fix(android): the cast relay spools a receiver's lead to disk

Fragments are 5-10 MB at a film's bitrate; dropped past 8 MB in memory, the
TV froze for their length. Each receiver now reads from its own spool file,
deleted with it; nothing is dropped short of a disk bound.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 29 insertions, 2 deletions

diff --git a/packages/meshbay-android/app/src/test/kotlin/org/meshbay/client/CastRelayTest.kt b/packages/meshbay-android/app/src/test/kotlin/org/meshbay/client/CastRelayTest.kt
index e11c8c0..1c604d0 100644
--- a/packages/meshbay-android/app/src/test/kotlin/org/meshbay/client/CastRelayTest.kt
+++ b/packages/meshbay-android/app/src/test/kotlin/org/meshbay/client/CastRelayTest.kt
@@ -17,9 +17,10 @@ import java.net.Socket
 
 /** The real relay on loopback, read with a raw socket: what a receiver sees. */
 class CastRelayTest {
-    private val relay = CastRelay { InetAddress.getByName("127.0.0.1") }
+    private val spool = java.nio.file.Files.createTempDirectory("relay-spool").toFile()
+    private val relay = CastRelay({ InetAddress.getByName("127.0.0.1") }, spool)
 
-    @After fun stop() = relay.stop()
+    @After fun stop() { relay.stop(); spool.deleteRecursively() }
 
     private class Reply(val status: Int, val headers: Map<String, String>, val body: ByteArray)
 
@@ -166,6 +167,32 @@ class CastRelayTest {
         }
     }
 
+    @Test fun `a receiver far behind loses nothing, and its spool goes with it`() {
+        // Fragments of 4 MB, ten of them pushed while the receiver has read
+        // none: far past the 8 MB the desktop drops at, which froze the TV.
+        val url = relay.start(null, null).getString("url")
+        val u = java.net.URI(url)
+        Socket(u.host, u.port).use { s ->
+            s.getOutputStream().write("GET ${u.rawPath}?${u.rawQuery} HTTP/1.1\r\nHost: x\r\n\r\n".toByteArray())
+            Thread.sleep(300)
+            val big = (0 until 10).map { box("moof", 16 + it) + box("mdat", 4 * 1024 * 1024 + it) }
+            big.forEach { relay.push(it) }
+            assertEquals("one spool file for the one receiver", 1, spool.listFiles()!!.size)
+            val input = DataInputStream(s.getInputStream())
+            while (true) { val l = StringBuilder(); while (true) { val c = input.read(); if (c == '\n'.code) break; l.append(c.toChar()) }; if (l.toString().trim().isEmpty()) break }
+            val body = ByteArrayOutputStream()
+            val want = big.sumOf { it.size }
+            while (body.size() < want) {
+                val size = StringBuilder().also { sb -> while (true) { val c = input.read(); if (c == '\n'.code) break; sb.append(c.toChar()) } }.toString().trim().toInt(16)
+                val buf = ByteArray(size); input.readFully(buf); body.write(buf); input.read(); input.read()
+            }
+            assertArrayEquals("every fragment, in order, none dropped", big.reduce { a, b -> a + b }, body.toByteArray())
+        }
+        Thread.sleep(300)
+        relay.stop()
+        assertEquals("the spool is deleted with the receiver", 0, spool.listFiles()!!.size)
+    }
+
     @Test fun `stopping closes the port`() {
         val url = relay.start(null, null).getString("url")
         relay.stop()