feat: optimisticly update members balance

Rough draft of updating group members balance after creating an expense or payment.
janczizikow · Apr 26, 2020 · a00fce0 · a00fce0
1 parent 2a34e2e
commit a00fce0
Show file tree

Hide file tree

Showing 3 changed files with 55 additions and 11 deletions.
diff --git a/lib/main.dart b/lib/main.dart
@@ -198,36 +198,44 @@ class _MyAppState extends State<MyApp> {
       child: Consumer<Api>(
         builder: (_, api, __) => MultiProvider(
           providers: [
-            ChangeNotifierProxyProvider2<Api, Auth, AccountProvider>(
+            ChangeNotifierProxyProvider<Auth, AccountProvider>(
               create: (_) => AccountProvider(api),
-              update: (_, api, auth, account) {
+              update: (_, auth, account) {
                 if (auth.forceLogoutTimestamp != null) {
                   account.reset();
                 }
                 return account;
               },
             ),
-            ChangeNotifierProxyProvider2<Api, Auth, GroupsProvider>(
+            ChangeNotifierProxyProvider<Auth, GroupsProvider>(
                 create: (_) => GroupsProvider(api),
-                update: (_, api, auth, groups) {
+                update: (_, auth, groups) {
                   if (auth.forceLogoutTimestamp != null) {
                     groups.reset();
                   }
                   groups.isAuthenticated =
                       auth.status == AuthStatus.AUTHENTICATED;
                   return groups;
                 }),
-            ChangeNotifierProxyProvider2<Api, Auth, InvitesProvider>(
+            ChangeNotifierProxyProvider<Auth, InvitesProvider>(
               create: (_) => InvitesProvider(api),
-              update: (_, api, auth, invites) {
+              update: (_, auth, invites) {
                 if (auth.forceLogoutTimestamp != null) {
                   invites.reset();
                 }
                 return invites;
               },
             ),
-            ChangeNotifierProvider(
+            ChangeNotifierProxyProvider2<Auth, GroupsProvider,
+                ExpensesProvider>(
               create: (_) => ExpensesProvider(api),
+              update: (_, auth, groups, expenses) {
+                expenses.groupsProvider = groups;
+                if (auth.forceLogoutTimestamp != null) {
+                  expenses.reset();
+                }
+                return expenses;
+              },
             ),
           ],
           child: Selector2<ThemeProvider, Auth, Tuple2<ThemeData, int>>(

diff --git a/lib/models/group.dart b/lib/models/group.dart
@@ -1,5 +1,6 @@
 import 'package:flutter/foundation.dart';
 import 'package:sliceit/models/member.dart';
+import 'package:sliceit/models/share.dart';
 
 class Group {
   final String id;
@@ -49,4 +50,21 @@ class Group {
   String memberFirstNameByUserId(String userId) {
     return members.firstWhere((member) => member.userId == userId).firstName;
   }
+
+  Member memberByUserId(String userId) {
+    return members.firstWhere((member) => member.userId == userId);
+  }
+
+  void optimisticBalanceUpdate(int total, List<Share> shares, String payerId) {
+    int diff;
+    // TODO: REFACTOR nested loop
+    for (Share share in shares) {
+      if (share.userId == payerId) {
+        diff = total - share.amount;
+        memberByUserId(share.userId).balance += diff;
+      } else {
+        memberByUserId(share.userId).balance -= share.amount;
+      }
+    }
+  }
 }
diff --git a/lib/providers/expenses.dart b/lib/providers/expenses.dart
@@ -1,15 +1,22 @@
 import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
 import 'package:sliceit/models/expense.dart';
 import 'package:sliceit/models/share.dart';
 import 'package:sliceit/providers/base.dart';
+import 'package:sliceit/providers/groups.dart';
 import 'package:sliceit/services/api.dart';
 
 class ExpensesProvider extends BaseProvider {
   final Api _api;
   final Map<String, List<Expense>> _expensesByGroupId = {};
+  GroupsProvider _groupsProvider;
 
   ExpensesProvider(this._api);
 
+  set groupsProvider(GroupsProvider groupsProvider) {
+    _groupsProvider = groupsProvider;
+  }
+
   List<Expense> byGroupId(String groupId) {
     if (_expensesByGroupId.containsKey(groupId)) {
       return _expensesByGroupId[groupId];
@@ -57,7 +64,7 @@ class ExpensesProvider extends BaseProvider {
     @required String currency,
     @required String date,
   }) async {
-    print(shares);
+    assert(_groupsProvider != null);
     status = Status.PENDING;
     try {
       final Expense expense = await _api.createExpense(
@@ -69,12 +76,16 @@ class ExpensesProvider extends BaseProvider {
         currency: currency,
         date: date,
       );
+
       if (_expensesByGroupId.containsKey(groupId)) {
         _expensesByGroupId[groupId].insert(0, expense);
       } else {
         _expensesByGroupId[groupId] = [expense];
       }
-      // TODO: Apply balance to the group!
+
+      _groupsProvider.selectedGroup
+          .optimisticBalanceUpdate(amount, shares, payerId);
+
       status = Status.RESOLVED;
     } catch (e) {
       status = Status.REJECTED;
@@ -90,6 +101,7 @@ class ExpensesProvider extends BaseProvider {
     @required String currency,
     @required String date,
   }) async {
+    assert(_groupsProvider != null);
     status = Status.PENDING;
     try {
       final Expense payment = await _api.createPayment(
@@ -100,20 +112,26 @@ class ExpensesProvider extends BaseProvider {
         currency: currency,
         date: date,
       );
+
       if (_expensesByGroupId.containsKey(groupId)) {
         _expensesByGroupId[groupId].insert(0, payment);
       } else {
         _expensesByGroupId[groupId] = [payment];
       }
-      // TODO: Apply balance to the group!
+
+      _groupsProvider.selectedGroup.optimisticBalanceUpdate(
+        amount,
+        [Share(userId: from, amount: 0), Share(userId: to, amount: amount)],
+        from,
+      );
+
       status = Status.RESOLVED;
     } catch (e) {
       status = Status.REJECTED;
       rethrow;
     }
   }
 
-//  TODO: reset
   void reset() {
     _expensesByGroupId.clear();
   }