Random reminder fixes

- Make random reminder calculation deterministic
- Don't fire reminders immediately on recurring tasks

app/src/main/java/com/todoroo/astrid/alarms/AlarmCalculator.kt

@@ -75,10 +75,16 @@ class AlarmCalculator(
      */
     private fun calculateNextRandomReminder(random: Random, task: Task, reminderPeriod: Long) =
         if (reminderPeriod > 0) {
+            val baseline = when {
+                task.reminderLast > 0 -> task.reminderLast
+                task.isRecurring -> task.modificationDate
+                else -> task.creationDate
+            }
+
+            val multiplier = 0.85f + 0.3f * random.nextFloat(task.id + baseline)
+
             maxOf(
-                task.reminderLast
-                    .coerceAtLeast(task.creationDate)
-                    .plus((reminderPeriod * (0.85f + 0.3f * random.nextFloat())).toLong()),
+                baseline.plus((reminderPeriod * multiplier).toLong()),
                 task.hideUntil
             )
         } else {

app/src/main/java/org/tasks/reminders/Random.java

@@ -1,10 +0,0 @@
-package org.tasks.reminders;
-
-public class Random {
-
-  private static final java.util.Random random = new java.util.Random();
-
-  public float nextFloat() {
-    return random.nextFloat();
-  }
-}

app/src/main/java/org/tasks/reminders/Random.kt

@@ -0,0 +1,14 @@
+package org.tasks.reminders
+
+import java.util.Random
+
+open class Random {
+    open fun nextFloat(seed: Long): Float {
+        random.setSeed(seed)
+        return random.nextFloat()
+    }
+
+    companion object {
+        private val random = Random()
+    }
+}

app/src/test/java/com/todoroo/astrid/alarms/AlarmCalculatorTest.kt

@@ -295,7 +295,7 @@ class AlarmCalculatorTest {
 
     @Test
     fun scheduleOverdueRandomReminder() {
-        random.seed = 0.3865f
+        random.stub = 0.3865f
         freezeAt(now) {
             val alarm = alarmCalculator.toAlarmEntry(
                 newTask(
@@ -316,7 +316,7 @@ class AlarmCalculatorTest {
 
     @Test
     fun scheduleOverdueRandomReminderForHiddenTask() {
-        random.seed = 0.3865f
+        random.stub = 0.3865f
         freezeAt(now) {
             val task = newTask(
                 with(REMINDER_LAST, now.minusDays(14)),
@@ -335,7 +335,7 @@ class AlarmCalculatorTest {
 
     @Test
     fun scheduleInitialRandomReminder() {
-        random.seed = 0.3865f
+        random.stub = 0.3865f
 
         freezeAt(now) {
             val alarm = alarmCalculator.toAlarmEntry(
@@ -358,7 +358,7 @@ class AlarmCalculatorTest {
 
     @Test
     fun scheduleNextRandomReminder() {
-        random.seed = 0.3865f
+        random.stub = 0.3865f
 
         freezeAt(now) {
             val alarm = alarmCalculator.toAlarmEntry(
@@ -379,9 +379,28 @@ class AlarmCalculatorTest {
         }
     }
 
+    @Test
+    fun randomReminderIsDeterministic() {
+        val calculator = AlarmCalculator(
+            isDefaultDueTimeEnabled = true,
+            random = Random(),
+            defaultDueTime = TimeUnit.HOURS.toMillis(13).toInt(),
+        )
+
+        freezeAt(now) {
+            val task = newTask(with(CREATION_TIME, now.minusDays(1)))
+            val alarm = Alarm(time = ONE_WEEK, type = TYPE_RANDOM)
+
+            val first = calculator.toAlarmEntry(task, alarm)
+            val second = calculator.toAlarmEntry(task, alarm)
+
+            assertEquals(first, second)
+        }
+    }
+
     internal class RandomStub : Random() {
-        var seed = 1.0f
+        var stub = 1.0f
 
-        override fun nextFloat() = seed
+        override fun nextFloat(seed: Long) = this.stub
     }
 }