feat(customization): system font, custom Google Fonts by URL, font size slider

lib/core/config/app_fonts.dart

@@ -1,37 +1,120 @@
 import 'package:flutter/material.dart';
 import 'package:google_fonts/google_fonts.dart';
+import 'package:shared_preferences/shared_preferences.dart';
 
 class AppFont {
   final String id;
   final String label;
-  final String googleFamily;
+  final String? googleFamily;
 
   const AppFont({
     required this.id,
     required this.label,
-    required this.googleFamily,
+    this.googleFamily,
   });
+
+  bool get isSystem => googleFamily == null;
+  bool get isCustom => id.startsWith(AppFonts.customPrefix);
 }
 
 class AppFonts {
   static const String prefKey = 'app_font';
+  static const String scalePrefKey = 'app_font_scale';
+  static const String customPrefKey = 'app_custom_fonts';
+  static const String customPrefix = 'g:';
 
-  static const List<AppFont> all = [
+  static const double minScale = 0.85;
+  static const double maxScale = 1.35;
+  static const double defaultScale = 1.0;
+
+  static const List<AppFont> builtIn = [
+    AppFont(id: 'system', label: 'Системный'),
     AppFont(id: 'inter', label: 'Inter', googleFamily: 'Inter'),
     AppFont(id: 'unbounded', label: 'Unbounded', googleFamily: 'Unbounded'),
   ];
 
-  static AppFont get fallback => all.first;
+  static AppFont get fallback => builtIn.first;
 
-  static AppFont byId(String? id) {
-    return all.firstWhere((f) => f.id == id, orElse: () => fallback);
+  static String customId(String family) => '$customPrefix$family';
+
+  static AppFont resolve(String id) {
+    if (id.startsWith(customPrefix)) {
+      final family = id.substring(customPrefix.length);
+      return AppFont(id: id, label: family, googleFamily: family);
+    }
+    return builtIn.firstWhere((f) => f.id == id, orElse: () => fallback);
   }
 
   static TextTheme textTheme(String id, TextTheme base) {
-    return GoogleFonts.getTextTheme(byId(id).googleFamily, base);
+    final family = resolve(id).googleFamily;
+    if (family == null) return base;
+    try {
+      return GoogleFonts.getTextTheme(family, base);
+    } catch (_) {
+      return base;
+    }
   }
 
   static TextStyle sample(String id, {required double fontSize}) {
-    return GoogleFonts.getFont(byId(id).googleFamily, fontSize: fontSize);
+    final family = resolve(id).googleFamily;
+    if (family == null) return TextStyle(fontSize: fontSize);
+    try {
+      return GoogleFonts.getFont(family, fontSize: fontSize);
+    } catch (_) {
+      return TextStyle(fontSize: fontSize);
+    }
+  }
+
+  static double clampScale(double scale) =>
+      scale.clamp(minScale, maxScale).toDouble();
+
+  static String? familyFromInput(String input) {
+    var value = input.trim();
+    if (value.isEmpty) return null;
+
+    final uri = Uri.tryParse(value);
+    if (uri != null && uri.host.contains('fonts.google.com')) {
+      final idx = uri.pathSegments.indexOf('specimen');
+      if (idx != -1 && idx + 1 < uri.pathSegments.length) {
+        value = uri.pathSegments[idx + 1];
+      }
+    }
+
+    try {
+      value = Uri.decodeComponent(value);
+    } catch (_) {}
+    value = value.replaceAll('+', ' ').trim();
+    return value.isEmpty ? null : value;
+  }
+
+  static String? matchGoogleFamily(String family) {
+    final map = GoogleFonts.asMap();
+    if (map.containsKey(family)) return family;
+    final lower = family.toLowerCase();
+    for (final key in map.keys) {
+      if (key.toLowerCase() == lower) return key;
+    }
+    return null;
+  }
+
+  static Future<List<String>> loadCustomFamilies() async {
+    final prefs = await SharedPreferences.getInstance();
+    return prefs.getStringList(customPrefKey) ?? const <String>[];
+  }
+
+  static Future<void> addCustomFamily(String family) async {
+    final prefs = await SharedPreferences.getInstance();
+    final list = prefs.getStringList(customPrefKey) ?? <String>[];
+    if (!list.contains(family)) {
+      list.add(family);
+      await prefs.setStringList(customPrefKey, list);
+    }
+  }
+
+  static Future<void> removeCustomFamily(String family) async {
+    final prefs = await SharedPreferences.getInstance();
+    final list = prefs.getStringList(customPrefKey) ?? <String>[];
+    list.remove(family);
+    await prefs.setStringList(customPrefKey, list);
   }
 }