pythonprobr · renzon · Nov 30, 2019 · Nov 29, 2019
diff --git a/Pipfile.lock b/Pipfile.lock
diff --git a/pythonpro/modules/models.py b/pythonpro/modules/models.py
@@ -14,6 +14,7 @@ class Content(OrderedModel):
     description = models.TextField()
     slug = models.SlugField(unique=True)
     _next_content_cache = _NoneCache
+    _previous_content_cache = _NoneCache
 
     class Meta:
         abstract = True
@@ -55,6 +56,24 @@ def _next_content_query_set(self):
         """Must provide a query set for next content"""
         raise NotImplementedError()
 
+    def previous_content(self):
+        if self._previous_content_cache is not _NoneCache:
+            return self._previous_content_cache
+        previous = self
+        while previous is not None:
+            try:
+                self._previous_content_cache = previous._previous_content_query_set().get()
+                break
+            except ObjectDoesNotExist:
+                previous = previous.parent()
+        else:
+            self._previous_content_cache = None
+        return self._previous_content_cache
+
+    def _previous_content_query_set(self):
+        """Must provide a query set for previous content"""
+        raise NotImplementedError()
+
     def module_slug(self):
         if self.parent() is None:
             return self.slug
@@ -95,6 +114,9 @@ def get_absolute_url(self):
     def _next_content_query_set(self):
         return Module.objects.filter(order=self.order + 1)
 
+    def _previous_content_query_set(self):
+        return Module.objects.filter(order=self.order - 1)
+
 
 class Section(Content):
     module = models.ForeignKey('Module', on_delete=models.CASCADE)
@@ -112,6 +134,9 @@ def parent(self):
     def _next_content_query_set(self):
         return Section.objects.filter(module=self.module, order=self.order + 1)
 
+    def _previous_content_query_set(self):
+        return Section.objects.filter(module=self.module, order=self.order - 1)
+
 
 class Chapter(Content):
     section = models.ForeignKey('Section', on_delete=models.CASCADE)
@@ -129,6 +154,9 @@ def parent(self):
     def _next_content_query_set(self):
         return Chapter.objects.filter(section=self.section, order=self.order + 1)
 
+    def _previous_content_query_set(self):
+        return Chapter.objects.filter(section=self.section, order=self.order - 1)
+
 
 class Topic(Content):
     chapter = models.ForeignKey('Chapter', on_delete=models.CASCADE)
@@ -147,3 +175,6 @@ def parent(self):
 
     def _next_content_query_set(self):
         return Topic.objects.filter(chapter=self.chapter, order=self.order + 1)
+
+    def _previous_content_query_set(self):
+        return Topic.objects.filter(chapter=self.chapter, order=self.order - 1)
diff --git a/pythonpro/modules/templates/topics/topic_detail.html b/pythonpro/modules/templates/topics/topic_detail.html
@@ -95,13 +95,22 @@ <h1 class="mt-4 mb-3">{{ topic.title }}</h1>
                             frameborder="0"
                             webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>
                 </div>
+                <div class="row mt-5 mb-5">
+                {% if topic.previous_content %}
+                    <div class="col-md text-md-left text-center">
+                        <a class="btn btn-success" href="{{ topic.previous_content.get_absolute_url }}">
+                           &laquo; <strong>{{ topic.previous_content.title }}</strong>
+                        </a>
+                    </div>
+                {% endif %}
                 {% if topic.next_content %}
-                    <div class="mt-5 mb-5" style="float: right">
-                        <a class="btn btn-success" href="{{ topic.next_content.get_absolute_url }}">
-                            Próximo Conteúdo: <strong>{{ topic.next_content.title }}</strong> &raquo;
+                    <div class="col-md text-md-right text-center mt-md-0 mt-2">
+                        <a class="btn btn-primary" href="{{ topic.next_content.get_absolute_url }}">
+                            <strong>{{ topic.next_content.title }}</strong> &raquo;
                         </a>
                     </div>
                 {% endif %}
+                </div>
                 <div id='discourse-comments'></div>
                 <script type="text/javascript">
                     DiscourseEmbed = {

diff --git a/pythonpro/modules/tests/test_previous_content.py b/pythonpro/modules/tests/test_previous_content.py
@@ -0,0 +1,95 @@
+import pytest
+from django.urls import reverse
+from model_mommy import mommy
+
+from pythonpro.django_assertions import dj_assert_contains, dj_assert_not_contains
+from pythonpro.modules.models import Chapter, Module, Section, Topic
+
+
+@pytest.fixture
+def module(db):
+    return mommy.make(Module)
+
+
+@pytest.fixture
+def section(module):
+    return mommy.make(Section, module=module)
+
+
+@pytest.fixture
+def chapter(section):
+    return mommy.make(Chapter, section=section)
+
+
+@pytest.fixture
+def topics(chapter):
+    return [mommy.make(Topic, chapter=chapter, order=i) for i in range(2)]
+
+
+@pytest.fixture
+def resp(client_with_member, django_user_model, topics):
+    next_topic = topics[1]
+    return client_with_member.get(
+        reverse('modules:topic_detail',
+                kwargs={'module_slug': next_topic.module_slug(), 'topic_slug': next_topic.slug}),
+        secure=True)
+
+
+@pytest.fixture
+def resp_first_topic(client_with_member, topics, logged_user):
+    first_topic = topics[0]
+    yield client_with_member.get(
+        reverse(
+            'modules:topic_detail', kwargs={'module_slug': first_topic.module_slug(), 'topic_slug': first_topic.slug}
+        ),
+        secure=True
+    )
+
+
+def test_topic_with_previous_topic(resp, topics):
+    previous_topic, _ = topics
+    dj_assert_contains(resp, previous_topic.get_absolute_url())
+
+
+def test_first_topic(resp_first_topic):
+    dj_assert_not_contains(resp_first_topic, 'Conteúdo Anterior')
+
+
+def test_first_topic_previous_chapter(section):
+    """Assert previous Chapter as previous content for the first Topic"""
+    previous_chapter, next_chapter = [mommy.make(Chapter, section=section, order=order) for order in range(2)]
+    topic = mommy.make(Topic, chapter=next_chapter)
+    assert previous_chapter == topic.previous_content()
+
+
+def test_topic_previous_section(module):
+    """Assert previous Section as previous content for the first Topic"""
+    previous_section, next_section = [mommy.make(Section, module=module, order=order) for order in range(2)]
+    chapter = mommy.make(Chapter, section=next_section)
+    topic = mommy.make(Topic, chapter=chapter)
+    assert previous_section == topic.previous_content()
+
+
+@pytest.mark.django_db
+def test_topic_previous_module():
+    """Assert previous Module as previous content for the first Topic"""
+    previous_module, next_module = [mommy.make(Module, order=order) for order in range(2)]
+    section = mommy.make(Section, module=next_module)
+    chapter = mommy.make(Chapter, section=section)
+    topic = mommy.make(Topic, chapter=chapter)
+    assert previous_module == topic.previous_content()
+
+
+def test_previous_topic_first_none(chapter):
+    """Assert None as previous content for the First Topic of First Chapter of First Section of First Module"""
+    topic = mommy.make(Topic, chapter=chapter)
+    assert topic.previous_content() is None
+
+
+def test_cache(chapter, mocker):
+    """Assert cache is used when calling previous content multiple times"""
+    topic = mommy.make(Topic, chapter=chapter)
+    mocker.spy(topic, '_previous_content_query_set')
+    for _ in range(3):
+        topic.previous_content()
+    assert topic._previous_content_query_set.call_count == 1