/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.frontend.xeditor.validation;
  
  import java.text.DecimalFormat;
  import java.text.DecimalFormatSymbols;
  import java.text.NumberFormat;
  import java.text.ParseException;
  import java.util.Locale;
  
  /**
   * Helper for decimal validators to convert string input into a decimal value for a given locale.
   * 
   * @author Frank L\u00FCtzenkirchen 
   */
  public class MCRDecimalConverter {
  
      private Locale locale = Locale.getDefault();
  
      public MCRDecimalConverter(String localeID) {
          this.locale = new Locale(localeID);
      }
  
      /**
       * Converts a given text string to a decimal number, using the given locale.
       * 
       * @param value the text strin
       * @return null, if the text contains illegal chars or can not be parsed
       */
      public Double string2double(String value) {
          if (hasIllegalCharacters(value)) {
              return null;
          }
  
          NumberFormat nf = NumberFormat.getNumberInstance(locale);
          if ((nf instanceof DecimalFormat) && hasMultipleDecimalSeparators(value, (DecimalFormat) nf)) {
              return null;
          }
  
          try {
              return nf.parse(value).doubleValue();
          } catch (ParseException e) {
              return null;
          }
      }
  
      private boolean hasMultipleDecimalSeparators(String string, DecimalFormat df) {
          DecimalFormatSymbols dfs = df.getDecimalFormatSymbols();
          String patternNonDecimalSeparators = "[^" + dfs.getDecimalSeparator() + "]";
          String decimalSeparatorsLeftOver = string.replaceAll(patternNonDecimalSeparators, "");
          return (decimalSeparatorsLeftOver.length() > 1);
      }
  
      private boolean hasIllegalCharacters(String string) {
          return !string.matches("[0-9,.]+");
      }
  }