powersync prototype (WIP)

lib/api_client.dart

@@ -0,0 +1,60 @@
+import 'dart:convert';
+import 'package:http/http.dart' as http;
+import 'package:logging/logging.dart';
+
+final log = Logger('powersync-test');
+
+class ApiClient {
+  final String baseUrl;
+
+  ApiClient(this.baseUrl);
+
+  Future<Map<String, dynamic>> authenticate(String username, String password) async {
+    final response = await http.post(
+      Uri.parse('$baseUrl/api/auth/'),
+      headers: {'Content-Type': 'application/json'},
+      body: json.encode({'username': username, 'password': password}),
+    );
+    if (response.statusCode == 200) {
+      return json.decode(response.body);
+    } else {
+      throw Exception('Failed to authenticate');
+    }
+  }
+
+  Future<Map<String, dynamic>> getToken(String userId) async {
+    final response = await http.get(
+      Uri.parse('$baseUrl/api/get_powersync_token/'),
+      headers: {'Content-Type': 'application/json'},
+    );
+    if (response.statusCode == 200) {
+      return json.decode(response.body);
+    } else {
+      throw Exception('Failed to fetch token');
+    }
+  }
+
+  Future<void> upsert(Map<String, dynamic> record) async {
+    await http.put(
+      Uri.parse('$baseUrl/api/upload_data/'),
+      headers: {'Content-Type': 'application/json'},
+      body: json.encode(record),
+    );
+  }
+
+  Future<void> update(Map<String, dynamic> record) async {
+    await http.patch(
+      Uri.parse('$baseUrl/api/upload_data/'),
+      headers: {'Content-Type': 'application/json'},
+      body: json.encode(record),
+    );
+  }
+
+  Future<void> delete(Map<String, dynamic> record) async {
+    await http.delete(
+      Uri.parse('$baseUrl/api/upload_data/'),
+      headers: {'Content-Type': 'application/json'},
+      body: json.encode(record),
+    );
+  }
+}

lib/app_config.dart

@@ -0,0 +1,4 @@
+class AppConfig {
+  static const String djangoUrl = 'http://192.168.2.223:6061';
+  static const String powersyncUrl = 'http://192.168.2.223:8080';
+}

lib/main.dart

@@ -16,10 +16,12 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_gen/gen_l10n/app_localizations.dart';
 import 'package:provider/provider.dart';
 import 'package:wger/core/locator.dart';
+import 'package:wger/powersync.dart';
 import 'package:wger/providers/add_exercise.dart';
 import 'package:wger/providers/base_provider.dart';
 import 'package:wger/providers/body_weight.dart';
@@ -52,15 +54,34 @@ import 'package:wger/screens/workout_plans_screen.dart';
 import 'package:wger/theme/theme.dart';
 import 'package:wger/widgets/core/about.dart';
 import 'package:wger/widgets/core/settings.dart';
+import 'package:logging/logging.dart';
 
 import 'providers/auth.dart';
 
 void main() async {
   //zx.setLogEnabled(kDebugMode);
+  Logger.root.level = Level.INFO;
+  Logger.root.onRecord.listen((record) {
+    if (kDebugMode) {
+      print('[${record.loggerName}] ${record.level.name}: ${record.time}: ${record.message}');
+
+      if (record.error != null) {
+        print(record.error);
+      }
+      if (record.stackTrace != null) {
+        print(record.stackTrace);
+      }
+    }
+  });
 
   // Needs to be called before runApp
   WidgetsFlutterBinding.ensureInitialized();
 
+  await openDatabase();
+
+  final loggedIn = await isLoggedIn();
+  print('is logged in $loggedIn');
+
   // Locator to initialize exerciseDB
   await ServiceLocator().configure();
   // Application

lib/models/schema.dart

@@ -0,0 +1,54 @@
+import 'package:powersync/powersync.dart';
+
+const todosTable = 'todos';
+
+// these are the same ones as in postgres, except for 'id'
+Schema schema = const Schema(([
+  Table(todosTable, [
+    Column.text('list_id'),
+    Column.text('created_at'),
+    Column.text('completed_at'),
+    Column.text('description'),
+    Column.integer('completed'),
+    Column.text('created_by'),
+    Column.text('completed_by'),
+  ], indexes: [
+    // Index to allow efficient lookup within a list
+    Index('list', [IndexedColumn('list_id')])
+  ]),
+  Table('lists',
+      [Column.text('created_at'), Column.text('name'), Column.text('owner_id')])
+]));
+
+// post gres columns:
+// todos:
+// id                                   | created_at                    | completed_at | description       | completed | created_by | completed_by | list_id
+// lists:
+// id                                   | created_at                    | name        | owner_id
+
+// diagnostics app:
+/*
+new Schema([
+  new Table({
+    name: 'lists', // same as flutter
+    columns: [
+      new Column({ name: 'created_at', type: ColumnType.TEXT }),
+      new Column({ name: 'name', type: ColumnType.TEXT }),
+      new Column({ name: 'owner_id', type: ColumnType.TEXT })
+    ]
+  }),
+  new Table({
+    name: 'todos', // misses completed_at and completed_by, until these actually get populated with something
+    columns: [
+      new Column({ name: 'created_at', type: ColumnType.TEXT }),
+      new Column({ name: 'description', type: ColumnType.TEXT }),
+      new Column({ name: 'completed', type: ColumnType.INTEGER }),
+      new Column({ name: 'created_by', type: ColumnType.TEXT }),
+      new Column({ name: 'list_id', type: ColumnType.TEXT })
+    ]
+  })
+])
+
+    Column.text('completed_at'),
+    Column.text('completed_by'),
+*/

lib/models/todo_item.dart

@@ -0,0 +1,50 @@
+import 'package:wger/models/schema.dart';
+
+import '../powersync.dart';
+import 'package:powersync/sqlite3.dart' as sqlite;
+
+/// TodoItem represents a result row of a query on "todos".
+///
+/// This class is immutable - methods on this class do not modify the instance
+/// directly. Instead, watch or re-query the data to get the updated item.
+/// confirm how the watch works. this seems like a weird pattern
+class TodoItem {
+  final String id;
+  final String description;
+  final String? photoId;
+  final bool completed;
+
+  TodoItem(
+      {required this.id,
+      required this.description,
+      required this.completed,
+      required this.photoId});
+
+  factory TodoItem.fromRow(sqlite.Row row) {
+    return TodoItem(
+        id: row['id'],
+        description: row['description'],
+        photoId: row['photo_id'],
+        completed: row['completed'] == 1);
+  }
+
+  Future<void> toggle() async {
+    if (completed) {
+      await db.execute(
+          'UPDATE $todosTable SET completed = FALSE, completed_by = NULL, completed_at = NULL WHERE id = ?',
+          [id]);
+    } else {
+      await db.execute(
+          'UPDATE $todosTable SET completed = TRUE, completed_by = ?, completed_at = datetime() WHERE id = ?',
+          [await getUserId(), id]);
+    }
+  }
+
+  Future<void> delete() async {
+    await db.execute('DELETE FROM $todosTable WHERE id = ?', [id]);
+  }
+
+  static Future<void> addPhoto(String photoId, String id) async {
+    await db.execute('UPDATE $todosTable SET photo_id = ? WHERE id = ?', [photoId, id]);
+  }
+}

lib/models/todo_list.dart

@@ -0,0 +1,96 @@
+import 'package:powersync/sqlite3.dart' as sqlite;
+
+import 'todo_item.dart';
+import '../powersync.dart';
+
+/// TodoList represents a result row of a query on "lists".
+///
+/// This class is immutable - methods on this class do not modify the instance
+/// directly. Instead, watch or re-query the data to get the updated list.
+class TodoList {
+  /// List id (UUID).
+  final String id;
+
+  /// Descriptive name.
+  final String name;
+
+  /// Number of completed todos in this list.
+  final int? completedCount;
+
+  /// Number of pending todos in this list.
+  final int? pendingCount;
+
+  TodoList({required this.id, required this.name, this.completedCount, this.pendingCount});
+
+  factory TodoList.fromRow(sqlite.Row row) {
+    return TodoList(
+        id: row['id'],
+        name: row['name'],
+        completedCount: row['completed_count'],
+        pendingCount: row['pending_count']);
+  }
+
+  /// Watch all lists.
+  static Stream<List<TodoList>> watchLists() {
+    // This query is automatically re-run when data in "lists" or "todos" is modified.
+    return db.watch('SELECT * FROM lists ORDER BY created_at, id').map((results) {
+      return results.map(TodoList.fromRow).toList(growable: false);
+    });
+  }
+
+  /// Watch all lists, with [completedCount] and [pendingCount] populated.
+  static Stream<List<TodoList>> watchListsWithStats() {
+    // This query is automatically re-run when data in "lists" or "todos" is modified.
+    return db.watch('''
+      SELECT
+        *,
+        (SELECT count() FROM todos WHERE list_id = lists.id AND completed = TRUE) as completed_count,
+        (SELECT count() FROM todos WHERE list_id = lists.id AND completed = FALSE) as pending_count
+      FROM lists
+      ORDER BY created_at
+    ''').map((results) {
+      return results.map(TodoList.fromRow).toList(growable: false);
+    });
+  }
+
+  /// Create a new list
+  static Future<TodoList> create(String name) async {
+    final results = await db.execute('''
+      INSERT INTO
+        lists(id, created_at, name, owner_id)
+        VALUES(uuid(), datetime(), ?, ?)
+      RETURNING *
+      ''', [name, await getUserId()]);
+    return TodoList.fromRow(results.first);
+  }
+
+  /// Watch items within this list.
+  Stream<List<TodoItem>> watchItems() {
+    return db.watch('SELECT * FROM todos WHERE list_id = ? ORDER BY created_at DESC, id',
+        parameters: [id]).map((event) {
+      return event.map(TodoItem.fromRow).toList(growable: false);
+    });
+  }
+
+  /// Delete this list.
+  Future<void> delete() async {
+    await db.execute('DELETE FROM lists WHERE id = ?', [id]);
+  }
+
+  /// Find list item.
+  static Future<TodoList> find(id) async {
+    final results = await db.get('SELECT * FROM lists WHERE id = ?', [id]);
+    return TodoList.fromRow(results);
+  }
+
+  /// Add a new todo item to this list.
+  Future<TodoItem> add(String description) async {
+    final results = await db.execute('''
+      INSERT INTO
+        todos(id, created_at, completed, list_id, description, created_by)
+        VALUES(uuid(), datetime(), FALSE, ?, ?, ?)
+      RETURNING *
+    ''', [id, description, await getUserId()]);
+    return TodoItem.fromRow(results.first);
+  }
+}

lib/powersync.dart

@@ -0,0 +1,132 @@
+// This file performs setup of the PowerSync database
+import 'package:logging/logging.dart';
+import 'package:path/path.dart';
+import 'package:path_provider/path_provider.dart';
+import 'package:powersync/powersync.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:wger/api_client.dart';
+
+import './app_config.dart';
+import './models/schema.dart';
+
+final log = Logger('powersync-django');
+
+/// Postgres Response codes that we cannot recover from by retrying.
+final List<RegExp> fatalResponseCodes = [
+  // Class 22 — Data Exception
+  // Examples include data type mismatch.
+  RegExp(r'^22...$'),
+  // Class 23 — Integrity Constraint Violation.
+  // Examples include NOT NULL, FOREIGN KEY and UNIQUE violations.
+  RegExp(r'^23...$'),
+  // INSUFFICIENT PRIVILEGE - typically a row-level security violation
+  RegExp(r'^42501$'),
+];
+
+class DjangoConnector extends PowerSyncBackendConnector {
+  PowerSyncDatabase db;
+
+  DjangoConnector(this.db);
+
+  final ApiClient apiClient = ApiClient(AppConfig.djangoUrl);
+
+  /// Get a token to authenticate against the PowerSync instance.
+  @override
+  Future<PowerSyncCredentials?> fetchCredentials() async {
+    final prefs = await SharedPreferences.getInstance();
+    final userId = prefs.getString('id');
+    if (userId == null) {
+      throw Exception('User does not have session');
+    }
+    // Somewhat contrived to illustrate usage, see auth docs here:
+    // https://docs.powersync.com/usage/installation/authentication-setup/custom
+    final session = await apiClient.getToken(userId);
+    return PowerSyncCredentials(endpoint: AppConfig.powersyncUrl, token: session['token']);
+  }
+
+  // Upload pending changes to Postgres via Django backend
+  // this is generic. on the django side we inspect the request and do model-specific operations
+  // would it make sense to do api calls here specific to the relevant model? (e.g. put to a todo-specific endpoint)
+  @override
+  Future<void> uploadData(PowerSyncDatabase database) async {
+    final transaction = await database.getNextCrudTransaction();
+
+    if (transaction == null) {
+      return;
+    }
+
+    try {
+      for (var op in transaction.crud) {
+        final record = {
+          'table': op.table,
+          'data': {'id': op.id, ...?op.opData},
+        };
+
+        switch (op.op) {
+          case UpdateType.put:
+            await apiClient.upsert(record);
+            break;
+          case UpdateType.patch:
+            await apiClient.update(record);
+            break;
+          case UpdateType.delete:
+            await apiClient.delete(record);
+            break;
+        }
+      }
+      await transaction.complete();
+    } on Exception catch (e) {
+      log.severe('Error uploading data', e);
+      // Error may be retryable - e.g. network error or temporary server error.
+      // Throwing an error here causes this call to be retried after a delay.
+      rethrow;
+    }
+  }
+}
+
+/// Global reference to the database
+late final PowerSyncDatabase db;
+
+// Hacky flag to ensure the database is only initialized once, better to do this with listeners
+bool _dbInitialized = false;
+
+Future<bool> isLoggedIn() async {
+  final prefs = await SharedPreferences.getInstance(); // Initialize SharedPreferences
+  final userId = prefs.getString('id');
+  return userId != null;
+}
+
+Future<String> getDatabasePath() async {
+  final dir = await getApplicationSupportDirectory();
+  return join(dir.path, 'powersync-demo.db');
+}
+
+// opens the database and connects if logged in
+Future<void> openDatabase() async {
+  // Open the local database
+  if (!_dbInitialized) {
+    db = PowerSyncDatabase(schema: schema, path: await getDatabasePath(), logger: attachedLogger);
+    await db.initialize();
+    _dbInitialized = true;
+  }
+
+  DjangoConnector? currentConnector;
+
+  if (await isLoggedIn()) {
+    // If the user is already logged in, connect immediately.
+    // Otherwise, connect once logged in.
+    currentConnector = DjangoConnector(db);
+    db.connect(connector: currentConnector);
+  }
+}
+
+/// Explicit sign out - clear database and log out.
+Future<void> logout() async {
+  await db.disconnectAndClear();
+}
+
+/// id of the user currently logged in
+Future<String?> getUserId() async {
+  final prefs = await SharedPreferences.getInstance();
+  return prefs.getString('id');
+}

linux/flutter/generated_plugin_registrant.cc

@@ -7,6 +7,7 @@
 #include "generated_plugin_registrant.h"
 
 #include <file_selector_linux/file_selector_plugin.h>
+#include <powersync_flutter_libs/powersync_flutter_libs_plugin.h>
 #include <sqlite3_flutter_libs/sqlite3_flutter_libs_plugin.h>
 #include <url_launcher_linux/url_launcher_plugin.h>
 
@@ -14,6 +15,9 @@ void fl_register_plugins(FlPluginRegistry* registry) {
   g_autoptr(FlPluginRegistrar) file_selector_linux_registrar =
       fl_plugin_registry_get_registrar_for_plugin(registry, "FileSelectorPlugin");
   file_selector_plugin_register_with_registrar(file_selector_linux_registrar);
+  g_autoptr(FlPluginRegistrar) powersync_flutter_libs_registrar =
+      fl_plugin_registry_get_registrar_for_plugin(registry, "PowersyncFlutterLibsPlugin");
+  powersync_flutter_libs_plugin_register_with_registrar(powersync_flutter_libs_registrar);
   g_autoptr(FlPluginRegistrar) sqlite3_flutter_libs_registrar =
       fl_plugin_registry_get_registrar_for_plugin(registry, "Sqlite3FlutterLibsPlugin");
   sqlite3_flutter_libs_plugin_register_with_registrar(sqlite3_flutter_libs_registrar);

linux/flutter/generated_plugins.cmake

@@ -4,6 +4,7 @@
 
 list(APPEND FLUTTER_PLUGIN_LIST
   file_selector_linux
+  powersync_flutter_libs
   sqlite3_flutter_libs
   url_launcher_linux
 )

macos/Flutter/GeneratedPluginRegistrant.swift

@@ -8,6 +8,7 @@ import Foundation
 import file_selector_macos
 import package_info_plus
 import path_provider_foundation
+import powersync_flutter_libs
 import rive_common
 import shared_preferences_foundation
 import sqlite3_flutter_libs
@@ -18,6 +19,7 @@ func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
   FileSelectorPlugin.register(with: registry.registrar(forPlugin: "FileSelectorPlugin"))
   FPPPackageInfoPlusPlugin.register(with: registry.registrar(forPlugin: "FPPPackageInfoPlusPlugin"))
   PathProviderPlugin.register(with: registry.registrar(forPlugin: "PathProviderPlugin"))
+  PowersyncFlutterLibsPlugin.register(with: registry.registrar(forPlugin: "PowersyncFlutterLibsPlugin"))
   RivePlugin.register(with: registry.registrar(forPlugin: "RivePlugin"))
   SharedPreferencesPlugin.register(with: registry.registrar(forPlugin: "SharedPreferencesPlugin"))
   Sqlite3FlutterLibsPlugin.register(with: registry.registrar(forPlugin: "Sqlite3FlutterLibsPlugin"))

pubspec.lock

@@ -329,6 +329,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.3.1"
+  fetch_api:
+    dependency: transitive
+    description:
+      name: fetch_api
+      sha256: "97f46c25b480aad74f7cc2ad7ccba2c5c6f08d008e68f95c1077286ce243d0e6"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.2.0"
+  fetch_client:
+    dependency: transitive
+    description:
+      name: fetch_client
+      sha256: "9666ee14536778474072245ed5cba07db81ae8eb5de3b7bf4a2d1e2c49696092"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.1.2"
   ffi:
     dependency: transitive
     description:
@@ -821,7 +837,7 @@ packages:
     source: hosted
     version: "1.0.2"
   logging:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: logging
       sha256: "623a88c9594aa774443aa3eb2d41807a48486b5613e67599fb4c41c0ad47c340"
@@ -892,6 +908,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "4.1.3"
+  mutex:
+    dependency: transitive
+    description:
+      name: mutex
+      sha256: "8827da25de792088eb33e572115a5eb0d61d61a3c01acbc8bcbe76ed78f1a1f2"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.1.0"
   nested:
     dependency: transitive
     description:
@@ -1060,6 +1084,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.5.1"
+  powersync:
+    dependency: "direct main"
+    description:
+      name: powersync
+      sha256: c6975007493617fdfc5945c3fab24ea2e6999ae300dd4d19d739713a4f2bcd96
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.6.3"
+  powersync_flutter_libs:
+    dependency: transitive
+    description:
+      name: powersync_flutter_libs
+      sha256: "449063aa4956c6be215ea7dfb9cc61255188e82cf7bc3f75621796fcc6615b70"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.1.0"
   process:
     dependency: transitive
     description:
@@ -1233,6 +1273,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.10.0"
+  sprintf:
+    dependency: transitive
+    description:
+      name: sprintf
+      sha256: "1fc9ffe69d4df602376b52949af107d8f5703b77cda567c4d7d86a0693120f23"
+      url: "https://pub.dev"
+    source: hosted
+    version: "7.0.0"
   sqlite3:
     dependency: transitive
     description:
@@ -1249,6 +1297,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.5.24"
+  sqlite3_web:
+    dependency: transitive
+    description:
+      name: sqlite3_web
+      sha256: "51fec34757577841cc72d79086067e3651c434669d5af557a5c106787198a76f"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.1.2-wip"
+  sqlite_async:
+    dependency: "direct main"
+    description:
+      name: sqlite_async
+      sha256: "79e636c857ed43f6cd5e5be72b36967a29f785daa63ff5b078bd34f74f44cb54"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.8.1"
   sqlparser:
     dependency: transitive
     description:
@@ -1337,6 +1401,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.3.2"
+  universal_io:
+    dependency: transitive
+    description:
+      name: universal_io
+      sha256: "1722b2dcc462b4b2f3ee7d188dad008b6eb4c40bbd03a3de451d82c78bba9aad"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.2.2"
   url_launcher:
     dependency: "direct main"
     description:
@@ -1401,6 +1473,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.1.1"
+  uuid:
+    dependency: transitive
+    description:
+      name: uuid
+      sha256: "83d37c7ad7aaf9aa8e275490669535c8080377cfa7a7004c24dfac53afffaa90"
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.4.2"
   vector_graphics:
     dependency: transitive
     description:

pubspec.yaml

@@ -33,6 +33,7 @@ dependencies:
     sdk: flutter
 
   android_metadata: ^0.2.1
+  powersync: ^1.5.5
   collection: ^1.17.0
   cupertino_icons: ^1.0.8
   equatable: ^2.0.5
@@ -70,6 +71,8 @@ dependencies:
   freezed_annotation: ^2.4.1
   clock: ^1.1.1
   flutter_svg_icons: ^0.0.1
+  sqlite_async: ^0.8.1
+  logging: ^1.2.0
 
 dependency_overrides:
   intl: ^0.19.0