/**

  * Copyright 2009 Timothy Johnston Licensed 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.

  */

 package com.timjohnstondev.unitconverter.view;

 import java.util.ArrayList;

 import java.util.List;

 import java.util.ResourceBundle;

 import javax.swing.text.AttributeSet;

 import javax.swing.text.BadLocationException;

 import javax.swing.text.PlainDocument;

 /**

  * This {@code PlainDocument} subclass has several regular expressions that the text can match to be considered a valid

  * number. Basically the text can be in the form of a standard number but with no commas or in the form of scientific

  * notation (#.###e#). Only digits, e and a period are allowable characters.

  */

 final class InputFilter extends PlainDocument

 {

   private ResourceBundle resources;

   private List <Character> allowableCharacters;

   /**

    * Default constructor to load {@code ResourceBundle}

    * 

    * @param allowableChars allowableChars

    */

   InputFilter(final String allowableChars)

   {

     resources = ResourceBundle.getBundle("com.timjohnstondev.unitconverter.view.View");

     allowableCharacters = asList(allowableChars);

   }

   @Override

   public void insertString(final int offset, final String text, final AttributeSet attr) throws BadLocationException

   {

     final String oldText = getText(0, getLength());

     final String newText = removeNonNumericChars(text);

     super.insertString(offset, newText, attr);

     if (!matchesPattern(getText(0, getLength())))

     {

       super.replace(0, getLength(), oldText, attr);

     }

   }

   private String removeNonNumericChars(final String text)

   {

     String number = "";

     for (char character : text.toCharArray())

     {

       if (allowableCharacters.contains(character))

       {

         number += character;

       }

     }

     return number;

   }

   private List <Character> asList(final String characters)

   {

     final char[] chars = characters.toCharArray();

     final List <Character> list = new ArrayList <Character>();

     for (char c : chars)

     {

       list.add(new Character(c));

     }

     return list;

   }

   private boolean matchesPattern(final String text)

   {

     return text.matches(resources.getString("InputFilter.inputPatternCombined"));

   }

 }