fix: recover contiguous live media gaps

Author: Priveetee

src/main/kotlin/dev/typetype/server/services/SabrLivePlayback.kt

@@ -108,13 +108,13 @@ internal fun SabrSessionHolder.isFutureLiveRequest(request: SabrSegmentRequest):
 internal fun SabrSessionHolder.isHistoricalLiveRequest(request: SabrSegmentRequest): Boolean {
     if (request.isInitializationSegment) return false
     val live = livePlaybackSnapshot()?.takeIf { it.active } ?: return false
+    val observed = observedMediaSegment(request.format) ?: return false
+    val requestEndMs = playbackSegmentEndMs(request.format, request.sequenceNumber)
+    if (requestEndMs < live.headTimeMs - LIVE_HISTORICAL_REQUEST_TOLERANCE_MS) return true
     lastServedSequence(request.format)?.let { lastServed ->
         if (request.sequenceNumber in lastServed..lastServed + LIVE_FUTURE_SEGMENT_TOLERANCE) return false
     }
-    val observed = observedMediaSegment(request.format) ?: return false
-    if (request.sequenceNumber < observed.header.sequenceNumber) return true
-    val requestEndMs = playbackSegmentEndMs(request.format, request.sequenceNumber)
-    return requestEndMs < live.headTimeMs - LIVE_HISTORICAL_REQUEST_TOLERANCE_MS
+    return request.sequenceNumber < observed.header.sequenceNumber
 }
 
 internal fun SabrSessionHolder.liveRetryAfterMs(blockedRequests: List<SabrSegmentRequest> = emptyList()): Long =

src/test/kotlin/dev/typetype/server/services/SabrLiveFutureRequestTest.kt

@@ -3,6 +3,7 @@ package dev.typetype.server.services
 import io.mockk.every
 import io.mockk.mockk
 import org.junit.jupiter.api.Assertions.assertFalse
+import org.junit.jupiter.api.Assertions.assertTrue
 import org.junit.jupiter.api.Test
 import org.schabi.newpipe.extractor.services.youtube.sabr.SabrMediaHeader
 import org.schabi.newpipe.extractor.services.youtube.sabr.SabrMediaSegment
@@ -63,8 +64,11 @@ class SabrLiveFutureRequestTest {
             lastRequestAt = Instant.EPOCH,
         )
         holder.observeMediaSegment(segment(audio.itag, 3_889, 7_776_000L))
+        holder.setLastServedSequence(audio.itag, 3_889)
+        val request = SabrSegmentRequest.media(audio, 3_890)
 
-        assertFalse(holder.isFutureLiveRequest(SabrSegmentRequest.media(audio, 3_890)))
+        assertFalse(holder.isFutureLiveRequest(request))
+        assertTrue(holder.isHistoricalLiveRequest(request))
     }
 
     private fun format(itag: Int): YoutubeSabrFormat = mockk {

src/test/kotlin/dev/typetype/server/services/SabrSeekRepositionPumpTest.kt

@@ -196,6 +196,7 @@ class SabrSeekRepositionPumpTest {
             every { session.pumpOnceStreamingForDemand(any(), request) } returns mockk(relaxed = true)
             val holder = holder(session, audio, video)
             holder.observeMediaSegment(mediaSegment(video.itag, sequence = 3_076))
+            holder.setLastServedSequence(video.itag, 3_076)
             holder.requestSegmentDemand(request)
             assertFalse(holder.isFutureLiveRequest(request))
             assertEquals(DEFAULT_PLAYBACK_RETRY_MS, holder.liveRetryAfterMs(listOf(request)))