//##header J2SE15
//#if defined(FOUNDATION10) || defined(J2SE13)
//#else
/*
 ********************************************************************************
 * Copyright (C) 2006-2008, Google, International Business Machines Corporation *
 * and others. All Rights Reserved.                                             *
 ********************************************************************************
 */
package com.ibm.icu.text;

import com.ibm.icu.impl.CalendarData;
import com.ibm.icu.impl.ICUResourceBundle;
import com.ibm.icu.impl.PatternTokenizer;
import com.ibm.icu.impl.Utility;
import com.ibm.icu.util.Calendar;
import com.ibm.icu.util.Freezable;
import com.ibm.icu.util.ULocale;
import com.ibm.icu.util.UResourceBundle;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

/**
 * This class provides flexible generation of date format patterns, like
 * "yy-MM-dd". The user can build up the generator by adding successive
 * patterns. Once that is done, a query can be made using a "skeleton", which is
 * a pattern which just includes the desired fields and lengths. The generator
 * will return the "best fit" pattern corresponding to that skeleton.
 * <p>
 * The main method people will use is getBestPattern(String skeleton), since
 * normally this class is pre-built with data from a particular locale. However,
 * generators can be built directly from other data as well.
 * <pre>
 * // some simple use cases
 * Date sampleDate = new Date(99, 9, 13, 23, 58, 59);
 * ULocale locale = ULocale.GERMANY;
 * TimeZone zone = TimeZone.getTimeZone(&quot;Europe/Paris&quot;);
 * 
 * // make from locale
 * 
 * DateTimePatternGenerator gen = DateTimePatternGenerator.getInstance(locale);
 * SimpleDateFormat format = new SimpleDateFormat(gen.getBestPattern(&quot;MMMddHmm&quot;),
 *     locale);
 * format.setTimeZone(zone);
 * assertEquals(&quot;simple format: MMMddHmm&quot;, 
 *     &quot;8:58 14. Okt&quot;,
 *     format.format(sampleDate));
 * // (a generator can be built from scratch, but that is not a typical use case)
 * 
 * // modify the generator by adding patterns
 * DateTimePatternGenerator.PatternInfo returnInfo = new DateTimePatternGenerator.PatternInfo();
 * gen.add(&quot;d'. von' MMMM&quot;, true, returnInfo);
 * // the returnInfo is mostly useful for debugging problem cases
 * format.applyPattern(gen.getBestPattern(&quot;MMMMddHmm&quot;));
 * assertEquals(&quot;modified format: MMMddHmm&quot;,
 *     &quot;8:58 14. von Oktober&quot;,
 *     format.format(sampleDate));
 * 
 * // get a pattern and modify it
 * format = (SimpleDateFormat) DateFormat.getDateTimeInstance(DateFormat.FULL,
 *     DateFormat.FULL, locale);
 * format.setTimeZone(zone);
 * String pattern = format.toPattern();
 * assertEquals(&quot;full-date&quot;,
 *     &quot;Donnerstag, 14. Oktober 1999 8:58 Uhr GMT+02:00&quot;,
 *     format.format(sampleDate));
 * 
 * // modify it to change the zone.
 * String newPattern = gen.replaceFieldTypes(pattern, &quot;vvvv&quot;);
 * format.applyPattern(newPattern);
 * assertEquals(&quot;full-date, modified zone&quot;,
 *     &quot;Donnerstag, 14. Oktober 1999 8:58 Uhr Frankreich&quot;,
 *     format.format(sampleDate));
 * </pre>
 * @stable ICU 3.6
 */
public class DateTimePatternGenerator implements Freezable, Cloneable {
    // debugging flags
    //static boolean SHOW_DISTANCE = false;
    // TODO add hack to fix months for CJK, as per bug ticket 1099
    
    /**
     * Create empty generator, to be constructed with add(...) etc.
     * @stable ICU 3.6
     */
    public static DateTimePatternGenerator getEmptyInstance() {
        return new DateTimePatternGenerator();
    }
    
    /**
     * Only for use by subclasses
     * @stable ICU 3.6
     */
    protected DateTimePatternGenerator() {         
    }
    
    /**
     * Construct a flexible generator according to data for a given locale.
     * @stable ICU 3.6
     */
    public static DateTimePatternGenerator getInstance() {
        return getInstance(ULocale.getDefault());
    }
    
    /**
     * Construct a flexible generator according to data for a given locale.
     * @param uLocale
     * @stable ICU 3.6
     */
    public static DateTimePatternGenerator getInstance(ULocale uLocale) {
        DateTimePatternGenerator result = new DateTimePatternGenerator();
        String lang = uLocale.getLanguage();
        if (lang.equals("zh") || lang.equals("ko") || lang.equals("ja")) {
          result.chineseMonthHack = true;
        }
        PatternInfo returnInfo = new PatternInfo();
        String hackPattern = null;
        // first load with the ICU patterns
        for (int i = DateFormat.FULL; i <= DateFormat.SHORT; ++i) {
            SimpleDateFormat df = (SimpleDateFormat) DateFormat.getDateInstance(i, uLocale);
            result.addPattern(df.toPattern(), false, returnInfo);
            df = (SimpleDateFormat) DateFormat.getTimeInstance(i, uLocale);
            result.addPattern(df.toPattern(), false, returnInfo);
            // HACK for hh:ss
            if (i == DateFormat.MEDIUM) {
                hackPattern = df.toPattern();
            }
        }

        ICUResourceBundle rb = (ICUResourceBundle) UResourceBundle.getBundleInstance(ICUResourceBundle.ICU_BASE_NAME, uLocale);
        rb = rb.getWithFallback("calendar");
        ICUResourceBundle gregorianBundle = rb.getWithFallback("gregorian");
        // CLDR item formats
        
        ICUResourceBundle itemBundle = gregorianBundle.getWithFallback("appendItems");
        for (int i=0; i<itemBundle.getSize(); ++i) {
            ICUResourceBundle formatBundle = (ICUResourceBundle)itemBundle.get(i);
            String formatName = itemBundle.get(i).getKey();
            String value = formatBundle.getString();
            result.setAppendItemFormat(getAppendFormatNumber(formatName), value);
        }
        
        // CLDR item names
        itemBundle = gregorianBundle.getWithFallback("fields");
        ICUResourceBundle fieldBundle, dnBundle;
        for (int i=0; i<TYPE_LIMIT; ++i) {
            if ( isCLDRFieldName(i) ) {
                fieldBundle = itemBundle.getWithFallback(CLDR_FIELD_NAME[i]);
                dnBundle = fieldBundle.getWithFallback("dn");
                String value = dnBundle.getString();
                //System.out.println("Field name:"+value);
                result.setAppendItemName(i, value);      		
        	}
        }
          
        // set the AvailableFormat in CLDR
        try {
           ICUResourceBundle formatBundle =  gregorianBundle.getWithFallback("availableFormats");
           //System.out.println("available format from current locale:"+uLocale.getName());
           for (int i=0; i<formatBundle.getSize(); ++i) { 
               String formatKey = formatBundle.get(i).getKey();
               String formatValue = formatBundle.get(i).getString();
               //System.out.println(" availableFormat:"+formatValue);
               result.setAvailableFormat(formatKey);
               result.addPattern(formatValue, false, returnInfo);
           } 
        }catch(Exception e) {
        }
       
        ULocale parentLocale=uLocale;
        while ( (parentLocale=parentLocale.getFallback()) != null) {
            ICUResourceBundle prb = (ICUResourceBundle) UResourceBundle.getBundleInstance(ICUResourceBundle.ICU_BASE_NAME, parentLocale);
            prb = prb.getWithFallback("calendar");
            ICUResourceBundle pGregorianBundle = prb.getWithFallback("gregorian");
            try {
                ICUResourceBundle formatBundle =  pGregorianBundle.getWithFallback("availableFormats");
                //System.out.println("available format from parent locale:"+parentLocale.getName());
                for (int i=0; i<formatBundle.getSize(); ++i) { 
                    String formatKey = formatBundle.get(i).getKey();
                    String formatValue = formatBundle.get(i).getString();
                    //System.out.println(" availableFormat:"+formatValue);
                    if (!result.isAvailableFormatSet(formatKey)) {
                        result.setAvailableFormat(formatKey);
                        result.addPattern(formatValue, false, returnInfo);
                        //System.out.println(" availableFormat:"+formatValue);
                    }
                } 
              
             }catch(Exception e) {
             }
             
        }
        
        // assume it is always big endian (ok for CLDR right now)
        // some languages didn't add mm:ss or HH:mm, so put in a hack to compute that from the short time.
        if (hackPattern != null) {
            hackTimes(result, returnInfo, hackPattern);
        }
        
        // set the datetime pattern. This is ugly code -- there should be a public interface for this
        Calendar cal = Calendar.getInstance(uLocale);
        CalendarData calData = new CalendarData(uLocale, cal.getType());
        String[] patterns = calData.get("DateTimePatterns").getStringArray();
        result.setDateTimeFormat(patterns[8]);
        
        // decimal point for seconds
        DecimalFormatSymbols dfs = new DecimalFormatSymbols(uLocale);
        result.setDecimal(String.valueOf(dfs.getDecimalSeparator()));
        return result;
    }
    
    private static void hackTimes(DateTimePatternGenerator result, PatternInfo returnInfo, String hackPattern) {
        result.fp.set(hackPattern);
        String mmss = new String();
        // to get mm:ss, we strip all but mm literal ss
        boolean gotMm = false;
        for (int i = 0; i < result.fp.items.size(); ++i) {
            Object item = result.fp.items.get(i);
            if (item instanceof String) {
                if (gotMm) {
                    mmss += result.fp.quoteLiteral(item.toString());
                }
            } else {
                char ch = item.toString().charAt(0);
                if (ch == 'm') {
                    gotMm = true;
                    mmss += item;
                } else if (ch == 's') {
                    if (!gotMm) {
                        break; // failed
                    }
                    mmss += item;
                    result.addPattern(mmss, false, returnInfo);
                    break;
                } else if (gotMm || ch == 'z' || ch == 'Z' || ch == 'v' || ch == 'V') {
                    break; // failed
                }
            }
        }
        // to get hh:mm, we strip (literal ss) and (literal S)
        // the easiest way to do this is to mark the stuff we want to nuke, then remove it in a second pass.
        BitSet variables = new BitSet();
        BitSet nuke = new BitSet();
        for (int i = 0; i < result.fp.items.size(); ++i) {
            Object item = result.fp.items.get(i);
            if (item instanceof VariableField) {
                variables.set(i);
                char ch = item.toString().charAt(0);
                if (ch == 's' || ch == 'S') {
                    nuke.set(i);
                    for (int j = i-1; j >= 0; ++j) {
                        if (variables.get(j)) break;
                        nuke.set(i);
                    }
                }
            }
        }
        String hhmm = getFilteredPattern(result.fp, nuke);
        result.addPattern(hhmm, false, returnInfo);
    }
    
    private static String getFilteredPattern(FormatParser fp, BitSet nuke) {
        String result = new String();
        for (int i = 0; i < fp.items.size(); ++i) {
            if (nuke.get(i)) continue;
            Object item = fp.items.get(i);
            if (item instanceof String) {
                result += fp.quoteLiteral(item.toString());
            } else {
                result += item.toString();
            }
        }
        return result;
    }
    
    /*private static int getAppendNameNumber(String string) {
        for (int i = 0; i < CLDR_FIELD_NAME.length; ++i) {
            if (CLDR_FIELD_NAME[i].equals(string)) return i;
        }
        return -1;
    }*/
    
    private static int getAppendFormatNumber(String string) {
        for (int i = 0; i < CLDR_FIELD_APPEND.length; ++i) {
            if (CLDR_FIELD_APPEND[i].equals(string)) return i;
        }
        return -1;
        
    }

    private static boolean isCLDRFieldName(int index) {
        if ((index<0) && (index>=TYPE_LIMIT)) {
            return false;
        }
        if (CLDR_FIELD_NAME[index].charAt(0) == '*') {
            return false;
        }
        else {
            return true;
        }
    }
    
    
    /**
     * Return the best pattern matching the input skeleton. It is guaranteed to
     * have all of the fields in the skeleton.
     * 
     * @param skeleton
     *            The skeleton is a pattern containing only the variable fields.
     *            For example, "MMMdd" and "mmhh" are skeletons.
     * @stable ICU 3.6
     */
    public String getBestPattern(String skeleton) {
      if (chineseMonthHack) {
        skeleton = skeleton.replaceAll("MMM+", "MM");
      }
        //if (!isComplete) complete();
        current.set(skeleton, fp);
        String best = getBestRaw(current, -1, _distanceInfo);
        if (_distanceInfo.missingFieldMask == 0 && _distanceInfo.extraFieldMask == 0) {
            // we have a good item. Adjust the field types
            return adjustFieldTypes(best, current, false);
        }
        int neededFields = current.getFieldMask();
        // otherwise break up by date and time.
        String datePattern = getBestAppending(neededFields & DATE_MASK);
        String timePattern = getBestAppending(neededFields & TIME_MASK);
        
        if (datePattern == null) return timePattern == null ? "" : timePattern;
        if (timePattern == null) return datePattern;
        return MessageFormat.format(getDateTimeFormat(), new Object[]{timePattern, datePattern});
    }
    
    /**
     * PatternInfo supplies output parameters for add(...). It is used because
     * Java doesn't have real output parameters. It is treated like a struct (eg
     * Point), so all fields are public.
     * 
     * @stable ICU 3.6
     */
    public static final class PatternInfo { // struct for return information
        /**
         * @stable ICU 3.6
         */
        public static final int OK = 0;
        
        /**
         * @stable ICU 3.6
         */
        public static final int BASE_CONFLICT = 1;
        
        /**
         * @stable ICU 3.6
         */
        public static final int CONFLICT = 2;
        
        /**
         * @stable ICU 3.6
         */
        public int status;
        
        /**
         * @stable ICU 3.6
         */
        public String conflictingPattern;
        
        /**
         * Simple constructor, since this is treated like a struct.
         * @stable ICU 3.6
         */
        public PatternInfo() {
        }
    }
    
    /**
     * Adds a pattern to the generator. If the pattern has the same skeleton as
     * an existing pattern, and the override parameter is set, then the previous
     * value is overriden. Otherwise, the previous value is retained. In either
     * case, the conflicting information is returned in PatternInfo.
     * <p>
     * Note that single-field patterns (like "MMM") are automatically added, and
     * don't need to be added explicitly!
     * 
     * @param override
     *            when existing values are to be overridden use true, otherwise
     *            use false.
     * @stable ICU 3.6
     */
    public DateTimePatternGenerator addPattern(String pattern, boolean override, PatternInfo returnInfo) {
        checkFrozen();
        DateTimeMatcher matcher = new DateTimeMatcher().set(pattern, fp);
        String basePattern = matcher.getBasePattern();
        String previousPatternWithSameBase = (String)basePattern_pattern.get(basePattern);
        if (previousPatternWithSameBase != null) {
            returnInfo.status = PatternInfo.BASE_CONFLICT;
            returnInfo.conflictingPattern = previousPatternWithSameBase;
            if (!override) return this;
        }
        String previousValue = (String)skeleton2pattern.get(matcher);
        if (previousValue != null) {
            returnInfo.status = PatternInfo.CONFLICT;
            returnInfo.conflictingPattern = previousValue;
            if (!override) return this;
        }
        returnInfo.status = PatternInfo.OK;
        returnInfo.conflictingPattern = "";
        skeleton2pattern.put(matcher, pattern);
        basePattern_pattern.put(basePattern, pattern);
        return this;
    }
    
    /**
     * Utility to return a unique skeleton from a given pattern. For example,
     * both "MMM-dd" and "dd/MMM" produce the skeleton "MMMdd".
     * 
     * @param pattern
     *            Input pattern, such as "dd/MMM"
     * @return skeleton, such as "MMMdd"
     * @stable ICU 3.6
     */
    public String getSkeleton(String pattern) {
        synchronized (this) { // synchronized since a getter must be thread-safe
            current.set(pattern, fp);
            return current.toString();
        }
    }
    
    /**
     * Utility to return a unique base skeleton from a given pattern. This is
     * the same as the skeleton, except that differences in length are minimized
     * so as to only preserve the difference between string and numeric form. So
     * for example, both "MMM-dd" and "d/MMM" produce the skeleton "MMMd"
     * (notice the single d).
     * 
     * @param pattern
     *            Input pattern, such as "dd/MMM"
     * @return skeleton, such as "MMMdd"
     * @stable ICU 3.6
     */
    public String getBaseSkeleton(String pattern) {
        synchronized (this) { // synchronized since a getter must be thread-safe
            current.set(pattern, fp);
            return current.getBasePattern();
        }
    }
    
    /**
     * Return a list of all the skeletons (in canonical form) from this class,
     * and the patterns that they map to.
     * 
     * @param result
     *            an output Map in which to place the mapping from skeleton to
     *            pattern. If you want to see the internal order being used,
     *            supply a LinkedHashMap. If the input value is null, then a
     *            LinkedHashMap is allocated.
     *            <p>
     *            <i>Issue: an alternate API would be to just return a list of
     *            the skeletons, and then have a separate routine to get from
     *            skeleton to pattern.</i>
     * @return the input Map containing the values.
     * @stable ICU 3.6
     */
    public Map getSkeletons(Map result) {
        if (result == null) result = new LinkedHashMap();
        for (Iterator it = skeleton2pattern.keySet().iterator(); it.hasNext();) {
            DateTimeMatcher item = (DateTimeMatcher) it.next();
            String pattern = (String) skeleton2pattern.get(item);
            if (CANONICAL_SET.contains(pattern)) continue;
            result.put(item.toString(), pattern);
        }
        return result;
    }
    
    /**
     * Return a list of all the base skeletons (in canonical form) from this class
     * @stable ICU 3.6
     */
    public Set getBaseSkeletons(Set result) {
        if (result == null) result = new HashSet();
        result.addAll(basePattern_pattern.keySet());
        return result;
    }
    
    /**
     * Adjusts the field types (width and subtype) of a pattern to match what is
     * in a skeleton. That is, if you supply a pattern like "d-M H:m", and a
     * skeleton of "MMMMddhhmm", then the input pattern is adjusted to be
     * "dd-MMMM hh:mm". This is used internally to get the best match for the
     * input skeleton, but can also be used externally.
     * 
     * @param pattern
     *            input pattern
     * @param skeleton
     * @return pattern adjusted to match the skeleton fields widths and
     *         subtypes.
     * @stable ICU 3.6
     */
    public String replaceFieldTypes(String pattern, String skeleton) {
        synchronized (this) { // synchronized since a getter must be thread-safe
            return adjustFieldTypes(pattern, current.set(skeleton, fp), false);
        }
    }
    
    /**
     * The date time format is a message format pattern used to compose date and
     * time patterns. The default value is "{0} {1}", where {0} will be replaced
     * by the date pattern and {1} will be replaced by the time pattern.
     * <p>
     * This is used when the input skeleton contains both date and time fields,
     * but there is not a close match among the added patterns. For example,
     * suppose that this object was created by adding "dd-MMM" and "hh:mm", and
     * its datetimeFormat is the default "{0} {1}". Then if the input skeleton
     * is "MMMdhmm", there is not an exact match, so the input skeleton is
     * broken up into two components "MMMd" and "hmm". There are close matches
     * for those two skeletons, so the result is put together with this pattern,
     * resulting in "d-MMM h:mm".
     * 
     * @param dateTimeFormat
     *            message format pattern, here {0} will be replaced by the date
     *            pattern and {1} will be replaced by the time pattern.
     * @stable ICU 3.6
     */
    public void setDateTimeFormat(String dateTimeFormat) {
        checkFrozen();
        this.dateTimeFormat = dateTimeFormat;
    }
    
    /**
     * Getter corresponding to setDateTimeFormat.
     * 
     * @return pattern
     * @stable ICU 3.6
     */
    public String getDateTimeFormat() {
        return dateTimeFormat;
    }
    
    /**
     * The decimal value is used in formatting fractions of seconds. If the
     * skeleton contains fractional seconds, then this is used with the
     * fractional seconds. For example, suppose that the input pattern is
     * "hhmmssSSSS", and the best matching pattern internally is "H:mm:ss", and
     * the decimal string is ",". Then the resulting pattern is modified to be
     * "H:mm:ss,SSSS"
     * 
     * @param decimal
     * @stable ICU 3.6
     */
    public void setDecimal(String decimal) {
        checkFrozen();
        this.decimal = decimal;
    }
    
    /**
     * Getter corresponding to setDecimal.
     * @return string corresponding to the decimal point
     * @stable ICU 3.6
     */
    public String getDecimal() {
        return decimal;
    }
    
    /**
     * Redundant patterns are those which if removed, make no difference in the
     * resulting getBestPattern values. This method returns a list of them, to
     * help check the consistency of the patterns used to build this generator.
     * 
     * @param output
     *            stores the redundant patterns that are removed. To get these
     *            in internal order, supply a LinkedHashSet. If null, a
     *            collection is allocated.
     * @return the collection with added elements.
     * @internal
     * @deprecated This API is ICU internal only.
     */
    public Collection getRedundants(Collection output) {
        synchronized (this) { // synchronized since a getter must be thread-safe
            if (output == null) output = new LinkedHashSet();
            for (Iterator it = skeleton2pattern.keySet().iterator(); it.hasNext();) {
                DateTimeMatcher cur = (DateTimeMatcher) it.next();
                String pattern = (String) skeleton2pattern.get(cur);
                if (CANONICAL_SET.contains(pattern)) continue;
                skipMatcher = cur;
                String trial = getBestPattern(cur.toString());
                if (trial.equals(pattern)) {
                    output.add(pattern);
                }
            }
            if (false) { // ordered
                DateTimePatternGenerator results = new DateTimePatternGenerator();
                PatternInfo pinfo = new PatternInfo();
                for (Iterator it = skeleton2pattern.keySet().iterator(); it.hasNext();) {
                    DateTimeMatcher cur = (DateTimeMatcher) it.next();
                    String pattern = (String) skeleton2pattern.get(cur);
                    if (CANONICAL_SET.contains(pattern)) continue;
                    //skipMatcher = current;
                    String trial = results.getBestPattern(cur.toString());
                    if (trial.equals(pattern)) {
                        output.add(pattern);
                    } else {
                        results.addPattern(pattern, false, pinfo);
                    }
                }
            }
            return output;
        }
    }
    
    // Field numbers, used for AppendItem functions
    
    /** 
     * @stable ICU 3.6
     */
    static final public int ERA = 0;
    
    /**
     * @stable ICU 3.6
     */
    static final public int YEAR = 1; 
    
    /**
     * @stable ICU 3.6
     */
    static final public int QUARTER = 2; 
    
    /**
     * @stable ICU 3.6
     */
    static final public int MONTH = 3;
    
    /**
     * @stable ICU 3.6
     */
    static final public int WEEK_OF_YEAR = 4; 
    
    /**
     * @stable ICU 3.6
     */
    static final public int WEEK_OF_MONTH = 5; 
    
    /**
     * @stable ICU 3.6
     */
    static final public int WEEKDAY = 6; 
    
    /**
     * @stable ICU 3.6
     */
    static final public int DAY = 7;
    
    /**
     * @stable ICU 3.6
     */
    static final public int DAY_OF_YEAR = 8; 
    
    /**
     * @stable ICU 3.6
     */
    static final public int DAY_OF_WEEK_IN_MONTH = 9; 
    
    /**
     * @stable ICU 3.6
     */
    static final public int DAYPERIOD = 10;
    
    /**
     * @stable ICU 3.6
     */
    static final public int HOUR = 11; 
    
    /**
     * @stable ICU 3.6
     */
    static final public int MINUTE = 12; 
    
    /**
     * @stable ICU 3.6
     */
    static final public int SECOND = 13; 
    
    /**
     * @stable ICU 3.6
     */
    static final public int FRACTIONAL_SECOND = 14;
    
    /**
     * @stable ICU 3.6
     */
    static final public int ZONE = 15; 
    
    /**
     * @stable ICU 3.6
     */
    static final public int TYPE_LIMIT = 16;
    
    /**
     * An AppendItem format is a pattern used to append a field if there is no
     * good match. For example, suppose that the input skeleton is "GyyyyMMMd",
     * and there is no matching pattern internally, but there is a pattern
     * matching "yyyyMMMd", say "d-MM-yyyy". Then that pattern is used, plus the
     * G. The way these two are conjoined is by using the AppendItemFormat for G
     * (era). So if that value is, say "{0}, {1}" then the final resulting
     * pattern is "d-MM-yyyy, G".
     * <p>
     * There are actually three available variables: {0} is the pattern so far,
     * {1} is the element we are adding, and {2} is the name of the element.
     * <p>
     * This reflects the way that the CLDR data is organized.
     * 
     * @param field
     *            such as ERA
     * @param value
     *            pattern, such as "{0}, {1}"
     * @stable ICU 3.6
     */
    public void setAppendItemFormat(int field, String value) {
        checkFrozen();
        appendItemFormats[field] = value;
    }
    
    /**
     * Getter corresponding to setAppendItemFormats. Values below 0 or at or
     * above TYPE_LIMIT are illegal arguments.
     * 
     * @param field
     * @return append pattern for field
     * @stable ICU 3.6
     */
    public String getAppendItemFormat(int field) {
        return appendItemFormats[field];
    }
    
    /**
     * Sets the names of fields, eg "era" in English for ERA. These are only
     * used if the corresponding AppendItemFormat is used, and if it contains a
     * {2} variable.
     * <p>
     * This reflects the way that the CLDR data is organized.
     * 
     * @param field
     * @param value
     * @stable ICU 3.6
     */
    public void setAppendItemName(int field, String value) {
        checkFrozen();
        appendItemNames[field] = value;
    }
    
    /**
     * Getter corresponding to setAppendItemNames. Values below 0 or at or above
     * TYPE_LIMIT are illegal arguments.
     * 
     * @param field
     * @return name for field
     * @stable ICU 3.6
     */
    public String getAppendItemName(int field) {
        return appendItemNames[field];
    }
    
    /**
     * Determines whether a skeleton contains a single field
     * 
     * @param skeleton
     * @return true or not
     * @internal
     * @deprecated This API is ICU internal only.
     */
    public static boolean isSingleField(String skeleton) {
        char first = skeleton.charAt(0);
        for (int i = 1; i < skeleton.length(); ++i) {
            if (skeleton.charAt(i) != first) return false;
        }
        return true;
    }
    
     /**
     * Add key to HashSet cldrAvailableFormatKeys.
     * 
     * @param key of the availableFormats in CLDR
     * @stable ICU 3.6
     */
    private void setAvailableFormat(String key) {
        checkFrozen();
        cldrAvailableFormatKeys.add(key);
    }
    
    /**
     * This function checks the corresponding slot of CLDR_AVAIL_FORMAT_KEY[]
     * has been added to DateTimePatternGenerator.
     * The function is to avoid the duplicate availableFomats added to
     * the pattern map from parent locales.
     * 
     * @param key of the availableFormatMask in CLDR
     * @return TRUE if the corresponding slot of CLDR_AVAIL_FORMAT_KEY[]
     * has been added to DateTimePatternGenerator.
     * @stable ICU 3.6
     */
    private boolean isAvailableFormatSet(String key) {
        return cldrAvailableFormatKeys.contains(key);
    }

    /**
     * Boilerplate for Freezable
     * @stable ICU 3.6
     */
    public boolean isFrozen() {
        return frozen;
    }
    
    /**
     * Boilerplate for Freezable
     * @stable ICU 3.6
     */
    public Object freeze() {
        frozen = true;
        return this;
    }
    
    /**
     * Boilerplate for Freezable
     * @stable ICU 3.6
     */
    public Object cloneAsThawed() {
        DateTimePatternGenerator result = (DateTimePatternGenerator) (this.clone());
        frozen = false;
        return result;
    }
    
    /**
     * Boilerplate
     * @stable ICU 3.6
     */
    public Object clone() {
        try {
            DateTimePatternGenerator result = (DateTimePatternGenerator) (super.clone());
            result.skeleton2pattern = (TreeMap) skeleton2pattern.clone();
            result.basePattern_pattern = (TreeMap) basePattern_pattern.clone();
            result.appendItemFormats = (String[]) appendItemFormats.clone();
            result.appendItemNames = (String[]) appendItemNames.clone();
            result.current = new DateTimeMatcher();
            result.fp = new FormatParser();
            result._distanceInfo = new DistanceInfo();
            
            result.frozen = false;
            return result;
        } catch (CloneNotSupportedException e) {
            throw new IllegalArgumentException("Internal Error");
        }
    }
    
    /**
     * Utility class for FormatParser. Immutable class that is only used to mark
     * the difference between a variable field and a literal string. Each
     * variable field must consist of 1 to n variable characters, representing
     * date format fields. For example, "VVVV" is valid while "V4" is not, nor
     * is "44".
     * 
     * @internal
     * @deprecated This API is ICU internal only.
     */
    public static class VariableField {
        private final String string;
        private final int canonicalIndex;
        
        /**
         * Create a variable field: equivalent to VariableField(string,false);
         * @param string
         * @internal
         * @deprecated This API is ICU internal only.
         */
        public VariableField(String string) {
            this(string, false);
        }
        /**
         * Create a variable field
         * @param string
         * @param strict TODO
         * @throws IllegalArgumentException if the variable field is not valid.
         * @internal
         * @deprecated This API is ICU internal only.
         */
        public VariableField(String string, boolean strict) {
            canonicalIndex = DateTimePatternGenerator.getCanonicalIndex(string, strict);
            if (canonicalIndex < 0) {
                throw new IllegalArgumentException("Illegal datetime field:\t"
                        + string);
            }
            this.string = string;
        }
        
        /**
         * Get the main type of this variable. These types are ERA, QUARTER,
         * MONTH, DAY, WEEK_OF_YEAR, WEEK_OF_MONTH, WEEKDAY, DAY, DAYPERIOD
         * (am/pm), HOUR, MINUTE, SECOND,FRACTIONAL_SECOND, ZONE. 
         * @return main type.
         * @internal
         * @deprecated This API is ICU internal only.
         */
        public int getType() {
            return types[canonicalIndex][1];
        }
        
        /**
         * Private method.
         */
        private int getCanonicalIndex() {
            return canonicalIndex;
        }

        /**
         * Get the string represented by this variable.
         * @internal
         * @deprecated This API is ICU internal only.
         */
        public String toString() {
            return string;
        }
    }
    
    /**
     * This class provides mechanisms for parsing a SimpleDateFormat pattern
     * or generating a new pattern, while handling the quoting. It represents
     * the result of the parse as a list of items, where each item is either a
     * literal string or a variable field. When parsing It can be used to find
     * out which variable fields are in a date format, and in what order, such
     * as for presentation in a UI as separate text entry fields. It can also be
     * used to construct new SimpleDateFormats.
     * <p>Example:
     * <pre>
    public boolean containsZone(String pattern) {
        for (Iterator it = formatParser.set(pattern).getItems().iterator(); it.hasNext();) {
            Object item = it.next();
            if (item instanceof VariableField) {
                VariableField variableField = (VariableField) item;
                if (variableField.getType() == DateTimePatternGenerator.ZONE) {
                    return true;
                }
            }
        }
        return false;
    }
     *  </pre>
     * @internal
     * @deprecated This API is ICU internal only.
     */
    static public class FormatParser {
        private transient PatternTokenizer tokenizer = new PatternTokenizer()
        .setSyntaxCharacters(new UnicodeSet("[a-zA-Z]"))
        .setExtraQuotingCharacters(new UnicodeSet("[[[:script=Latn:][:script=Cyrl:]]&[[:L:][:M:]]]"))
        //.setEscapeCharacters(new UnicodeSet("[^\\u0020-\\u007E]")) // WARNING: DateFormat doesn't accept \\uXXXX
        .setUsingQuote(true);
        private List items = new ArrayList();
        
        /**
         * Construct an empty date format parser, to which strings and variables can be added with set(...).
         * @internal
         * @deprecated This API is ICU internal only.
         */
        public FormatParser() {
        }

        /**
         * Parses the string into a list of items.
         * @param string
         * @return this, for chaining
         * @internal
         * @deprecated This API is ICU internal only.
         */
        final public FormatParser set(String string) {
            return set(string, false);
        }
        
        /**
         * Parses the string into a list of items, taking into account all of the quoting that may be going on.
         * @param string
         * @param strict If true, then only allows exactly those lengths specified by CLDR for variables. For example, "hh:mm aa" would throw an exception.
         * @return this, for chaining
         * @internal
         * @deprecated This API is ICU internal only.
         */
        public FormatParser set(String string, boolean strict) {
            items.clear();
            if (string.length() == 0) return this;
            tokenizer.setPattern(string);
            StringBuffer buffer = new StringBuffer();
            StringBuffer variable = new StringBuffer();
            while (true) {
                buffer.setLength(0);
                int status = tokenizer.next(buffer);
                if (status == PatternTokenizer.DONE) break;
                if (status == PatternTokenizer.SYNTAX) {
                    if (variable.length() != 0 && buffer.charAt(0) != variable.charAt(0)) {
                        addVariable(variable, false);
                    }
                    variable.append(buffer);
                } else {
                    addVariable(variable, false);
                    items.add(buffer.toString());
                }
            }
            addVariable(variable, false);
            return this;
        }
        
        private void addVariable(StringBuffer variable, boolean strict) {
            if (variable.length() != 0) {
                items.add(new VariableField(variable.toString(), strict));
                variable.setLength(0);
            }
        }
        
//        /** Private method. Return a collection of fields. These will be a mixture of literal Strings and VariableFields. Any "a" variable field is removed.
//         * @param output List to append the items to. If null, is allocated as an ArrayList.
//         * @return list
//         */
//        private List getVariableFields(List output) {
//            if (output == null) output = new ArrayList();
//            main:
//                for (Iterator it = items.iterator(); it.hasNext();) {
//                    Object item = it.next();
//                    if (item instanceof VariableField) {
//                        String s = item.toString();
//                        switch(s.charAt(0)) {
//                        //case 'Q': continue main; // HACK
//                        case 'a': continue main; // remove
//                        }
//                        output.add(item);
//                    }
//                }
//            //System.out.println(output);
//            return output;
//        }
        
//        /**
//         * Produce a string which concatenates all the variables. That is, it is the logically the same as the input with all literals removed.
//         * @return a string which is a concatenation of all the variable fields
//         * @internal
//         * @deprecated This API is ICU internal only.
//         */
//        public String getVariableFieldString() {
//            List list = getVariableFields(null);
//            StringBuffer result = new StringBuffer();
//            for (Iterator it = list.iterator(); it.hasNext();) {
//                String item = it.next().toString();
//                result.append(item);
//            }
//            return result.toString();
//        }
        
        /**
         * Returns modifiable list which is a mixture of Strings and VariableFields, in the order found during parsing. The strings represent literals, and have all quoting removed. Thus the string "dd 'de' MM" will parse into three items:
         * <pre>
         * VariableField: dd
         * String: " de "
         * VariableField: MM
         * </pre>
         * The list is modifiable, so you can add any strings or variables to it, or remove any items.
         * @return modifiable list of items.
         * @internal
         * @deprecated This API is ICU internal only.
         */
        public List getItems() {
            return items;
        }
        
        /** Provide display form of formatted input. Each literal string is quoted if necessary.. That is, if the input was "hh':'mm", the result would be "hh:mm", since the ":" doesn't need quoting. See quoteLiteral().
         * @return printable output string
         * @internal
         * @deprecated This API is ICU internal only.
         */
        public String toString() {
            return toString(0, items.size());
        }
        
        /**
         * Provide display form of a segment of the parsed input. Each literal string is minimally quoted. That is, if the input was "hh':'mm", the result would be "hh:mm", since the ":" doesn't need quoting. See quoteLiteral().
         * @param start item to start from
         * @param limit last item +1
         * @return printable output string
         * @internal
         * @deprecated This API is ICU internal only.
         */
        public String toString(int start, int limit) {
            StringBuffer result = new StringBuffer();
            for (int i = start; i < limit; ++i) {
                Object item = items.get(i);
                if (item instanceof String) {
                    String itemString = (String) item;
                    result.append(tokenizer.quoteLiteral(itemString));
                } else {
                    result.append(items.get(i).toString());
                }
            }
            return result.toString();
        }
        
        /**
         * Returns true if it has a mixture of date and time variable fields: that is, at least one date variable and at least one time variable.
         * @return true or false
         * @internal
         * @deprecated This API is ICU internal only.
         */
        public boolean hasDateAndTimeFields() {
            int foundMask = 0;
            for (Iterator it = items.iterator(); it.hasNext();) {
                Object item = it.next();
                if (item instanceof VariableField) {
                    int type = ((VariableField)item).getType();
                    foundMask |= 1 << type;    
                }
            }
            boolean isDate = (foundMask & DATE_MASK) != 0;
            boolean isTime = (foundMask & TIME_MASK) != 0;
            return isDate && isTime;
        }
        
//        /**
//         * Internal routine
//         * @param value
//         * @param result
//         * @return list
//         * @internal
//         * @deprecated This API is ICU internal only.
//         */
//        public List getAutoPatterns(String value, List result) {
//            if (result == null) result = new ArrayList();
//            int fieldCount = 0;
//            int minField = Integer.MAX_VALUE;
//            int maxField = Integer.MIN_VALUE;
//            for (Iterator it = items.iterator(); it.hasNext();) {
//                Object item = it.next();
//                if (item instanceof VariableField) {
//                    try {
//                        int type = ((VariableField)item).getType();
//                        if (minField > type) minField = type;
//                        if (maxField < type) maxField = type;
//                        if (type == ZONE || type == DAYPERIOD || type == WEEKDAY) return result; // skip anything with zones                    
//                        fieldCount++;
//                    } catch (Exception e) {
//                        return result; // if there are any funny fields, return
//                    }
//                }
//            }
//            if (fieldCount < 3) return result; // skip
//            // trim from start
//            // trim first field IF there are no letters around it
//            // and it is either the min or the max field
//            // first field is either 0 or 1
//            for (int i = 0; i < items.size(); ++i) {
//                Object item = items.get(i);
//                if (item instanceof VariableField) {
//                    int type = ((VariableField)item).getType();
//                    if (type != minField && type != maxField) break;
//                    
//                    if (i > 0) {
//                        Object previousItem = items.get(0);
//                        if (alpha.containsSome(previousItem.toString())) break;
//                    }
//                    int start = i+1;
//                    if (start < items.size()) {
//                        Object nextItem = items.get(start);
//                        if (nextItem instanceof String) {
//                            if (alpha.containsSome(nextItem.toString())) break;
//                            start++; // otherwise skip over string
//                        }
//                    }
//                    result.add(toString(start, items.size()));
//                    break;
//                }
//            }
//            // now trim from end
//            for (int i = items.size()-1; i >= 0; --i) {
//                Object item = items.get(i);
//                if (item instanceof VariableField) {
//                    int type = ((VariableField)item).getType();
//                    if (type != minField && type != maxField) break;
//                    if (i < items.size() - 1) {
//                        Object previousItem = items.get(items.size() - 1);
//                        if (alpha.containsSome(previousItem.toString())) break;
//                    }
//                    int end = i-1;
//                    if (end > 0) {
//                        Object nextItem = items.get(end);
//                        if (nextItem instanceof String) {
//                            if (alpha.containsSome(nextItem.toString())) break;
//                            end--; // otherwise skip over string
//                        }
//                    }
//                    result.add(toString(0, end+1));
//                    break;
//                }
//            }
//            
//            return result;
//        }
        
//        private static UnicodeSet alpha = new UnicodeSet("[:alphabetic:]");
        
//        private int getType(Object item) {
//            String s = item.toString();
//            int canonicalIndex = getCanonicalIndex(s);
//            if (canonicalIndex < 0) {
//                throw new IllegalArgumentException("Illegal field:\t"
//                        + s);
//            }
//            int type = types[canonicalIndex][1];
//            return type;
//        }
        
        /**
         *  Each literal string is quoted as needed. That is, the ' quote marks will only be added if needed. The exact pattern of quoting is not guaranteed, thus " de la " could be quoted as " 'de la' " or as " 'de' 'la' ".
         * @param string
         * @return string with quoted literals
         * @internal
         * @deprecated This API is ICU internal only.
         */
        public Object quoteLiteral(String string) {
            return tokenizer.quoteLiteral(string);
        }
        
    }
    // ========= PRIVATES ============
    
    private TreeMap skeleton2pattern = new TreeMap(); // items are in priority order
    private TreeMap basePattern_pattern = new TreeMap(); // items are in priority order
    private String decimal = "?";
    private String dateTimeFormat = "{0} {1}";
    private String[] appendItemFormats = new String[TYPE_LIMIT];
    private String[] appendItemNames = new String[TYPE_LIMIT];
    {
        for (int i = 0; i < TYPE_LIMIT; ++i) {
            appendItemFormats[i] = "{0} \u251C{2}: {1}\u2524";
            appendItemNames[i] = "F" + i;
        }
    }
    
    private transient DateTimeMatcher current = new DateTimeMatcher();
    private transient FormatParser fp = new FormatParser();
    private transient DistanceInfo _distanceInfo = new DistanceInfo();
    //private transient boolean isComplete = false;
    private transient DateTimeMatcher skipMatcher = null; // only used temporarily, for internal purposes
    private transient boolean frozen = false;
    
    private transient boolean chineseMonthHack = false;
    
    private static final int FRACTIONAL_MASK = 1<<FRACTIONAL_SECOND;
    private static final int SECOND_AND_FRACTIONAL_MASK = (1<<SECOND) | (1<<FRACTIONAL_SECOND);
    
    private void checkFrozen() {
        if (isFrozen()) {
            throw new UnsupportedOperationException("Attempt to modify frozen object");
        }
    }
    
    /**
     * We only get called here if we failed to find an exact skeleton. We have broken it into date + time, and look for the pieces.
     * If we fail to find a complete skeleton, we compose in a loop until we have all the fields.
     */
    private String getBestAppending(int missingFields) {
        String resultPattern = null;
        if (missingFields != 0) {
            resultPattern = getBestRaw(current, missingFields, _distanceInfo);
            resultPattern = adjustFieldTypes(resultPattern, current, false);
            
            while (_distanceInfo.missingFieldMask != 0) { // precondition: EVERY single field must work!
                
                // special hack for SSS. If we are missing SSS, and we had ss but found it, replace the s field according to the 
                // number separator
                if ((_distanceInfo.missingFieldMask & SECOND_AND_FRACTIONAL_MASK) == FRACTIONAL_MASK
                        && (missingFields & SECOND_AND_FRACTIONAL_MASK) == SECOND_AND_FRACTIONAL_MASK) {
                    resultPattern = adjustFieldTypes(resultPattern, current, true);
                    _distanceInfo.missingFieldMask &= ~FRACTIONAL_MASK; // remove bit
                    continue;
                }
                
                int startingMask = _distanceInfo.missingFieldMask;
                String temp = getBestRaw(current, _distanceInfo.missingFieldMask, _distanceInfo);
                temp = adjustFieldTypes(temp, current, false);
                int foundMask = startingMask & ~_distanceInfo.missingFieldMask;
                int topField = getTopBitNumber(foundMask);
                resultPattern = MessageFormat.format(getAppendFormat(topField), new Object[]{resultPattern, temp, getAppendName(topField)});
            }
        }
        return resultPattern;
    }
    
    private String getAppendName(int foundMask) {
        return "'" + appendItemNames[foundMask] + "'";
    }
    private String getAppendFormat(int foundMask) {
        return appendItemFormats[foundMask];
    }
    
//    /**
//     * @param current2
//     * @return
//     */
//    private String adjustSeconds(DateTimeMatcher current2) {
//        // TODO Auto-generated method stub
//        return null;
//    }
    
    /**
     * @param foundMask
     * @return
     */
    private int getTopBitNumber(int foundMask) {
        int i = 0;
        while (foundMask != 0) {
            foundMask >>>= 1;
            ++i;
        }
        return i-1;
    }
    
    /**
     * 
     */
    private void complete() {
        PatternInfo patternInfo = new PatternInfo();
        // make sure that every valid field occurs once, with a "default" length
        for (int i = 0; i < CANONICAL_ITEMS.length; ++i) {
            //char c = (char)types[i][0];
            addPattern(String.valueOf(CANONICAL_ITEMS[i]), false, patternInfo);
        }
        //isComplete = true;
    }
    {
        complete();
    }
    
    /**
     * 
     */
    private String getBestRaw(DateTimeMatcher source, int includeMask, DistanceInfo missingFields) {
//      if (SHOW_DISTANCE) System.out.println("Searching for: " + source.pattern 
//      + ", mask: " + showMask(includeMask));
        int bestDistance = Integer.MAX_VALUE;
        String bestPattern = "";
        DistanceInfo tempInfo = new DistanceInfo();
        for (Iterator it = skeleton2pattern.keySet().iterator(); it.hasNext();) {
            DateTimeMatcher trial = (DateTimeMatcher) it.next();
            if (trial.equals(skipMatcher)) continue;
            int distance = source.getDistance(trial, includeMask, tempInfo);
//          if (SHOW_DISTANCE) System.out.println("\tDistance: " + trial.pattern + ":\t" 
//          + distance + ",\tmissing fields: " + tempInfo);
            if (distance < bestDistance) {
                bestDistance = distance;
                bestPattern = (String) skeleton2pattern.get(trial);
                missingFields.setTo(tempInfo);
                if (distance == 0) break;
            }
        }
        return bestPattern;
    }
    
    /**
     * @param fixFractionalSeconds TODO
     * 
     */
    private String adjustFieldTypes(String pattern, DateTimeMatcher inputRequest, boolean fixFractionalSeconds) {
        fp.set(pattern);
        StringBuffer newPattern = new StringBuffer();
        for (Iterator it = fp.getItems().iterator(); it.hasNext();) {
            Object item = it.next();
            if (item instanceof String) {
                newPattern.append(fp.quoteLiteral((String)item));
            } else {
                final VariableField variableField = (VariableField) item;
                String field = variableField.toString();
//                int canonicalIndex = getCanonicalIndex(field, true);
//                if (canonicalIndex < 0) {
//                    continue; // don't adjust
//                }
//                int type = types[canonicalIndex][1];
                int type = variableField.getType();
                
                if (fixFractionalSeconds && type == SECOND) {
                    String newField = inputRequest.original[FRACTIONAL_SECOND];
                    field = field + decimal + newField;
                } else if (inputRequest.type[type] != 0) {
                    String newField = inputRequest.original[type];
                    // normally we just replace the field. However HOUR is special; we only change the length
                    if (type != HOUR) {
                        field = newField;
                    } else if (field.length() != newField.length()){
                        char c = field.charAt(0);
                        field = "";
                        for (int i = newField.length(); i > 0; --i) field += c;
                    }
                }
                newPattern.append(field);
            }
        }
        //if (SHOW_DISTANCE) System.out.println("\tRaw: " + pattern);
        return newPattern.toString();
    }
    
//  public static String repeat(String s, int count) {
//  StringBuffer result = new StringBuffer();
//  for (int i = 0; i < count; ++i) {
//  result.append(s);
//  }
//  return result.toString();
//  }
    
    /**
     * internal routine
     * @param pattern
     * @return field value
     * @internal
     * @deprecated This API is ICU internal only.
     */
    public String getFields(String pattern) {
        fp.set(pattern);
        StringBuffer newPattern = new StringBuffer();
        for (Iterator it = fp.getItems().iterator(); it.hasNext();) {
            Object item = it.next();
            if (item instanceof String) {
                newPattern.append(fp.quoteLiteral((String)item));
            } else {
                newPattern.append("{" + getName(item.toString()) + "}");
            }
        }
        return newPattern.toString();
    }
    
    private static String showMask(int mask) {
        String result = "";
        for (int i = 0; i < TYPE_LIMIT; ++i) {
            if ((mask & (1<<i)) == 0) continue;
            if (result.length() != 0) result += " | ";
            result += FIELD_NAME[i] + " ";
        }
        return result;
    }
    
    static private String[] CLDR_FIELD_APPEND = {
        "Era", "Year", "Quarter", "Month", "Week", "*", "Day-Of-Week", 
        "Day", "*", "*", "*", 
        "Hour", "Minute", "Second", "*", "Timezone"
    };
    
    static private String[] CLDR_FIELD_NAME = {
        "era", "year", "*", "month", "week", "*", "weekday", 
        "day", "*", "*", "dayperiod", 
        "hour", "minute", "second", "*", "zone"
    };
    
    static private String[] FIELD_NAME = {
        "Era", "Year", "Quarter", "Month", "Week_in_Year", "Week_in_Month", "Weekday", 
        "Day", "Day_Of_Year", "Day_of_Week_in_Month", "Dayperiod", 
        "Hour", "Minute", "Second", "Fractional_Second", "Zone"
    };
    
    
    static private String[] CANONICAL_ITEMS = {
        "G", "y", "Q", "M", "w", "W", "e", 
        "d", "D", "F", 
        "H", "m", "s", "S", "v"
    };
    
    static private Set CANONICAL_SET = new HashSet(Arrays.asList(CANONICAL_ITEMS));
    private Set cldrAvailableFormatKeys = new HashSet(20);
    
    static final private int 
    DATE_MASK = (1<<DAYPERIOD) - 1,
    TIME_MASK = (1<<TYPE_LIMIT) - 1 - DATE_MASK;
    
    static final private int // numbers are chosen to express 'distance'
    DELTA = 0x10,
    NUMERIC = 0x100,
    NONE = 0,
    NARROW = -0x100,
    SHORT = -0x101,
    LONG = -0x102,
    EXTRA_FIELD =   0x10000,
    MISSING_FIELD = 0x1000;
    
    
    static private String getName(String s) {
        int i = getCanonicalIndex(s, true);
        String name = FIELD_NAME[types[i][1]];
        int subtype = types[i][2];
        boolean string = subtype < 0;
        if (string) subtype = -subtype;
        if (subtype < 0) name += ":S";
        else name += ":N";
        return name;
    }
    
    /**
     * Get the canonical index, or return -1 if illegal.
     * @param s
     * @param strict TODO
     * @return
     */
    static private int getCanonicalIndex(String s, boolean strict) {
        int len = s.length();
        if (len == 0) {
            return -1;
        }
        int ch = s.charAt(0);
        //      verify that all are the same character
        for (int i = 1; i < len; ++i) {
            if (s.charAt(i) != ch) {
                return -1; 
            }
        }
        int bestRow = -1;
        for (int i = 0; i < types.length; ++i) {
            int[] row = types[i];
            if (row[0] != ch) continue;
            bestRow = i;
            if (row[3] > len) continue;
            if (row[row.length-1] < len) continue;
            return i;
        }
        return strict ? -1 : bestRow;
    }
    
    static private int[][] types = {
        // the order here makes a difference only when searching for single field.
        // format is:
        // pattern character, main type, weight, min length, weight
        {'G', ERA, SHORT, 1, 3},
        {'G', ERA, LONG, 4},
        
        {'y', YEAR, NUMERIC, 1, 20},
        {'Y', YEAR, NUMERIC + DELTA, 1, 20},
        {'u', YEAR, NUMERIC + 2*DELTA, 1, 20},
        
        {'Q', QUARTER, NUMERIC, 1, 2},
        {'Q', QUARTER, SHORT, 3},
        {'Q', QUARTER, LONG, 4},
        
        {'q', QUARTER, NUMERIC + DELTA, 1, 2},
        {'q', QUARTER, SHORT + DELTA, 3},
        {'q', QUARTER, LONG + DELTA, 4},
        
        {'M', MONTH, NUMERIC, 1, 2},
        {'M', MONTH, SHORT, 3},
        {'M', MONTH, LONG, 4},
        {'M', MONTH, NARROW, 5},
        {'L', MONTH, NUMERIC + DELTA, 1, 2},
        {'L', MONTH, SHORT - DELTA, 3},
        {'L', MONTH, LONG - DELTA, 4},
        {'L', MONTH, NARROW - DELTA, 5},
        
        {'w', WEEK_OF_YEAR, NUMERIC, 1, 2},
        {'W', WEEK_OF_MONTH, NUMERIC + DELTA, 1},
        
        {'e', WEEKDAY, NUMERIC + DELTA, 1, 2},
        {'e', WEEKDAY, SHORT - DELTA, 3},
        {'e', WEEKDAY, LONG - DELTA, 4},
        {'e', WEEKDAY, NARROW - DELTA, 5},
        {'E', WEEKDAY, SHORT, 1, 3},
        {'E', WEEKDAY, LONG, 4},
        {'E', WEEKDAY, NARROW, 5},
        {'c', WEEKDAY, NUMERIC + 2*DELTA, 1, 2},
        {'c', WEEKDAY, SHORT - 2*DELTA, 3},
        {'c', WEEKDAY, LONG - 2*DELTA, 4},
        {'c', WEEKDAY, NARROW - 2*DELTA, 5},
        
        {'d', DAY, NUMERIC, 1, 2},
        {'D', DAY_OF_YEAR, NUMERIC + DELTA, 1, 3},
        {'F', DAY_OF_WEEK_IN_MONTH, NUMERIC + 2*DELTA, 1},
        {'g', DAY, NUMERIC + 3*DELTA, 1, 20}, // really internal use, so we don't care
        
        {'a', DAYPERIOD, SHORT, 1},
        
        {'H', HOUR, NUMERIC + 10*DELTA, 1, 2}, // 24 hour
        {'k', HOUR, NUMERIC + 11*DELTA, 1, 2},
        {'h', HOUR, NUMERIC, 1, 2}, // 12 hour
        {'K', HOUR, NUMERIC + DELTA, 1, 2},
        {'j', HOUR, NUMERIC + 20*DELTA, 1, 2},
        
        {'m', MINUTE, NUMERIC, 1, 2},
        
        {'s', SECOND, NUMERIC, 1, 2},
        {'S', FRACTIONAL_SECOND, NUMERIC + DELTA, 1, 1000},
        {'A', SECOND, NUMERIC + 2*DELTA, 1, 1000},
        
        {'v', ZONE, SHORT - 2*DELTA, 1},
        {'v', ZONE, LONG - 2*DELTA, 4},
        {'z', ZONE, SHORT, 1, 3},
        {'z', ZONE, LONG, 4},
        {'Z', ZONE, SHORT - DELTA, 1, 3},
        {'Z', ZONE, LONG - DELTA, 4},
        {'V', ZONE, SHORT - DELTA, 1, 3},
        {'V', ZONE, LONG - DELTA, 4},
    };
    
    private static class DateTimeMatcher implements Comparable {
        //private String pattern = null;
        private int[] type = new int[TYPE_LIMIT];
        private String[] original = new String[TYPE_LIMIT];
        private String[] baseOriginal = new String[TYPE_LIMIT];
        
        // just for testing; fix to make multi-threaded later
        // private static FormatParser fp = new FormatParser();
        
        public String toString() {
            StringBuffer result = new StringBuffer();
            for (int i = 0; i < TYPE_LIMIT; ++i) {
                if (original[i].length() != 0) result.append(original[i]);
            }
            return result.toString();
        }
        
        String getBasePattern() {
            StringBuffer result = new StringBuffer();
            for (int i = 0; i < TYPE_LIMIT; ++i) {
                if (baseOriginal[i].length() != 0) result.append(baseOriginal[i]);
            }
            return result.toString();
        }
        
        DateTimeMatcher set(String pattern, FormatParser fp) {
            for (int i = 0; i < TYPE_LIMIT; ++i) {
                type[i] = NONE;
                original[i] = "";
                baseOriginal[i] = "";
            }
            fp.set(pattern);
            for (Iterator it = fp.getItems().iterator(); it.hasNext();) {
                Object obj = it.next();
                if (!(obj instanceof VariableField)) {
                    continue;
                }
                VariableField item = (VariableField)obj;
                String field = item.toString();
                if (field.charAt(0) == 'a') continue; // skip day period, special case
                int canonicalIndex = item.getCanonicalIndex();
//                if (canonicalIndex < 0) {
//                    throw new IllegalArgumentException("Illegal field:\t"
//                            + field + "\t in " + pattern);
//                }
                int[] row = types[canonicalIndex];
                int typeValue = row[1];
                if (original[typeValue].length() != 0) {
                    throw new IllegalArgumentException("Conflicting fields:\t"
                            + original[typeValue] + ", " + field + "\t in " + pattern);
                }
                original[typeValue] = field;
                char repeatChar = (char)row[0];
                int repeatCount = row[3];
                if (repeatCount > 3) repeatCount = 3; // hack to discard differences
                if ("GEzvQ".indexOf(repeatChar) >= 0) repeatCount = 1;
                baseOriginal[typeValue] = Utility.repeat(String.valueOf(repeatChar),repeatCount);
                int subTypeValue = row[2];
                if (subTypeValue > 0) subTypeValue += field.length();
                type[typeValue] = (byte) subTypeValue;
            }
            return this;
        }
        
        /**
         * 
         */
        int getFieldMask() {
            int result = 0;
            for (int i = 0; i < type.length; ++i) {
                if (type[i] != 0) result |= (1<<i);
            }
            return result;
        }
        
        /**
         * 
         */
        void extractFrom(DateTimeMatcher source, int fieldMask) {
            for (int i = 0; i < type.length; ++i) {
                if ((fieldMask & (1<<i)) != 0) {
                    type[i] = source.type[i];
                    original[i] = source.original[i];
                } else {
                    type[i] = NONE;
                    original[i] = "";
                }
            }
        }
        
        int getDistance(DateTimeMatcher other, int includeMask, DistanceInfo distanceInfo) {
            int result = 0;
            distanceInfo.clear();
            for (int i = 0; i < type.length; ++i) {
                int myType = (includeMask & (1<<i)) == 0 ? 0 : type[i];
                int otherType = other.type[i];
                if (myType == otherType) continue; // identical (maybe both zero) add 0
                if (myType == 0) { // and other is not
                    result += EXTRA_FIELD;
                    distanceInfo.addExtra(i);
                } else if (otherType == 0) { // and mine is not
                    result += MISSING_FIELD;
                    distanceInfo.addMissing(i);
                } else {
                    result += Math.abs(myType - otherType); // square of mismatch
                }
            }
            return result;
        }
        
        public int compareTo(Object o) {
            DateTimeMatcher that = (DateTimeMatcher) o;
            for (int i = 0; i < original.length; ++i) {
                int comp = original[i].compareTo(that.original[i]);
                if (comp != 0) return -comp;
            }
            return 0;
        }       
        
        public boolean equals(Object other) {
            if (other == null) return false;
            DateTimeMatcher that = (DateTimeMatcher) other;
            for (int i = 0; i < original.length; ++i) {
                if (!original[i].equals(that.original[i])) return false;
            }
            return true;
        }       
        public int hashCode() {
            int result = 0;
            for (int i = 0; i < original.length; ++i) {
                result ^= original[i].hashCode();
            }
            return result;
        }       
    }
    
    private static class DistanceInfo {
        int missingFieldMask;
        int extraFieldMask;
        void clear() {
            missingFieldMask = extraFieldMask = 0;
        }
        /**
         * 
         */
        void setTo(DistanceInfo other) {
            missingFieldMask = other.missingFieldMask;
            extraFieldMask = other.extraFieldMask;
        }
        void addMissing(int field) {
            missingFieldMask |= (1<<field);
        }
        void addExtra(int field) {
            extraFieldMask |= (1<<field);
        }
        public String toString() {
            return "missingFieldMask: " + DateTimePatternGenerator.showMask(missingFieldMask)
            + ", extraFieldMask: " + DateTimePatternGenerator.showMask(extraFieldMask);
        }
    }
}
//#endif
//eof