fix: keep the device awake until an alarm or timer starts ringing

The fire broadcast's wake lock ended with the receiver, and the ring
services only took their own after a database read, so a dozing device
could suspend in between and ring late. Both receivers now hold a short
timed wake lock across the hand-off, and the alarm service takes its own
before the read.

app/src/main/java/de/jeanlucmakiola/clockula/alarm/receiver/AlarmFireReceiver.kt

@@ -5,6 +5,7 @@ import android.content.Intent
 import dagger.hilt.android.AndroidEntryPoint
 import de.jeanlucmakiola.clockula.alarm.AlarmEngine
 import de.jeanlucmakiola.clockula.alarm.AlarmIntents
+import de.jeanlucmakiola.clockula.ring.HandoffWakeLock
 import de.jeanlucmakiola.floret.di.ApplicationScope
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.launch
@@ -32,6 +33,7 @@ class AlarmFireReceiver : HiltBroadcastReceiver() {
 
         val alarmId = intent.getLongExtra(AlarmIntents.EXTRA_ALARM_ID, 0L)
         val action = intent.action ?: return
+        if (action == AlarmIntents.ACTION_FIRE) HandoffWakeLock.acquire(context, "clockula:alarm-fire")
         val pendingResult = goAsync()
         scope.launch {
             try {

app/src/main/java/de/jeanlucmakiola/clockula/alarm/ring/AlarmRingService.kt

@@ -67,6 +67,8 @@ class AlarmRingService : Service() {
         // foreground service a few seconds to post its notification, and a
         // database read is not something to spend them on.
         startForegroundPreparing()
+        // Also before the read: the fire broadcast's own wake lock is gone by now.
+        acquireWakeLock()
         ringing = scope.launch {
             val session = engine.ringSession()
             if (session == null) {
@@ -89,7 +91,6 @@ class AlarmRingService : Service() {
 
     private fun ring(session: RingSession) {
         startForeground(session)
-        acquireWakeLock()
 
         // Vibration first: the sound may take seconds to open when another app
         // plays it, and the ring must not be still until then.

app/src/main/java/de/jeanlucmakiola/clockula/ring/HandoffWakeLock.kt

@@ -0,0 +1,28 @@
+package de.jeanlucmakiola.clockula.ring
+
+import android.content.Context
+import android.os.PowerManager
+
+/**
+ * Keeps the CPU awake across the gap between an AlarmManager broadcast and the
+ * service it starts. The platform's own wake lock ends with the receiver, and
+ * the service takes its own only after a database read, so without this a
+ * dozing device can suspend in between and ring minutes late.
+ *
+ * Timed rather than released: the service holds its own lock well before the
+ * timeout, and a lock that outlives a crashed hand-off cannot leak.
+ */
+object HandoffWakeLock {
+
+    private const val TIMEOUT_MILLIS = 30_000L
+
+    fun acquire(context: Context, tag: String) {
+        val power = context.getSystemService(PowerManager::class.java) ?: return
+        runCatching {
+            power.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, tag).apply {
+                setReferenceCounted(false)
+                acquire(TIMEOUT_MILLIS)
+            }
+        }
+    }
+}

app/src/main/java/de/jeanlucmakiola/clockula/timer/receiver/TimerExpiryReceiver.kt

@@ -4,6 +4,7 @@ import android.content.Context
 import android.content.Intent
 import dagger.hilt.android.AndroidEntryPoint
 import de.jeanlucmakiola.clockula.alarm.receiver.HiltBroadcastReceiver
+import de.jeanlucmakiola.clockula.ring.HandoffWakeLock
 import de.jeanlucmakiola.clockula.timer.TimerEngine
 import de.jeanlucmakiola.floret.di.ApplicationScope
 import kotlinx.coroutines.CoroutineScope
@@ -28,6 +29,7 @@ class TimerExpiryReceiver : HiltBroadcastReceiver() {
     override fun onReceive(context: Context, intent: Intent) {
         super.onReceive(context, intent)
 
+        HandoffWakeLock.acquire(context, "clockula:timer-expiry")
         val pendingResult = goAsync()
         scope.launch {
             try {