#=======================================================================
#
#   Python Lexical Analyser
#
#   Actions for use in token specifications
#
#=======================================================================

class Action:

  def same_as(self, other):
    return self is other


class Return(Action):
  """
  Internal Plex action which causes |value| to
  be returned as the value of the associated token
  """

  value = None

  def __init__(self, value):
    self.value = value

  def perform(self, token_stream, text):
    return self.value

  def same_as(self, other):
    return isinstance(other, Return) and self.value == other.value

  def __repr__(self):
    return "Return(%s)" % repr(self.value)


class Call(Action):
  """
  Internal Plex action which causes a function to be called.
  """

  function = None

  def __init__(self, function):
    self.function = function

  def perform(self, token_stream, text):
    return self.function(token_stream, text)

  def __repr__(self):
    return "Call(%s)" % self.function.__name__

  def same_as(self, other):
    return isinstance(other, Call) and self.function is other.function


class Begin(Action):
  """
  Begin(state_name) is a Plex action which causes the Scanner to
  enter the state |state_name|. See the docstring of Plex.Lexicon 
  for more information.
  """

  state_name = None

  def __init__(self, state_name):
    self.state_name = state_name

  def perform(self, token_stream, text):
    token_stream.begin(self.state_name)

  def __repr__(self):
    return "Begin(%s)" % self.state_name

  def same_as(self, other):
    return isinstance(other, Begin) and self.state_name == other.state_name


class Ignore(Action):
  """
  IGNORE is a Plex action which causes its associated token
  to be ignored. See the docstring of Plex.Lexicon  for more 
  information.
  """
  def perform(self, token_stream, text):
    return None

  def __repr__(self):
    return "IGNORE"

IGNORE = Ignore()
IGNORE.__doc__ = Ignore.__doc__

class Text(Action):
  """
  TEXT is a Plex action which causes the text of a token to
  be returned as the value of the token. See the docstring of 
  Plex.Lexicon  for more information.
  """

  def perform(self, token_stream, text):
    return text

  def __repr__(self):
    return "TEXT"

TEXT = Text()
TEXT.__doc__ = Text.__doc__


