feat: load video poster from Educast videos

Load the video poster for videos that are stored from Educast.
So the migration to use the desktop mp4 migration to use the real stream
m3u8 format will continue to show the video poster (preview,
thumbnail).

fccn/nau-technical#708

Author: igobranco

nau_openedx_extensions/apps.py

@@ -40,4 +40,17 @@ def ready(self):
         """
         Method to perform actions after apps registry is ended
         """
+        # Override the default Video xBlock the _poster private function.
+        # Override the class was giving more work because of the html dependencies
+        # was being loaded from the new package. So it was more easy just replace the
+        # method implementation.
+        from xmodule.video_block.video_block import \
+            VideoBlock  # pylint: disable=import-error,import-outside-toplevel # noqa
+
         from nau_openedx_extensions import signals  # pylint: disable=import-outside-toplevel,unused-import # noqa
+        from nau_openedx_extensions.xblocks.video_block import \
+            get_educast_poster_factory  # pylint: disable=import-outside-toplevel # noqa
+
+        # Replace the method in the original VideoBlock class
+        prev_poster_func = VideoBlock._poster  # pylint: disable=protected-access
+        VideoBlock._poster = get_educast_poster_factory(prev_poster_func)  # pylint: disable=protected-access

nau_openedx_extensions/xblocks/__init__.py

@@ -0,0 +1,85 @@
+"""
+Test cases for the customized VideoBlock _poster method for Educast videos.
+"""
+from django.test import TestCase
+
+from nau_openedx_extensions.xblocks.video_block import get_educast_poster_factory
+
+
+class FakeVideoBlock():
+    """
+    A fake VideoBlock XBlock class for testing
+    """
+    def __init__(self):
+        self.html5_sources = {}
+
+
+class TestVideoBlock(TestCase):
+    """
+    Test cases for the customized VideoBlock _poster method for Educast videos.
+    """
+    def test_get_educast_poster_https(self):
+        """
+        Test the customized _poster method for VideoBlock.
+        """
+        # Create a mock previous _poster method
+        def mock_prev_poster(self):  # pylint: disable=unused-argument
+            return None
+
+        # Create the customized _poster method
+        customized_poster_method = get_educast_poster_factory(mock_prev_poster)
+
+        # Create an instance of VideoBlock and set html5_sources
+        video_block = FakeVideoBlock()
+        video_block.html5_sources = ['https://dev.educast.fccn.pt/vod/clips/bum66sthd/streaming.m3u8']
+
+        # Call the customized _poster method
+        poster_url = customized_poster_method(video_block)
+
+        # Verify the poster URL is as expected
+        expected_url = 'https://dev.educast.fccn.pt/img/clips/bum66sthd/delivery/cover'
+        self.assertEqual(poster_url, expected_url)
+
+    def test_get_educast_poster_http(self):
+        """
+        Test the customized _poster method for VideoBlock.
+        """
+        # Create a mock previous _poster method
+        def mock_prev_poster(self):  # pylint: disable=unused-argument
+            return None
+
+        # Create the customized _poster method
+        customized_poster_method = get_educast_poster_factory(mock_prev_poster)
+
+        # Create an instance of VideoBlock and set html5_sources
+        video_block = FakeVideoBlock()
+        video_block.html5_sources = ['http://educast.fccn.pt/vod/clips/fdgfdgfdgfdg/streaming.m3u8']
+
+        # Call the customized _poster method
+        poster_url = customized_poster_method(video_block)
+
+        # Verify the poster URL is as expected
+        expected_url = 'http://educast.fccn.pt/img/clips/fdgfdgfdgfdg/delivery/cover'
+        self.assertEqual(poster_url, expected_url)
+
+    def test_get_educast_poster_no_protocol(self):
+        """
+        Test the customized _poster method for VideoBlock.
+        """
+        # Create a mock previous _poster method
+        def mock_prev_poster(self):  # pylint: disable=unused-argument
+            return None
+
+        # Create the customized _poster method
+        customized_poster_method = get_educast_poster_factory(mock_prev_poster)
+
+        # Create an instance of VideoBlock and set html5_sources
+        video_block = FakeVideoBlock()
+        video_block.html5_sources = ['//educast.fccn.pt/vod/clips/aaaaaa/streaming.m3u8']
+
+        # Call the customized _poster method
+        poster_url = customized_poster_method(video_block)
+
+        # Verify the poster URL is as expected
+        expected_url = '//educast.fccn.pt/img/clips/aaaaaa/delivery/cover'
+        self.assertEqual(poster_url, expected_url)

nau_openedx_extensions/xblocks/tests/__init__.py

@@ -0,0 +1,31 @@
+"""
+Custom video block extensions for NAU Open edX.
+"""
+import re
+
+
+def get_educast_poster_factory(prev_poster_func):
+    """
+    Factory to create a customized _poster method for VideoBlock.
+    This allows us to inject custom logic while retaining access to the original method.
+    """
+
+    def get_educast_poster(self):
+        """
+        Override the default poster URL logic to customize the poster image.
+        """
+        poster_url = prev_poster_func(self)
+        if not poster_url and self.html5_sources:
+            video_src = next(iter(self.html5_sources), None)
+            is_educast = 'educast.fccn.pt' in video_src  # to work for both educast staging and production
+            if is_educast:
+                # from video src like https://staging.educast.fccn.pt/vod/clips/bum66sthd/streaming.m3u8
+                # extract the server base url https://educast.fccn.pt or http://educast.fccn.pt or //educast.fccn.pt
+                server_base_url = re.match(r'^(https?://[^/]+|//[^/]+)', video_src).group(1)
+                # extract the educast video id like bumu66sthd
+                educast_video_id = re.search(r'/clips/([^/]+)/', video_src).group(1)
+                # construct poster url like https://educast.fccn.pt/img/clips/jpojtray/delivery/cover
+                poster_url = f"{server_base_url}/img/clips/{educast_video_id}/delivery/cover"
+        return poster_url
+
+    return get_educast_poster