Implement remote file system

sqlite3_web/lib/src/client.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 import 'dart:js_interop';
 import 'dart:js_interop_unsafe';
+import 'dart:typed_data';
 
 import 'package:sqlite3/common.dart';
 import 'package:web/web.dart'
@@ -142,6 +143,66 @@ final class RemoteDatabase implements Database {
   }
 }
 
+final class RemoteFileSystem implements FileSystem {
+  final RemoteDatabase database;
+
+  RemoteFileSystem(this.database);
+
+  @override
+  Future<bool> exists(FileType type) async {
+    final response = await database.connection.sendRequest(
+      FileSystemExistsQuery(
+        databaseId: database.databaseId,
+        fsType: type,
+        requestId: 0,
+      ),
+      MessageType.simpleSuccessResponse,
+    );
+
+    return (response.response as JSBoolean).toDart;
+  }
+
+  @override
+  Future<void> flush() async {
+    await database.connection.sendRequest(
+      FileSystemFlushRequest(databaseId: database.databaseId, requestId: 0),
+      MessageType.simpleSuccessResponse,
+    );
+  }
+
+  @override
+  Future<Uint8List> readFile(FileType type) async {
+    final response = await database.connection.sendRequest(
+      FileSystemAccess(
+        databaseId: database.databaseId,
+        requestId: 0,
+        buffer: null,
+        fsType: type,
+      ),
+      MessageType.simpleSuccessResponse,
+    );
+
+    final buffer = (response.response as JSArrayBuffer);
+    return buffer.toDart.asUint8List();
+  }
+
+  @override
+  Future<void> writeFile(FileType type, Uint8List content) async {
+    // We need to copy since we're about to transfer contents over
+    final copy = Uint8List(content.length)..setAll(0, content);
+
+    await database.connection.sendRequest(
+      FileSystemAccess(
+        databaseId: database.databaseId,
+        requestId: 0,
+        buffer: copy.buffer.toJS,
+        fsType: type,
+      ),
+      MessageType.simpleSuccessResponse,
+    );
+  }
+}
+
 final class WorkerConnection extends ProtocolChannel {
   final StreamController<Notification> notifications =
       StreamController.broadcast();

sqlite3_web/lib/src/protocol.dart

@@ -22,6 +22,7 @@ enum MessageType<T extends Message> {
   runQuery<RunQuery>(),
   fileSystemExists<FileSystemExistsQuery>(),
   fileSystemAccess<FileSystemAccess>(),
+  fileSystemFlush<FileSystemFlushRequest>(),
   connect<ConnectRequest>(),
   startFileSystemServer<StartFileSystemServer>(),
   updateRequest<UpdateStreamRequest>(),
@@ -86,6 +87,7 @@ sealed class Message {
       MessageType.runQuery => RunQuery.deserialize(object),
       MessageType.fileSystemExists => FileSystemExistsQuery.deserialize(object),
       MessageType.fileSystemAccess => FileSystemAccess.deserialize(object),
+      MessageType.fileSystemFlush => FileSystemFlushRequest.deserialize(object),
       MessageType.connect => ConnectRequest.deserialize(object),
       MessageType.closeDatabase => CloseDatabase.deserialize(object),
       MessageType.openAdditionalConnection =>
@@ -348,6 +350,24 @@ final class FileSystemExistsQuery extends Request {
   }
 }
 
+/// Requests the worker to flush the file system for a database.
+final class FileSystemFlushRequest extends Request {
+  @override
+  MessageType<Message> get type => MessageType.fileSystemFlush;
+
+  FileSystemFlushRequest({
+    required super.databaseId,
+    required super.requestId,
+  });
+
+  factory FileSystemFlushRequest.deserialize(JSObject object) {
+    return FileSystemFlushRequest(
+      databaseId: object.databaseId,
+      requestId: object.requestId,
+    );
+  }
+}
+
 /// Read or write to files of an opened database.
 ///
 /// For reads, other side will respond with a [SimpleSuccessResponse] containing
@@ -385,8 +405,6 @@ final class FileSystemAccess extends Request {
     object[_UniqueFieldNames.buffer] = buffer;
     object[_UniqueFieldNames.fileType] = fsType.index.toJS;
 
-    // false positive? dart2js seems to emit a null check as it should
-    // ignore: pattern_never_matches_value_type
     if (buffer case final buffer?) {
       transferred.add(buffer);
     }
@@ -462,6 +480,9 @@ final class OpenAdditonalConnection extends Request {
   MessageType<Message> get type => MessageType.openAdditionalConnection;
 }
 
+@JS('ArrayBuffer')
+external JSFunction get _arrayBufferConstructor;
+
 final class SimpleSuccessResponse extends Response {
   final JSAny? response;
 
@@ -481,6 +502,10 @@ final class SimpleSuccessResponse extends Response {
   void serialize(JSObject object, List<JSObject> transferred) {
     super.serialize(object, transferred);
     object[_UniqueFieldNames.responseData] = response;
+
+    if (response.instanceof(_arrayBufferConstructor)) {
+      transferred.add(response as JSObject);
+    }
   }
 }
 

sqlite3_web/lib/src/types.dart

@@ -76,12 +76,13 @@ final class RemoteException implements Exception {
 }
 
 abstract class FileSystem {
-  StorageMode get storage;
-  String get databaseName;
-
   Future<bool> exists(FileType type);
   Future<Uint8List> readFile(FileType type);
   Future<void> writeFile(FileType type, Uint8List content);
+
+  /// If the file system hosting the database in the worker is not synchronous,
+  /// flushes pending writes.
+  Future<void> flush();
 }
 
 /// An enumeration of features not supported by the current browsers.

sqlite3_web/lib/src/worker.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 import 'dart:js_interop';
 import 'dart:js_interop_unsafe';
+import 'dart:typed_data';
 import 'package:sqlite3/wasm.dart';
 import 'package:stream_channel/stream_channel.dart';
 import 'package:web/web.dart'
@@ -21,6 +22,7 @@ import 'database.dart';
 import 'channel.dart';
 import 'protocol.dart';
 import 'shared.dart';
+import 'types.dart';
 
 sealed class WorkerEnvironment {
   WorkerEnvironment._();
@@ -239,10 +241,46 @@ final class _ClientConnection extends ProtocolChannel
         await database.close();
         return SimpleSuccessResponse(
             response: null, requestId: request.requestId);
-      case FileSystemExistsQuery():
-        throw UnimplementedError();
-      case FileSystemAccess():
-        throw UnimplementedError();
+      case FileSystemFlushRequest():
+        if (database?.database.vfs case IndexedDbFileSystem idb) {
+          await idb.flush();
+        }
+
+        return SimpleSuccessResponse(
+            response: null, requestId: request.requestId);
+      case FileSystemExistsQuery(:final fsType):
+        await database!.database.opened;
+        final vfs = database.database.vfs!;
+        final exists = vfs.xAccess(fsType.pathInVfs, 0) == 1;
+
+        return SimpleSuccessResponse(
+            response: exists.toJS, requestId: request.requestId);
+      case FileSystemAccess(:final buffer, :final fsType):
+        await database!.database.opened;
+        final vfs = database.database.vfs!;
+        final file = vfs
+            .xOpen(
+                Sqlite3Filename(fsType.pathInVfs), SqlFlag.SQLITE_OPEN_CREATE)
+            .file;
+
+        try {
+          if (buffer != null) {
+            final asDartBuffer = buffer.toDart;
+            file.xTruncate(asDartBuffer.lengthInBytes);
+            file.xWrite(asDartBuffer.asUint8List(), 0);
+
+            return SimpleSuccessResponse(
+                response: null, requestId: request.requestId);
+          } else {
+            final buffer = Uint8List(file.xFileSize());
+            file.xRead(buffer, 0);
+
+            return SimpleSuccessResponse(
+                response: buffer.buffer.toJS, requestId: request.requestId);
+          }
+        } finally {
+          file.xClose();
+        }
     }
   }
 
@@ -268,6 +306,13 @@ final class _ClientConnection extends ProtocolChannel
   }
 }
 
+extension on FileType {
+  String get pathInVfs => switch (this) {
+        FileType.database => '/database',
+        FileType.journal => '/database-journal',
+      };
+}
+
 final class DatabaseState {
   final WorkerRunner runner;
   final int id;