##
# Example 1: simulate opening and closing resources after is usage.
##
class Operation(object):
    def __init__(self):
        print('Initializing...')
        self.status = 'initial'

    def __enter__(self):
        print('Opening...')
        self.status = 'open'
        return self

    def __exit__(self, type, value, traceback):
        print('Closing...')
        self.status = 'closed'
        print('Status: {}'.format(self.status))
        # print('Type: {}'.format(type))
        # print('Traceback: {}'.format(traceback))
        # return True


with Operation() as operation:
    print('Running...')
    print('Status: {}'.format(operation.status))
    # raise NotImplementedError('foo')


##
# Example 2: imitate the TestCase.assertRaises() method.
##
class UnitTest(object):
    def assertRaises(self, exception):
        self.exception = exception
        return self

    def __enter__(self):
        return self.exception

    def __exit__(self, type, value, traceback):
        if self.exception == type:
            print('Exception mached!')
            return True
        else:
            print('Exception not mached or not raised!')
            return False


test = UnitTest()

with test.assertRaises(NotImplementedError) as error:
    raise NotImplementedError

with test.assertRaises(NotImplementedError) as error:
    print('Not raising any exception...')

##
# Example 3: try using the contextmanager decorator + generator
##
from contextlib import contextmanager


class UnitTestPlus(object):
    @contextmanager
    def assertRaises(self, exception):
        try:
            yield exception
            print('Exception not mached or not raised!')
        except exception:
            print('Exception mached!')


test = UnitTestPlus()

with test.assertRaises(NotImplementedError) as error:
    raise NotImplementedError

with test.assertRaises(NotImplementedError) as error:
    print('Not raising any exception...')