fix: fill progressive SABR seek windows

Author: Priveetee

src/main/kotlin/dev/typetype/server/routes/SabrPlaybackWindowBuilder.kt

@@ -15,6 +15,8 @@ import dev.typetype.server.services.resolvePlaybackStartMs
 import org.schabi.newpipe.extractor.services.youtube.sabr.SabrSegmentRequest
 import org.schabi.newpipe.extractor.services.youtube.sabr.YoutubeSabrFormat
 
+private const val MAX_SEGMENTS_PER_TRACK = 12
+
 internal class SabrPlaybackWindowBuilder(private val sabrSessionStore: SabrSessionStore) {
     suspend fun build(
         holder: SabrSessionHolder,
@@ -140,6 +142,7 @@ internal class SabrPlaybackWindowBuilder(private val sabrSessionStore: SabrSessi
                     seq = progressive.nextSequence
                     coveredEndMs = progressive.coveredEndMs
                     if (coveredEndMs >= goalEndMs) break
+                    if (progressive.hasReadableMedia) continue
                     blockedRequest = SabrSegmentRequest.media(format, seq)
                     blockedBy = "${format.trackName()}:${format.itag}:$seq pending"
                     break
@@ -214,7 +217,4 @@ internal class SabrPlaybackWindowBuilder(private val sabrSessionStore: SabrSessi
     ) {
         fun covers(requiredEndMs: Long): Boolean = (track.segments.isNotEmpty() || atEnd) && coveredEndMs >= requiredEndMs
     }
-    private companion object {
-        const val MAX_SEGMENTS_PER_TRACK = 12
-    }
 }

src/main/kotlin/dev/typetype/server/routes/SabrProgressivePlaybackWindow.kt

@@ -11,9 +11,14 @@ import org.schabi.newpipe.extractor.services.youtube.sabr.YoutubeSabrFormat
 internal data class SabrProgressiveWindowSegment(
     val sequence: Int,
     val response: SabrPlaybackWindowSegment,
+    val hasReadableMedia: Boolean,
 )
 
-internal data class SabrProgressiveWindowAppend(val nextSequence: Int, val coveredEndMs: Long)
+internal data class SabrProgressiveWindowAppend(
+    val nextSequence: Int,
+    val coveredEndMs: Long,
+    val hasReadableMedia: Boolean,
+)
 
 internal fun MutableList<SabrPlaybackWindowSegment>.appendProgressiveWindowSegment(
     holder: SabrSessionHolder,
@@ -27,6 +32,7 @@ internal fun MutableList<SabrPlaybackWindowSegment>.appendProgressiveWindowSegme
     return SabrProgressiveWindowAppend(
         segment.sequence + 1,
         segment.response.startMs + segment.response.durationMs,
+        segment.hasReadableMedia,
     )
 }
 
@@ -52,6 +58,7 @@ internal fun SabrSessionHolder.progressiveWindowSegment(
             startMs = startMs,
             durationMs = durationMs,
         ),
+        actual != null,
     )
 }
 

src/test/kotlin/dev/typetype/server/routes/SabrProgressivePlaybackWindowTest.kt

@@ -81,6 +81,46 @@ class SabrProgressivePlaybackWindowTest {
         assertEquals(9_985L, result.response.audio.segments.single().durationMs)
     }
 
+    @Test
+    fun `vod window includes enough progressive segments to satisfy the buffer goal`() = runTest {
+        val audio = format(140, isAudio = true)
+        val video = format(299, isAudio = false)
+        val state = mockk<YoutubeSabrStreamState>(relaxed = true)
+        every { state.getSegmentNumberAtOrAfterTimeMs(any(), 5_731_077L) } returns 1
+        val session = mockk<YoutubeSabrSession>(relaxed = true)
+        every { session.streamState } returns state
+        every { session.getCachedSegment(any()) } returns null
+        every { session.getReadableSegment(any()) } answers {
+            val request = firstArg<SabrSegmentRequest>()
+            val durationMs = if (request.format.isAudio) 10_000L else 6_000L
+            readableSegment(
+                request.format,
+                sequence = request.sequenceNumber,
+                startMs = 5_731_000L + (request.sequenceNumber - 1L) * durationMs,
+                durationMs = durationMs,
+            )
+        }
+        val holder = holder(session, audio, video)
+        val store = mockk<SabrSessionStore>()
+        coEvery { store.cachedSegment(holder, any()) } returns null
+
+        val result = SabrPlaybackWindowBuilder(store).build(
+            holder,
+            SabrPlaybackWindowRequest(
+                generation = 0L,
+                playerTimeMs = 5_731_077L,
+                videoItag = video.itag,
+                audioItag = audio.itag,
+                bufferGoalMs = 30_000L,
+            ),
+        )
+
+        assertTrue(result.isReady)
+        assertTrue(result.blockedRequests.isEmpty())
+        assertEquals(6, requireNotNull(result.response.video).segments.size)
+        assertEquals(4, result.response.audio.segments.size)
+    }
+
     private fun readableSegment(
         format: YoutubeSabrFormat,
         sequence: Int = 1,