import os
import unittest
import collections
import email
from email.message import Message
from email._policybase import compat32
from test.support import load_package_tests

landmark = __file__

# Load all tests in package
def load_tests(*args):
    return load_package_tests(os.path.dirname(__file__), *args)


# helper code used by a number of test modules.

def openfile(filename, *args, **kws):
    path = os.path.join(os.path.dirname(landmark), 'data', filename)
    return open(path, *args, **kws)


# Base test class
class TestEmailBase(unittest.TestCase):

    maxDiff = None
    # Currently the default policy is compat32.  By setting that as the default
    # here we make minimal changes in the test_email tests compared to their
    # pre-3.3 state.
    policy = compat32
    # Likewise, the default message object is Message.
    message = Message

    def __init__(self, *args, **kw):
        super().__init__(*args, **kw)
        self.addTypeEqualityFunc(bytes, self.assertBytesEqual)

    # Backward compatibility to minimize test_email test changes.
    ndiffAssertEqual = unittest.TestCase.assertEqual

    def _msgobj(self, filename):
        with openfile(filename) as fp:
            return email.message_from_file(fp, policy=self.policy)

    def _str_msg(self, string, message=None, policy=None):
        if policy is None:
            policy = self.policy
        if message is None:
            message = self.message
        return email.message_from_string(string, message, policy=policy)

    def _bytes_msg(self, bytestring, message=None, policy=None):
        if policy is None:
            policy = self.policy
        if message is None:
            message = self.message
        return email.message_from_bytes(bytestring, message, policy=policy)

    def _make_message(self):
        return self.message(policy=self.policy)

    def _bytes_repr(self, b):
        return [repr(x) for x in b.splitlines(keepends=True)]

    def assertBytesEqual(self, first, second, msg):
        """Our byte strings are really encoded strings; improve diff output"""
        self.assertEqual(self._bytes_repr(first), self._bytes_repr(second))

    def assertDefectsEqual(self, actual, expected):
        self.assertEqual(len(actual), len(expected), actual)
        for i in range(len(actual)):
            self.assertIsInstance(actual[i], expected[i],
                                    'item {}'.format(i))


def parameterize(cls):
    """A test method parameterization class decorator.

    Parameters are specified as the value of a class attribute that ends with
    the string '_params'.  Call the portion before '_params' the prefix.  Then
    a method to be parameterized must have the same prefix, the string
    '_as_', and an arbitrary suffix.

    The value of the _params attribute may be either a dictionary or a list.
    The values in the dictionary and the elements of the list may either be
    single values, or a list.  If single values, they are turned into single
    element tuples.  However derived, the resulting sequence is passed via
    *args to the parameterized test function.

    In a _params dictionary, the keys become part of the name of the generated
    tests.  In a _params list, the values in the list are converted into a
    string by joining the string values of the elements of the tuple by '_' and
    converting any blanks into '_'s, and this become part of the name.
    The  full name of a generated test is a 'test_' prefix, the portion of the
    test function name after the  '_as_' separator, plus an '_', plus the name
    derived as explained above.

    For example, if we have:

        count_params = range(2)

        def count_as_foo_arg(self, foo):
            self.assertEqual(foo+1, myfunc(foo))

    we will get parameterized test methods named:
        test_foo_arg_0
        test_foo_arg_1
        test_foo_arg_2

    Or we could have:

        example_params = {'foo': ('bar', 1), 'bing': ('bang', 2)}

        def example_as_myfunc_input(self, name, count):
            self.assertEqual(name+str(count), myfunc(name, count))

    and get:
        test_myfunc_input_foo
        test_myfunc_input_bing

    Note: if and only if the generated test name is a valid identifier can it
    be used to select the test individually from the unittest command line.

    The values in the params dict can be a single value, a tuple, or a
    dict.  If a single value of a tuple, it is passed to the test function
    as positional arguments.  If a dict, it is a passed via **kw.

    """
    paramdicts = {}
    testers = collections.defaultdict(list)
    for name, attr in cls.__dict__.items():
        if name.endswith('_params'):
            if not hasattr(attr, 'keys'):
                d = {}
                for x in attr:
                    if not hasattr(x, '__iter__'):
                        x = (x,)
                    n = '_'.join(str(v) for v in x).replace(' ', '_')
                    d[n] = x
                attr = d
            paramdicts[name[:-7] + '_as_'] = attr
        if '_as_' in name:
            testers[name.split('_as_')[0] + '_as_'].append(name)
    testfuncs = {}
    for name in paramdicts:
        if name not in testers:
            raise ValueError("No tester found for {}".format(name))
    for name in testers:
        if name not in paramdicts:
            raise ValueError("No params found for {}".format(name))
    for name, attr in cls.__dict__.items():
        for paramsname, paramsdict in paramdicts.items():
            if name.startswith(paramsname):
                testnameroot = 'test_' + name[len(paramsname):]
                for paramname, params in paramsdict.items():
                    if hasattr(params, 'keys'):
                        test = (lambda self, name=name, params=params:
                                    getattr(self, name)(**params))
                    else:
                        test = (lambda self, name=name, params=params:
                                        getattr(self, name)(*params))
                    testname = testnameroot + '_' + paramname
                    test.__name__ = testname
                    testfuncs[testname] = test
    for key, value in testfuncs.items():
        setattr(cls, key, value)
    return cls
