the calls to next().
     * @param sourceText the source string.
     * @param order the collation object.
     */
    CollationElementIterator(String sourceText, RuleBasedCollator owner) {
        this.owner = owner;
        ordering = owner.getTables();
        if ( sourceText.length() != 0 ) {
            text = new Normalizer(sourceText, owner.getDecomposition());
        }
    }

    /**
     * CollationElementIterator constructor.  This takes the source string and
     * the collation object.  The cursor will walk thru the source string based
     * on the predefined collation rules.  If the source string is empty,
     * NULLORDER will be returned on the calls to next().
     * @param sourceText the source string.
     * @param order the collation object.
     */
    CollationElementIterator(CharacterIterator sourceText, RuleBasedCollator owner) {
        this.owner = owner;
        ordering = owner.getTables();
        text = new Normalizer(sourceText, owner.getDecomposition());
    }
    /**
     * Resets the cursor to the beginning of the string.  The next call
     * to next() will return the first collation element in the string.
     */
    public void reset()
    {
        if (text != null) {
            text.reset();
            text.setDecomposition(owner.getDecomposition());
        }
        buffer = null;
        expIndex = 0;
        swapOrder = 0;
    }

    /**
     * Get the next collation element in the string.  <p>This iterator iterates
     * over a sequence of collation elements that were built from the string.
     * Because there isn't necessarily a one-to-one mapping from characters to
     * collation elements, this doesn't mean the same thing as "return the
     * collation element [or ordering priority] of the next character in the
     * string".</p>
     * <p>This function returns the collation element that the iterator is currently
     * pointing to and then updates the internal pointer to point to the next element.
     * previous() updates the pointer first and then returns the element.  This
     * means that when you change direction while iterating (i.e., call next() and
     * then call previous(), or call previous() and then call next()), you'll get
     * back the same element twice.</p>
     */
    public int next()
    {
        if (text == null) {
            return NULLORDER;
        } else if (text.getDecomposition() != owner.getDecomposition()) {
            text.setDecomposition(owner.getDecomposition());
        }

        if (buffer != null) {
            if (expIndex < buffer.length) {
                return strengthOrder(buffer[expIndex++]);
            } else {
                buffer = null;
                expIndex = 0;
            }
        } else if (swapOrder != 0) {
            int order = swapOrder << 16;
            swapOrder = 0;
            return order;
        }

        char ch = text.next();
        if (ch == Normalizer.DONE) {
            return NULLORDER;
        }

        int value = ordering.getUnicodeOrder(ch);
        if (value == RuleBasedCollator.UNMAPPED) {
            swapOrder = ch;
            return UNMAPPEDCHARVALUE;
        }
        else if (value >= RuleBasedCollator.CONTRACTCHARINDEX) {
            value = nextContractChar(ch);
        }
        if (value >= RuleBasedCollator.EXPANDCHARINDEX) {
            buffer = ordering.getExpandValueList(value);
            expIndex = 0;
            value = buffer[expIndex++];
        }
        return strengthOrder(value);
    }

    /**
     * Get the previous collation element in the string.  <p>This iterator iterates
     * over a sequence of collation elements that were built from the string.
     * Because there isn't necessarily a one-to-one mapping from characters to
     * collation elements, this doesn't mean the same thing as "return the
     * collation element [or ordering priority] of the previous character in the
     * string".</p>
     * <p>This function updates the iterator's internal pointer to point to the
     * collation element preceding the one it's currently pointing to and then
     * returns that element, while next() returns the current element and then
     * updates the pointer.  This means that when you change direction while
     * iterating (i.e., call next() and then call previous(), or call previous()
     * and then call next()), you'll get back the same element twice.</p>
     */
    public int previous()
    {
        if (text == null) {
            return NULLORDER;
        } else if (text.getDecomposition() != owner.getDecomposition()) {
            text.setDecomposition(owner.getDecomposition());
        }

        if (buffer != null) {
            if (expIndex > 0) {
                return strengthOrder(buffer[--expIndex]);
            } else {
                buffer = null;
                expIndex = 0;
            }
        } else if (swapOrder != 0) {
              int order = swapOrder << 16;
            swapOrder = 0;
            return order;
        }
        char ch = text.previous();
        if (ch == Normalizer.DONE) {
            return NULLORDER;
        }

        int value = ordering.getUnicodeOrder(ch);

        if (value == RuleBasedCollator.UNMAPPED) {
            swapOrder = UNMAPPEDCHARVALUE;
            return ch;
        } else if (value >= RuleBasedCollator.CONTRACTCHARINDEX) {
            value = prevContractChar(ch);
        }
        if (value >= RuleBasedCollator.EXPANDCHARINDEX) {
            buffer = ordering.getExpandValueList(value);
            expIndex = buffer.length;
            value = buffer[--expIndex];
        }
        return strengthOrder(value);
    }

    /**
     * Return the primary component of a collation element.
     * @param order the collation element
     * @return the element's primary component
     */
    public final static int primaryOrder(int order)
    {
        order &= RBCollationTables.PRIMARYORDERMASK;
        return (order >>> RBCollationTables.PRIMARYORDERSHIFT);
    }
    /**
     * Return the secondary component of a collation element.
     * @param order the collation element
     * @return the element's secondary component
     */
    public final static short secondaryOrder(int order)
    {
        order = order & RBCollationTables.SECONDARYORDERMASK;
        return ((short)(order >> RBCollationTables.SECONDARYORDERSHIFT));
    }
    /**
     * Return the tertiary component of a collation element.
     * @param order the collation element
     * @return the element's tertiary component
     */
    public final static short tertiaryOrder(int order)
    {
        return ((short)(order &= RBCollationTables.TERTIARYORDERMASK));
    }

    /**
     *  Get the comparison order in the desired strength.  Ignore the other
     *  differences.
     *  @param order The order value
     */
    final int strengthOrder(int order)
    {
        int s = owner.getStrength();
        if (s == Collator.PRIMARY)
        {
            order &= RBCollationTables.PRIMARYDIFFERENCEONLY;
        } else if (s == Collator.SECONDARY)
        {
            order &= RBCollationTables.SECONDARYDIFFERENCEONLY;
        }
        return order;
    }

    /**
      * Sets the iterator to point to the collation element corresponding to
      * the specified character (the parameter is a CHARACTER offset in the
      * original string, not an offset into its corresponding sequence of
      * collation elements).  The value returned by the next call to next()
      * will be the collation element corresponding to the specified position
      * in the text.  If that position is in the middle of a contracting
      * character sequence, the result of the next call to next() is the
      * collation element for that sequence.  This means that getOffset()
      * is not guaranteed to return the same value as was passed to a preceding
      * call to setOffset().
      *
      * @param newOffset The new character offset into the original text.
      */
    public void setOffset(int newOffset)
    {
        if (text != null) {
            if (newOffset < text.getText().getBeginIndex()
                || newOffset >= text.getText().getEndIndex()) {
                    text.setOffset(newOffset);
            } else {
                text.setOffset(newOffset + 1);

                // if the desired character isn't used in a contracting character
                // sequence, bypass all the backing-up logic-- we're sitting on
                // the right character already
                char c = text.previous();
                if (ordering.usedInContractSeq(c)) {
                    // walk backwards through the string until we see a character
                    // that DOESN'T participate in a contracting character sequence
                    while (ordering.usedInContractSeq(c)) {
                        c = text.previous();
                    }

                    // now walk forward using this object's next() method until
                    // we pass the starting point and set our current position
                    // to the beginning of the last "character" before or at
                    // our starting position
                    int last = text.getOffset();
                    while (text.getOffset() <= newOffset) {
                        last = text.getOffset();
                        next();
                    }
                    text.setOffset(last);
                }
            }
        }
        buffer = null;
        expIndex = 0;
        swapOrder = 0;
    }

    /**
      * Returns the character offset in the original text corresponding to the next
      * collation element.  (That is, getOffset() returns the position in the text
      * corresponding to the collation element that will be returned by the next
      * call to next().)  This value will always be the index of the FIRST character
      * corresponding to the collation element (a contracting character sequence is
      * when two or more characters all correspond to the same collation element).
      * This means if you do setOffset(x) followed immediately by getOffset(), getOffset()
      * won't necessarily return x.
      *
      * @return The character offset in the original text corresponding to the collation
      * element that will be returned by the next call to next().
      */
    public int getOffset()
    {
        return (text != null) ? text.getOffset() : 0;
    }


    /**
      * Return the maximum length of any expansion sequences that end
      * with the specified comparison order.
      * @param order a collation order returned by previous or next.
      * @return the maximum length of any expansion sequences ending
      *         with the specified order.
      */
    public int getMaxExpansion(int order)
    {
        return ordering.getMaxExpansion(order);
    }

    //============================================================
    // Package-visible methods that should eventually be made public
    //============================================================

    /**
     * Set a new string over which to iterate.
     *
     * @param str the new source text.
     */
    public void setText(String source)
    {
        buffer = null;
        swapOrder = 0;
        expIndex = 0;
        if (text == null) {
            text = new Normalizer(source, owner.getDecomposition());
        } else {
            text.setDecomposition(owner.getDecomposition());
            text.setText(source);
        }
    }

    /**
     * Set a new string over which to iterate.
     *
     * @param str the new source text.
     */
    public void setText(CharacterIterator source)
    {
        buffer = null;
        swapOrder = 0;
        expIndex = 0;
        if (text == null) {
            text = new Normalizer(source, owner.getDecomposition());
        } else {
            text.setDecomposition(owner.getDecomposition());
            text.setText(source);
        }
    }

    //============================================================
    // privates
    //============================================================

    /**
     *  Check if a comparison order is ignorable.
     *  @return true if a character is ignorable, false otherwise.
     */
    final static boolean isIgnorable(int order)
    {
        return ((primaryOrder(order) == 0) ? true : false);
    }

    /**
     * Get the ordering priority of the next contracting character in the
     * string.
     * @param ch the starting character of a contracting character token
     * @return the next contracting character's ordering.  Returns NULLORDER
     * if the end of string is reached.
     */
    private int nextContractChar(char ch)
    {
        // First get the ordering of this single character,
        // which is always the first element in the list
        Vector list = ordering.getContractValues(ch);
        EntryPair pair = (EntryPair)list.firstElement();
        int order = pair.value;

        // find out the length of the longest contracting character sequence in the list.
        // There's logic in the builder code to make sure the longest sequence is always
        // the last.
        pair = (EntryPair)list.lastElement();
        int maxLength = pair.entryName.length();
        
        // (the Normalizer is cloned here so that the seeking we do in the next loop
        // won't affect our real position in the text)
        Normalizer tempText = (Normalizer)text.clone();

        // extract the next maxLength characters in the string (we have to do this using the
        // Normalizer to ensure that our offsets correspond to those the rest of the
        // iterator is using) and store it in "fragment".
        tempText.previous();
        key.setLength(0);
        char c = tempText.next();
        while (maxLength > 0 && c != Normalizer.DONE) {
            key.append(c);
            --maxLength;
            c = tempText.next();
        }
        String fragment = key.toString();

        // now that we have that fragment, iterate through this list looking for the
        // longest sequence that matches the characters in the actual text.  (maxLength
        // is used here to keep track of the length of the longest sequence)
        // Upon exit from this loop, maxLength will contain the length of the matching
        // sequence and order will contain the collation-element value corresponding
        // to this sequence
        maxLength = 1;
        for (int i = list.size() - 1; i > 0; i--) {
            pair = (EntryPair)list.elementAt(i);
            if (!pair.fwd)
                continue;
                
            if (fragment.startsWith(pair.entryName) && pair.entryName.length()
                    > maxLength) {
                maxLength = pair.entryName.length();
                order = pair.value;
            }
        }

        // seek our current iteration position to the end of the matching sequence
        // and return the appropriate collation-element value (if there was no matching
        // sequence, we're already seeked to the right position and order already contains
        // the correct collation-element value for the single character)
        while (maxLength > 1) {
            text.next();
            --maxLength;
        }
        return order;
    }

    /**
     * Get the ordering priority of the previous contracting character in the
     * string.
     * @param ch the starting character of a contracting character token
     * @return the next contracting character's ordering.  Returns NULLORDER
     * if the end of string is reached.
     */
    private int prevContractChar(char ch)
    {
        // This function is identical to nextContractChar(), except that we've
        // switched things so that the next() and previous() calls on the Normalizer
        // are switched and so that we skip entry pairs with the fwd flag turned on
        // rather than off.  Notice that we still use append() and startsWith() when
        // working on the fragment.  This is because the entry pairs that are used
        // in reverse iteration have their names reversed already.
        Vector list = ordering.getContractValues(ch);
        EntryPair pair = (EntryPair)list.firstElement();
        int order = pair.value;

        pair = (EntryPair)list.lastElement();
        int maxLength = pair.entryName.length();
        
        Normalizer tempText = (Normalizer)text.clone();

        tempText.next();
        key.setLength(0);
        char c = tempText.previous();
        while (maxLength > 0 && c != Normalizer.DONE) {
            key.append(c);
            --maxLength;
            c = tempText.previous();
        }
        String fragment = key.toString();

        maxLength = 1;
        for (int i = list.size() - 1; i > 0; i--) {
            pair = (EntryPair)list.elementAt(i);
            if (pair.fwd)
                continue;
                
            if (fragment.startsWith(pair.entryName) && pair.entryName.length()
                    > maxLength) {
                maxLength = pair.entryName.length();
                order = pair.value;
            }
        }

        while (maxLength > 1) {
            text.previous();
            --maxLength;
        }
        return order;
    }

    final static int UNMAPPEDCHARVALUE = 0x7FFF0000;

    private Normalizer text = null;
    private int[] buffer = null;
    private int expIndex = 0;
    private StringBuffer key = new StringBuffer(5);
    private int swapOrder = 0;
    private RBCollationTables ordering;
    private RuleBasedCollator owner;
}