refactor(chat): single owner for display kinds and REST row ids (#1364)

app/src/test/java/com/m57/hermescontrol/ui/chat/ChatMessageIdentityTest.kt

@@ -0,0 +1,34 @@
+package com.m57.hermescontrol.ui.chat
+
+import com.m57.hermescontrol.data.local.canonicalMessageOrder
+import com.m57.hermescontrol.ui.chat.fullbleed.isTimelineMarker
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+/** Issue #1336: one owner for the REST row-id format and the known display kinds. */
+class ChatMessageIdentityTest {
+    @Test
+    fun restIdsRoundTripThroughTheSingleFormatOwner() {
+        val id = RestMessageId.of("s-1", 42)
+
+        assertEquals("rest-s-1-42", id)
+        assertTrue(RestMessageId.isRest(id))
+        assertFalse(RestMessageId.isRest("ws-42"))
+        assertEquals(42L, canonicalMessageOrder(id, "s-1"))
+        assertNull(canonicalMessageOrder(RestMessageId.of("other", 42), "s-1"))
+        assertEquals(id, ChatMessage(id = id, role = MessageRole.USER, content = "").canonicalRestId)
+    }
+
+    @Test
+    fun onlyUnknownOrMarkerKindsAreTimelineMarkers() {
+        fun kind(value: String?) = ChatMessage(role = MessageRole.USER, content = "x", displayKind = value)
+
+        DisplayKind.nonMarkerKinds.forEach { assertFalse(it, kind(it).isTimelineMarker()) }
+        assertTrue(kind(DisplayKind.MODEL_SWITCH).isTimelineMarker())
+        assertTrue(kind("future_backend_kind").isTimelineMarker())
+        assertFalse(kind(null).isTimelineMarker())
+    }
+}