added option to limit one answer per question per person

9 files changed, 68 insertions, 8 deletions

diff --git a/askbot/conf/forum_data_rules.py b/askbot/conf/forum_data_rules.py
index a26aa4b3..b7077a15 100644
--- a/askbot/conf/forum_data_rules.py
+++ b/askbot/conf/forum_data_rules.py
@@ -122,6 +122,17 @@ settings.register(
 settings.register(
     livesettings.BooleanValue(
         FORUM_DATA_RULES,
+        'LIMIT_ONE_ANSWER_PER_USER',
+        default = True,
+        description = _(
+            'Limit one answer per question per user'
+        )
+    )
+)
+
+settings.register(
+    livesettings.BooleanValue(
+        FORUM_DATA_RULES,
         'TAGS_ARE_REQUIRED',
         description = _('Are tags required?'),
         default = False,
diff --git a/askbot/doc/source/changelog.rst b/askbot/doc/source/changelog.rst
index 00918e76..ea52b8df 100644
--- a/askbot/doc/source/changelog.rst
+++ b/askbot/doc/source/changelog.rst
@@ -3,6 +3,7 @@ Changes in Askbot
 
 Development version
 -------------------
+* Optionally allow limiting one answer per question per person (Evgeny)
 * Added management command `build_livesettings_cache` (Adolfo)
 * Welcome email for the case when replying by email is enabled (Evgeny)
 * Detection of email signature based on the response to the welcome email (Evgeny)
diff --git a/askbot/exceptions.py b/askbot/exceptions.py
index d2d5ddf0..12802e7e 100644
--- a/askbot/exceptions.py
+++ b/askbot/exceptions.py
@@ -19,6 +19,11 @@ class InsufficientReputation(exceptions.PermissionDenied):
     """
     pass
 
+class AnswerAlreadyGiven(exceptions.PermissionDenied):
+    """Raised when user attempts to post a second answer
+    to the same question"""
+    pass
+
 class DuplicateCommand(exceptions.PermissionDenied):
     """exception class to indicate that something
     that can happen only once was attempted for the second time
diff --git a/askbot/models/__init__.py b/askbot/models/__init__.py
index ed0d876a..1c884ed6 100644
--- a/askbot/models/__init__.py
+++ b/askbot/models/__init__.py
@@ -551,9 +551,16 @@ def user_assert_can_post_question(self):
     )
 
 
-def user_assert_can_post_answer(self):
+def user_assert_can_post_answer(self, thread = None):
     """same as user_can_post_question
     """
+    limit_answers = askbot_settings.LIMIT_ONE_ANSWER_PER_USER
+    if limit_answers and thread.has_answer_by_user(self):
+        message = _(
+            'Sorry, you already gave an answer, please edit it instead.'
+        )
+        raise askbot_exceptions.AnswerAlreadyGiven(message)
+
     self.assert_can_post_question()
 
 
@@ -1718,7 +1725,7 @@ def user_post_answer(
             assert(error_message is not None)
             raise django_exceptions.PermissionDenied(error_message)
 
-    self.assert_can_post_answer()
+    self.assert_can_post_answer(thread = question.thread)
 
     if getattr(question, 'post_type', '') != 'question':
         raise TypeError('question argument must be provided')
diff --git a/askbot/models/question.py b/askbot/models/question.py
index 1729b531..3453ff7c 100644
--- a/askbot/models/question.py
+++ b/askbot/models/question.py
@@ -498,6 +498,14 @@ class Thread(models.Model):
                 output += answer.format_for_email_as_subthread()
         return output
 
+    def get_answers_by_user(self, user):
+        """regardless - deleted or not"""
+        return self.posts.filter(post_type = 'answer', author = user)
+
+    def has_answer_by_user(self, user):
+        #use len to cache the queryset
+        return len(self.get_answers_by_user(user)) > 0
+
     def tagname_meta_generator(self):
         return u','.join([unicode(tag) for tag in self.get_tag_names()])
 
@@ -920,6 +928,7 @@ class AnonymousQuestion(AnonymousContent):
 
     def publish(self,user):
         added_at = datetime.datetime.now()
+        #todo: wrong - use User.post_question() instead
         Thread.objects.create_new(
             title = self.title,
             added_at = added_at,
diff --git a/askbot/skins/default/templates/question/content.html b/askbot/skins/default/templates/question/content.html
index f01c68e0..66b3014b 100644
--- a/askbot/skins/default/templates/question/content.html
+++ b/askbot/skins/default/templates/question/content.html
@@ -29,8 +29,16 @@
 {% endif %}
 
 {# ==== START: question/new_answer_form.html ==== #}
-{% include "question/new_answer_form.html" %}
-{# ==== END: question/new_answer_form.html ==== #}
+{# buttons below cannot be cached yet #}
+{% if user_already_gave_answer %}
+    <a
+        class="submit"
+        href="{% url "edit_answer" previous_answer.id %}"
+    >{% trans %}Edit Your Previous Answer{% endtrans %}</a>
+    <span>{% trans %}(only one answer per question is allowed){% endtrans %}</span>
+{% else %}
+    {% include "question/new_answer_form.html" %}
+{% endif %}
 {% if question.closed == False and request.user == question.author %}{# this is outside the form on purpose #}
 <input 
   type="button"
diff --git a/askbot/tests/badge_tests.py b/askbot/tests/badge_tests.py
index dbb37dde..b66eadcc 100644
--- a/askbot/tests/badge_tests.py
+++ b/askbot/tests/badge_tests.py
@@ -68,7 +68,8 @@ class BadgeTests(AskbotTestCase):
         self.assert_have_badge(badge_key, recipient = self.u2, expected_count = 1)
         
         #post another question and check that there are no new badges
-        answer2 = self.post_answer(user = self.u2, question = question)
+        question2 = self.post_question(user = self.u1)
+        answer2 = self.post_answer(user = self.u2, question = question2)
         answer2.score = min_score - 1
         answer2.save()
         self.u1.upvote(answer2)
@@ -269,7 +270,8 @@ class BadgeTests(AskbotTestCase):
         answer = self.post_answer(user = self.u2, question = question)
         self.u1.accept_best_answer(answer)
         self.assert_have_badge('scholar', recipient = self.u1)
-        answer2 = self.post_answer(user = self.u2, question = question)
+        question2 = self.post_question(user = self.u1)
+        answer2 = self.post_answer(user = self.u2, question = question2)
         self.u1.accept_best_answer(answer2)
         self.assert_have_badge(
             'scholar',
diff --git a/askbot/views/readers.py b/askbot/views/readers.py
index c73b0c35..5f4d9ee4 100644
--- a/askbot/views/readers.py
+++ b/askbot/views/readers.py
@@ -455,7 +455,7 @@ def question(request, id):#refactor - long subroutine. display question body, an
         user_post_id_list = [
             id for id in post_to_author if post_to_author[id] == request.user.id
         ]
-        
+
     #resolve page number and comment number for permalinks
     show_comment_position = None
     if show_comment:
@@ -520,7 +520,7 @@ def question(request, id):#refactor - long subroutine. display question body, an
         is_cacheable = False
     elif show_comment_position > askbot_settings.MAX_COMMENTS_TO_SHOW:
         is_cacheable = False
-        
+
     answer_form = AnswerForm(
         initial = {
             'wiki': question_post.wiki and askbot_settings.WIKI_ON,
@@ -532,6 +532,16 @@ def question(request, id):#refactor - long subroutine. display question body, an
         request.user.is_authenticated() and request.user.can_post_comment()
     )
 
+    user_already_gave_answer = False
+    previous_answer = None
+    if request.user.is_authenticated():
+        if askbot_settings.LIMIT_ONE_ANSWER_PER_USER:
+            for answer in answers:
+                if answer.author == request.user:
+                    user_already_gave_answer = True
+                    previous_answer = answer
+                    break
+
     data = {
         'is_cacheable': False,#is_cacheable, #temporary, until invalidation fix
         'long_time': const.LONG_TIME,#"forever" caching
@@ -545,6 +555,8 @@ def question(request, id):#refactor - long subroutine. display question body, an
         'user_votes': user_votes,
         'user_post_id_list': user_post_id_list,
         'user_can_post_comment': user_can_post_comment,#in general
+        'user_already_gave_answer': user_already_gave_answer,
+        'previous_answer': previous_answer,
         'tab_id' : answer_sort_method,
         'favorited' : favorited,
         'similar_threads' : thread.get_similar_threads(),
diff --git a/askbot/views/writers.py b/askbot/views/writers.py
index 232dbaea..9a2de128 100644
--- a/askbot/views/writers.py
+++ b/askbot/views/writers.py
@@ -24,6 +24,7 @@ from django.core import exceptions
 from django.conf import settings
 from django.views.decorators import csrf
 
+from askbot import exceptions as askbot_exceptions
 from askbot import forms
 from askbot import models
 from askbot.skins.loaders import render_into_skin
@@ -499,6 +500,10 @@ def answer(request, id):#process a new answer
                                         timestamp = update_time,
                                     )
                     return HttpResponseRedirect(answer.get_absolute_url())
+                except askbot_exceptions.AnswerAlreadyGiven, e:
+                    request.user.message_set.create(message = unicode(e))
+                    answer = question.thread.get_answers_by_user(request.user)[0]
+                    return HttpResponseRedirect(answer.get_absolute_url())
                 except exceptions.PermissionDenied, e:
                     request.user.message_set.create(message = unicode(e))
             else: