feat(saic): read the current guidance instead of waiting for a change

The five callbacks registered on the adapter are change notifications. A car
standing still with a guidance already running publishes nothing, because
nothing changed — so the first vehicle capture could not tell "the adapter
says nothing" from "nothing happened to say", which is exactly the question
CP-040 turns on.

IGeneralService answers getGuideStatus, getRemainingTimes,
getRemainingDistance and getRoadName synchronously, on the binder this
already binds. SaicNav's note that the head unit offers no synchronous read
of remaining distance was read off IMapService; the general service does
answer.

readNow reports the current trip and keeps whatever the listener has already
seen where a getter answers nothing. A distance or time of zero reads as
unknown: the service initialises both to zero and answers zero before any
guidance has run, and a remaining distance of exactly zero is not a case any
forecast needs.

Transaction codes from saicadapterservice_overseas_eh32; the census still
guards against an R67 shift.

Refs: CP-040

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: malys

CHANGELOG.md

@@ -6,6 +6,18 @@ All notable changes to this project are documented here. Format follows
 
 ## [Unreleased]
 
+### Added
+
+- **Guidance can be read, not only waited for.** The five listener callbacks are change
+  notifications, so a car standing still with a guidance already running publishes nothing —
+  which made a parked capture unable to tell "the adapter says nothing" from "nothing happened
+  to say". `IGeneralService` answers `getGuideStatus`, `getRemainingTimes`, `getRemainingDistance`
+  and `getRoadName` synchronously on the binder already bound, so `SaicNavGuidance.readNow`
+  reports the current trip on demand. `SaicNav`'s note that the head unit answers no synchronous
+  question about a trip was read off `IMapService`; the general service does answer. A distance
+  or time of zero is treated as unreadable, as the service returns zero before any guidance has
+  run.
+
 ### Fixed
 
 - **`PERF_VEHICLE_SPEED` already reports km/h on SWI68, and was being converted a second time.**

lib/src/main/java/com/evsuite/hardware/saic/SaicNavGuidance.kt

@@ -44,6 +44,13 @@ object SaicNavGuidance {
     private const val TX_REGISTER_LISTENER = 1
     private const val TX_UNREGISTER_LISTENER = 2
 
+    // Synchronous getters on the same interface. SaicNav's note that the head unit answers no
+    // synchronous question about a trip was read off IMapService; IGeneralService does answer.
+    private const val TX_GET_ROAD_NAME = 29
+    private const val TX_GET_GUIDE_STATUS = 31
+    private const val TX_GET_REMAINING_TIMES = 33
+    private const val TX_GET_REMAINING_DISTANCE = 34
+
     private val service = SaicService.byComponent(PACKAGE, CLASS, "nav-guidance")
 
     /**
@@ -81,6 +88,38 @@ object SaicNavGuidance {
      */
     fun latest(): NavGuidance = state
 
+    /**
+     * The current guidance, read rather than waited for.
+     *
+     * The five callbacks are change notifications: a car standing still with a guidance
+     * already running publishes nothing, because nothing changed. That made a parked capture
+     * unable to tell "the adapter says nothing" from "nothing happened to say", which is the
+     * distinction CP-040 turns on. These getters answer on demand instead.
+     *
+     * Values seen so far by the listener are kept where a getter answers nothing, so a caller
+     * gets the best of both without choosing between them.
+     */
+    fun readNow(): NavGuidance {
+        val target = binder() ?: return state
+        fun int(code: Int) = SaicAidl.callInt(target, DESCRIPTOR, code)
+        // The service initialises these to 0 and answers 0 before any guidance has run, which
+        // is the same answer an arrived route would give. Unknown is the cheaper reading: a
+        // remaining distance of exactly zero is not a case any forecast needs.
+        val distance = int(TX_GET_REMAINING_DISTANCE)?.takeIf { it > 0 }
+        val minutes = int(TX_GET_REMAINING_TIMES)?.takeIf { it > 0 }
+        val status = int(TX_GET_GUIDE_STATUS)
+        val road = SaicAidl.callString(target, DESCRIPTOR, TX_GET_ROAD_NAME)?.takeIf {
+            it.isNotBlank()
+        }
+        val seen = state
+        return seen.copy(
+            guideStatus = status ?: seen.guideStatus,
+            remainingDistanceRaw = distance ?: seen.remainingDistanceRaw,
+            remainingMinutes = minutes ?: seen.remainingMinutes,
+            road = road ?: seen.road,
+        )
+    }
+
     /** Transaction codes seen so far, with counts. See [TransactionCensus]. */
     fun census(): Map<Int, Int> = census.snapshot()