fix(server): battery alerts when low, not when charged

lib/view/page/server/card/metric.dart

@@ -3,6 +3,7 @@ import 'package:icons_plus/icons_plus.dart';
 import 'package:material_ui/material_ui.dart';
 import 'package:server_box/core/extension/context/locale.dart';
 import 'package:server_box/data/model/app/server_detail_card.dart';
+import 'package:server_box/data/model/server/battery.dart';
 import 'package:server_box/data/model/server/gpu.dart';
 import 'package:server_box/data/model/server/server.dart';
 import 'package:server_box/data/provider/server/single.dart';
@@ -58,6 +59,10 @@ const kNetTrafficIcon = MingCute.chart_bar_line;
 /// and the extra slot's ranking all mean the same thing by "over".
 const kServerAlertPercent = 85.0;
 
+/// The charge at which a battery running on itself is worth a look: the one
+/// reading whose trouble is at the bottom rather than the top.
+const kServerBatteryLowPercent = 20.0;
+
 /// One reading, as a card draws it.
 ///
 /// The same object is the row and the chart: promoting a row is choosing which
@@ -76,7 +81,8 @@ final class ServerMetric {
     required this.format,
     this.percent,
     this.binary = false,
-  });
+    bool? over,
+  }) : _over = over;
 
   final ServerMetricKind kind;
   final String label;
@@ -128,8 +134,12 @@ final class ServerMetric {
   /// rather than of 10.
   final bool binary;
 
-  /// Whether this reading is past [kServerAlertPercent].
-  bool get over => percent != null && percent! * 100 >= kServerAlertPercent;
+  final bool? _over;
+
+  /// Whether this reading is past its line: [kServerAlertPercent] for a share
+  /// of something that runs out, unless the reading says otherwise.
+  bool get over =>
+      _over ?? (percent != null && percent! * 100 >= kServerAlertPercent);
 }
 
 /// Which reading a machine is being watched by, remembered per machine.
@@ -661,6 +671,12 @@ List<ServerMetric> _readings(ServerState srv) {
         note: [battery.status.name, ?battery.name].join(' · '),
         bigNote: battery.status.name,
         percent: percent == null ? null : percent / 100,
+        // Full is where a battery should be. Low is only trouble while it is
+        // what the machine runs on.
+        over:
+            percent != null &&
+            percent <= kServerBatteryLowPercent &&
+            battery.status == BatteryStatus.discharging,
         samples: h.battery.toList(),
         times: times,
         format: ReadingFmt.pct,

test/unit/server/server_card_readings_test.dart

@@ -1,4 +1,5 @@
 import 'package:flutter_test/flutter_test.dart';
+import 'package:server_box/data/model/server/battery.dart';
 import 'package:server_box/data/model/server/conn.dart';
 import 'package:server_box/data/model/server/cpu.dart';
 import 'package:server_box/data/model/server/disk.dart';
@@ -8,6 +9,7 @@ import 'package:server_box/data/model/server/server.dart';
 import 'package:server_box/data/model/server/system.dart';
 import 'package:server_box/data/model/server/temp.dart';
 import 'package:server_box/data/provider/server/single.dart';
+import 'package:server_box/data/res/chart_palette.dart';
 import 'package:server_box/view/page/server/card/metric.dart';
 
 import '../../helpers/spi_fixture.dart';
@@ -153,4 +155,26 @@ void main() {
     srv.status.cpu.brand.clear();
     expect(serverCardReadings(srv).all.first.note, '×2');
   });
+
+  test('a battery is over its line when low and discharging, not when full', () {
+    ServerMetric battery(int percent, BatteryStatus status) {
+      final srv = state();
+      srv.status.batteries.add(Battery(status: status, percent: percent));
+      return serverCardReadings(srv).all.firstWhere(
+        (m) => m.kind == ServerMetricKind.battery,
+      );
+    }
+
+    // #1673: a charged laptop turned its machine's dot yellow.
+    expect(battery(97, BatteryStatus.discharging).over, isFalse);
+    expect(battery(100, BatteryStatus.full).over, isFalse);
+    expect(battery(15, BatteryStatus.discharging).over, isTrue);
+    expect(battery(15, BatteryStatus.charging).over, isFalse);
+
+    final srv = state();
+    srv.status.batteries.add(
+      const Battery(status: BatteryStatus.discharging, percent: 97),
+    );
+    expect(serverStateDot(srv), StatePalette.running);
+  });
 }