feat: adds RDA for intake of vitamins and certain elements based on

canada health values

lib/services/nutrient_data_service.dart

@@ -0,0 +1,40 @@
+import 'dart:convert';
+
+import 'package:flutter/services.dart';
+
+import '../models/nutrient.dart';
+
+class NutrientDataService {
+  static final NutrientDataService _instance = NutrientDataService._internal();
+
+  factory NutrientDataService() {
+    return _instance;
+  }
+
+  NutrientDataService._internal();
+
+  List<Nutrient>? _nutrients;
+
+  Future<List<Nutrient>> get nutrients async {
+    if (_nutrients != null) {
+      return _nutrients!;
+    }
+    await _loadNutrientData();
+    return _nutrients!;
+  }
+
+  Future<void> _loadNutrientData() async {
+    try {
+      final String response = await rootBundle.loadString('assets/canada_health.json');
+      final data = await json.decode(response);
+      final nutrientsData = data['nutrients'] as Map<String, dynamic>;
+
+      _nutrients = nutrientsData.entries.map((entry) {
+        return Nutrient.fromJson(entry.key, entry.value);
+      }).toList();
+    } catch (e) {
+      print('Error loading nutrient data: $e');
+      _nutrients = [];
+    }
+  }
+}