[mob][photos] suggestions undo button

mobile/lib/face/db.dart

@@ -841,6 +841,18 @@ class FaceMLDataDB {
     await db.executeBatch(sql, parameterSets);
   }
 
+  Future<void> removeNotPersonFeedback({
+    required String personID,
+    required int clusterID,
+  }) async {
+    final db = await instance.asyncDB;
+
+    const String sql = '''
+      DELETE FROM $notPersonFeedback WHERE $personIdColumn = ? AND $clusterIDColumn = ?
+    ''';
+    await db.execute(sql, [personID, clusterID]);
+  }
+
   Future<void> removeClusterToPerson({
     required String personID,
     required int clusterID,

mobile/lib/ui/viewer/people/person_cluster_suggestion.dart

@@ -10,14 +10,21 @@ import "package:photos/face/db.dart";
 import "package:photos/face/model/person.dart";
 import "package:photos/models/file/file.dart";
 import 'package:photos/services/machine_learning/face_ml/feedback/cluster_feedback.dart';
+import "package:photos/services/machine_learning/face_ml/person/person_service.dart";
 import "package:photos/theme/ente_theme.dart";
 import "package:photos/ui/components/buttons/button_widget.dart";
 import "package:photos/ui/components/models/button_type.dart";
-// import "package:photos/ui/viewer/people/add_person_action_sheet.dart";
 import "package:photos/ui/viewer/people/cluster_page.dart";
 import "package:photos/ui/viewer/people/person_clusters_page.dart";
 import "package:photos/ui/viewer/search/result/person_face_widget.dart";
 
+class SuggestionUserFeedback {
+  final bool accepted;
+  final ClusterSuggestion suggestion;
+
+  SuggestionUserFeedback(this.accepted, this.suggestion);
+}
+
 class PersonReviewClusterSuggestion extends StatefulWidget {
   final PersonEntity person;
 
@@ -36,6 +43,8 @@ class _PersonClustersState extends State<PersonReviewClusterSuggestion> {
   Key futureBuilderKeySuggestions = UniqueKey();
   Key futureBuilderKeyFaceThumbnails = UniqueKey();
   bool canGiveFeedback = true;
+  List<SuggestionUserFeedback> pastUserFeedback = [];
+  List<ClusterSuggestion> allSuggestions = [];
 
   // Declare a variable for the future
   late Future<List<ClusterSuggestion>> futureClusterSuggestions;
@@ -61,6 +70,13 @@ class _PersonClustersState extends State<PersonReviewClusterSuggestion> {
       appBar: AppBar(
         title: const Text('Review suggestions'),
         actions: [
+          if (pastUserFeedback.isNotEmpty)
+            IconButton(
+              icon: const Icon(Icons.undo_outlined),
+              onPressed: () async {
+                await _undoLastFeedback();
+              },
+            ),
           IconButton(
             icon: const Icon(Icons.history_outlined),
             onPressed: () {
@@ -87,7 +103,7 @@ class _PersonClustersState extends State<PersonReviewClusterSuggestion> {
               );
             }
 
-            final allSuggestions = snapshot.data!;
+            allSuggestions = snapshot.data!;
             final numberOfDifferentSuggestions = allSuggestions.length;
             final currentSuggestion = allSuggestions[currentSuggestionIndex];
             final int clusterID = currentSuggestion.clusterIDToMerge;
@@ -166,6 +182,13 @@ class _PersonClustersState extends State<PersonReviewClusterSuggestion> {
     if (!canGiveFeedback) {
       return;
     }
+    // Store the feedback in case the user wants to revert
+    pastUserFeedback.add(
+      SuggestionUserFeedback(
+        yesOrNo,
+        allSuggestions[currentSuggestionIndex],
+      ),
+    );
     if (yesOrNo) {
       canGiveFeedback = false;
       await FaceMLDataDB.instance.assignClusterToPerson(
@@ -448,4 +471,36 @@ class _PersonClustersState extends State<PersonReviewClusterSuggestion> {
     }
     return faceCrops;
   }
+
+  Future<void> _undoLastFeedback() async {
+    if (pastUserFeedback.isNotEmpty) {
+      final SuggestionUserFeedback lastFeedback = pastUserFeedback.removeLast();
+      if (lastFeedback.accepted) {
+        await PersonService.instance.removeClusterToPerson(
+          personID: widget.person.remoteID,
+          clusterID: lastFeedback.suggestion.clusterIDToMerge,
+        );
+      } else {
+        await FaceMLDataDB.instance.removeNotPersonFeedback(
+          personID: widget.person.remoteID,
+          clusterID: lastFeedback.suggestion.clusterIDToMerge,
+        );
+      }
+
+      // futureClusterSuggestions =
+      //     pastUserFeedback.map((element) => element.suggestion)
+      //         as Future<List<ClusterSuggestion>>;
+
+      fetch = false;
+      futureClusterSuggestions = futureClusterSuggestions.then((list) {
+        return list
+            .sublist(currentSuggestionIndex)
+            ..insert(0, lastFeedback.suggestion);
+      });
+      currentSuggestionIndex = 0;
+      futureBuilderKeySuggestions = UniqueKey();
+      futureBuilderKeyFaceThumbnails = UniqueKey();
+      setState(() {});
+    }
+  }
 }