feat: add historical data

lib/services/bar_tab_service.dart

@@ -1,3 +1,4 @@
+import 'dart:convert';
 import 'dart:math';
 
 import 'package:drift/drift.dart';
@@ -10,6 +11,7 @@ import '../models/closed_tab.dart';
 import '../models/closed_tab_item.dart';
 import '../models/payment_method.dart';
 import '../models/product.dart';
+import '../models/tab_event.dart';
 import '../models/tab_item.dart';
 import '../models/tab_item_purchase.dart';
 
@@ -69,11 +71,13 @@ abstract class BarTabService {
   /// The tab itself stays open under the same customer name.
   ///
   /// Throws [TabVersionConflictException] when [expectedVersion] is given and
-  /// the tab changed since.
+  /// the tab changed since. [commandId] is the remote command that requested
+  /// the settlement, if any.
   Future<void> closeTab(
     String tabId, {
     PaymentMethod paymentMethod = PaymentMethod.cash,
     int? expectedVersion,
+    String? commandId,
   });
 
   Future<List<ClosedTab>> getClosedTabs();
@@ -91,9 +95,11 @@ abstract class BarTabService {
 
 class DriftBarTabService implements BarTabService {
   final AppDatabase database;
+  final TabEventFactory eventFactory;
   final _uuid = const Uuid();
 
-  DriftBarTabService({required this.database});
+  DriftBarTabService({required this.database, TabEventFactory? eventFactory})
+    : eventFactory = eventFactory ?? TabEventFactory();
 
   TabItemPurchase _mapPurchaseRow(TabItemPurchaseRow row) {
     return TabItemPurchase(
@@ -255,6 +261,21 @@ class DriftBarTabService implements BarTabService {
     )..where((item) => item.tabId.equals(tabId))).go();
   }
 
+  /// Queues [event] in the outbox. Call it inside the transaction that makes
+  /// the change, so the change and its event are stored together or not at
+  /// all.
+  Future<void> _recordEvent(TabEvent event) async {
+    await database
+        .into(database.tabEvents)
+        .insert(
+          TabEventsCompanion.insert(
+            id: event.id,
+            payload: jsonEncode(event.payload),
+            createdAt: DateTime.now(),
+          ),
+        );
+  }
+
   Future<void> _incrementTabVersion(String tabId) async {
     await (database.update(
       database.barTabs,
@@ -341,6 +362,15 @@ class DriftBarTabService implements BarTabService {
 
       for (final item in tab.items) {
         await database.increaseStock(item.productId, item.quantity);
+        await _recordEvent(
+          eventFactory.lineRemoved(
+            tabId: tab.id,
+            customerName: tab.customerName,
+            productName: item.productName,
+            unitPriceInCents: item.unitPriceInCents,
+            quantity: item.quantity,
+          ),
+        );
       }
 
       await _deleteItemsOfTab(tabId);
@@ -356,6 +386,9 @@ class DriftBarTabService implements BarTabService {
     required Product product,
   }) async {
     await database.transaction(() async {
+      final tabRow = await _getTabRow(tabId);
+      if (tabRow == null) throw TabNotFoundException(tabId);
+
       await database.decreaseStock(product.id, 1);
 
       final existingItem =
@@ -373,6 +406,16 @@ class DriftBarTabService implements BarTabService {
           TabItemsCompanion(quantity: Value(existingItem.quantity + 1)),
         );
         await _recordPurchase(existingItem.id);
+        // The line keeps the price it was first added at
+        await _recordEvent(
+          eventFactory.lineAdded(
+            tabId: tabId,
+            customerName: tabRow.customerName,
+            productName: existingItem.productName,
+            unitPriceInCents: existingItem.unitPriceInCents,
+            quantity: 1,
+          ),
+        );
       } else {
         final tabItemId = _uuid.v4();
 
@@ -390,6 +433,15 @@ class DriftBarTabService implements BarTabService {
               ),
             );
         await _recordPurchase(tabItemId);
+        await _recordEvent(
+          eventFactory.lineAdded(
+            tabId: tabId,
+            customerName: tabRow.customerName,
+            productName: product.name,
+            unitPriceInCents: product.priceInCents,
+            quantity: 1,
+          ),
+        );
       }
 
       await _incrementTabVersion(tabId);
@@ -429,6 +481,20 @@ class DriftBarTabService implements BarTabService {
             ..where((row) => row.id.equals(tabItemId)))
           .write(TabItemsCompanion(quantity: Value(newQuantity)));
 
+      final tabRow = await _getTabRow(item.tabId);
+      final lineEvent = actualDelta > 0
+          ? eventFactory.lineAdded
+          : eventFactory.lineRemoved;
+      await _recordEvent(
+        lineEvent(
+          tabId: item.tabId,
+          customerName: tabRow?.customerName ?? '',
+          productName: item.productName,
+          unitPriceInCents: item.unitPriceInCents,
+          quantity: actualDelta.abs(),
+        ),
+      );
+
       await _incrementTabVersion(item.tabId);
 
       return actualDelta;
@@ -440,6 +506,7 @@ class DriftBarTabService implements BarTabService {
     String tabId, {
     PaymentMethod paymentMethod = PaymentMethod.cash,
     int? expectedVersion,
+    String? commandId,
   }) async {
     await database.transaction(() async {
       final tabRow = await _getTabRow(tabId);
@@ -488,6 +555,34 @@ class DriftBarTabService implements BarTabService {
         ]);
       });
 
+      // One settlement, not a removal per line: these drinks were sold
+      final settledItems = [
+        for (final item in items)
+          if (item.quantity > 0) item,
+      ];
+      if (settledItems.isNotEmpty) {
+        await _recordEvent(
+          eventFactory.settled(
+            tabId: tabId,
+            customerName: tabRow.customerName,
+            amountInCents: settledItems.fold(
+              0,
+              (total, item) => total + item.lineTotalInCents,
+            ),
+            paymentMethod: paymentMethod,
+            commandId: commandId,
+            items: [
+              for (final item in settledItems)
+                (
+                  productName: item.productName,
+                  quantity: item.quantity,
+                  unitPriceInCents: item.unitPriceInCents,
+                ),
+            ],
+          ),
+        );
+      }
+
       await _deleteItemsOfTab(tabId);
       await _incrementTabVersion(tabId);
     });