From 359d8e07ef5cb585fff13031d075d7c949135317 Mon Sep 17 00:00:00 2001
From: Mica White <botahamec@outlook.com>
Date: Tue, 13 Jan 2026 22:51:59 -0500
Subject: Complete settings page

---
 lib/jotai.dart | 150 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 150 insertions(+)
 create mode 100644 lib/jotai.dart

(limited to 'lib/jotai.dart')

diff --git a/lib/jotai.dart b/lib/jotai.dart
new file mode 100644
index 0000000..a415e13
--- /dev/null
+++ b/lib/jotai.dart
@@ -0,0 +1,150 @@
+import 'package:flutter/material.dart';
+import 'package:geolocator/geolocator.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+import 'package:speedometer/main.dart';
+
+String _defaultToString(dynamic value) => value.toString();
+
+void Function(T) storageObserver<T>(
+  String key, [
+  String Function(T) toString = _defaultToString,
+]) {
+  return (T value) => SharedPreferencesAsync().setString(key, toString(value));
+}
+
+Future<T> fromString<T>(
+  String key,
+  List<T> options, [
+  String Function(T) toString = _defaultToString,
+]) {
+  return SharedPreferencesAsync()
+      .getString(key)
+      .then(
+        (value) => options.firstWhere((option) => value == toString(option)),
+      );
+}
+
+Observable<T> observablePreference<T>(
+  String key,
+  T defaultValue,
+  List<T> options, [
+  String Function(T) toString = _defaultToString,
+]) => Observable(
+  defaultValue,
+  loadValue: fromString(key, options, toString),
+  observers: [storageObserver(key, toString)],
+);
+
+final speedUnitsObservable = observablePreference('speedUnits', null, [
+  ...SpeedUnit.values,
+  null,
+]);
+final themeModeObservable = observablePreference(
+  'themeMode',
+  ThemeMode.system,
+  ThemeMode.values,
+);
+final primaryColorObservable = observablePreference(
+  "primaryColor",
+  Colors.red,
+  [...Colors.primaries, Colors.grey],
+  (color) => color.toARGB32().toString(),
+);
+final showMarginOfErrorObservable = observablePreference(
+  "showMarginOfError",
+  true,
+  [true, false],
+);
+final locationAccuracyObservable = observablePreference(
+  "locationAccuracy",
+  LocationAccuracy.best,
+  LocationAccuracy.values,
+);
+
+class Observable<T> {
+  T _value;
+  final List<void Function(T)?> _observers = [];
+
+  Observable(
+    this._value, {
+    Future<T>? loadValue,
+    List<void Function(T)?>? observers,
+  }) {
+    if (observers != null) {
+      _observers.addAll(observers);
+    }
+
+    if (loadValue != null) {
+      loadValue.then((value) => this.value = value);
+    }
+  }
+
+  T get value => _value;
+  set value(T value) {
+    if (value == _value) {
+      return;
+    }
+
+    _value = value;
+
+    for (var observer in _observers) {
+      if (observer != null) {
+        observer(_value);
+      }
+    }
+  }
+
+  int subscribe(void Function(T) onChange) {
+    final id = _observers.length;
+    _observers.add(onChange);
+    return id;
+  }
+
+  void unsubscribe(int subscriberId) {
+    _observers[subscriberId] = null;
+  }
+}
+
+class ObserverBuilder<T> extends StatefulWidget {
+  final Observable<T> observable;
+  final Widget Function(BuildContext, T, void Function(T)) builder;
+
+  const ObserverBuilder({
+    required this.observable,
+    required this.builder,
+    super.key,
+  });
+
+  @override
+  State<ObserverBuilder<T>> createState() => _ObserverState<T>();
+}
+
+class _ObserverState<T> extends State<ObserverBuilder<T>> {
+  late T _value;
+  late int _subscriberId;
+
+  @override
+  void initState() {
+    super.initState();
+    _subscriberId = widget.observable.subscribe(
+      (value) => setState(() => _value = value),
+    );
+    _value = widget.observable.value;
+  }
+
+  @override
+  void dispose() {
+    super.dispose();
+    widget.observable.unsubscribe(_subscriberId);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return widget.builder(
+      context,
+      _value,
+      (value) => widget.observable.value = value,
+    );
+  }
+}
-- 
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