Record crashes on the device so "two weeks without one" can be checked

The milestone asks for two weeks in the living room without a crash. Nobody
reads logcat on a TV, and by the time someone says "it was gone yesterday"
the log has rotated — the criterion had no evidence behind it.

CrashLog keeps the last ten crashes in the app's own files: timestamp,
version, and the top of the stack. Nothing is sent anywhere. The settings
show either "Kein Absturz aufgezeichnet" or the newest one, and clicking
the row clears the record — so the two weeks start when you say they do.

Verified by crashing the app on purpose: the entry appears as
"26.08.2026 18:10 · 0.11.5" with the exception below it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/src/main/java/dev/castarr/tv/CrashLog.kt

@@ -0,0 +1,70 @@
+package dev.castarr.tv
+
+import android.content.Context
+import java.io.File
+import java.text.SimpleDateFormat
+import java.util.Date
+import java.util.Locale
+
+/**
+ * Keeps a short record of crashes on the device.
+ *
+ * "Two weeks in the living room without a crash" is only a criterion if a
+ * crash leaves a trace. Nobody reads logcat on a TV, and by the time someone
+ * mentions "it was gone yesterday" the log has long rotated.
+ *
+ * Deliberately local: no reporting service, nothing leaves the device.
+ */
+object CrashLog {
+
+    private const val FILE = "crashes.log"
+    private const val SEPARATOR = "\n---\n"
+
+    /** How many crashes are kept; older ones fall off the front. */
+    const val KEEP = 10
+
+    /** Lines of stack trace per entry — enough to place it, not a dump. */
+    const val TRACE_LINES = 12
+
+    fun install(context: Context, version: String) {
+        val previous = Thread.getDefaultUncaughtExceptionHandler()
+        Thread.setDefaultUncaughtExceptionHandler { thread, error ->
+            runCatching { append(context, render(System.currentTimeMillis(), version, error)) }
+            previous?.uncaughtException(thread, error)
+        }
+    }
+
+    /** One entry: when, which version, and the top of the stack. */
+    fun render(at: Long, version: String, error: Throwable): String {
+        val stamp = SimpleDateFormat("dd.MM.yyyy HH:mm", Locale.GERMANY).format(Date(at))
+        val trace = error.stackTraceToString()
+            .lineSequence()
+            .take(TRACE_LINES)
+            .joinToString("\n")
+        return "$stamp · $version\n$trace"
+    }
+
+    /** Newest last, at most [KEEP] entries. */
+    fun trim(entries: List<String>, keep: Int = KEEP): List<String> =
+        entries.filter { it.isNotBlank() }.takeLast(keep)
+
+    fun entries(context: Context): List<String> = runCatching {
+        val file = File(context.filesDir, FILE)
+        if (!file.exists()) return emptyList()
+        file.readText().split(SEPARATOR).filter { it.isNotBlank() }
+    }.getOrDefault(emptyList())
+
+    /** First line of the newest entry, or null when nothing ever crashed. */
+    fun lastSummary(context: Context): String? =
+        entries(context).lastOrNull()?.lineSequence()?.firstOrNull()
+
+    fun clear(context: Context) {
+        runCatching { File(context.filesDir, FILE).delete() }
+    }
+
+    private fun append(context: Context, entry: String) {
+        val file = File(context.filesDir, FILE)
+        val kept = trim(entries(context) + entry)
+        file.writeText(kept.joinToString(SEPARATOR))
+    }
+}

app/src/main/java/dev/castarr/tv/MainActivity.kt

@@ -37,6 +37,8 @@ class MainActivity : ComponentActivity(), ControlServer.Listener {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
+        // Before anything else, so a crash during start-up is recorded too.
+        CrashLog.install(applicationContext, BuildConfig.VERSION_NAME)
         audioManager = getSystemService(AUDIO_SERVICE) as AudioManager
         val auth = DeviceAuth(this)
         state = AppState(

app/src/main/java/dev/castarr/tv/ui/SettingsScreen.kt

@@ -259,6 +259,19 @@ fun SettingsScreen(state: AppState) {
                     "Erweitert",
                     subtitle = "M3U/EPG-Adressen von Hand eintragen",
                 ) { state.screen = AppState.Screen.ADVANCED }
+                // "Zwei Wochen ohne Absturz" ist nur nachprüfbar, wenn ein
+                // Absturz überhaupt eine Spur hinterlässt.
+                val lastCrash = remember(pairingEpoch) {
+                    dev.castarr.tv.CrashLog.lastSummary(context)
+                }
+                SettingRow(
+                    "Stabilität",
+                    subtitle = lastCrash?.let { "Letzter Absturz: $it · Klicken löscht" }
+                        ?: "Kein Absturz aufgezeichnet",
+                ) {
+                    dev.castarr.tv.CrashLog.clear(context)
+                    pairingEpoch++
+                }
             }
         }
 

tests/unit/CrashLogTest.kt

@@ -0,0 +1,47 @@
+package dev.castarr.tv
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class CrashLogTest {
+
+    @Test
+    fun `an entry names the time, the version and the top of the stack`() {
+        val error = IllegalStateException("Senderliste leer")
+        // 26.08.2026, 19:12 (MESZ)
+        val entry = CrashLog.render(1787764320000L, "0.12.0", error)
+        val lines = entry.lines()
+        assertTrue(lines.first().contains("0.12.0"))
+        assertTrue(lines.first().contains("26.08.2026"))
+        assertTrue(entry.contains("IllegalStateException"))
+        assertTrue(entry.contains("Senderliste leer"))
+    }
+
+    @Test
+    fun `a long stack is cut down to something readable`() {
+        val error = RuntimeException("tief")
+        val entry = CrashLog.render(0L, "0.12.0", error)
+        // Kopfzeile plus höchstens TRACE_LINES Zeilen Stack.
+        assertTrue(entry.lines().size <= CrashLog.TRACE_LINES + 1)
+    }
+
+    @Test
+    fun `only the newest entries are kept`() {
+        val entries = (1..15).map { "Absturz $it" }
+        val kept = CrashLog.trim(entries)
+        assertEquals(CrashLog.KEEP, kept.size)
+        assertEquals("Absturz 15", kept.last())
+        assertEquals("Absturz 6", kept.first())
+    }
+
+    @Test
+    fun `blank entries are dropped instead of counting`() {
+        assertEquals(listOf("echt"), CrashLog.trim(listOf("", "  ", "echt")))
+    }
+
+    @Test
+    fun `nothing recorded stays nothing`() {
+        assertEquals(emptyList<String>(), CrashLog.trim(emptyList()))
+    }
+}