From 9f7359a297423fd1d3dbafe89e6b38a97c54d60d Mon Sep 17 00:00:00 2001
From: Bo Bayles <bbayles@gmail.com>
Date: Tue, 24 Sep 2024 10:51:37 -0500
Subject: [PATCH] Support Low Latency playlists with omitted LAST-MSN

---
 m3u8/model.py       |  5 +++--
 tests/playlists.py  | 52 +++++++++++++++++++++++++++++++++++++++++++++
 tests/test_model.py |  8 +++++++
 3 files changed, 63 insertions(+), 2 deletions(-)

diff --git a/m3u8/model.py b/m3u8/model.py
index 7f293d1f..9bc16071 100644
--- a/m3u8/model.py
+++ b/m3u8/model.py
@@ -1294,7 +1294,7 @@ def __str__(self):
 
 
 class RenditionReport(BasePathMixin):
-    def __init__(self, base_uri, uri, last_msn, last_part=None):
+    def __init__(self, base_uri, uri, last_msn=None, last_part=None):
         self.base_uri = base_uri
         self.uri = uri
         self.last_msn = last_msn
@@ -1303,7 +1303,8 @@ def __init__(self, base_uri, uri, last_msn, last_part=None):
     def dumps(self):
         report = []
         report.append("URI=" + quoted(self.uri))
-        report.append("LAST-MSN=" + str(self.last_msn))
+        if self.last_msn is not None:
+            report.append("LAST-MSN=" + str(self.last_msn))
         if self.last_part is not None:
             report.append("LAST-PART=" + str(self.last_part))
 
diff --git a/tests/playlists.py b/tests/playlists.py
index c3403dbc..56c05f71 100755
--- a/tests/playlists.py
+++ b/tests/playlists.py
@@ -1111,6 +1111,58 @@
 #EXT-X-RENDITION-REPORT:URI="../4M/waitForMSN.php",LAST-MSN=273,LAST-PART=3
 """
 
+LOW_LATENCY_OMITTED_ATTRIBUTES = """
+#EXTM3U
+#EXT-X-VERSION:7
+#EXT-X-TARGETDURATION:2
+#EXT-X-SERVER-CONTROL:CAN-BLOCK-RELOAD=YES,PART-HOLD-BACK=2.171
+#EXT-X-PART-INF:PART-TARGET=1.034
+#EXT-X-MAP:URI="init_data.m4s"
+#EXT-X-MEDIA-SEQUENCE:6342
+#EXT-X-PROGRAM-DATE-TIME:2024-09-24T15:31:57.350+00:00
+#EXTINF:2,
+chunk_6342.m4s
+#EXT-X-PROGRAM-DATE-TIME:2024-09-24T15:31:59.350+00:00
+#EXTINF:2,
+chunk_6343.m4s
+#EXT-X-PROGRAM-DATE-TIME:2024-09-24T15:32:01.350+00:00
+#EXTINF:2,
+chunk_6344.m4s
+#EXT-X-PROGRAM-DATE-TIME:2024-09-24T15:32:03.350+00:00
+#EXTINF:2,
+chunk_6345.m4s
+#EXT-X-PROGRAM-DATE-TIME:2024-09-24T15:32:05.350+00:00
+#EXTINF:2,
+chunk_6346.m4s
+#EXT-X-PROGRAM-DATE-TIME:2024-09-24T15:32:07.350+00:00
+#EXTINF:2,
+chunk_6347.m4s
+#EXT-X-PROGRAM-DATE-TIME:2024-09-24T15:32:09.350+00:00
+#EXTINF:2,
+chunk_6348.m4s
+#EXT-X-PROGRAM-DATE-TIME:2024-09-24T15:32:11.350+00:00
+#EXT-X-PART:DURATION=1,URI="chunk_6349.0.m4s",INDEPENDENT=YES
+#EXT-X-PART:DURATION=1,URI="chunk_6349.1.m4s"
+#EXTINF:2,
+chunk_6349.m4s
+#EXT-X-PROGRAM-DATE-TIME:2024-09-24T15:32:13.350+00:00
+#EXT-X-PART:DURATION=1,URI="chunk_6350.0.m4s",INDEPENDENT=YES
+#EXT-X-PART:DURATION=1,URI="chunk_6350.1.m4s"
+#EXTINF:2,
+chunk_6350.m4s
+#EXT-X-PROGRAM-DATE-TIME:2024-09-24T15:32:15.350+00:00
+#EXT-X-PART:DURATION=1,URI="chunk_6351.0.m4s?skid=default&signature=NjZmYzFjODBfYzY3NGRlODc4Zjk1MjM1OGNmMmE3NjhiM2E2NTUyNGI1Y2JiYzMyZDU5YTFjNTQzODI2MjI5ZTllZmNhMDZmNQ==&zone=1",INDEPENDENT=YES
+#EXT-X-PART:DURATION=1,URI="chunk_6351.1.m4s?skid=default&signature=NjZmYzFjODBfMDcwMjA0OTZlMTE3Y2RiN2VjOGY2YjE2MDE2NTAwZThlN2Q3NjUyZTAzM2YxZTZlZmFlZTg1ZThmZWEyZmQ4Ng==&zone=1"
+#EXTINF:2,
+chunk_6350.m4s
+#EXT-X-PRELOAD-HINT:TYPE=PART,URI="chunk_6352.0.m4s?skid=default&signature=NjZmYzFjODBfMzkyZmNiOWNjNmY5N2EwN2QwNTU3YTA3M2Q0ZTRlMWU2YjliZDMyM2Y0MTRmYTY5OTdhODIyMmIwY2QwOWY1NQ==&zone=1"
+#EXT-X-RENDITION-REPORT:URI="rendition_1.m3u8"
+#EXT-X-RENDITION-REPORT:URI="rendition_2.m3u8"
+#EXT-X-RENDITION-REPORT:URI="rendition_3.m3u8"
+#EXT-X-RENDITION-REPORT:URI="rendition_4.m3u8"
+#EXT-X-RENDITION-REPORT:URI="rendition_5.m3u8"
+"""
+
 LOW_LATENCY_WITH_PRELOAD_AND_BYTERANGES_PLAYLIST = """
 #EXTM3U
 #EXTINF:4.08,
diff --git a/tests/test_model.py b/tests/test_model.py
index abeb61dc..8185fe38 100755
--- a/tests/test_model.py
+++ b/tests/test_model.py
@@ -1345,6 +1345,14 @@ def test_ll_playlist():
     assert obj.preload_hint.base_uri == "http://localhost/test_base_uri"
 
 
+def test_ll_playlist_omitted_attributes():
+    # RFC 8216 4.4.5.4 states that even the required attribute LAST-MSN
+    # can be omitted in certain conditions.
+    obj = m3u8.M3U8(playlists.LOW_LATENCY_OMITTED_ATTRIBUTES)
+    text = obj.dumps()
+    assert '#EXT-X-RENDITION-REPORT:URI="rendition_1.m3u8"\n' in text
+
+
 def test_add_rendition_report_to_playlist():
     obj = m3u8.M3U8()