text: #------------------------------------------------------------------------------
  # Copyright (c) 2013, Nucleic Development Team.
  #
  # Distributed under the terms of the Modified BSD License.
  #
  # The full license is in the file COPYING.txt, distributed with this software.
  #------------------------------------------------------------------------------
  import re
  
  from atom.api import Atom, Bool, Typed, Enum, Str, Str
  
  
  class Validator(Atom):
      """ The base class for creating widget text validators.
  
      This class is abstract. It's abstract api must be implemented by a
      subclass in order to be usable.
  
      """
      #: An optional message to associate with the validator. This message
      #: may be used by the toolkit to display information to the user
      #: about what went wrong.
      message = Str()
  
      def validate(self, text):
          """ Validate the text as the user types.
  
          This method is called on every keystroke to validate the text
          as the user inputs characters. It should be efficient. This is
          an abstract method which must be implemented by subclasses.
  
          Parameters
          ----------
          text : unicode
              The unicode text entered by the user.
  
          Returns
          -------
          result : bool
              True if the text is valid, False otherwise.
  
          """
          raise NotImplementedError
  
      def fixup(self, text):
          """ An optional method to fix invalid user input.
  
          This method will be called if user attempts to apply text which
          is not valid. This method may convert the text to a valid form.
          The returned text will be retested for validity. The default
          implementation of this method is a no-op.
  
          Returns
          -------
          result : unicode
              The optionally modified input text.
  
          """
          return text
  
  
  class IntValidator(Validator):
      """ A concrete Validator which handles integer input.
  
      This validator ensures that the text represents an integer within a
      specified range in a specified base.
  
      """
      #: The minimum value allowed for the int, inclusive, or None if
      #: there is no lower bound.
      minimum = Typed(int)
  
      #: The maximum value allowed for the int, inclusive, or None if
      #: there is no upper bound.
      maximum = Typed(int)
  
      #: The base in which the int is represented.
      base = Enum(10, 2, 8, 16)
  
      def validate(self, text):
          """ Validates the given text matches the integer range.
  
          Parameters
          ----------
          text : unicode
              The unicode text edited by the client widget.
  
          Returns
          -------
          result : bool
              True if the text is valid, False otherwise.
  
          """
          try:
              value = int(text, self.base)
          except ValueError:
              return False
          minimum = self.minimum
          if minimum is not None and value < minimum:
              return False
          maximum = self.maximum
          if maximum is not None and value > maximum:
              return False
          return True
  
  
  class FloatValidator(Validator):
      """ A concrete Validator which handles floating point input.
  
      This validator ensures that the text represents a floating point
      number within a specified range.
  
      """
      #: The minimum value allowed for the float, inclusive, or None if
      #: there is no lower bound.
      minimum = Typed(float)
  
      #: The maximum value allowed for the float, inclusive, or None if
      #: there is no upper bound.
      maximum = Typed(float)
  
      #: Whether or not to allow exponents like '1e6' in the input.
      allow_exponent = Bool(True)
  
      def validate(self, text):
          """ Validates the given text matches the float range.
  
          Parameters
          ----------
          text : unicode
              The unicode text edited by the client widget.
  
          Returns
          -------
          result : bool
              True if the text is valid, False otherwise.
  
          """
          try:
              value = float(text)
          except ValueError:
              return False
          minimum = self.minimum
          if minimum is not None and value < minimum:
              return False
          maximum = self.maximum
          if maximum is not None and value > maximum:
              return False
          if not self.allow_exponent and 'e' in text.lower():
              return False
          return True
  
  
  class RegexValidator(Validator):
      """ A concrete Validator which handles text input.
  
      This validator ensures that the text matches a provided regular
      expression string.
  
      """
      #: The regular expression string to use for validation. The default
      #: regex matches everything.
      regex = Str(r'.*')
  
      def validate(self, text):
          """ Validates the given text matches the regular expression.
  
          Parameters
          ----------
          text : unicode
              The unicode text edited by the client widget.
  
          Returns
          -------
          result : bool
              True if the text is valid, False otherwise.
  
          """
          return bool(re.match(self.regex, text))
  