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.

2 files changed, 140 insertions, 3 deletions

diff --git a/app/src/main/java/org/terst/feedreader/ui/MainActivity.kt b/app/src/main/java/org/terst/feedreader/ui/MainActivity.kt
index 85bc2b3..dff9858 100644
--- a/app/src/main/java/org/terst/feedreader/ui/MainActivity.kt
+++ b/app/src/main/java/org/terst/feedreader/ui/MainActivity.kt
@@ -1,6 +1,12 @@
 package org.terst.feedreader.ui
 
+import android.app.AlarmManager
+import android.content.Intent
+import android.net.Uri
+import android.os.Build
 import android.os.Bundle
+import android.provider.Settings
+import android.util.Log
 import android.webkit.CookieManager
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
@@ -16,9 +22,13 @@ import androidx.navigation.compose.composable
 import androidx.navigation.compose.rememberNavController
 import androidx.navigation.navArgument
 import org.terst.feedreader.work.FeedFetchWorker
+import org.terst.feedreader.work.MorningFetchReceiver
 import java.net.URLDecoder
 import java.net.URLEncoder
 
+private const val TAG = "MainActivity"
+private const val KEY_REQUESTED_EXACT_ALARM = "requestedExactAlarmPermission"
+
 const val UNREAD_FEED_ID = "__unread__"
 const val SAVED_FEED_ID = "__saved__"
 const val OLDER_FEED_ID = "__older__"
@@ -32,10 +42,12 @@ fun decodeNavArg(value: String): String = URLDecoder.decode(value, "UTF-8")
 class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        // The only implicit fetch trigger left: a fresh cold launch. No periodic
-        // WorkManager job and no background alarm any more -- per user request, refreshing
-        // only ever happens here or from an explicit tap on the refresh button.
+        requestedExactAlarmPermission = savedInstanceState?.getBoolean(KEY_REQUESTED_EXACT_ALARM) ?: false
+        // A fresh cold launch always fetches immediately; the 5am alarm below is the only
+        // other trigger left (no periodic WorkManager job any more) -- otherwise refreshing
+        // only happens via an explicit tap on the refresh button.
         FeedFetchWorker.fetchNow(applicationContext)
+        maybeScheduleMorningFetch()
         // Explicit, even though it defaults on -- BrowserScreen relies on cookies set
         // during a site login surviving into the reader's later extraction requests.
         CookieManager.getInstance().setAcceptCookie(true)
@@ -49,6 +61,53 @@ class MainActivity : ComponentActivity() {
             }
         }
     }
+
+    // Re-checked on resume too, not just onCreate -- returning here from the "Alarms &
+    // reminders" Settings screen (below) is an onResume, not a fresh onCreate, and the
+    // alarm should get armed the moment permission is actually granted rather than
+    // needing a full app relaunch.
+    override fun onResume() {
+        super.onResume()
+        maybeScheduleMorningFetch()
+    }
+
+    // onCreate's own onStart/onResume fires once automatically as part of normal startup,
+    // right after onCreate -- before the user has done anything -- so without this guard,
+    // a not-yet-granted permission would launch the Settings screen twice back to back
+    // (once from onCreate, immediately again from that auto-triggered onResume). Restored
+    // from savedInstanceState in onCreate (see below), not left as a plain field that
+    // silently resets to false on every config change -- a rotation while still ungranted
+    // used to re-trigger the Settings screen every time the device rotated.
+    private var requestedExactAlarmPermission = false
+
+    override fun onSaveInstanceState(outState: Bundle) {
+        super.onSaveInstanceState(outState)
+        outState.putBoolean(KEY_REQUESTED_EXACT_ALARM, requestedExactAlarmPermission)
+    }
+
+    // Runs unconditionally on every onCreate/onResume -- must never let an exception
+    // escape from here, or a device/OEM quirk around the exact-alarm APIs would crash
+    // the app on every single launch. A wake-up alarm failing to schedule just isn't
+    // worth that; worst case it's logged and tries again next launch.
+    private fun maybeScheduleMorningFetch() {
+        try {
+            val alarmManager = getSystemService(AlarmManager::class.java) ?: return
+            val canScheduleExact = Build.VERSION.SDK_INT < Build.VERSION_CODES.S || alarmManager.canScheduleExactAlarms()
+            if (canScheduleExact) {
+                MorningFetchReceiver.scheduleNext(applicationContext)
+            } else if (!requestedExactAlarmPermission) {
+                requestedExactAlarmPermission = true
+                // Android 12+ only: exact alarms require a one-time user grant via Settings,
+                // there's no in-app permission dialog for this one. Sends the user straight to
+                // this app's page in the "Alarms & reminders" settings screen.
+                startActivity(
+                    Intent(Settings.ACTION_REQUEST_SCHEDULE_EXACT_ALARM, Uri.parse("package:$packageName"))
+                )
+            }
+        } catch (e: Exception) {
+            Log.e(TAG, "Failed to schedule or request permission for morning fetch", e)
+        }
+    }
 }
 
 @Composable
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)
+            }
+        }
+    }
+}