Use an 8-digit token for each car so it is easy to share.

app/src/main/java/com/racingapp/pitlog/data/AppDatabase.kt

@@ -253,7 +253,7 @@ abstract class AppDatabase : RoomDatabase() {
                             db.execSQL(
                                 """
                                 INSERT INTO cars (carName, raceClass, discipline, token, updatedAt, syncRev, deleted, pending)
-                                VALUES ('$DEFAULT_CAR', '$DEFAULT_CLASS', '$DEFAULT_DISCIPLINE', lower(hex(randomblob(32))), 1, 0, 0, 1)
+                                VALUES ('$DEFAULT_CAR', '$DEFAULT_CLASS', '$DEFAULT_DISCIPLINE', printf('%08d', abs(random()) % 100000000), 1, 0, 0, 1)
                                 """.trimIndent(),
                             )
                         }

app/src/main/java/com/racingapp/pitlog/data/RaceDao.kt

@@ -132,6 +132,15 @@ interface RaceDao {
     @Query("SELECT * FROM cars WHERE id = :id")
     suspend fun carById(id: Long): Car?
 
+    @Query("UPDATE race_nights SET pending = 1 WHERE carId = :carId")
+    suspend fun markNightsPending(carId: Long)
+
+    @Query("UPDATE runs SET pending = 1 WHERE nightId IN (SELECT id FROM race_nights WHERE carId = :carId)")
+    suspend fun markRunsPending(carId: Long)
+
+    @Query("UPDATE setup_sheets SET pending = 1 WHERE carId = :carId")
+    suspend fun markSheetsPending(carId: Long)
+
     @Query("SELECT * FROM cars WHERE token = :token LIMIT 1")
     suspend fun carByToken(token: String): Car?
 

app/src/main/java/com/racingapp/pitlog/data/Repository.kt

@@ -1,5 +1,6 @@
 package com.racingapp.pitlog.data
 
+import java.security.MessageDigest
 import java.security.SecureRandom
 import java.util.UUID
 import kotlinx.coroutines.flow.Flow
@@ -24,28 +25,39 @@ suspend fun ensureCars(dao: RaceDao, preferences: SyncPreferences) {
         preferences.selectedCarId = id
         return
     }
-    val first = cars.firstOrNull { !it.deleted } ?: cars.first()
-    if (first.token.isBlank()) {
-        val kept = preferences.token.trim().ifBlank { newCarToken() }
-        val rev = if (kept == preferences.token.trim() && first.syncRev == 0L) preferences.rev else first.syncRev
-        dao.updateCar(first.copy(token = kept, syncRev = rev, pending = true))
+    for (car in cars) {
+        if (isEightDigitToken(car.token)) continue
+        val source = car.token.ifBlank { preferences.token.trim() }
+        val next = if (source.isBlank()) newCarToken() else eightDigitToken(source)
+        dao.updateCar(car.copy(token = next, syncRev = 0, pending = true))
+        dao.markNightsPending(car.id)
+        dao.markRunsPending(car.id)
+        dao.markSheetsPending(car.id)
     }
+    val first = cars.firstOrNull { !it.deleted } ?: cars.first()
     val selected = preferences.selectedCarId
     if (selected == 0L || cars.none { it.id == selected && !it.deleted }) {
         preferences.selectedCarId = first.id
     }
 }
 
-fun newCarToken(): String {
-    val bytes = ByteArray(32)
-    SecureRandom().nextBytes(bytes)
-    return bytes.joinToString("") { "%02x".format(it) }
+fun newCarToken(): String = "%08d".format(SecureRandom().nextInt(100_000_000))
+
+fun eightDigitToken(current: String): String {
+    val digest = MessageDigest.getInstance("SHA-256").digest(current.toByteArray(Charsets.UTF_8))
+    var value = 0L
+    for (index in 0 until 4) {
+        value = (value shl 8) or (digest[index].toLong() and 0xff)
+    }
+    return "%08d".format(value % 100_000_000L)
 }
 
+fun isEightDigitToken(token: String): Boolean = token.length == 8 && token.all { it.isDigit() }
+
 fun cleanCarToken(raw: String): String {
     val line = raw.trim().lineSequence().firstOrNull().orEmpty().trim()
     val withoutLabel = if (line.startsWith("token:", ignoreCase = true)) line.substringAfter(":").trim() else line
-    return withoutLabel.lowercase()
+    return withoutLabel.filter { !it.isWhitespace() }.lowercase()
 }
 
 class Repository(
@@ -125,7 +137,7 @@ class Repository(
 
     suspend fun joinCar(raw: String): String {
         val token = cleanCarToken(raw)
-        if (token.length < 16 || token.any { it !in '0'..'9' && it !in 'a'..'f' }) {
+        if (!isEightDigitToken(token)) {
             return "That token doesn't look right."
         }
         val existing = dao.carByToken(token)

app/src/main/java/com/racingapp/pitlog/ui/settings/SettingsScreen.kt

@@ -230,7 +230,7 @@ fun SettingsScreen(onBack: () -> Unit) {
                 )
                 SectionLabel("This car's token")
                 Text(
-                    "Share this token with another phone, then on that phone use Add a car from a token. That phone syncs this car. A different car gets a different token, so it can sync with different phones.",
+                    "This token is 8 digits. Share it with another phone, then on that phone use Add a car from a token. That phone syncs this car. A different car gets a different token.",
                     color = MaterialTheme.colorScheme.onSurfaceVariant,
                 )
                 SelectionContainer {