# Copyright 2016 Google Inc. All Rights Reserved.
#
# 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.
"""Defines ExpressionGenerator class."""
import abc


class ExpressionGenerator:
  """Abstract base class for building snippets of code for a JavaScript engine.

  Implementations of the private abstract methods should return a C++ expression
  that will evaluate the described condition. The public methods return
  callables that take a single argument, which is the value to be tested.
  """
  __metaclass__ = abc.ABCMeta

  @abc.abstractmethod
  def is_undefined(self, arg):
    pass

  @abc.abstractmethod
  def is_undefined_or_null(self, arg):
    pass

  @abc.abstractmethod
  def is_number(self, arg):
    pass

  @abc.abstractmethod
  def inherits_interface(self, interface_name, arg):
    pass