Serializing/deserializing methods for Event instances (#251)

* `.fromJson` and `.toJson` added + move utils func

* Use nullable static method to parse string json

* Update event.dart

* Fix test

* Tests for encoding/decoding json

* Store intersection in local var

* Remove exception thrown for nullable return

* Use conditionals to check for any type errors

* Test case added to check for invalid eventData

* Update CHANGELOG.md

* Refactor `Event.fromJson` to use pattern matching

* Use package:collection for comparing eventData

* Use range for collection version

* `fromLabel` static method renaming

* Fix test by refactoring unrelated DashTool static method

* Remove `when` clause and check inside if statement

* `_deepCollectionEquality` to global scope + nit fix

* Remove collection dep + schema in dartdoc + nit fixes

* Add'l context to `Event.fromJson` static method

* Store intersection in local variable

* Refactor `DashTool.fromLabel`

pkgs/unified_analytics/CHANGELOG.md

@@ -4,6 +4,7 @@
 - Get rid of `late` variables throughout implementation class, `AnalyticsImpl`
 - Any error events (`Event.analyticsException`) encountered within package will be sent when invoking `Analytics.close`; replacing `ErrorHandler` functionality
 - Exposing new method for `FakeAnalytics.sendPendingErrorEvents` to send error events on command
+- Added `Event.fromJson` static method to generate instance of `Event` from JSON
 
 ## 5.8.8
 

pkgs/unified_analytics/lib/src/enums.dart

@@ -153,6 +153,11 @@ enum DashEvent {
     required this.description,
     this.toolOwner,
   });
+
+  /// This takes in the string label for a given [DashEvent] and returns the
+  /// enum for that string label.
+  static DashEvent? fromLabel(String label) =>
+      DashEvent.values.where((e) => e.label == label).firstOrNull;
 }
 
 /// Officially-supported clients of this package as logical
@@ -199,10 +204,9 @@ enum DashTool {
 
   /// This takes in the string label for a given [DashTool] and returns the
   /// enum for that string label.
-  static DashTool getDashToolByLabel(String label) {
-    for (final tool in DashTool.values) {
-      if (tool.label == label) return tool;
-    }
+  static DashTool fromLabel(String label) {
+    final tool = DashTool.values.where((t) => t.label == label).firstOrNull;
+    if (tool != null) return tool;
 
     throw Exception('The tool $label from the survey metadata file is not '
         'a valid DashTool enum value\n'

pkgs/unified_analytics/lib/src/event.dart

@@ -5,7 +5,6 @@
 import 'dart:convert';
 
 import 'enums.dart';
-import 'utils.dart';
 
 final class Event {
   final DashEvent eventName;
@@ -455,7 +454,6 @@ final class Event {
       : eventName = DashEvent.hotReloadTime,
         eventData = {'timeMs': timeMs};
 
-  // TODO: eliasyishak, add better dartdocs to explain each param
   /// Events to be sent for the Flutter Hot Runner.
   Event.hotRunnerInfo({
     required String label,
@@ -507,6 +505,7 @@ final class Event {
           if (reloadVMTimeInMs != null) 'reloadVMTimeInMs': reloadVMTimeInMs,
         };
 
+  // TODO: eliasyishak, add better dartdocs to explain each param
   /// Event that is emitted periodically to report the number of times each lint
   /// has been enabled.
   ///
@@ -708,6 +707,10 @@ final class Event {
           if (label != null) 'label': label,
         };
 
+  /// Private constructor to be used when deserializing JSON into an instance
+  /// of [Event].
+  Event._({required this.eventName, required this.eventData});
+
   @override
   int get hashCode => Object.hash(eventName, jsonEncode(eventData));
 
@@ -716,11 +719,66 @@ final class Event {
       other is Event &&
       other.runtimeType == runtimeType &&
       other.eventName == eventName &&
-      compareEventData(other.eventData, eventData);
+      _compareEventData(other.eventData, eventData);
 
-  @override
-  String toString() => jsonEncode({
+  /// Converts an instance of [Event] to JSON.
+  String toJson() => jsonEncode({
         'eventName': eventName.label,
         'eventData': eventData,
       });
+
+  @override
+  String toString() => toJson();
+
+  /// Utility function to take in two maps [a] and [b] and compares them
+  /// to ensure that they have the same keys and values
+  bool _compareEventData(Map<String, Object?> a, Map<String, Object?> b) {
+    final keySetA = a.keys.toSet();
+    final keySetB = b.keys.toSet();
+    final intersection = keySetA.intersection(keySetB);
+
+    // Ensure that the keys are the same for each object
+    if (intersection.length != keySetA.length ||
+        intersection.length != keySetB.length) {
+      return false;
+    }
+
+    // Ensure that each of the key's values are the same
+    for (final key in a.keys) {
+      if (a[key] != b[key]) return false;
+    }
+
+    return true;
+  }
+
+  /// Returns a valid instance of [Event] if [json] follows the correct schema.
+  ///
+  /// Common use case for this static method involves clients of this package
+  /// that have a client-server setup where the server sends events that the
+  /// client creates.
+  static Event? fromJson(String json) {
+    try {
+      final jsonMap = jsonDecode(json) as Map<String, Object?>;
+
+      // Ensure that eventName is a string and a valid label and
+      // eventData is a nested object
+      if (jsonMap
+          case {
+            'eventName': final String eventName,
+            'eventData': final Map<String, Object?> eventData,
+          }) {
+        final dashEvent = DashEvent.fromLabel(eventName);
+        if (dashEvent == null) return null;
+
+        return Event._(
+          eventName: dashEvent,
+          eventData: eventData,
+        );
+      }
+
+      return null;
+    } on FormatException {
+      return null;
+    }
+  }
 }

pkgs/unified_analytics/lib/src/survey_handler.dart

@@ -134,10 +134,9 @@ class Survey {
         samplingRate = json['samplingRate'] is String
             ? double.parse(json['samplingRate'] as String)
             : json['samplingRate'] as double,
-        excludeDashToolList =
-            (json['excludeDashTools'] as List<dynamic>).map((e) {
-          return DashTool.getDashToolByLabel(e as String);
-        }).toList(),
+        excludeDashToolList = (json['excludeDashTools'] as List<dynamic>)
+            .map((e) => DashTool.fromLabel(e as String))
+            .toList(),
         conditionList = (json['conditions'] as List<dynamic>).map((e) {
           return Condition.fromJson(e as Map<String, dynamic>);
         }).toList(),

pkgs/unified_analytics/lib/src/utils.dart

@@ -36,26 +36,6 @@ bool checkDirectoryForWritePermissions(Directory directory) {
   return fileStat.modeString()[1] == 'w';
 }
 
-/// Utility function to take in two maps [a] and [b] and compares them
-/// to ensure that they have the same keys and values
-bool compareEventData(Map<String, Object?> a, Map<String, Object?> b) {
-  final keySetA = a.keys.toSet();
-  final keySetB = b.keys.toSet();
-
-  // Ensure that the keys are the same for each object
-  if (keySetA.intersection(keySetB).length != keySetA.length ||
-      keySetA.intersection(keySetB).length != keySetB.length) {
-    return false;
-  }
-
-  // Ensure that each of the key's values are the same
-  for (final key in a.keys) {
-    if (a[key] != b[key]) return false;
-  }
-
-  return true;
-}
-
 /// Format time as 'yyyy-MM-dd HH:mm:ss Z' where Z is the difference between the
 /// timezone of t and UTC formatted according to RFC 822.
 String formatDateTime(DateTime t) {

pkgs/unified_analytics/test/event_test.dart

@@ -556,7 +556,9 @@ void main() {
   test('Confirm all constructors were checked', () {
     var constructorCount = 0;
     for (var declaration in reflectClass(Event).declarations.keys) {
-      if (declaration.toString().contains('Event.')) constructorCount++;
+      // Count public constructors but omit private constructors
+      if (declaration.toString().contains('Event.') &&
+          !declaration.toString().contains('Event._')) constructorCount++;
     }
 
     // Change this integer below if your PR either adds or removes
@@ -568,4 +570,55 @@ void main() {
             '`pkgs/unified_analytics/test/event_test.dart` '
             'to reflect the changes made');
   });
+
+  test('Serializing event to json successful', () {
+    final event = Event.analyticsException(
+      workflow: 'workflow',
+      error: 'error',
+      description: 'description',
+    );
+
+    final expectedResult = '{"eventName":"analytics_exception",'
+        '"eventData":{"workflow":"workflow",'
+        '"error":"error",'
+        '"description":"description"}}';
+
+    expect(event.toJson(), expectedResult);
+  });
+
+  test('Deserializing string to event successful', () {
+    final eventJson = '{"eventName":"analytics_exception",'
+        '"eventData":{"workflow":"workflow",'
+        '"error":"error",'
+        '"description":"description"}}';
+
+    final eventConstructed = Event.fromJson(eventJson);
+    expect(eventConstructed, isNotNull);
+    eventConstructed!;
+
+    expect(eventConstructed.eventName, DashEvent.analyticsException);
+    expect(eventConstructed.eventData, {
+      'workflow': 'workflow',
+      'error': 'error',
+      'description': 'description',
+    });
+  });
+
+  test('Deserializing string to event unsuccessful for invalid eventName', () {
+    final eventJson = '{"eventName":"NOT_VALID_NAME",'
+        '"eventData":{"workflow":"workflow",'
+        '"error":"error",'
+        '"description":"description"}}';
+
+    final eventConstructed = Event.fromJson(eventJson);
+    expect(eventConstructed, isNull);
+  });
+
+  test('Deserializing string to event unsuccessful for invalid eventData', () {
+    final eventJson = '{"eventName":"analytics_exception",'
+        '"eventData": "not_valid_event_data"}';
+
+    final eventConstructed = Event.fromJson(eventJson);
+    expect(eventConstructed, isNull);
+  });
 }