fix(todo): only a full wait counts towards lying still (ADR 0033, D32)

Asking for fixes at a new interval brings one at once, so each doubling
brought the next: on the emulator's walk the wait went from 30 s to
120 s within 40 s, and would reach 5 min within a couple of minutes,
leaving someone who sets off again unnoticed for that long. A still fix
now counts only once at least three quarters of the wait asked for
has passed; a move still starts over at once.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/todo/halkyon_todo_flutter/android/app/src/main/kotlin/app/halkyon/todo/LocationDwell.kt

@@ -58,6 +58,20 @@ object LocationDwell {
   /** Whether the phone, [moved] metres since the last fix, lies still. */
   fun still(moved: Float): Boolean = moved < STILL_METRES
 
+  /**
+   * How many fixes the phone has lain still, [before] this one, [moved] metres
+   * from the last and [waited] milliseconds after it, [asked] being the wait
+   * asked for. A move starts over. A fix sooner than asked says nothing (a
+   * quarter short still counts, as Android may hand one over a little early):
+   * asking anew brings one at once, and counting those reached the longest
+   * wait within a minute or two.
+   */
+  fun stillFixes(before: Int, moved: Float, waited: Long, asked: Long): Int = when {
+    !still(moved) -> 0
+    waited * 4 >= asked * 3 -> before + 1
+    else -> before
+  }
+
   /**
    * How long until the next fix: as long as reaching the nearest circle,
    * [metres] away, takes at the fastest, doubled for each of [stillFixes]

apps/todo/halkyon_todo_flutter/android/app/src/main/kotlin/app/halkyon/todo/LocationWatchService.kt

@@ -110,7 +110,16 @@ class LocationWatchService : Service(), LocationListener {
     val accuracy = if (fix.hasAccuracy()) fix.accuracy else null
     LocationReminders.log(this, "fix, ${accuracy ?: "?"} m")
     if (!LocationDwell.usable(accuracy)) return
-    stillFixes = if (before != null && LocationDwell.still(before.distanceTo(fix))) stillFixes + 1 else 0
+    stillFixes = if (before == null) {
+      0
+    } else {
+      LocationDwell.stillFixes(
+        before = stillFixes,
+        moved = before.distanceTo(fix),
+        waited = (fix.elapsedRealtimeNanos - before.elapsedRealtimeNanos) / 1_000_000,
+        asked = requested ?: 0,
+      )
+    }
     last = fix
     LocationReminders.seen(this, fix.latitude, fix.longitude)
     ask(next(fix))

apps/todo/halkyon_todo_flutter/android/app/src/test/kotlin/app/halkyon/todo/LocationDwellTest.kt

@@ -101,4 +101,37 @@ class LocationDwellTest {
     assertTrue(LocationDwell.still(moved = 49f))
     assertFalse(LocationDwell.still(moved = 50f))
   }
+
+  @Test
+  fun `a still fix after the wait asked for counts`() {
+    assertEquals(3, LocationDwell.stillFixes(before = 2, moved = 10f, waited = 60_000L, asked = 60_000L))
+    assertEquals(3, LocationDwell.stillFixes(before = 2, moved = 10f, waited = 45_000L, asked = 60_000L))
+  }
+
+  @Test
+  fun `a fix sooner than asked for says nothing of lying still`() {
+    assertEquals(2, LocationDwell.stillFixes(before = 2, moved = 10f, waited = 5_000L, asked = 60_000L))
+    assertEquals(2, LocationDwell.stillFixes(before = 2, moved = 10f, waited = 44_000L, asked = 60_000L))
+  }
+
+  @Test
+  fun `a move starts over, however soon it came`() {
+    assertEquals(0, LocationDwell.stillFixes(before = 3, moved = 50f, waited = 5_000L, asked = 240_000L))
+    assertEquals(0, LocationDwell.stillFixes(before = 3, moved = 900f, waited = 240_000L, asked = 240_000L))
+  }
+
+  @Test
+  fun `a phone lying still takes minutes to reach the longest wait`() {
+    // Each wait is asked anew, which brings a fix at once: the fix in the
+    // emulator's walk that doubled it within seconds, 5 Nov 2026.
+    var fixes = 0
+    var elapsed = 0L
+    while (LocationDwell.interval(metres = 1_000f, stillFixes = fixes) < LocationDwell.LATEST_MILLIS) {
+      val asked = LocationDwell.interval(metres = 1_000f, stillFixes = fixes)
+      fixes = LocationDwell.stillFixes(fixes, moved = 0f, waited = 5_000L, asked = asked)
+      fixes = LocationDwell.stillFixes(fixes, moved = 0f, waited = asked, asked = asked)
+      elapsed += 5_000L + asked
+    }
+    assertTrue(elapsed >= 7 * 60_000L)
+  }
 }