Restore the 5am morning-fetch alarm

Reverts part of the previous commit: the explicit refresh button and
fetch-on-launch stay, but the user still wants the background 5am alarm so
articles are fresh before the app is opened, not just the periodic hourly
WorkManager job.

1 files changed, 78 insertions, 0 deletions

diff --git a/app/src/main/java/org/terst/feedreader/work/MorningFetchReceiver.kt b/app/src/main/java/org/terst/feedreader/work/MorningFetchReceiver.kt
new file mode 100644
index 0000000..c897046
--- /dev/null
+++ b/app/src/main/java/org/terst/feedreader/work/MorningFetchReceiver.kt
@@ -0,0 +1,78 @@
+package org.terst.feedreader.work
+
+import android.app.AlarmManager
+import android.app.PendingIntent
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.os.Build
+import android.util.Log
+import java.util.Calendar
+
+private const val TAG = "MorningFetch"
+
+/**
+ * Wakes the device at a fixed time every morning to run a feed fetch, so the app has
+ * fresh articles ready before the user ever opens it. Uses an exact alarm
+ * (setExactAndAllowWhileIdle) specifically so this one wake survives Doze without
+ * requesting the much broader "ignore battery optimizations" exemption -- the user wants
+ * battery optimization left on otherwise, just this one daily wake-up.
+ */
+class MorningFetchReceiver : BroadcastReceiver() {
+    override fun onReceive(context: Context, intent: Intent) {
+        try {
+            // A reboot only needs the alarm re-armed (AlarmManager alarms don't survive a
+            // restart) -- an actual fetch isn't due just because the phone restarted.
+            if (intent.action != Intent.ACTION_BOOT_COMPLETED) {
+                FeedFetchWorker.fetchNow(context)
+            }
+        } catch (e: Exception) {
+            Log.e(TAG, "Failed to enqueue morning fetch for action=${intent.action}", e)
+        }
+        scheduleNext(context)
+    }
+
+    companion object {
+        private const val HOUR = 5
+        private const val MINUTE = 0
+        private const val ACTION_MORNING_FETCH = "org.terst.feedreader.MORNING_FETCH"
+
+        private fun nextTriggerMillis(): Long {
+            val now = Calendar.getInstance()
+            val next = Calendar.getInstance().apply {
+                set(Calendar.HOUR_OF_DAY, HOUR)
+                set(Calendar.MINUTE, MINUTE)
+                set(Calendar.SECOND, 0)
+                set(Calendar.MILLISECOND, 0)
+            }
+            if (next.timeInMillis <= now.timeInMillis) {
+                next.add(Calendar.DAY_OF_MONTH, 1)
+            }
+            return next.timeInMillis
+        }
+
+        /** No-ops quietly if the exact-alarm permission isn't granted yet (Android 12+) --
+         *  MainActivity is what prompts for that; this just skips scheduling until it's there.
+         *  Also survives any failure from AlarmManager itself (logged, not crashed): this runs
+         *  unconditionally from MainActivity.onCreate/onResume on every single launch, so an
+         *  unguarded exception here would crash the app on every open -- a background wake-up
+         *  alarm failing to schedule isn't worth that; just log it and let the next app open
+         *  try again. */
+        fun scheduleNext(context: Context) {
+            try {
+                val alarmManager = context.getSystemService(Context.ALARM_SERVICE) as? AlarmManager ?: return
+                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S && !alarmManager.canScheduleExactAlarms()) {
+                    return
+                }
+                val intent = Intent(context, MorningFetchReceiver::class.java).setAction(ACTION_MORNING_FETCH)
+                val pendingIntent = PendingIntent.getBroadcast(
+                    context, 0, intent,
+                    PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
+                )
+                alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, nextTriggerMillis(), pendingIntent)
+            } catch (e: Exception) {
+                Log.e(TAG, "Failed to schedule morning fetch alarm", e)
+            }
+        }
+    }
+}