Frontend first draft

frontend/pshared/lib/provider/template.dart

@@ -0,0 +1,170 @@
+import 'package:flutter/material.dart';
+
+import 'package:collection/collection.dart';
+
+import 'package:pshared/models/permission_bound_storable.dart';
+import 'package:pshared/provider/exception.dart';
+import 'package:pshared/provider/resource.dart';
+import 'package:pshared/service/template.dart';
+
+
+List<T> mergeLists<T>({
+  required List<T> lhs,
+  required List<T> rhs,
+  required Comparable Function(T) getKey, // Extracts ID dynamically
+  required int Function(T, T) compare,
+  required T Function(T, T) merge,
+}) {
+  final result = <T>[];
+  final map = {for (var item in lhs) getKey(item): item};
+
+  for (var updated in rhs) {
+    final key = getKey(updated);
+    map[key] = merge(map[key] ?? updated, updated);
+  }
+
+  result.addAll(map.values);
+  result.sort(compare);
+  return result;
+}
+
+/// A generic provider that wraps a [BasicService] instance
+/// to manage state (loading, error, data) without re‑implementing service logic.
+class GenericProvider<T extends PermissionBoundStorable> extends ChangeNotifier {
+  final BasicService<T> service;
+
+  Resource<List<T>> _resource = Resource(data: []);
+  Resource<List<T>> get resource => _resource;
+
+  List<T> get items => List.unmodifiable(_resource.data ?? []);
+  bool get isLoading => _resource.isLoading;
+  bool get isEmpty => items.isEmpty;
+  Object? get error => _resource.error;
+
+  String? _currentObjectRef; // Stores the currently selected project ref
+  T? get currentObject => _resource.data?.firstWhereOrNull(
+    (object) => object.id == _currentObjectRef,
+  );
+
+  T? getItemById(String id) => items.firstWhereOrNull((item) => item.id == id);
+
+  GenericProvider({required this.service});
+
+
+  bool Function(T)? _filterPredicate;
+
+  List<T> get filteredItems => _filterPredicate != null ? items.where(_filterPredicate!).toList() : items;
+
+  void setFilterPredicate(bool Function(T)? predicate) {
+    _filterPredicate = predicate;
+    notifyListeners();
+  }
+
+  void clearFilter() => setFilterPredicate(null);
+
+  void _setResource(Resource<List<T>> newResource) {
+    _resource = newResource;
+    notifyListeners();
+  }
+
+  Future<void> loadFuture(Future<List<T>> future) async {
+    _setResource(_resource.copyWith(isLoading: true));
+    try {
+      final list = await future;
+      _setResource(Resource(data: list, isLoading: false));
+    } catch (e) {
+      _setResource(
+        _resource.copyWith(isLoading: false, error: toException(e)),
+      );
+      rethrow;
+    }
+  }
+
+  Future<void> load(String organizationRef, String? parentRef) async {
+    if (parentRef != null) {
+      return loadFuture(service.list(organizationRef, parentRef));
+    }
+  }
+
+  Future<void> loadItem(String itemRef) async {
+    return loadFuture((() async => [await service.get(itemRef)])());
+  }
+
+
+  List<T> merge(List<T> rhs) => mergeLists<T>(
+    lhs: items,
+    rhs: rhs,
+    getKey: (item) => item.id,  // Key extractor
+    compare: (a, b) => a.id.compareTo(b.id), // Sorting logic
+    merge: (existing, updated) => updated, // Replace with the updated version
+  );
+
+  Future<T> get(String objectRef) async {
+    _setResource(_resource.copyWith(isLoading: true));
+    try {
+      final item = await service.get(objectRef);
+      _setResource(Resource(data: merge([item]), isLoading: false));
+      return item;
+    } catch (e) {
+      _setResource(_resource.copyWith(isLoading: false, error: toException(e)));
+      rethrow;
+    }
+  }
+
+  Future<T> createObject(String organizationRef, Map<String, dynamic> request) async {
+    _setResource(_resource.copyWith(isLoading: true));
+    try {
+      final newObject = await service.create(organizationRef, request);
+      _setResource(Resource(data: [...items, ...newObject], isLoading: false));
+      return newObject.first;
+    } catch (e) {
+      _setResource(_resource.copyWith(isLoading: false, error: toException(e)));
+      rethrow;
+    }
+  }
+
+  Future<void> update(Map<String, dynamic> request) async {
+    _setResource(_resource.copyWith(isLoading: true));
+    try {
+      final list = await service.update(request);
+      _setResource(Resource(data: merge(list), isLoading: false));
+    } catch (e) {
+      _setResource(_resource.copyWith(isLoading: false, error: toException(e)));
+      rethrow;
+    }
+  }
+
+  Future<void> delete(String objectRef) async {
+    _setResource(_resource.copyWith(isLoading: true));
+
+    try {
+      await service.delete(objectRef);
+      if (_currentObjectRef == objectRef) {
+        _currentObjectRef = null;
+      }
+
+      _setResource(Resource(
+        data: _resource.data?.where((p) => p.id != objectRef).toList(),
+        isLoading: false,
+      ));
+    } catch (e) {
+      _setResource(Resource(data: _resource.data, isLoading: false, error: toException(e)));
+      rethrow;
+    }
+  }
+
+  bool setCurrentObject(String? objectRef) {
+    if (objectRef == null) {
+      _currentObjectRef = null;
+      notifyListeners();
+      return true;
+    }
+    if (_resource.data?.any((p) => p.id == objectRef) ?? false) {
+      _currentObjectRef = objectRef;
+      notifyListeners();
+      return true;
+    }
+
+    return false; // Object not found
+  }
+}