Drive Android decoding by codec readiness and bounded working frames

tools/chatgui-android/app/src/test/java/com/utun/chat/data/StreamDecodePumpTest.kt

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+package com.utun.chat.data
+
+import org.junit.Assert.*
+import org.junit.Test
+import java.util.ArrayDeque
+
+class StreamDecodePumpTest {
+    private data class Frame(override val pts: Long) : StreamDecodePump.Frame
+    private class Codec(val depth: Int) {
+        val queued = ArrayDeque<Frame>()
+        var released = 0
+        var blocked = false
+        var finishing = false
+        var held = false
+        var nextIndex = 0
+        val pump = StreamDecodePump<Frame>(
+            submit = { if (blocked) false else { queued.addLast(it); true } },
+            receive = {
+                if (held || (queued.size < depth && !finishing) || queued.isEmpty()) null
+                else { held = true; StreamDecodePump.Output(nextIndex++, queued.removeFirst().pts) }
+            },
+            release = { _, _ -> check(held); held = false; released++ }
+        )
+    }
+
+    @Test fun fourAndEightFramePipelinesStartWithFrozenPresentationClock() {
+        for (depth in listOf(4, 8)) {
+            val codec = Codec(depth)
+            repeat(depth) { i ->
+                assertTrue(codec.pump.wantsInput)
+                codec.pump.offer(Frame(i * 66666L), i * 66666L)
+                codec.pump.step(0, i * 66666L)
+            }
+            assertEquals(depth.toLong(), codec.pump.inputCount)
+            assertEquals(1L, codec.pump.outputCount)
+            assertEquals(1, codec.released)
+            assertEquals(0L, codec.pump.firstOutputPts)
+            assertEquals((depth - 1) * 66666L, codec.pump.decoderLeadUs)
+        }
+    }
+
+    @Test fun futureOutputStopsReadsAndNeverReleasesEarly() {
+        val codec = Codec(1)
+        codec.pump.offer(Frame(100000), 0); codec.pump.step(0, 0)
+        assertFalse(codec.pump.wantsInput); assertNotNull(codec.pump.output); assertEquals(0, codec.released)
+        codec.pump.step(99999, 15_000_000); codec.pump.checkProgress(15_000_000, false)
+        assertEquals(0, codec.released)
+        codec.pump.step(100000, 15_000_001)
+        assertEquals(1, codec.released); assertTrue(codec.pump.wantsInput)
+    }
+
+    @Test fun blockedCodecKeepsOneInputAndReportsStall() {
+        val codec = Codec(4); codec.blocked = true
+        codec.pump.offer(Frame(0), 0); codec.pump.step(0, 0)
+        assertNotNull(codec.pump.input); assertFalse(codec.pump.wantsInput)
+        try { codec.pump.checkProgress(10_000_001, false); fail("Stalled decoder must fail") }
+        catch (expected: IllegalStateException) { assertTrue(expected.message!!.contains("no output progress")) }
+    }
+
+    @Test fun networkPauseKeepsReferencesAndAllowsIncompletePipelineToResume() {
+        val codec = Codec(4)
+        repeat(2) { i -> codec.pump.offer(Frame(i * 40000L), i * 40000L); codec.pump.step(0, i * 40000L) }
+        codec.pump.checkProgress(20_000_000, false)
+        repeat(2) { i ->
+            val now = 20_000_000 + i * 40000L
+            codec.pump.offer(Frame((i + 2) * 40000L), now); codec.pump.step(0, now); codec.pump.checkProgress(now, false)
+        }
+        assertEquals(4L, codec.pump.inputCount); assertEquals(1, codec.released)
+    }
+
+    @Test fun finishDrainsShortStreamAndPreservesTheLastPicture() {
+        val codec = Codec(8)
+        repeat(3) { i -> codec.pump.offer(Frame(i * 40000L), i * 40000L); codec.pump.step(0, i * 40000L) }
+        assertEquals(0, codec.released); codec.finishing = true
+        codec.pump.step(0, 120000); assertEquals(1, codec.released); assertFalse(codec.pump.wantsInput)
+        codec.pump.step(40000, 160000); assertEquals(2, codec.released)
+        codec.pump.step(80000, 200000); assertEquals(3, codec.released)
+    }
+}