# -*- coding: utf-8 -*-

# test/scaffold.py
# Part of ‘python-daemon’, an implementation of PEP 3143.
#
# Copyright © 2007–2016 Ben Finney <ben+python@benfinney.id.au>
#
# This is free software: you may copy, modify, and/or distribute this work
# under the terms of the Apache License, version 2.0 as published by the
# Apache Software Foundation.
# No warranty expressed or implied. See the file ‘LICENSE.ASF-2’ for details.

""" Scaffolding for unit test modules.
    """

from __future__ import (absolute_import, unicode_literals)

import unittest
import doctest
import logging
import os
import sys
import operator
import textwrap
from copy import deepcopy
import functools

try:
    # Python 2 has both ‘str’ (bytes) and ‘unicode’ (text).
    basestring = basestring
    unicode = unicode
except NameError:
    # Python 3 names the Unicode data type ‘str’.
    basestring = str
    unicode = str

import testscenarios
import testtools.testcase


# Disable all but the most critical logging messages.
logging.disable(logging.CRITICAL)


def get_function_signature(func):
    """ Get the function signature as a mapping of attributes.

        :param func: The function object to interrogate.
        :return: A mapping of the components of a function signature.

        The signature is constructed as a mapping:

        * 'name': The function's defined name.
        * 'arg_count': The number of arguments expected by the function.
        * 'arg_names': A sequence of the argument names, as strings.
        * 'arg_defaults': A sequence of the default values for the arguments.
        * 'var_args': The name bound to remaining positional arguments.
        * 'var_kw_args': The name bound to remaining keyword arguments.

        """
    try:
        # Python 3 function attributes.
        func_code = func.__code__
        func_defaults = func.__defaults__
    except AttributeError:
        # Python 2 function attributes.
        func_code = func.func_code
        func_defaults = func.func_defaults

    arg_count = func_code.co_argcount
    arg_names = func_code.co_varnames[:arg_count]

    arg_defaults = {}
    if func_defaults is not None:
        arg_defaults = dict(
                (name, value)
                for (name, value) in
                    zip(arg_names[::-1], func_defaults[::-1]))

    signature = {
            'name': func.__name__,
            'arg_count': arg_count,
            'arg_names': arg_names,
            'arg_defaults': arg_defaults,
            }

    non_pos_names = list(func_code.co_varnames[arg_count:])
    COLLECTS_ARBITRARY_POSITIONAL_ARGS = 0x04
    if func_code.co_flags & COLLECTS_ARBITRARY_POSITIONAL_ARGS:
        signature['var_args'] = non_pos_names.pop(0)
    COLLECTS_ARBITRARY_KEYWORD_ARGS = 0x08
    if func_code.co_flags & COLLECTS_ARBITRARY_KEYWORD_ARGS:
        signature['var_kw_args'] = non_pos_names.pop(0)

    return signature


def format_function_signature(func):
    """ Format the function signature as printable text.

        :param func: The function object to interrogate.
        :return: A formatted text representation of the function signature.

        The signature is rendered a text; for example::

            foo(spam, eggs, ham=True, beans=None, *args, **kwargs)

        """
    signature = get_function_signature(func)

    args_text = []
    for arg_name in signature['arg_names']:
        if arg_name in signature['arg_defaults']:
            arg_text = "{name}={value!r}".format(
                    name=arg_name, value=signature['arg_defaults'][arg_name])
        else:
            arg_text = "{name}".format(
                    name=arg_name)
        args_text.append(arg_text)
    if 'var_args' in signature:
        args_text.append("*{var_args}".format(signature))
    if 'var_kw_args' in signature:
        args_text.append("**{var_kw_args}".format(signature))
    signature_args_text = ", ".join(args_text)

    func_name = signature['name']
    signature_text = "{name}({args})".format(
            name=func_name, args=signature_args_text)

    return signature_text


class TestCase(testtools.testcase.TestCase):
    """ Test case behaviour. """

    def failUnlessOutputCheckerMatch(self, want, got, msg=None):
        """ Fail unless the specified string matches the expected.

            :param want: The desired output pattern.
            :param got: The actual text to match.
            :param msg: A message to prefix on the failure message.
            :return: ``None``.
            :raises self.failureException: If the text does not match.

            Fail the test unless ``want`` matches ``got``, as determined by
            a ``doctest.OutputChecker`` instance. This is not an equality
            check, but a pattern match according to the ``OutputChecker``
            rules.

            """
        checker = doctest.OutputChecker()
        want = textwrap.dedent(want)
        source = ""
        example = doctest.Example(source, want)
        got = textwrap.dedent(got)
        checker_optionflags = functools.reduce(operator.or_, [
                doctest.ELLIPSIS,
                ])
        if not checker.check_output(want, got, checker_optionflags):
            if msg is None:
                diff = checker.output_difference(
                        example, got, checker_optionflags)
                msg = "\n".join([
                        "Output received did not match expected output",
                        "{diff}",
                        ]).format(
                            diff=diff)
            raise self.failureException(msg)

    assertOutputCheckerMatch = failUnlessOutputCheckerMatch

    def failUnlessFunctionInTraceback(self, traceback, function, msg=None):
        """ Fail if the function is not in the traceback.

            :param traceback: The traceback object to interrogate.
            :param function: The function object to match.
            :param msg: A message to prefix on the failure message.
            :return: ``None``.

            :raises self.failureException: If the function is not in the
                traceback.

            Fail the test if the function ``function`` is not at any of the
            levels in the traceback object ``traceback``.

            """
        func_in_traceback = False
        expected_code = function.func_code
        current_traceback = traceback
        while current_traceback is not None:
            if expected_code is current_traceback.tb_frame.f_code:
                func_in_traceback = True
                break
            current_traceback = current_traceback.tb_next

        if not func_in_traceback:
            if msg is None:
                msg = (
                        "Traceback did not lead to original function"
                        " {function}"
                        ).format(
                            function=function)
            raise self.failureException(msg)

    assertFunctionInTraceback = failUnlessFunctionInTraceback

    def failUnlessFunctionSignatureMatch(self, first, second, msg=None):
        """ Fail if the function signatures do not match.

            :param first: The first function to compare.
            :param second: The second function to compare.
            :param msg: A message to prefix to the failure message.
            :return: ``None``.

            :raises self.failureException: If the function signatures do
                not match.

            Fail the test if the function signature does not match between
            the ``first`` function and the ``second`` function.

            The function signature includes:

            * function name,

            * count of named parameters,

            * sequence of named parameters,

            * default values of named parameters,

            * collector for arbitrary positional arguments,

            * collector for arbitrary keyword arguments.

            """
        first_signature = get_function_signature(first)
        second_signature = get_function_signature(second)

        if first_signature != second_signature:
            if msg is None:
                first_signature_text = format_function_signature(first)
                second_signature_text = format_function_signature(second)
                msg = (textwrap.dedent("""\
                        Function signatures do not match:
                            {first!r} != {second!r}
                        Expected:
                            {first_text}
                        Got:
                            {second_text}""")
                        ).format(
                            first=first_signature,
                            first_text=first_signature_text,
                            second=second_signature,
                            second_text=second_signature_text,
                            )
            raise self.failureException(msg)

    assertFunctionSignatureMatch = failUnlessFunctionSignatureMatch


class TestCaseWithScenarios(testscenarios.WithScenarios, TestCase):
    """ Test cases run per scenario. """


class Exception_TestCase(TestCaseWithScenarios):
    """ Test cases for exception classes. """

    def test_exception_instance(self):
        """ Exception instance should be created. """
        self.assertIsNot(self.instance, None)

    def test_exception_types(self):
        """ Exception instance should match expected types. """
        for match_type in self.types:
            self.assertIsInstance(self.instance, match_type)


def make_exception_scenarios(scenarios):
    """ Make test scenarios for exception classes.

        :param scenarios: Sequence of scenarios.
        :return: List of scenarios with additional mapping entries.

        Use this with `testscenarios` to adapt `Exception_TestCase`_ for
        any exceptions that need testing.

        Each scenario is a tuple (`name`, `map`) where `map` is a mapping
        of attributes to be applied to each test case. Attributes map must
        contain items for:

            :key exc_type:
                The exception type to be tested.
            :key min_args:
                The minimum argument count for the exception instance
                initialiser.
            :key types:
                Sequence of types that should be superclasses of each
                instance of the exception type.

        """
    updated_scenarios = deepcopy(scenarios)
    for (name, scenario) in updated_scenarios:
        args = (None,) * scenario['min_args']
        scenario['args'] = args
        instance = scenario['exc_type'](*args)
        scenario['instance'] = instance

    return updated_scenarios


# Local variables:
# coding: utf-8
# mode: python
# End:
# vim: fileencoding=utf-8 filetype=python :