/* ====================================================================
   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
   the License.  You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

   2012 - Alfresco Software, Ltd.
   Alfresco Software has modified source of this file
   The details of changes as svn diff can be found in svn at location root/projects/3rd-party/src 
==================================================================== */
package org.apache.poi.ss.usermodel;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.text.DateFormat;
import java.text.DateFormatSymbols;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.FieldPosition;
import java.text.Format;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Observable;
import java.util.Observer;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.poi.ss.format.CellFormat;
import org.apache.poi.ss.format.CellFormatResult;
import org.apache.poi.ss.util.DateFormatConverter;
import org.apache.poi.ss.util.NumberToTextConverter;
import org.apache.poi.util.LocaleUtil;
import org.apache.poi.util.POILogFactory;
import org.apache.poi.util.POILogger;


/**
 * DataFormatter contains methods for formatting the value stored in an
 * Cell. This can be useful for reports and GUI presentations when you
 * need to display data exactly as it appears in Excel. Supported formats
 * include currency, SSN, percentages, decimals, dates, phone numbers, zip
 * codes, etc.
 * <p>
 * Internally, formats will be implemented using subclasses of {@link Format}
 * such as {@link DecimalFormat} and {@link java.text.SimpleDateFormat}. Therefore the
 * formats used by this class must obey the same pattern rules as these Format
 * subclasses. This means that only legal number pattern characters ("0", "#",
 * ".", "," etc.) may appear in number formats. Other characters can be
 * inserted <em>before</em> or <em> after</em> the number pattern to form a
 * prefix or suffix.
 * </p>
 * <p>
 * For example the Excel pattern <code>"$#,##0.00 "USD"_);($#,##0.00 "USD")"
 * </code> will be correctly formatted as "$1,000.00 USD" or "($1,000.00 USD)".
 * However the pattern <code>"00-00-00"</code> is incorrectly formatted by
 * DecimalFormat as "000000--". For Excel formats that are not compatible with
 * DecimalFormat, you can provide your own custom {@link Format} implementation
 * via <code>DataFormatter.addFormat(String,Format)</code>. The following
 * custom formats are already provided by this class:
 * </p>
 * <pre>
 * <ul><li>SSN "000-00-0000"</li>
 *     <li>Phone Number "(###) ###-####"</li>
 *     <li>Zip plus 4 "00000-0000"</li>
 * </ul>
 * </pre>
 * <p>
 * If the Excel format pattern cannot be parsed successfully, then a default
 * format will be used. The default number format will mimic the Excel General
 * format: "#" for whole numbers and "#.##########" for decimal numbers. You
 * can override the default format pattern with <code>
 * DataFormatter.setDefaultNumberFormat(Format)</code>. <b>Note:</b> the
 * default format will only be used when a Format cannot be created from the
 * cell's data format string.
 *
 * <p>
 * Note that by default formatted numeric values are trimmed.
 * Excel formats can contain spacers and padding and the default behavior is to strip them off.
 * </p>
 * <p>Example:</p>
 * <p>
 * Consider a numeric cell with a value <code>12.343</code> and format <code>"##.##_ "</code>.
 *  The trailing underscore and space ("_ ") in the format adds a space to the end and Excel formats this cell as <code>"12.34 "</code>,
 *  but <code>DataFormatter</code> trims the formatted value and returns <code>"12.34"</code>.
 * </p>
 * You can enable spaces by passing the <code>emulateCSV=true</code> flag in the <code>DateFormatter</code> cosntructor.
 * If set to true, then the output tries to conform to what you get when you take an xls or xlsx in Excel and Save As CSV file:
 * <ul>
 *  <li>returned values are not trimmed</li>
 *  <li>Invalid dates are formatted as  255 pound signs ("#")</li>
 *  <li>simulate Excel's handling of a format string of all # when the value is 0.
 *   Excel will output "", <code>DataFormatter</code> will output "0".
 * </ul>
 * <p>
 *  Some formats are automatically "localized" by Excel, eg show as mm/dd/yyyy when
 *   loaded in Excel in some Locales but as dd/mm/yyyy in others. These are always
 *   returned in the "default" (US) format, as stored in the file. 
 *  Some format strings request an alternate locale, eg 
 *   <code>[$-809]d/m/yy h:mm AM/PM</code> which explicitly requests UK locale.
 *   These locale directives are (currently) ignored.
 *  You can use {@link DateFormatConverter} to do some of this localisation if
 *   you need it. 
 */
public class DataFormatter implements Observer {
    private static final String defaultFractionWholePartFormat = "#";
    private static final String defaultFractionFractionPartFormat = "#/##";
    /** Pattern to find a number format: "0" or  "#" */
    private static final Pattern numPattern = Pattern.compile("[0#]+");

    /** Pattern to find days of week as text "ddd...." */
    private static final Pattern daysAsText = Pattern.compile("([d]{3,})", Pattern.CASE_INSENSITIVE);

    /** Pattern to find "AM/PM" marker */
    private static final Pattern amPmPattern = Pattern.compile("((A|P)[M/P]*)", Pattern.CASE_INSENSITIVE);

    /** 
     * A regex to find locale patterns like [$$-1009] and [$?-452].
     * Note that we don't currently process these into locales 
     */
    private static final Pattern localePatternGroup = Pattern.compile("(\\[\\$[^-\\]]*-[0-9A-Z]+\\])");

    /**
     * A regex to match the colour formattings rules.
     * Allowed colours are: Black, Blue, Cyan, Green,
     *  Magenta, Red, White, Yellow, "Color n" (1<=n<=56)
     */
    private static final Pattern colorPattern = 
       Pattern.compile("(\\[BLACK\\])|(\\[BLUE\\])|(\\[CYAN\\])|(\\[GREEN\\])|" +
       		"(\\[MAGENTA\\])|(\\[RED\\])|(\\[WHITE\\])|(\\[YELLOW\\])|" +
       		"(\\[COLOR\\s*\\d\\])|(\\[COLOR\\s*[0-5]\\d\\])", Pattern.CASE_INSENSITIVE);

    /**
     * A regex to identify a fraction pattern.
     * This requires that replaceAll("\\?", "#") has already been called 
     */
    private static final Pattern fractionPattern = Pattern.compile("(?:([#\\d]+)\\s+)?(#+)\\s*\\/\\s*([#\\d]+)");

    /**
     * A regex to strip junk out of fraction formats
     */
    private static final Pattern fractionStripper = Pattern.compile("(\"[^\"]*\")|([^ \\?#\\d\\/]+)");

    /**
     * A regex to detect if an alternate grouping character is used
     *  in a numeric format 
     */
    private static final Pattern alternateGrouping = Pattern.compile("([#0]([^.#0])[#0]{3})");
    
    /**
      * Cells formatted with a date or time format and which contain invalid date or time values
     *  show 255 pound signs ("#").
      */
     private static final String invalidDateTimeString;
     static {
         StringBuilder buf = new StringBuilder();
         for(int i = 0; i < 255; i++) buf.append('#');
         invalidDateTimeString = buf.toString();
     }

    /**
     * The decimal symbols of the locale used for formatting values.
     */
    private DecimalFormatSymbols decimalSymbols;

    /**
     * The date symbols of the locale used for formatting values.
     */
    private DateFormatSymbols dateSymbols;

    /**
     * A default date format, if no date format was given
     */
    private DateFormat defaultDateformat;
    
    /** <em>General</em> format for numbers. */
    private Format generalNumberFormat;

    /** A default format to use when a number pattern cannot be parsed. */
    private Format defaultNumFormat;

    /**
     * A map to cache formats.
     *  Map<String,Format> formats
     */
    private final Map<String,Format> formats = new HashMap<String,Format>();

    private final boolean emulateCSV;

    /** stores the locale valid it the last formatting call */
    private Locale locale;
    
    /** stores if the locale should change according to {@link LocaleUtil#getUserLocale()} */
    private boolean localeIsAdapting;
    
    private class LocaleChangeObservable extends Observable {
        void checkForLocaleChange() {
            checkForLocaleChange(LocaleUtil.getUserLocale());
        }
        void checkForLocaleChange(Locale newLocale) {
            if (!localeIsAdapting) return;
            if (newLocale.equals(locale)) return;
            super.setChanged();
            notifyObservers(newLocale);
        }
    }
    
    /** the Observable to notify, when the locale has been changed */
    private final LocaleChangeObservable localeChangedObservable = new LocaleChangeObservable();
    
    /** For logging any problems we find */
    private static POILogger logger = POILogFactory.getLogger(DataFormatter.class);
    
    /**
     * Creates a formatter using the {@link Locale#getDefault() default locale}.
     */
    public DataFormatter() {
        this(false);
    }

    /**
     * Creates a formatter using the {@link Locale#getDefault() default locale}.
     *
     * @param  emulateCSV whether to emulate CSV output.
     */
    public DataFormatter(boolean emulateCSV) {
        this(LocaleUtil.getUserLocale(), true, emulateCSV);
    }

    /**
     * Creates a formatter using the given locale.
     */
    public DataFormatter(Locale locale) {
        this(locale, false);
    }

    /**
     * Creates a formatter using the given locale.
     *
     * @param  emulateCSV whether to emulate CSV output.
     */
    public DataFormatter(Locale locale, boolean emulateCSV) {
        this(locale, false, emulateCSV);
    }

    /**
     * Creates a formatter using the given locale.
     * @param  localeIsAdapting (true only if locale is not user-specified)
     * @param  emulateCSV whether to emulate CSV output.
     */
    private DataFormatter(Locale locale, boolean localeIsAdapting, boolean emulateCSV) {
        this.localeIsAdapting = true;
        localeChangedObservable.addObserver(this);
        // localeIsAdapting must be true prior to this first checkForLocaleChange call.
        localeChangedObservable.checkForLocaleChange(locale);
        // set localeIsAdapting so subsequent checks perform correctly
        // (whether a specific locale was provided to this DataFormatter or DataFormatter should
        // adapt to the current user locale as the locale changes)
        this.localeIsAdapting = localeIsAdapting;
        this.emulateCSV = emulateCSV;
    }

    /**
     * Return a Format for the given cell if one exists, otherwise try to
     * create one. This method will return <code>null</code> if the any of the
     * following is true:
     * <ul>
     * <li>the cell's style is null</li>
     * <li>the style's data format string is null or empty</li>
     * <li>the format string cannot be recognized as either a number or date</li>
     * </ul>
     *
     * @param cell The cell to retrieve a Format for
     * @return A Format for the format String
     */
    private Format getFormat(Cell cell) {
        if ( cell.getCellStyle() == null) {
            return null;
        }

        int formatIndex = cell.getCellStyle().getDataFormat();
        String formatStr = cell.getCellStyle().getDataFormatString();
        if(formatStr == null || formatStr.trim().length() == 0) {
            return null;
        }
        return getFormat(cell.getNumericCellValue(), formatIndex, formatStr);
    }

    private Format getFormat(double cellValue, int formatIndex, String formatStrIn) {
        localeChangedObservable.checkForLocaleChange();
        
//      // Might be better to separate out the n p and z formats, falling back to p when n and z are not set.
//      // That however would require other code to be re factored.
//      String[] formatBits = formatStrIn.split(";");
//      int i = cellValue > 0.0 ? 0 : cellValue < 0.0 ? 1 : 2; 
//      String formatStr = (i < formatBits.length) ? formatBits[i] : formatBits[0];

        String formatStr = formatStrIn;
        
        // Excel supports 3+ part conditional data formats, eg positive/negative/zero,
        //  or (>1000),(>0),(0),(negative). As Java doesn't handle these kinds
        //  of different formats for different ranges, just +ve/-ve, we need to 
        //  handle these ourselves in a special way.
        // For now, if we detect 3+ parts, we call out to CellFormat to handle it
        // TODO Going forward, we should really merge the logic between the two classes
        if (formatStr.contains(";") &&
                formatStr.indexOf(';') != formatStr.lastIndexOf(';')) {
            try {
                // Ask CellFormat to get a formatter for it
                CellFormat cfmt = CellFormat.getInstance(formatStr);
                // CellFormat requires callers to identify date vs not, so do so
                Object cellValueO = Double.valueOf(cellValue);
                if (DateUtil.isADateFormat(formatIndex, formatStr) && 
                        // don't try to handle Date value 0, let a 3 or 4-part format take care of it 
                        ((Double)cellValueO).doubleValue() != 0.0) {
                    cellValueO = DateUtil.getJavaDate(cellValue);
                }
                // Wrap and return (non-cachable - CellFormat does that)
                return new CellFormatResultWrapper( cfmt.apply(cellValueO) );
            } catch (Exception e) {
                logger.log(POILogger.WARN, "Formatting failed for format " + formatStr + ", falling back", e);
            }
        }
        
       // Excel's # with value 0 will output empty where Java will output 0. This hack removes the # from the format.
       if (emulateCSV && cellValue == 0.0 && formatStr.contains("#") && !formatStr.contains("0")) {
           formatStr = formatStr.replaceAll("#", "");
       }
       
        // See if we already have it cached
        Format format = formats.get(formatStr);
        if (format != null) {
            return format;
        }
        
        // Is it one of the special built in types, General or @?
        if ("General".equalsIgnoreCase(formatStr) || "@".equals(formatStr)) {
            return generalNumberFormat;
        }
        
        // Build a formatter, and cache it
        format = createFormat(cellValue, formatIndex, formatStr);
        formats.put(formatStr, format);
        return format;
    }

    /**
     * Create and return a Format based on the format string from a  cell's
     * style. If the pattern cannot be parsed, return a default pattern.
     *
     * @param cell The Excel cell
     * @return A Format representing the excel format. May return null.
     */
    public Format createFormat(Cell cell) {

        int formatIndex = cell.getCellStyle().getDataFormat();
        String formatStr = cell.getCellStyle().getDataFormatString();
        return createFormat(cell.getNumericCellValue(), formatIndex, formatStr);
    }

    private Format createFormat(double cellValue, int formatIndex, String sFormat) {
        localeChangedObservable.checkForLocaleChange();
        
        String formatStr = sFormat;
        
        // Remove colour formatting if present
        Matcher colourM = colorPattern.matcher(formatStr);
        while(colourM.find()) {
           String colour = colourM.group();
           
           // Paranoid replacement...
           int at = formatStr.indexOf(colour);
           if(at == -1) break;
           String nFormatStr = formatStr.substring(0,at) +
              formatStr.substring(at+colour.length());
           if(nFormatStr.equals(formatStr)) break;

           // Try again in case there's multiple
           formatStr = nFormatStr;
           colourM = colorPattern.matcher(formatStr);
        }

        // Strip off the locale information, we use an instance-wide locale for everything
        Matcher m = localePatternGroup.matcher(formatStr);
        while(m.find()) {
            String match = m.group();
            String symbol = match.substring(match.indexOf('$') + 1, match.indexOf('-'));
            if (symbol.indexOf('$') > -1) {
                symbol = symbol.substring(0, symbol.indexOf('$')) +
                        '\\' +
                        symbol.substring(symbol.indexOf('$'), symbol.length());
            }
            formatStr = m.replaceAll(symbol);
            m = localePatternGroup.matcher(formatStr);
        }

        // Check for special cases
        if(formatStr == null || formatStr.trim().length() == 0) {
            return getDefaultFormat(cellValue);
        }
        
        if ("General".equalsIgnoreCase(formatStr) || "@".equals(formatStr)) {
           return generalNumberFormat;
        }

        if(DateUtil.isADateFormat(formatIndex,formatStr) &&
                DateUtil.isValidExcelDate(cellValue)) {
            return createDateFormat(formatStr, cellValue);
        }
        // Excel supports fractions in format strings, which Java doesn't
        if (formatStr.contains("#/") || formatStr.contains("?/")) {
            String[] chunks = formatStr.split(";");
            for (String chunk1 : chunks) {
                String chunk = chunk1.replaceAll("\\?", "#");
                Matcher matcher = fractionStripper.matcher(chunk);
                chunk = matcher.replaceAll(" ");
                chunk = chunk.replaceAll(" +", " ");
                Matcher fractionMatcher = fractionPattern.matcher(chunk);
                //take the first match
                if (fractionMatcher.find()) {
                    String wholePart = (fractionMatcher.group(1) == null) ? "" : defaultFractionWholePartFormat;
                    return new FractionFormat(wholePart, fractionMatcher.group(3));
                }
            }
            
            // Strip custom text in quotes and escaped characters for now as it can cause performance problems in fractions.
            //String strippedFormatStr = formatStr.replaceAll("\\\\ ", " ").replaceAll("\\\\.", "").replaceAll("\"[^\"]*\"", " ").replaceAll("\\?", "#");
            //System.out.println("formatStr: "+strippedFormatStr);
            return new FractionFormat(defaultFractionWholePartFormat, defaultFractionFractionPartFormat);
        }
        
        if (numPattern.matcher(formatStr).find()) {
            return createNumberFormat(formatStr, cellValue);
        }

        if (emulateCSV) {
            return new ConstantStringFormat(cleanFormatForNumber(formatStr));
        }
        // TODO - when does this occur?
        return null;
    }
    
 
    private Format createDateFormat(String pFormatStr, double cellValue) {
        String formatStr = pFormatStr;
        formatStr = formatStr.replaceAll("\\\\-","-");
        formatStr = formatStr.replaceAll("\\\\,",",");
        formatStr = formatStr.replaceAll("\\\\\\.","."); // . is a special regexp char
        formatStr = formatStr.replaceAll("\\\\ "," ");
        formatStr = formatStr.replaceAll("\\\\/","/"); // weird: m\\/d\\/yyyy 
        formatStr = formatStr.replaceAll(";@", "");
        formatStr = formatStr.replaceAll("\"/\"", "/"); // "/" is escaped for no reason in: mm"/"dd"/"yyyy
        formatStr = formatStr.replace("\"\"", "'");	// replace Excel quoting with Java style quoting
        formatStr = formatStr.replaceAll("\\\\T","'T'"); // Quote the T is iso8601 style dates


        boolean hasAmPm = false;
        Matcher amPmMatcher = amPmPattern.matcher(formatStr);
        while (amPmMatcher.find()) {
            formatStr = amPmMatcher.replaceAll("@");
            hasAmPm = true;
            amPmMatcher = amPmPattern.matcher(formatStr);
        }
        formatStr = formatStr.replaceAll("@", "a");


        Matcher dateMatcher = daysAsText.matcher(formatStr);
        if (dateMatcher.find()) {
            String match = dateMatcher.group(0).toUpperCase(Locale.ROOT).replaceAll("D", "E");
            formatStr = dateMatcher.replaceAll(match);
        }

        // Convert excel date format to SimpleDateFormat.
        // Excel uses lower and upper case 'm' for both minutes and months.
        // From Excel help:
        /*
            The "m" or "mm" code must appear immediately after the "h" or"hh"
            code or immediately before the "ss" code; otherwise, Microsoft
            Excel displays the month instead of minutes."
          */

        StringBuilder sb = new StringBuilder();
        char[] chars = formatStr.toCharArray();
        boolean mIsMonth = true;
        List<Integer> ms = new ArrayList<Integer>();
        boolean isElapsed = false;
        for(int j=0; j<chars.length; j++) {
            char c = chars[j];
            if (c == '\'') {
                sb.append(c);
                j++;

                // skip until the next quote
                while(j<chars.length) {
                    c = chars[j];
                    sb.append(c);
                    if(c == '\'') {
                        break;
                    }
                    j++;
                }
            }
            else if (c == '[' && !isElapsed) {
                isElapsed = true;
                mIsMonth = false;
                sb.append(c);
            }
            else if (c == ']' && isElapsed) {
                isElapsed = false;
                sb.append(c);
            }
            else if (isElapsed) {
            if (c == 'h' || c == 'H') {
                    sb.append('H');
                }
                else if (c == 'm' || c == 'M') {
                    sb.append('m');
                }
                else if (c == 's' || c == 'S') {
                    sb.append('s');
                }
                else {
                    sb.append(c);
                }
            }
            else if (c == 'h' || c == 'H') {
                mIsMonth = false;
                if (hasAmPm) {
                    sb.append('h');
                } else {
                    sb.append('H');
                }
            }
            else if (c == 'm' || c == 'M') {
                if(mIsMonth) {
                    sb.append('M');
                    ms.add(
                            Integer.valueOf(sb.length() -1)
                    );
                } else {
                    sb.append('m');
                }
            }
            else if (c == 's' || c == 'S') {
                sb.append('s');
                // if 'M' precedes 's' it should be minutes ('m')
                for (int index : ms) {
                    if (sb.charAt(index) == 'M') {
                        sb.replace(index, index + 1, "m");
                    }
                }
                mIsMonth = true;
                ms.clear();
            }
            else if (Character.isLetter(c)) {
                mIsMonth = true;
                ms.clear();
                if (c == 'y' || c == 'Y') {
                    sb.append('y');
                }
                else if (c == 'd' || c == 'D') {
                    sb.append('d');
                }
                else {
                    sb.append(c);
                }
            }
            else {
                sb.append(c);
            }
        }
        formatStr = sb.toString();

        try {
            return new ExcelStyleDateFormatter(formatStr, dateSymbols);
        } catch(IllegalArgumentException iae) {

            // the pattern could not be parsed correctly,
            // so fall back to the default number format
            return getDefaultFormat(cellValue);
        }

    }

    private String cleanFormatForNumber(String formatStr) {
        StringBuilder sb = new StringBuilder(formatStr);

        if (emulateCSV) {
            // Requested spacers with "_" are replaced by a single space.
            // Full-column-width padding "*" are removed.
            // Not processing fractions at this time. Replace ? with space.
            // This matches CSV output.
            for (int i = 0; i < sb.length(); i++) {
                char c = sb.charAt(i);
                if (c == '_' || c == '*' || c == '?') {
                    if (i > 0 && sb.charAt((i - 1)) == '\\') {
                        // It's escaped, don't worry
                        continue;
                    }
                    if (c == '?') {
                        sb.setCharAt(i, ' ');
                    } else if (i < sb.length() - 1) {
                        // Remove the character we're supposed
                        //  to match the space of / pad to the
                        //  column width with
                        if (c == '_') {
                            sb.setCharAt(i + 1, ' ');
                        } else {
                            sb.deleteCharAt(i + 1);
                        }
                        // Remove the character too
                        sb.deleteCharAt(i);
                        i--;
                    }
                }
            }
        } else {
            // If they requested spacers, with "_",
            //  remove those as we don't do spacing
            // If they requested full-column-width
            //  padding, with "*", remove those too
            for (int i = 0; i < sb.length(); i++) {
                char c = sb.charAt(i);
                if (c == '_' || c == '*') {
                    if (i > 0 && sb.charAt((i - 1)) == '\\') {
                        // It's escaped, don't worry
                        continue;
                    }
                    if (i < sb.length() - 1) {
                        // Remove the character we're supposed
                        //  to match the space of / pad to the
                        //  column width with
                        sb.deleteCharAt(i + 1);
                    }
                    // Remove the _ too
                    sb.deleteCharAt(i);
                    i--;
                }
            }
        }

        // Now, handle the other aspects like 
        //  quoting and scientific notation
        for(int i = 0; i < sb.length(); i++) {
           char c = sb.charAt(i);
            // remove quotes and back slashes
            if (c == '\\' || c == '"') {
                sb.deleteCharAt(i);
                i--;

            // for scientific/engineering notation
            } else if (c == '+' && i > 0 && sb.charAt(i - 1) == 'E') {
                sb.deleteCharAt(i);
                i--;
            }
        }

        return sb.toString();
    }

    private Format createNumberFormat(String formatStr, double cellValue) {
        String format = cleanFormatForNumber(formatStr);
        DecimalFormatSymbols symbols = decimalSymbols;
        
        // Do we need to change the grouping character?
        // eg for a format like #'##0 which wants 12'345 not 12,345
        Matcher agm = alternateGrouping.matcher(format);
        if (agm.find()) {
            char grouping = agm.group(2).charAt(0);
            // Only replace the grouping character if it is not the default
            // grouping character for the US locale (',') in order to enable
            // correct grouping for non-US locales.
            if (grouping!=',') {
                symbols = DecimalFormatSymbols.getInstance(locale);

                symbols.setGroupingSeparator(grouping);
                String oldPart = agm.group(1);
                String newPart = oldPart.replace(grouping, ',');
                format = format.replace(oldPart, newPart);
            }
        }
        
        try {
            DecimalFormat df = new DecimalFormat(format, symbols);
            setExcelStyleRoundingMode(df);
            return df;
        } catch(IllegalArgumentException iae) {

            // the pattern could not be parsed correctly,
            // so fall back to the default number format
            return getDefaultFormat(cellValue);
        }
    }

    /**
     * Returns a default format for a cell.
     * @param cell The cell
     * @return a default format
     */
    public Format getDefaultFormat(Cell cell) {
        return getDefaultFormat(cell.getNumericCellValue());
    }
    private Format getDefaultFormat(double cellValue) {
        localeChangedObservable.checkForLocaleChange();
        
        // for numeric cells try user supplied default
        if (defaultNumFormat != null) {
            return defaultNumFormat;

          // otherwise use general format
        }
        return generalNumberFormat;
    }
    
    /**
     * Performs Excel-style date formatting, using the
     *  supplied Date and format
     */
    private String performDateFormatting(Date d, Format dateFormat) {
       return (dateFormat != null ? dateFormat : defaultDateformat).format(d);
    }

    /**
     * Returns the formatted value of an Excel date as a <tt>String</tt> based
     * on the cell's <code>DataFormat</code>. i.e. "Thursday, January 02, 2003"
     * , "01/02/2003" , "02-Jan" , etc.
     *
     * @param cell The cell
     * @return a formatted date string
     */
    private String getFormattedDateString(Cell cell) {
        Format dateFormat = getFormat(cell);
        if(dateFormat instanceof ExcelStyleDateFormatter) {
           // Hint about the raw excel value
           ((ExcelStyleDateFormatter)dateFormat).setDateToBeFormatted(
                 cell.getNumericCellValue()
           );
        }
        Date d = cell.getDateCellValue();
        return performDateFormatting(d, dateFormat);
    }

    /**
     * Returns the formatted value of an Excel number as a <tt>String</tt>
     * based on the cell's <code>DataFormat</code>. Supported formats include
     * currency, percents, decimals, phone number, SSN, etc.:
     * "61.54%", "$100.00", "(800) 555-1234".
     *
     * @param cell The cell
     * @return a formatted number string
     */
    private String getFormattedNumberString(Cell cell) {

        Format numberFormat = getFormat(cell);
        double d = cell.getNumericCellValue();
        if (numberFormat == null) {
            return String.valueOf(d);
        }
        String formatted = numberFormat.format(new Double(d));
        return formatted.replaceFirst("E(\\d)", "E+$1"); // to match Excel's E-notation
    }

    /**
     * Formats the given raw cell value, based on the supplied
     *  format index and string, according to excel style rules.
     * @see #formatCellValue(Cell)
     */
    public String formatRawCellContents(double value, int formatIndex, String formatString) {
        return formatRawCellContents(value, formatIndex, formatString, false);
    }
    /**
     * Formats the given raw cell value, based on the supplied
     *  format index and string, according to excel style rules.
     * @see #formatCellValue(Cell)
     */
    public String formatRawCellContents(double value, int formatIndex, String formatString, boolean use1904Windowing) {
        localeChangedObservable.checkForLocaleChange();
        
        // Is it a date?
        if(DateUtil.isADateFormat(formatIndex,formatString)) {
            if(DateUtil.isValidExcelDate(value)) {
                Format dateFormat = getFormat(value, formatIndex, formatString);
                if(dateFormat instanceof ExcelStyleDateFormatter) {
                    // Hint about the raw excel value
                    ((ExcelStyleDateFormatter)dateFormat).setDateToBeFormatted(value);
                }
                Date d = DateUtil.getJavaDate(value, use1904Windowing);
                return performDateFormatting(d, dateFormat);
            }
            // RK: Invalid dates are 255 #s.
            if (emulateCSV) {
                return invalidDateTimeString;
            }
        }
        
        // else Number
        Format numberFormat = getFormat(value, formatIndex, formatString);
        if (numberFormat == null) {
            return String.valueOf(value);
        }
        
        // When formatting 'value', double to text to BigDecimal produces more
        // accurate results than double to Double in JDK8 (as compared to
        // previous versions). However, if the value contains E notation, this
        // would expand the values, which we do not want, so revert to
        // original method.
        String result;
        final String textValue = NumberToTextConverter.toText(value);
        if (textValue.indexOf('E') > -1) {
            result = numberFormat.format(new Double(value));
        }
        else {
            result = numberFormat.format(new BigDecimal(textValue));
        }
        // Complete scientific notation by adding the missing +.
        if (result.indexOf('E') > -1 && !result.contains("E-")) {
            result = result.replaceFirst("E", "E+");
        }
        return result;
    }

    /**
     * <p>
     * Returns the formatted value of a cell as a <tt>String</tt> regardless
     * of the cell type. If the Excel format pattern cannot be parsed then the
     * cell value will be formatted using a default format.
     * </p>
     * <p>When passed a null or blank cell, this method will return an empty
     * String (""). Formulas in formula type cells will not be evaluated.
     * </p>
     *
     * @param cell The cell
     * @return the formatted cell value as a String
     */
    public String formatCellValue(Cell cell) {
        return formatCellValue(cell, null);
    }

    /**
     * <p>
     * Returns the formatted value of a cell as a <tt>String</tt> regardless
     * of the cell type. If the Excel format pattern cannot be parsed then the
     * cell value will be formatted using a default format.
     * </p>
     * <p>When passed a null or blank cell, this method will return an empty
     * String (""). Formula cells will be evaluated using the given
     * {@link FormulaEvaluator} if the evaluator is non-null. If the
     * evaluator is null, then the formula String will be returned. The caller
     * is responsible for setting the currentRow on the evaluator
     *</p>
     *
     * @param cell The cell (can be null)
     * @param evaluator The FormulaEvaluator (can be null)
     * @return a string value of the cell
     */
    public String formatCellValue(Cell cell, FormulaEvaluator evaluator) {
        localeChangedObservable.checkForLocaleChange();
        
        if (cell == null) {
            return "";
        }

        CellType cellType = cell.getCellTypeEnum();
        if (cellType == CellType.FORMULA) {
            if (evaluator == null) {
                return cell.getCellFormula();
            }
            cellType = evaluator.evaluateFormulaCellEnum(cell);
        }
        switch (cellType) {
            case NUMERIC :

                if (DateUtil.isCellDateFormatted(cell)) {
                    return getFormattedDateString(cell);
                }
                return getFormattedNumberString(cell);

            case STRING :
                return cell.getRichStringCellValue().getString();

            case BOOLEAN :
                return String.valueOf(cell.getBooleanCellValue());
            case BLANK :
                return "";
            case ERROR:
                return FormulaError.forInt(cell.getErrorCellValue()).getString();
            default:
                throw new RuntimeException("Unexpected celltype (" + cellType + ")");
        }
    }


    /**
     * <p>
     * Sets a default number format to be used when the Excel format cannot be
     * parsed successfully. <b>Note:</b> This is a fall back for when an error
     * occurs while parsing an Excel number format pattern. This will not
     * affect cells with the <em>General</em> format.
     * </p>
     * <p>
     * The value that will be passed to the Format's format method (specified
     * by <code>java.text.Format#format</code>) will be a double value from a
     * numeric cell. Therefore the code in the format method should expect a
     * <code>Number</code> value.
     * </p>
     *
     * @param format A Format instance to be used as a default
     * @see java.text.Format#format
     */
    public void setDefaultNumberFormat(Format format) {
        for (Map.Entry<String, Format> entry : formats.entrySet()) {
            if (entry.getValue() == generalNumberFormat) {
                entry.setValue(format);
            }
        }
        defaultNumFormat = format;
    }

    /**
     * Adds a new format to the available formats.
     * <p>
     * The value that will be passed to the Format's format method (specified
     * by <code>java.text.Format#format</code>) will be a double value from a
     * numeric cell. Therefore the code in the format method should expect a
     * <code>Number</code> value.
     * </p>
     * @param excelFormatStr The data format string
     * @param format A Format instance
     */
    public void addFormat(String excelFormatStr, Format format) {
        formats.put(excelFormatStr, format);
    }

    // Some custom formats

    /**
     * @return a <tt>DecimalFormat</tt> with parseIntegerOnly set <code>true</code>
     */
    private static DecimalFormat createIntegerOnlyFormat(String fmt) {
        DecimalFormatSymbols dsf = DecimalFormatSymbols.getInstance(Locale.ROOT);
        DecimalFormat result = new DecimalFormat(fmt, dsf);
        result.setParseIntegerOnly(true);
        return result;
    }
    
    /**
     * Enables excel style rounding mode (round half up) on the 
     *  Decimal Format given.
     */
    public static void setExcelStyleRoundingMode(DecimalFormat format) {
        setExcelStyleRoundingMode(format, RoundingMode.HALF_UP);
    }

    /**
     * Enables custom rounding mode on the given Decimal Format.
     * @param format DecimalFormat
     * @param roundingMode RoundingMode
     */
    public static void setExcelStyleRoundingMode(DecimalFormat format, RoundingMode roundingMode) {
       format.setRoundingMode(roundingMode);
    }

    /**
     * If the Locale has been changed via {@link LocaleUtil#setUserLocale(Locale)} the stored
     * formats need to be refreshed. All formats which aren't originated from DataFormatter
     * itself, i.e. all Formats added via {@link DataFormatter#addFormat(String, Format)} and
     * {@link DataFormatter#setDefaultNumberFormat(Format)}, need to be added again.
     * To notify callers, the returned {@link Observable} should be used.
     * The Object in {@link Observer#update(Observable, Object)} is the new Locale.
     *
     * @return the listener object, where callers can register themselves
     */
    public Observable getLocaleChangedObservable() {
        return localeChangedObservable;
    }

    /**
     * Update formats when locale has been changed
     *
     * @param observable usually this is our own Observable instance
     * @param localeObj only reacts on Locale objects
     */
    public void update(Observable observable, Object localeObj) {
        if (!(localeObj instanceof Locale))  return;
        Locale newLocale = (Locale)localeObj;
        if (!localeIsAdapting || newLocale.equals(locale)) return;
        
        locale = newLocale;
        
        dateSymbols = DateFormatSymbols.getInstance(locale);
        decimalSymbols = DecimalFormatSymbols.getInstance(locale);
        generalNumberFormat = new ExcelGeneralNumberFormat(locale);

        // taken from Date.toString()
        defaultDateformat = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy", dateSymbols);
        defaultDateformat.setTimeZone(LocaleUtil.getUserTimeZone());       

        // init built-in formats

        formats.clear();
        Format zipFormat = ZipPlusFourFormat.instance;
        addFormat("00000\\-0000", zipFormat);
        addFormat("00000-0000", zipFormat);

        Format phoneFormat = PhoneFormat.instance;
        // allow for format string variations
        addFormat("[<=9999999]###\\-####;\\(###\\)\\ ###\\-####", phoneFormat);
        addFormat("[<=9999999]###-####;(###) ###-####", phoneFormat);
        addFormat("###\\-####;\\(###\\)\\ ###\\-####", phoneFormat);
        addFormat("###-####;(###) ###-####", phoneFormat);

        Format ssnFormat = SSNFormat.instance;
        addFormat("000\\-00\\-0000", ssnFormat);
        addFormat("000-00-0000", ssnFormat);
    }


    /**
     * Format class for Excel's SSN format. This class mimics Excel's built-in
     * SSN formatting.
     *
     * @author James May
     */
    @SuppressWarnings("serial")
   private static final class SSNFormat extends Format {
        public static final Format instance = new SSNFormat();
        private static final DecimalFormat df = createIntegerOnlyFormat("000000000");
        private SSNFormat() {
            // enforce singleton
        }

        /** Format a number as an SSN */
        public static String format(Number num) {
            String result = df.format(num);
            return result.substring(0, 3) + '-' +
                    result.substring(3, 5) + '-' +
                    result.substring(5, 9);
        }

        @Override
        public StringBuffer format(Object obj, StringBuffer toAppendTo, FieldPosition pos) {
            return toAppendTo.append(format((Number)obj));
        }

        @Override
        public Object parseObject(String source, ParsePosition pos) {
            return df.parseObject(source, pos);
        }
    }

    /**
     * Format class for Excel Zip + 4 format. This class mimics Excel's
     * built-in formatting for Zip + 4.
     * @author James May
     */
    @SuppressWarnings("serial")
   private static final class ZipPlusFourFormat extends Format {
        public static final Format instance = new ZipPlusFourFormat();
        private static final DecimalFormat df = createIntegerOnlyFormat("000000000");
        private ZipPlusFourFormat() {
            // enforce singleton
        }

        /** Format a number as Zip + 4 */
        public static String format(Number num) {
            String result = df.format(num);
            return result.substring(0, 5) + '-' +
                    result.substring(5, 9);
        }

        @Override
        public StringBuffer format(Object obj, StringBuffer toAppendTo, FieldPosition pos) {
            return toAppendTo.append(format((Number)obj));
        }

        @Override
        public Object parseObject(String source, ParsePosition pos) {
            return df.parseObject(source, pos);
        }
    }

    /**
     * Format class for Excel phone number format. This class mimics Excel's
     * built-in phone number formatting.
     * @author James May
     */
    @SuppressWarnings("serial")
   private static final class PhoneFormat extends Format {
        public static final Format instance = new PhoneFormat();
        private static final DecimalFormat df = createIntegerOnlyFormat("##########");
        private PhoneFormat() {
            // enforce singleton
        }

        /** Format a number as a phone number */
        public static String format(Number num) {
            String result = df.format(num);
            StringBuilder sb = new StringBuilder();
            String seg1, seg2, seg3;
            int len = result.length();
            if (len <= 4) {
                return result;
            }

            seg3 = result.substring(len - 4, len);
            seg2 = result.substring(Math.max(0, len - 7), len - 4);
            seg1 = result.substring(Math.max(0, len - 10), Math.max(0, len - 7));

            if(seg1.trim().length() > 0) {
                sb.append('(').append(seg1).append(") ");
            }
            if(seg2.trim().length() > 0) {
                sb.append(seg2).append('-');
            }
            sb.append(seg3);
            return sb.toString();
        }

        @Override
        public StringBuffer format(Object obj, StringBuffer toAppendTo, FieldPosition pos) {
            return toAppendTo.append(format((Number)obj));
        }

        @Override
        public Object parseObject(String source, ParsePosition pos) {
            return df.parseObject(source, pos);
        }
    }
    

    /**
     * Format class that does nothing and always returns a constant string.
     *
     * This format is used to simulate Excel's handling of a format string
     * of all # when the value is 0. Excel will output "", Java will output "0".
     *
     * @see DataFormatter#createFormat(double, int, String)
     */
    @SuppressWarnings("serial")
   private static final class ConstantStringFormat extends Format {
        private static final DecimalFormat df = createIntegerOnlyFormat("##########");
        private final String str;
        public ConstantStringFormat(String s) {
            str = s;
        }

        @Override
        public StringBuffer format(Object obj, StringBuffer toAppendTo, FieldPosition pos) {
            return toAppendTo.append(str);
        }

        @Override
        public Object parseObject(String source, ParsePosition pos) {
            return df.parseObject(source, pos);
        }
    }
    /**
     * Workaround until we merge {@link DataFormatter} with {@link CellFormat}.
     * Constant, non-cachable wrapper around a {@link CellFormatResult} 
     */
    @SuppressWarnings("serial")
    private final class CellFormatResultWrapper extends Format {
        private final CellFormatResult result;
        private CellFormatResultWrapper(CellFormatResult result) {
            this.result = result;
        }
        public StringBuffer format(Object obj, StringBuffer toAppendTo, FieldPosition pos) {
            if (emulateCSV) {
                return toAppendTo.append(result.text);
            } else {
                return toAppendTo.append(result.text.trim());
            }
        }
        public Object parseObject(String source, ParsePosition pos) {
            return null; // Not supported
        }
    }
}