choice.py

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

from __future__ import division

__copyright__ = "Copyright (C) 2014 Andreas Kloeckner"

__license__ = """
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
"""


import django.forms as forms
from django.utils.safestring import mark_safe

from relate.utils import StyledForm
from course.page.base import (
        AnswerFeedback, PageBaseWithTitle, PageBaseWithValue, markup_to_html)
from course.content import remove_prefix
from course.validation import validate_markup, ValidationError

import six


class ChoiceAnswerForm(StyledForm):
    def __init__(self, field, *args, **kwargs):
        super(ChoiceAnswerForm, self).__init__(*args, **kwargs)

        self.fields["choice"] = field


class ChoiceQuestion(PageBaseWithTitle, PageBaseWithValue):
    """
    A page asking the participant to choose one of multiple answers.

    .. attribute:: id

        |id-page-attr|

    .. attribute:: type

        ``ChoiceQuestion``

    .. attribute:: access_rules

        |access-rules-page-attr|

    .. attribute:: title

        |title-page-attr|

    .. attribute:: value

        |value-page-attr|

    .. attribute:: prompt

        The page's prompt, written in :ref:`markup`.

    .. attribute:: choices

        A list of choices, each in :ref:`markup`. Correct
        choices are indicated by the prefix ``~CORRECT~``.

    .. attribute:: shuffle

        Optional. ``True`` or ``False``. If true, the choices will
        be presented in random order.
    """

    CORRECT_TAG = "~CORRECT~"

    @classmethod
    def process_choice_string(cls, page_context, s):
        s = remove_prefix(cls.CORRECT_TAG, s)
        s = markup_to_html(page_context, s)
        # allow HTML in option
        s = mark_safe(s)

        return s

    def __init__(self, vctx, location, page_desc):
        super(ChoiceQuestion, self).__init__(vctx, location, page_desc)

        correct_choice_count = 0
        for choice_idx, choice in enumerate(page_desc.choices):
            if not isinstance(choice, six.string_types):
                raise ValidationError("%s, choice %d: not a string"
                        % (location, choice_idx+1))

            if choice.startswith(self.CORRECT_TAG):
                correct_choice_count += 1

            if vctx is not None:
                validate_markup(vctx, location,
                        remove_prefix(self.CORRECT_TAG, choice))

        if correct_choice_count < 1:
            raise ValidationError("%s: one or more correct answer(s) "
                    "expected, %d found" % (location, correct_choice_count))

    def required_attrs(self):
        return super(ChoiceQuestion, self).required_attrs() + (
                ("prompt", "markup"),
                ("choices", list),
                )

    def allowed_attrs(self):
        return super(ChoiceQuestion, self).allowed_attrs() + (
                ("shuffle", bool),
                )

    def markup_body_for_title(self):
        return self.page_desc.prompt

    def body(self, page_context, page_data):
        return markup_to_html(page_context, self.page_desc.prompt)

    def make_page_data(self):
        import random
        perm = range(len(self.page_desc.choices))
        if getattr(self.page_desc, "shuffle", False):
            random.shuffle(perm)

        return {"permutation": perm}

    def make_choice_form(self, page_context, page_data, *args, **kwargs):
        permutation = page_data["permutation"]

        choices = tuple(
                (i,  self.process_choice_string(
                    page_context, self.page_desc.choices[src_i]))
                for i, src_i in enumerate(permutation))

        return ChoiceAnswerForm(
            forms.TypedChoiceField(
                choices=tuple(choices),
                coerce=int,
                widget=forms.RadioSelect()),
            *args, **kwargs)

    def make_form(self, page_context, page_data,
            answer_data, answer_is_final):
        if answer_data is not None:
            form_data = {"choice": answer_data["choice"]}
            form = self.make_choice_form(page_context, page_data, form_data)
        else:
            form = self.make_choice_form(page_context, page_data)

        if answer_is_final:
            form.fields['choice'].widget.attrs['disabled'] = True

        return form

    def post_form(self, page_context, page_data, post_data, files_data):
        return self.make_choice_form(
                    page_context, page_data, post_data, files_data)

    def answer_data(self, page_context, page_data, form, files_data):
        return {"choice": form.cleaned_data["choice"]}

    def unpermuted_correct_indices(self):
        result = []
        for i, choice_text in enumerate(self.page_desc.choices):
            if choice_text.startswith(self.CORRECT_TAG):
                result.append(i)

        return result

    def grade(self, page_context, page_data, answer_data, grade_data):
        if answer_data is None:
            return AnswerFeedback(correctness=0,
                    feedback="No answer provided.",
                    normalized_answer=None)

        permutation = page_data["permutation"]
        choice = answer_data["choice"]

        if permutation[choice] in self.unpermuted_correct_indices():
            correctness = 1
        else:
            correctness = 0

        return AnswerFeedback(correctness=correctness,
                normalized_answer=self.process_choice_string(
                    page_context,
                    self.page_desc.choices[permutation[choice]]))

    def correct_answer(self, page_context, page_data, answer_data, grade_data):
        corr_idx = self.unpermuted_correct_indices()[0]
        return ("A correct answer is:%s"
                % self.process_choice_string(
                    page_context,
                    self.page_desc.choices[corr_idx]).lstrip())