Add thread list endpoint to the new discussion API

This is an initial implementation that only allows retrieval of all
threads for a course and only returns an easily computed subset of the
fields that are needed, in order to keep this change from getting too
large.

JIRA: MA-641

lms/djangoapps/discussion_api/api.py

 """
 Discussion API internal interface
 """
+from django.http import Http404
+
 from collections import defaultdict
 
+from lms.lib.comment_client.thread import Thread
+from discussion_api.pagination import get_paginated_data
 from django_comment_client.utils import get_accessible_discussion_modules
 
 
@@ -63,3 +67,62 @@ def get_course_topics(course, user):
         "courseware_topics": courseware_topics,
         "non_courseware_topics": non_courseware_topics,
     }
+
+
+def _cc_thread_to_api_thread(thread):
+    """
+    Convert a thread data dict from the comment_client format (which is a direct
+    representation of the format returned by the comments service) to the format
+    used in this API
+    """
+    ret = {
+        key: thread[key]
+        for key in [
+            "id",
+            "course_id",
+            "created_at",
+            "updated_at",
+            "type",
+            "title",
+            "pinned",
+            "closed",
+        ]
+    }
+    ret.update({
+        "topic_id": thread["commentable_id"],
+        "raw_body": thread["body"],
+        "comment_count": thread["comments_count"],
+        "unread_comment_count": thread["unread_comments_count"],
+    })
+    return ret
+
+
+def get_thread_list(request, course_key, page, page_size):
+    """
+    Return the list of all discussion threads pertaining to the given course
+
+    Parameters:
+
+    request: The django request objects used for build_absolute_uri
+    course_key: The key of the course to get discussion threads for
+    page: The page number (1-indexed) to retrieve
+    page_size: The number of threads to retrieve per page
+
+    Returns:
+
+    A paginated result containing a list of threads; see
+    discussion_api.views.ThreadViewSet for more detail.
+    """
+    threads, result_page, num_pages, _ = Thread.search({
+        "course_id": unicode(course_key),
+        "page": page,
+        "per_page": page_size
+    })
+    # The comments service returns the last page of results if the requested
+    # page is beyond the last page, but we want be consistent with DRF's general
+    # behavior and return a 404 in that case
+    if result_page != page:
+        raise Http404
+
+    results = [_cc_thread_to_api_thread(thread) for thread in threads]
+    return get_paginated_data(request, results, page, num_pages)

lms/djangoapps/discussion_api/forms.py

+"""
+Discussion API forms
+"""
+from django.core.exceptions import ValidationError
+from django.forms import Form, CharField, IntegerField
+
+from opaque_keys import InvalidKeyError
+from opaque_keys.edx.locator import CourseLocator
+
+
+class ThreadListGetForm(Form):
+    """
+    A form to validate query parameters in the thread list retrieval endpoint
+    """
+    course_id = CharField()
+    page = IntegerField(required=False, min_value=1)
+    page_size = IntegerField(required=False, min_value=1)
+
+    def clean_course_id(self):
+        """Validate course_id"""
+        value = self.cleaned_data["course_id"]
+        try:
+            return CourseLocator.from_string(value)
+        except InvalidKeyError:
+            raise ValidationError("'{}' is not a valid course id".format(value))
+
+    def clean_page(self):
+        """Return given valid page or default of 1"""
+        return self.cleaned_data.get("page") or 1
+
+    def clean_page_size(self):
+        """Return given valid page_size (capped at 100) or default of 10"""
+        return min(self.cleaned_data.get("page_size") or 10, 100)

lms/djangoapps/discussion_api/pagination.py

+"""
+Discussion API pagination support
+"""
+from rest_framework.pagination import BasePaginationSerializer, NextPageField, PreviousPageField
+
+
+class _PaginationSerializer(BasePaginationSerializer):
+    """
+    A pagination serializer without the count field, because the Comments
+    Service does not return result counts
+    """
+    next = NextPageField(source="*")
+    previous = PreviousPageField(source="*")
+
+
+class _Page(object):
+    """
+    Implements just enough of the django.core.paginator.Page interface to allow
+    PaginationSerializer to work.
+    """
+    def __init__(self, object_list, page_num, num_pages):
+        """
+        Create a new page containing the given objects, with the given page
+        number and number of pages
+        """
+        self.object_list = object_list
+        self.page_num = page_num
+        self.num_pages = num_pages
+
+    def has_next(self):
+        """Returns True if there is a page after this one, otherwise False"""
+        return self.page_num < self.num_pages
+
+    def has_previous(self):
+        """Returns True if there is a page before this one, otherwise False"""
+        return self.page_num > 1
+
+    def next_page_number(self):
+        """Returns the number of the next page"""
+        return self.page_num + 1
+
+    def previous_page_number(self):
+        """Returns the number of the previous page"""
+        return self.page_num - 1
+
+
+def get_paginated_data(request, results, page_num, per_page):
+    """
+    Return a dict with the following values:
+
+    next: The URL for the next page
+    previous: The URL for the previous page
+    results: The results on this page
+    """
+    return _PaginationSerializer(
+        instance=_Page(results, page_num, per_page),
+        context={"request": request}
+    ).data

lms/djangoapps/discussion_api/tests/test_api.py

@@ -3,11 +3,18 @@ Tests for Discussion API internal interface
 """
 from datetime import datetime, timedelta
 
+import httpretty
 import mock
 from pytz import UTC
 
+from django.http import Http404
+from django.test.client import RequestFactory
+
+from opaque_keys.edx.locator import CourseLocator
+
 from courseware.tests.factories import BetaTesterFactory, StaffFactory
-from discussion_api.api import get_course_topics
+from discussion_api.api import get_course_topics, get_thread_list
+from discussion_api.tests.utils import CommentsServiceMockMixin
 from openedx.core.djangoapps.course_groups.models import CourseUserGroupPartitionGroup
 from openedx.core.djangoapps.course_groups.tests.helpers import CohortFactory
 from student.tests.factories import UserFactory
@@ -304,3 +311,171 @@ class GetCourseTopicsTest(ModuleStoreTestCase):
             "non_courseware_topics": [],
         }
         self.assertEqual(staff_actual, staff_expected)
+
+
+@httpretty.activate
+class GetThreadListTest(CommentsServiceMockMixin, ModuleStoreTestCase):
+    """Test for get_thread_list"""
+    def setUp(self):
+        super(GetThreadListTest, self).setUp()
+        self.maxDiff = None  # pylint: disable=invalid-name
+        self.request = RequestFactory().get("/test_path")
+        self.course_key = CourseLocator.from_string("a/b/c")
+
+    def get_thread_list(self, threads, page=1, page_size=1, num_pages=1):
+        """
+        Register the appropriate comments service response, then call
+        get_thread_list and return the result.
+        """
+        self.register_get_threads_response(threads, page, num_pages)
+        ret = get_thread_list(self.request, self.course_key, page, page_size)
+        return ret
+
+    def test_empty(self):
+        self.assertEqual(
+            self.get_thread_list([]),
+            {
+                "results": [],
+                "next": None,
+                "previous": None,
+            }
+        )
+
+    def test_basic_query_params(self):
+        self.get_thread_list([], page=6, page_size=14)
+        self.assert_last_query_params({
+            "course_id": [unicode(self.course_key)],
+            "page": ["6"],
+            "per_page": ["14"],
+            "recursive": ["False"],
+        })
+
+    def test_thread_content(self):
+        source_threads = [
+            {
+                "id": "test_thread_id_0",
+                "course_id": unicode(self.course_key),
+                "commentable_id": "topic_x",
+                "created_at": "2015-04-28T00:00:00Z",
+                "updated_at": "2015-04-28T11:11:11Z",
+                "type": "discussion",
+                "title": "Test Title",
+                "body": "Test body",
+                "pinned": False,
+                "closed": False,
+                "comments_count": 5,
+                "unread_comments_count": 3,
+            },
+            {
+                "id": "test_thread_id_1",
+                "course_id": unicode(self.course_key),
+                "commentable_id": "topic_y",
+                "created_at": "2015-04-28T22:22:22Z",
+                "updated_at": "2015-04-28T00:33:33Z",
+                "type": "question",
+                "title": "Another Test Title",
+                "body": "More content",
+                "pinned": False,
+                "closed": True,
+                "comments_count": 18,
+                "unread_comments_count": 0,
+            },
+            {
+                "id": "test_thread_id_2",
+                "course_id": unicode(self.course_key),
+                "commentable_id": "topic_x",
+                "created_at": "2015-04-28T00:44:44Z",
+                "updated_at": "2015-04-28T00:55:55Z",
+                "type": "discussion",
+                "title": "Yet Another Test Title",
+                "body": "Still more content",
+                "pinned": True,
+                "closed": False,
+                "comments_count": 0,
+                "unread_comments_count": 0,
+            },
+        ]
+        expected_threads = [
+            {
+                "id": "test_thread_id_0",
+                "course_id": unicode(self.course_key),
+                "topic_id": "topic_x",
+                "created_at": "2015-04-28T00:00:00Z",
+                "updated_at": "2015-04-28T11:11:11Z",
+                "type": "discussion",
+                "title": "Test Title",
+                "raw_body": "Test body",
+                "pinned": False,
+                "closed": False,
+                "comment_count": 5,
+                "unread_comment_count": 3,
+            },
+            {
+                "id": "test_thread_id_1",
+                "course_id": unicode(self.course_key),
+                "topic_id": "topic_y",
+                "created_at": "2015-04-28T22:22:22Z",
+                "updated_at": "2015-04-28T00:33:33Z",
+                "type": "question",
+                "title": "Another Test Title",
+                "raw_body": "More content",
+                "pinned": False,
+                "closed": True,
+                "comment_count": 18,
+                "unread_comment_count": 0,
+            },
+            {
+                "id": "test_thread_id_2",
+                "course_id": unicode(self.course_key),
+                "topic_id": "topic_x",
+                "created_at": "2015-04-28T00:44:44Z",
+                "updated_at": "2015-04-28T00:55:55Z",
+                "type": "discussion",
+                "title": "Yet Another Test Title",
+                "raw_body": "Still more content",
+                "pinned": True,
+                "closed": False,
+                "comment_count": 0,
+                "unread_comment_count": 0,
+            },
+        ]
+        self.assertEqual(
+            self.get_thread_list(source_threads),
+            {
+                "results": expected_threads,
+                "next": None,
+                "previous": None,
+            }
+        )
+
+    def test_pagination(self):
+        # N.B. Empty thread list is not realistic but convenient for this test
+        self.assertEqual(
+            self.get_thread_list([], page=1, num_pages=3),
+            {
+                "results": [],
+                "next": "http://testserver/test_path?page=2",
+                "previous": None,
+            }
+        )
+        self.assertEqual(
+            self.get_thread_list([], page=2, num_pages=3),
+            {
+                "results": [],
+                "next": "http://testserver/test_path?page=3",
+                "previous": "http://testserver/test_path?page=1",
+            }
+        )
+        self.assertEqual(
+            self.get_thread_list([], page=3, num_pages=3),
+            {
+                "results": [],
+                "next": None,
+                "previous": "http://testserver/test_path?page=2",
+            }
+        )
+
+        # Test page past the last one
+        self.register_get_threads_response([], page=3, num_pages=3)
+        with self.assertRaises(Http404):
+            get_thread_list(self.request, self.course_key, page=4, page_size=10)

lms/djangoapps/discussion_api/tests/test_forms.py

+"""
+Tests for Discussion API forms
+"""
+from unittest import TestCase
+
+from opaque_keys.edx.locator import CourseLocator
+
+from discussion_api.forms import ThreadListGetForm
+
+
+class ThreadListGetFormTest(TestCase):
+    """Tests for ThreadListGetForm"""
+    def setUp(self):
+        super(ThreadListGetFormTest, self).setUp()
+        self.form_data = {
+            "course_id": "Foo/Bar/Baz",
+            "page": "2",
+            "page_size": "13",
+        }
+
+    def get_form(self, expected_valid):
+        """
+        Return a form bound to self.form_data, asserting its validity (or lack
+        thereof) according to expected_valid
+        """
+        form = ThreadListGetForm(self.form_data)
+        self.assertEqual(form.is_valid(), expected_valid)
+        return form
+
+    def assert_error(self, expected_field, expected_message):
+        """
+        Create a form bound to self.form_data, assert its invalidity, and assert
+        that its error dictionary contains one entry with the expected field and
+        message
+        """
+        form = self.get_form(expected_valid=False)
+        self.assertEqual(form.errors, {expected_field: [expected_message]})
+
+    def assert_field_value(self, field, expected_value):
+        """
+        Create a form bound to self.form_data, assert its validity, and assert
+        that the given field in the cleaned data has the expected value
+        """
+        form = self.get_form(expected_valid=True)
+        self.assertEqual(form.cleaned_data[field], expected_value)
+
+    def test_basic(self):
+        form = self.get_form(expected_valid=True)
+        self.assertEqual(
+            form.cleaned_data,
+            {
+                "course_id": CourseLocator.from_string("Foo/Bar/Baz"),
+                "page": 2,
+                "page_size": 13,
+            }
+        )
+
+    def test_missing_course_id(self):
+        self.form_data.pop("course_id")
+        self.assert_error("course_id", "This field is required.")
+
+    def test_invalid_course_id(self):
+        self.form_data["course_id"] = "invalid course id"
+        self.assert_error("course_id", "'invalid course id' is not a valid course id")
+
+    def test_missing_page(self):
+        self.form_data.pop("page")
+        self.assert_field_value("page", 1)
+
+    def test_invalid_page(self):
+        self.form_data["page"] = "0"
+        self.assert_error("page", "Ensure this value is greater than or equal to 1.")
+
+    def test_missing_page_size(self):
+        self.form_data.pop("page_size")
+        self.assert_field_value("page_size", 10)
+
+    def test_zero_page_size(self):
+        self.form_data["page_size"] = "0"
+        self.assert_error("page_size", "Ensure this value is greater than or equal to 1.")
+
+    def test_excessive_page_size(self):
+        self.form_data["page_size"] = "101"
+        self.assert_field_value("page_size", 100)

lms/djangoapps/discussion_api/tests/test_pagination.py

+"""
+Tests for Discussion API pagination support
+"""
+from unittest import TestCase
+
+from django.test import RequestFactory
+
+from discussion_api.pagination import get_paginated_data
+
+
+class PaginationSerializerTest(TestCase):
+    """Tests for PaginationSerializer"""
+    def do_case(self, objects, page_num, num_pages, expected):
+        """
+        Make a dummy request, and assert that get_paginated_data with the given
+        parameters returns the expected result
+        """
+        request = RequestFactory().get("/test")
+        actual = get_paginated_data(request, objects, page_num, num_pages)
+        self.assertEqual(actual, expected)
+
+    def test_empty(self):
+        self.do_case(
+            [], 1, 0,
+            {
+                "next": None,
+                "previous": None,
+                "results": [],
+            }
+        )
+
+    def test_only_page(self):
+        self.do_case(
+            ["foo"], 1, 1,
+            {
+                "next": None,
+                "previous": None,
+                "results": ["foo"],
+            }
+        )
+
+    def test_first_of_many(self):
+        self.do_case(
+            ["foo"], 1, 3,
+            {
+                "next": "http://testserver/test?page=2",
+                "previous": None,
+                "results": ["foo"],
+            }
+        )
+
+    def test_last_of_many(self):
+        self.do_case(
+            ["foo"], 3, 3,
+            {
+                "next": None,
+                "previous": "http://testserver/test?page=2",
+                "results": ["foo"],
+            }
+        )
+
+    def test_middle_of_many(self):
+        self.do_case(
+            ["foo"], 2, 3,
+            {
+                "next": "http://testserver/test?page=3",
+                "previous": "http://testserver/test?page=1",
+                "results": ["foo"],
+            }
+        )

lms/djangoapps/discussion_api/tests/test_views.py

@@ -4,11 +4,13 @@ Tests for Discussion API views
 from datetime import datetime
 import json
 
+import httpretty
 import mock
 from pytz import UTC
 
 from django.core.urlresolvers import reverse
 
+from discussion_api.tests.utils import CommentsServiceMockMixin
 from student.tests.factories import CourseEnrollmentFactory, UserFactory
 from util.testing import UrlResetMixin
 from xmodule.modulestore.django import modulestore
@@ -17,12 +19,16 @@ from xmodule.modulestore.tests.factories import CourseFactory
 from xmodule.tabs import DiscussionTab
 
 
-class CourseTopicsViewTest(UrlResetMixin, ModuleStoreTestCase):
-    """Tests for CourseTopicsView"""
-
+class DiscussionAPIViewTestMixin(CommentsServiceMockMixin, UrlResetMixin):
+    """
+    Mixin for common code in tests of Discussion API views. This includes
+    creation of common structures (e.g. a course, user, and enrollment), logging
+    in the test client, utility functions, and a test case for unauthenticated
+    requests. Subclasses must set self.url in their setUp methods.
+    """
     @mock.patch.dict("django.conf.settings.FEATURES", {"ENABLE_DISCUSSION_SERVICE": True})
     def setUp(self):
-        super(CourseTopicsViewTest, self).setUp()
+        super(DiscussionAPIViewTestMixin, self).setUp()
         self.maxDiff = None  # pylint: disable=invalid-name
         self.course = CourseFactory.create(
             org="x",
@@ -34,9 +40,13 @@ class CourseTopicsViewTest(UrlResetMixin, ModuleStoreTestCase):
         self.password = "password"
         self.user = UserFactory.create(password=self.password)
         CourseEnrollmentFactory.create(user=self.user, course_id=self.course.id)
-        self.url = reverse("course_topics", kwargs={"course_id": unicode(self.course.id)})
         self.client.login(username=self.user.username, password=self.password)
 
+    def login_unenrolled_user(self):
+        """Create a user not enrolled in the course and log it in"""
+        unenrolled_user = UserFactory.create(password=self.password)
+        self.client.login(username=unenrolled_user.username, password=self.password)
+
     def assert_response_correct(self, response, expected_status, expected_content):
         """
         Assert that the response has the given status code and parsed content
@@ -54,6 +64,13 @@ class CourseTopicsViewTest(UrlResetMixin, ModuleStoreTestCase):
             {"developer_message": "Authentication credentials were not provided."}
         )
 
+
+class CourseTopicsViewTest(DiscussionAPIViewTestMixin, ModuleStoreTestCase):
+    """Tests for CourseTopicsView"""
+    def setUp(self):
+        super(CourseTopicsViewTest, self).setUp()
+        self.url = reverse("course_topics", kwargs={"course_id": unicode(self.course.id)})
+
     def test_non_existent_course(self):
         response = self.client.get(
             reverse("course_topics", kwargs={"course_id": "non/existent/course"})
@@ -65,8 +82,7 @@ class CourseTopicsViewTest(UrlResetMixin, ModuleStoreTestCase):
         )
 
     def test_not_enrolled(self):
-        unenrolled_user = UserFactory.create(password=self.password)
-        self.client.login(username=unenrolled_user.username, password=self.password)
+        self.login_unenrolled_user()
         response = self.client.get(self.url)
         self.assert_response_correct(
             response,
@@ -98,3 +114,93 @@ class CourseTopicsViewTest(UrlResetMixin, ModuleStoreTestCase):
                 }],
             }
         )
+
+
+@httpretty.activate
+class ThreadViewSetListTest(DiscussionAPIViewTestMixin, ModuleStoreTestCase):
+    """Tests for ThreadViewSet list"""
+    def setUp(self):
+        super(ThreadViewSetListTest, self).setUp()
+        self.url = reverse("thread-list")
+
+    def test_course_id_missing(self):
+        response = self.client.get(self.url)
+        self.assert_response_correct(
+            response,
+            400,
+            {"field_errors": {"course_id": "This field is required."}}
+        )
+
+    def test_not_enrolled(self):
+        self.login_unenrolled_user()
+        response = self.client.get(self.url, {"course_id": unicode(self.course.id)})
+        self.assert_response_correct(
+            response,
+            404,
+            {"developer_message": "Not found."}
+        )
+
+    def test_basic(self):
+        source_threads = [{
+            "id": "test_thread",
+            "course_id": unicode(self.course.id),
+            "commentable_id": "test_topic",
+            "created_at": "2015-04-28T00:00:00Z",
+            "updated_at": "2015-04-28T11:11:11Z",
+            "type": "discussion",
+            "title": "Test Title",
+            "body": "Test body",
+            "pinned": False,
+            "closed": False,
+            "comments_count": 5,
+            "unread_comments_count": 3,
+        }]
+        expected_threads = [{
+            "id": "test_thread",
+            "course_id": unicode(self.course.id),
+            "topic_id": "test_topic",
+            "created_at": "2015-04-28T00:00:00Z",
+            "updated_at": "2015-04-28T11:11:11Z",
+            "type": "discussion",
+            "title": "Test Title",
+            "raw_body": "Test body",
+            "pinned": False,
+            "closed": False,
+            "comment_count": 5,
+            "unread_comment_count": 3,
+        }]
+        self.register_get_threads_response(source_threads, page=1, num_pages=2)
+        response = self.client.get(self.url, {"course_id": unicode(self.course.id)})
+        self.assert_response_correct(
+            response,
+            200,
+            {
+                "results": expected_threads,
+                "next": "http://testserver/api/discussion/v1/threads/?course_id=x%2Fy%2Fz&page=2",
+                "previous": None,
+            }
+        )
+        self.assert_last_query_params({
+            "course_id": [unicode(self.course.id)],
+            "page": ["1"],
+            "per_page": ["10"],
+            "recursive": ["False"],
+        })
+
+    def test_pagination(self):
+        self.register_get_threads_response([], page=1, num_pages=1)
+        response = self.client.get(
+            self.url,
+            {"course_id": unicode(self.course.id), "page": "18", "page_size": "4"}
+        )
+        self.assert_response_correct(
+            response,
+            404,
+            {"developer_message": "Not found."}
+        )
+        self.assert_last_query_params({
+            "course_id": [unicode(self.course.id)],
+            "page": ["18"],
+            "per_page": ["4"],
+            "recursive": ["False"],
+        })

lms/djangoapps/discussion_api/tests/utils.py

+"""
+Discussion API test utilities
+"""
+import json
+
+import httpretty
+
+
+class CommentsServiceMockMixin(object):
+    """Mixin with utility methods for mocking the comments service"""
+    def register_get_threads_response(self, threads, page, num_pages):
+        """Register a mock response for GET on the CS thread list endpoint"""
+        httpretty.register_uri(
+            httpretty.GET,
+            "http://localhost:4567/api/v1/threads",
+            body=json.dumps({
+                "collection": threads,
+                "page": page,
+                "num_pages": num_pages,
+            }),
+            status=200
+        )
+
+    def assert_last_query_params(self, expected_params):
+        """
+        Assert that the last mock request had the expected query parameters
+        """
+        actual_params = dict(httpretty.last_request().querystring)
+        actual_params.pop("request_id")  # request_id is random
+        self.assertEqual(actual_params, expected_params)

lms/djangoapps/discussion_api/urls.py

@@ -2,10 +2,15 @@
 Discussion API URLs
 """
 from django.conf import settings
-from django.conf.urls import patterns, url
+from django.conf.urls import include, patterns, url
 
-from discussion_api.views import CourseTopicsView
+from rest_framework.routers import SimpleRouter
 
+from discussion_api.views import CourseTopicsView, ThreadViewSet
+
+
+ROUTER = SimpleRouter()
+ROUTER.register("threads", ThreadViewSet, base_name="thread")
 
 urlpatterns = patterns(
     "discussion_api",
@@ -14,4 +19,5 @@ urlpatterns = patterns(
         CourseTopicsView.as_view(),
         name="course_topics"
     ),
+    url("^v1/", include(ROUTER.urls)),
 )

lms/djangoapps/discussion_api/views.py

 """
 Discussion API views
 """
+from django.core.exceptions import ValidationError
 from django.http import Http404
 
 from rest_framework.authentication import OAuth2Authentication, SessionAuthentication
 from rest_framework.permissions import IsAuthenticated
 from rest_framework.response import Response
 from rest_framework.views import APIView
+from rest_framework.viewsets import ViewSet
 
 from opaque_keys.edx.locator import CourseLocator
 
 from courseware.courses import get_course_with_access
-from discussion_api.api import get_course_topics
+from discussion_api.api import get_course_topics, get_thread_list
+from discussion_api.forms import ThreadListGetForm
 from openedx.core.lib.api.view_utils import DeveloperErrorViewMixin
 from xmodule.tabs import DiscussionTab
 
 
-class CourseTopicsView(DeveloperErrorViewMixin, APIView):
+class _ViewMixin(object):
+    """
+    Mixin to provide common characteristics and utility functions for Discussion
+    API views
+    """
+    authentication_classes = (OAuth2Authentication, SessionAuthentication)
+    permission_classes = (IsAuthenticated,)
+
+    def get_course_or_404(self, user, course_key):
+        """
+        Get the course descriptor, raising Http404 if the course is not found,
+        the user cannot access forums for the course, or the discussion tab is
+        disabled for the course.
+        """
+        course = get_course_with_access(user, 'load_forum', course_key)
+        if not any([isinstance(tab, DiscussionTab) for tab in course.tabs]):
+            raise Http404
+        return course
+
+
+class CourseTopicsView(_ViewMixin, DeveloperErrorViewMixin, APIView):
     """
     **Use Cases**
 
@@ -42,13 +65,81 @@ class CourseTopicsView(DeveloperErrorViewMixin, APIView):
         * non_courseware_topics: The list of topic trees that are not linked to
               courseware. Items are of the same format as in courseware_topics.
     """
-    authentication_classes = (OAuth2Authentication, SessionAuthentication)
-    permission_classes = (IsAuthenticated,)
-
     def get(self, request, course_id):
         """Implements the GET method as described in the class docstring."""
         course_key = CourseLocator.from_string(course_id)
-        course = get_course_with_access(request.user, 'load_forum', course_key)
-        if not any([isinstance(tab, DiscussionTab) for tab in course.tabs]):
-            raise Http404
+        course = self.get_course_or_404(request.user, course_key)
         return Response(get_course_topics(course, request.user))
+
+
+class ThreadViewSet(_ViewMixin, DeveloperErrorViewMixin, ViewSet):
+    """
+    **Use Cases**
+
+        Retrieve the list of threads for a course.
+
+    **Example Requests**:
+
+        GET /api/discussion/v1/threads/?course_id=ExampleX/Demo/2015
+
+    **GET Parameters**:
+
+        * course_id (required): The course to retrieve threads for
+
+        * page: The (1-indexed) page to retrieve (default is 1)
+
+        * page_size: The number of items per page (default is 10, max is 100)
+
+    **Response Values**:
+
+        * results: The list of threads. Each item in the list includes:
+
+            * id: The id of the thread
+
+            * course_id: The id of the thread's course
+
+            * topic_id: The id of the thread's topic
+
+            * created_at: The ISO 8601 timestamp for the creation of the thread
+
+            * updated_at: The ISO 8601 timestamp for the last modification of
+                the thread, which may not have been an update of the title/body
+
+            * type: The thread's type (either "question" or "discussion")
+
+            * title: The thread's title
+
+            * raw_body: The thread's raw body text without any rendering applied
+
+            * pinned: Boolean indicating whether the thread has been pinned
+
+            * closed: Boolean indicating whether the thread has been closed
+
+            * comment_count: The number of comments within the thread
+
+            * unread_comment_count: The number of comments within the thread
+                that were created or updated since the last time the user read
+                the thread
+
+        * next: The URL of the next page (or null if first page)
+
+        * previous: The URL of the previous page (or null if last page)
+    """
+    def list(self, request):
+        """
+        Implements the GET method for the list endpoint as described in the
+        class docstring.
+        """
+        form = ThreadListGetForm(request.GET)
+        if not form.is_valid():
+            raise ValidationError(form.errors)
+        course_key = form.cleaned_data["course_id"]
+        self.get_course_or_404(request.user, course_key)
+        return Response(
+            get_thread_list(
+                request,
+                course_key,
+                form.cleaned_data["page"],
+                form.cleaned_data["page_size"]
+            )
+        )

openedx/core/lib/api/view_utils.py

 """
 Utilities related to API views
 """
+from django.core.exceptions import NON_FIELD_ERRORS, ValidationError
 from django.http import Http404
 
 from rest_framework.exceptions import APIException
@@ -19,10 +20,31 @@ class DeveloperErrorViewMixin(object):
         """
         return Response({"developer_message": developer_message}, status=status_code)
 
+    def make_validation_error_response(self, validation_error):
+        """
+        Build a 400 error response from the given ValidationError
+        """
+        if hasattr(validation_error, "message_dict"):
+            response_obj = {}
+            message_dict = dict(validation_error.message_dict)
+            non_field_error_list = message_dict.pop(NON_FIELD_ERRORS, None)
+            if non_field_error_list:
+                response_obj["developer_message"] = non_field_error_list[0]
+            if message_dict:
+                response_obj["field_errors"] = {
+                    field: message_dict[field][0]
+                    for field in message_dict
+                }
+            return Response(response_obj, status=400)
+        else:
+            return self.make_error_response(400, validation_error.messages[0])
+
     def handle_exception(self, exc):
         if isinstance(exc, APIException):
             return self.make_error_response(exc.status_code, exc.detail)
         elif isinstance(exc, Http404):
             return self.make_error_response(404, "Not found.")
+        elif isinstance(exc, ValidationError):
+            return self.make_validation_error_response(exc)
         else:
             raise