AnalyticsStorage: Add an API to fetch the events as a transaction

lib/analytics/storage.dart

@@ -1,21 +1,42 @@
+import 'dart:math' as math;
 import 'dart:typed_data';
 
 import 'package:buffer/buffer.dart';
+import 'package:function_types/function_types.dart';
+import 'package:meta/meta.dart';
 import 'package:path/path.dart' as p;
+import 'package:synchronized/synchronized.dart';
 import 'package:universal_io/io.dart';
 
 import 'generated/analytics.pb.dart' as pb;
 
 class AnalyticsStorage {
   final String folderPath;
+  late String currentFile;
 
-  AnalyticsStorage(this.folderPath);
+  final _lock = Lock();
+
+  var numEventsThisSession = 0;
+
+  AnalyticsStorage(this.folderPath) {
+    _resetFile();
+  }
+
+  void _resetFile() {
+    var nowUtc = DateTime.now().toUtc();
+    var name = nowUtc.millisecondsSinceEpoch.toString();
+    currentFile = p.join(folderPath, name);
+  }
 
   Future<void> appendEvent(pb.Event event) async {
-    var eventData = event.writeToBuffer();
+    await _lock.synchronized(() {
+      return appendEventToFile(event, currentFile);
+    });
+  }
 
-    var filePath = p.join(folderPath, 'analytics');
-    // print(filePath);
+  @visibleForTesting
+  Future<void> appendEventToFile(pb.Event event, String filePath) async {
+    var eventData = event.writeToBuffer();
 
     var intData = ByteData(4);
     intData.setInt32(0, eventData.length);
@@ -25,11 +46,12 @@ class AnalyticsStorage {
     builder.add(eventData);
 
     await File(filePath).writeAsBytes(builder.toBytes(), mode: FileMode.append);
+    numEventsThisSession++;
   }
 
-  Future<List<pb.Event>> fetchAll() async {
-    var file = File(p.join(folderPath, 'analytics'));
-    var bytes = await file.readAsBytes();
+  @visibleForTesting
+  Future<List<pb.Event>> fetchFromFile(String filePath) async {
+    var bytes = await File(filePath).readAsBytes();
     var events = <pb.Event>[];
 
     var reader = ByteDataReader(copy: false);
@@ -43,4 +65,54 @@ class AnalyticsStorage {
     }
     return events;
   }
+
+  Future<List<String>> _availableFiles() async {
+    var paths = <String>[];
+
+    var dir = Directory(folderPath);
+    await for (var entity in dir.list()) {
+      if (entity is! File) {
+        assert(false, "Analytics directory contains non Files");
+        continue;
+      }
+
+      if (entity.path == currentFile) {
+        continue;
+      }
+
+      paths.add(entity.path);
+    }
+
+    return paths;
+  }
+
+  // If the callback returns 'true' then the events are deleted
+  // otherwise a subsequent call to fetchAll will return them!
+  Future<void> fetchAll(Func1<List<pb.Event>, Future<bool>> callback) async {
+    await _lock.synchronized(_resetFile);
+
+    var allEvents = <pb.Event>[];
+    var filePaths = await _availableFiles();
+    for (var filePath in filePaths) {
+      var events = await fetchFromFile(filePath);
+      allEvents.addAll(events);
+    }
+
+    var shouldDelete = await callback(allEvents);
+    if (shouldDelete) {
+      for (var filePath in filePaths) {
+        File(filePath).deleteSync();
+      }
+    }
+  }
+
+  Future<DateTime> oldestEvent() async {
+    var fileNames = (await _availableFiles()).map(p.basename);
+    var timestamps = fileNames.map(int.parse);
+    var smallest = timestamps.reduce(math.min);
+
+    return DateTime.fromMillisecondsSinceEpoch(smallest, isUtc: true);
+  }
 }
+
+// FIXME: Error handling?

test/analytics/storage_test.dart

@@ -1,4 +1,7 @@
+import 'dart:math';
+
 import 'package:fixnum/fixnum.dart';
+import 'package:path/path.dart' as p;
 import 'package:test/test.dart';
 import 'package:universal_io/io.dart';
 
@@ -7,25 +10,72 @@ import 'package:gitjournal/analytics/storage.dart';
 
 void main() {
   test('Read and write', () async {
-    var dt = DateTime.now().add(const Duration(days: -1));
-    var ev = pb.Event(
-      name: 'test',
-      date: Int64(dt.millisecondsSinceEpoch ~/ 1000),
-      params: {'a': 'hello'},
-      pseudoId: 'id',
-      userProperties: {'b': 'c'},
-      sessionID: 'session',
-    );
+    var ev1 = _randomEvent();
+    var ev2 = _randomEvent();
+
+    var dir = await Directory.systemTemp.createTemp('_analytics_');
+    var af = p.join(dir.path, "analytics");
+
+    var storage = AnalyticsStorage(dir.path);
+    await storage.appendEventToFile(ev1, af);
+    await storage.appendEventToFile(ev2, af);
+
+    var events = await storage.fetchFromFile(af);
+    expect(events.length, 2);
+    expect(events[0].toDebugString(), ev1.toDebugString());
+    expect(events[1].toDebugString(), ev2.toDebugString());
+    // expect(events[0], ev);
+  });
+
+  test('Fetch All', () async {
+    var ev1 = _randomEvent();
+    var ev2 = _randomEvent();
+    var ev3 = _randomEvent();
 
     var dir = await Directory.systemTemp.createTemp('_analytics_');
     var storage = AnalyticsStorage(dir.path);
-    await storage.appendEvent(ev);
-    await storage.appendEvent(ev);
 
-    var events = await storage.fetchAll();
-    expect(events.length, 2);
-    expect(events[0].toDebugString(), ev.toDebugString());
-    expect(events[1].toDebugString(), ev.toDebugString());
-    // expect(events[0], ev);
+    await storage.appendEvent(ev1);
+    await storage.appendEvent(ev2);
+
+    await storage.fetchAll((events) async {
+      expect(events.length, 2);
+      expect(events[0].toDebugString(), ev1.toDebugString());
+      expect(events[1].toDebugString(), ev2.toDebugString());
+      return false;
+    });
+
+    await storage.appendEvent(ev3);
+    await storage.fetchAll((events) async {
+      expect(events.length, 3);
+      expect(events[0].toDebugString(), ev1.toDebugString());
+      expect(events[1].toDebugString(), ev2.toDebugString());
+      expect(events[2].toDebugString(), ev3.toDebugString());
+      return true;
+    });
+
+    await storage.fetchAll((events) async {
+      expect(events.length, 0);
+      return true;
+    });
+
+    await storage.fetchAll((events) async {
+      expect(events.length, 0);
+      return false;
+    });
   });
 }
+
+pb.Event _randomEvent() {
+  var random = Random();
+  var dt = DateTime.now().add(Duration(days: random.nextInt(5000) * -1));
+  var ev = pb.Event(
+    name: 'test-' + random.nextInt(100).toString(),
+    date: Int64(dt.millisecondsSinceEpoch ~/ 1000),
+    params: {'a': 'hello'},
+    pseudoId: 'id',
+    userProperties: {'b': 'c'},
+    sessionID: 'session',
+  );
+  return ev;
+}