#!/usr/bin/python2.5

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"""This module contains the Question Model."""

__authors__ = [

  '"Todd Larsen" <tlarsen@google.com>',

]

from google.appengine.ext import db

import soc.models.work

class Question(soc.models.work.Work):

  """Model of a Question, which is a specialized form of Work.

  Specific types of Questions are actually implemented in subclasses.

  The specific way that the properties and relations inherited from

  Work are used with a Question are described below.

    work.title:  the title of the Question, used for finding the

      Question in a list of Questions

    work.author:  the author of the Work referred to by this relation

      is the original author of the actual Question, regardless of

      which Quizzes might incorporate the Question

    work.reviews:  even Questions can be "reviewed" (possibly commented

      on during creation or annotated once put into use).

    work.content:  the Question text, asked to the respondent

    linkable.scope:  used to scope (and, when combined with

      linkable.link_id, uniquely identify) a Question in the same way the

      property are used with Documents, etc.

    linkable.link_id:  used to identify (and, when combined with

      linkable.scope, *uniquely* identify) a Question in the same way

      these properties are used with Documents, etc.

  In addition to any explicit ReferenceProperties in the Question Model

  and those inherited as described above, a Question entity participates

  in these relationships:

    answers)  a 1:many relationship, where each Question has many different

      Answers associated with it as parts of Responses to Quizzes.  This is

      implemented as the 'answers' back-reference Query of the Answer model

      'question' reference.  It is currently unclear how useful this

      back-reference will be, since the same Question could be used in

      multiple different Quizzes. Given this, 'answers' currently only

      exists for completeness.

    quizzes)  a many:many relationship between Questions and the Quizzes

      that collect them into a set.  This relation is not explicitly

      implemented, but can be obtained via a query something like:

        quizzes_with_a_question = db.GqlQuery(

            "SELECT * FROM Quiz where questions = :1",

            a_question.key())

      Such queries are probably only needed when a Question might be

      altered, in order to find which Quizzes will be affected.

  The properties in this Model do not have verbose_name or help_text,

  because the dynamic nature of the forms required to create, edit, and

  use entities of this Model make them pretty useless.

  ######################################################################

  # TODO(tlarsen): the following verbose comments can be removed later,

    when these ideas are implemented in the views and controllers; they

    are here now so that the concepts will not be lost before that time.

  The recommended use for the combination of linkable.scope and

  linkable.link_id is to keep the *same* link_id when copying and

  modifying an existing Question for a new Program (or instance of a

  Group that is per-Program), while changing the linkable.scope to

  represent the Program and Group "ownership" of the Question.  For

  example, if a Question asking about prior GSoC participation needed

  to have an additional choice (see the choice_ids and choices properties

  below), it is desirable to keep the same linkable.link_id (and also

  simply append new choice_ids and choices to keep the old answer values

  compatible).  An existing Question in the above example might be identified

  as something like:

    Question:google/gsoc2009/gsoc_past_participation

    <type>:<Sponsor>/<Program>/<link_id> 

  To make it possible to query for gsoc_past_participation answers regardless

  of the Program, the next year, new values are added to choice_ids and

  choices in a new Question copied from the one above, which would then

  be named something (still unique) like:

    Question:google/gsoc2010/gsoc_past_participation

  Care just needs to be taken to keep the existing choice_ids and choices

  compatible.

  Other interesting possibilities also exist, such as asking about GSoC

  participation of the GHOP participants (some GHOP high school students

  have actually previously been GSoC mentors, for example).  To produce

  unique statistics for GHOP that could also be aggregated overall in

  combination with GSoC, the gsoc_past_participation Question would be

  duplicated (unaltered) to something like:

    Question:google/ghop2009/gsoc_past_participation

  To get the combined results, query on a link_id of

  gsoc_past_participation.  For more targeted results, include the

  scope to make the query more specific.

  Question creation to permit use cases like the one above is going to

  be a bit of an "advanced" skill, possibly.  "Doing it wrong" the first

  time a Question is created will make it difficult to implement stuff

  like multiple-choice Questions that "grow" new choices year-over-year.

  A dynamic form is most definitely going to be needed to implement the

  Question creation and editing for multiple-choice questions.

  """

  #: db.ListProperty of short, plain-text, "link_id-like" strings

  #: representing the "encoded" answer choices (must be strings compatible

  #: with being query arguments and being used in HTML controls and POST

  #: responses).

  #:

  #: If empty (None or an empty list), it is assumed that this Question

  #: is *not* a multiple choice question.  In that case, the UI should

  #: display the Question as a textarea in forms and accept any plain-text.

  #:

  #: If non-empty, max_answers helps determine how the UI should display

  #: the Question.  Also, controller logic needs to validate if the

  #: strings in the 'answers' property of the Answer entity come only

  #: from this list.

  #:

  #: Once Answers to this Question have been stored in the Datastore,

  #: choice_ids and choices should *not* be modified.  An existing

  #: Question can be duplicated and then modified (but, it will be a

  #: different question as a result).

  choice_ids = db.ListProperty(item_type=str)

  #: db.ListProperty of human-readable choice strings, in the same order

  #: as, and corresponding to, the "encoded" choices in the choice_ids

  #: db.ListProperty. 

  choices = db.ListProperty(item_type=str)

  #: db.IntegerProperty indicating the maximum number of answer values

  #: permitted for this question.  If 'choices' does not contain a list of

  #: choice strings, this value is ignored (but should still only be 1).

  #:

  #: If there are 'choices' and this value is 1, the UI should render the

  #: Question in forms as a single-choice control ("radio buttons").

  #:

  #: If there are 'choices' and this value is greater than 1, the UI should

  #: render the question as a list of check-boxes.

  #:

  #: max_answers greater than 1 combined with choices enables Questions

  #: like, for example, "...select the three most important...".

  max_answers = db.IntegerProperty(default=1)

  #: field storing whether the Answer to a Question is optional

  is_optional = db.BooleanProperty(default=False)