feat(proj): init

mobile/lib/data/models/expense.dart

@@ -0,0 +1,82 @@
+import 'package:please_pay_me/data/models/json.dart';
+
+class Expense {
+  const Expense({
+    required this.id,
+    required this.budgetId,
+    required this.amount,
+    required this.spentAt,
+    this.note,
+  });
+
+  factory Expense.fromJson(Map<String, dynamic> json) {
+    return Expense(
+      id: asInt(json['id']),
+      budgetId: asInt(json['budget_id']),
+      amount: asDouble(json['amount']),
+      spentAt: asDate(json['spent_at']),
+      note: asStringOrNull(json['note']),
+    );
+  }
+
+  final int id;
+  final int budgetId;
+  final double amount;
+  final DateTime spentAt;
+  final String? note;
+}
+
+class ExpensesPage {
+  const ExpensesPage({
+    required this.page,
+    required this.totalPages,
+    required this.totalCount,
+    required this.pageSize,
+    required this.totalSum,
+    required this.items,
+    this.budgetId,
+  });
+
+  factory ExpensesPage.fromJson(Map<String, dynamic> json) {
+    return ExpensesPage(
+      page: asInt(json['page'], fallback: 1),
+      totalPages: asInt(json['total_pages'], fallback: 1),
+      totalCount: asInt(json['total_count']),
+      pageSize: asInt(json['page_size'], fallback: 20),
+      totalSum: asDouble(json['total_sum']),
+      budgetId: json['budget_id'] == null ? null : asInt(json['budget_id']),
+      items: asList(json['items']).map(Expense.fromJson).toList(),
+    );
+  }
+
+  static const empty = ExpensesPage(
+    page: 1,
+    totalPages: 1,
+    totalCount: 0,
+    pageSize: 20,
+    totalSum: 0,
+    items: [],
+  );
+
+  final int page;
+  final int totalPages;
+  final int totalCount;
+  final int pageSize;
+  final double totalSum;
+  final int? budgetId;
+  final List<Expense> items;
+
+  bool get hasMore => page < totalPages;
+
+  ExpensesPage copyWithItems(List<Expense> items, {int? page}) {
+    return ExpensesPage(
+      page: page ?? this.page,
+      totalPages: totalPages,
+      totalCount: totalCount,
+      pageSize: pageSize,
+      totalSum: totalSum,
+      budgetId: budgetId,
+      items: items,
+    );
+  }
+}