# 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.
import functools


def def_method(f, *args, **kwargs):
    @functools.wraps(f)
    def new_method(self):
        return f(self, *args, **kwargs)

    return new_method


def parameterized_class(cls):
    """A class decorator for running parameterized test cases.
    Mark your class with @parameterized_class.
    Mark your test cases with @parameterized.
    """
    test_functions = {
        k: v for k, v in vars(cls).items() if k.startswith('test')
    }
    for name, f in test_functions.items():
        if not hasattr(f, '_test_data'):
            continue

        # remove the original test function from the class
        delattr(cls, name)

        # add a new test function to the class for each entry in f._test_data
        for tag, args in f._test_data.items():
            new_name = "{0}_{1}".format(f.__name__, tag)
            if hasattr(cls, new_name):
                raise Exception(
                    "Parameterized test case '{0}.{1}' created from '{0}.{2}' "
                    "already exists".format(cls.__name__, new_name, name))

            # Using `def new_method(self): f(self, **args)` is not sufficient
            # (all new_methods use the same args value due to late binding).
            # Instead, use this factory function.
            new_method = def_method(f, **args)

            # To add a method to a class, available for all instances:
            #   MyClass.method = types.MethodType(f, None, MyClass)
            setattr(cls, new_name, new_method)
    return cls


def parameterized(data):
    """A function decorator for parameterized test cases.
    Example:
        @parameterized({
            'zero': dict(val=0),
            'one': dict(val=1),
        })
        def test_val(self, val):
            self.assertEqual(self.get_val(), val)
    The above will generate two test cases:
        `test_val_zero` which runs with val=0
        `test_val_one` which runs with val=1
    :param data: A dictionary that looks like {tag: {arg1: val1, ...}}
    """

    def wrapped(f):
        f._test_data = data
        return f

    return wrapped
