putbytes: check the install response cookie again

libpebble3/src/commonMain/kotlin/io/rebble/libpebblecommon/connection/endpointmanager/putbytes/PutBytesSession.kt

@@ -123,7 +123,14 @@ class PutBytesSession(
 
     suspend fun sendInstall(cookie: UInt) {
         val installResponse = putBytesService.sendInstall(cookie)
-        // TODO this fired?
-//        check(installResponse.cookie.get() == cookie) { "Received response for wrong cookie" }
+        val responseCookie = installResponse.cookie.get()
+        // Firmware answers an install with cookie 0: prv_cleanup_and_send_response reads
+        // s_pb_state.token, and the commit that precedes an install has already reset the
+        // transfer state. That is why this check used to fire on every install. Zero is
+        // tolerated so the check can come back for the firmware that answers properly, while
+        // a cookie belonging to some other transfer is still caught.
+        check(responseCookie == cookie || responseCookie == 0u) {
+            "Received response for wrong cookie"
+        }
     }
 }

libpebble3/src/jvmTest/kotlin/io/rebble/libpebblecommon/connection/endpointmanager/putbytes/PutBytesSessionTest.kt

@@ -0,0 +1,54 @@
+package io.rebble.libpebblecommon.connection.endpointmanager.putbytes
+
+import TestPebbleProtocolHandler
+import io.rebble.libpebblecommon.di.ConnectionCoroutineScope
+import io.rebble.libpebblecommon.packets.PutBytesInstall
+import io.rebble.libpebblecommon.packets.PutBytesResponse
+import io.rebble.libpebblecommon.packets.PutBytesResult
+import io.rebble.libpebblecommon.services.PutBytesService
+import kotlinx.coroutines.test.TestScope
+import kotlinx.coroutines.test.runTest
+import org.junit.Test
+import kotlin.test.assertFailsWith
+
+class PutBytesSessionTest {
+    private fun ack(cookie: UInt) = PutBytesResponse().apply {
+        result.set(PutBytesResult.ACK.value)
+        this.cookie.set(cookie)
+    }
+
+    /** A session whose watch answers every install with [answerWith]. */
+    private suspend fun TestScope.sessionAnswering(answerWith: UInt): PutBytesSession {
+        val handler = TestPebbleProtocolHandler { packet ->
+            if (packet is PutBytesInstall) {
+                receivePacket(ack(answerWith))
+            }
+        }
+        val service = PutBytesService(
+            handler,
+            ConnectionCoroutineScope(backgroundScope.coroutineContext),
+        )
+        service.init()
+        testScheduler.runCurrent()
+        return PutBytesSession(service)
+    }
+
+    @Test
+    fun anInstallAnsweredWithItsOwnCookieIsAccepted() = runTest {
+        sessionAnswering(answerWith = 7u).sendInstall(7u)
+    }
+
+    @Test
+    fun anInstallAnsweredWithZeroIsAccepted() = runTest {
+        // What the firmware actually sends: prv_cleanup_and_send_response reads
+        // s_pb_state.token, which the preceding commit already cleared.
+        sessionAnswering(answerWith = 0u).sendInstall(7u)
+    }
+
+    @Test
+    fun anInstallAnsweredForAnotherTransferIsNot() = runTest {
+        val session = sessionAnswering(answerWith = 8u)
+
+        assertFailsWith<IllegalStateException> { session.sendInstall(7u) }
+    }
+}