From c748d563e40fac173117c8853cc7b28bef7b1507 Mon Sep 17 00:00:00 2001
From: Navin Karkera <navin@opencraft.com>
Date: Fri, 24 Jan 2025 09:30:17 +0530
Subject: [PATCH] feat: entity link view

---
 .../rest_api/v2/serializers/__init__.py       |  1 +
 .../rest_api/v2/serializers/downstreams.py    | 33 +++++++++++++++++++
 .../contentstore/rest_api/v2/urls.py          |  8 ++++-
 .../rest_api/v2/views/downstreams.py          | 31 ++++++++++++++---
 4 files changed, 68 insertions(+), 5 deletions(-)
 create mode 100644 cms/djangoapps/contentstore/rest_api/v2/serializers/downstreams.py

diff --git a/cms/djangoapps/contentstore/rest_api/v2/serializers/__init__.py b/cms/djangoapps/contentstore/rest_api/v2/serializers/__init__.py
index 6e102bab44a1..83bc02b685e4 100644
--- a/cms/djangoapps/contentstore/rest_api/v2/serializers/__init__.py
+++ b/cms/djangoapps/contentstore/rest_api/v2/serializers/__init__.py
@@ -1,3 +1,4 @@
 """Module for v2 serializers."""
 
+from cms.djangoapps.contentstore.rest_api.v2.serializers.downstreams import PublishableEntityLinksSerializer
 from cms.djangoapps.contentstore.rest_api.v2.serializers.home import CourseHomeTabSerializerV2
diff --git a/cms/djangoapps/contentstore/rest_api/v2/serializers/downstreams.py b/cms/djangoapps/contentstore/rest_api/v2/serializers/downstreams.py
new file mode 100644
index 000000000000..fe778119f646
--- /dev/null
+++ b/cms/djangoapps/contentstore/rest_api/v2/serializers/downstreams.py
@@ -0,0 +1,33 @@
+"""
+Serializers for upstream -> downstream entity links.
+"""
+
+from rest_framework import serializers
+
+DATETIME_FORMAT = '%Y-%m-%dT%H:%M:%SZ'
+
+
+class PublishableEntityLinksSerializer(serializers.Serializer):
+    """
+    Serializer for publishable entity links.
+    """
+    upstream_usage_key = serializers.CharField(read_only=True)
+    upstream_context_key = serializers.CharField(read_only=True)
+    upstream_context_title = serializers.CharField(read_only=True)
+    upstream_version = serializers.IntegerField(read_only=True)
+    downstream_usage_key = serializers.CharField(read_only=True)
+    downstream_context_title = serializers.CharField(read_only=True)
+    downstream_context_key = serializers.CharField(read_only=True)
+    version_synced = serializers.IntegerField(read_only=True)
+    version_declined = serializers.IntegerField(read_only=True)
+    created = serializers.DateTimeField(format=DATETIME_FORMAT, read_only=True)
+    updated = serializers.DateTimeField(format=DATETIME_FORMAT, read_only=True)
+    ready_to_sync = serializers.SerializerMethodField()
+
+    def get_ready_to_sync(self, obj):
+        """Calculate ready_to_sync field"""
+        return bool(
+            obj.upstream_version and
+            obj.upstream_version > (obj.version_synced or 0) and
+            obj.upstream_version > (obj.version_declined or 0)
+        )
diff --git a/cms/djangoapps/contentstore/rest_api/v2/urls.py b/cms/djangoapps/contentstore/rest_api/v2/urls.py
index 3e653d07fbcf..690e78799336 100644
--- a/cms/djangoapps/contentstore/rest_api/v2/urls.py
+++ b/cms/djangoapps/contentstore/rest_api/v2/urls.py
@@ -3,7 +3,8 @@
 from django.conf import settings
 from django.urls import path, re_path
 
-from cms.djangoapps.contentstore.rest_api.v2.views import home, downstreams
+from cms.djangoapps.contentstore.rest_api.v2.views import downstreams, home
+
 app_name = "v2"
 
 urlpatterns = [
@@ -23,6 +24,11 @@
         downstreams.DownstreamView.as_view(),
         name="downstream"
     ),
+    re_path(
+        f'^upstreams/{settings.COURSE_KEY_PATTERN}$',
+        downstreams.UpstreamListView.as_view(),
+        name='upstream-list'
+    ),
     re_path(
         fr'^downstreams/{settings.USAGE_KEY_PATTERN}/sync$',
         downstreams.SyncFromUpstreamView.as_view(),
diff --git a/cms/djangoapps/contentstore/rest_api/v2/views/downstreams.py b/cms/djangoapps/contentstore/rest_api/v2/views/downstreams.py
index 8c0d651910a6..f3d4f4460654 100644
--- a/cms/djangoapps/contentstore/rest_api/v2/views/downstreams.py
+++ b/cms/djangoapps/contentstore/rest_api/v2/views/downstreams.py
@@ -67,11 +67,21 @@
 from rest_framework.views import APIView
 from xblock.core import XBlock
 
+from openedx_learning.api import authoring
+
+from cms.djangoapps.contentstore.rest_api.v2.serializers import PublishableEntityLinksSerializer
 from cms.lib.xblock.upstream_sync import (
-    UpstreamLink, UpstreamLinkException, NoUpstream, BadUpstream, BadDownstream,
-    fetch_customizable_fields, sync_from_upstream, decline_sync, sever_upstream_link
+    BadDownstream,
+    BadUpstream,
+    NoUpstream,
+    UpstreamLink,
+    UpstreamLinkException,
+    decline_sync,
+    fetch_customizable_fields,
+    sever_upstream_link,
+    sync_from_upstream,
 )
-from common.djangoapps.student.auth import has_studio_write_access, has_studio_read_access
+from common.djangoapps.student.auth import has_studio_read_access, has_studio_write_access
 from openedx.core.lib.api.view_utils import (
     DeveloperErrorViewMixin,
     view_auth_classes,
@@ -79,7 +89,6 @@
 from xmodule.modulestore.django import modulestore
 from xmodule.modulestore.exceptions import ItemNotFoundError
 
-
 logger = logging.getLogger(__name__)
 
 
@@ -108,6 +117,20 @@ class _AuthenticatedRequest(Request):
 #         ...
 
 
+@view_auth_classes()
+class UpstreamListView(DeveloperErrorViewMixin, APIView):
+    """
+    Serves course->library publishable entity links
+    """
+    def get(self, request: _AuthenticatedRequest, course_key_string: str):
+        """
+        Fetches publishable entity links for given course key
+        """
+        links = authoring.get_entity_links_by_downstream(downstream_context_key=course_key_string)
+        serializer = PublishableEntityLinksSerializer(links, many=True)
+        return Response(serializer.data)
+
+
 @view_auth_classes(is_authenticated=True)
 class DownstreamView(DeveloperErrorViewMixin, APIView):
     """