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Merge pull request #29 from appinteractive/main
Adding Middleware support
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‎README.md‎

Lines changed: 54 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -97,8 +97,61 @@ You can also authenticate with a token:
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await db.authenticate('your-auth-token');
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```
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### Basic Queries
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### Middleware
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SurrealDB Flutter client supports middleware that allows you to intercept and modify requests before they are sent to the database. This is particularly useful for implementing token refresh functionality or adding logging.
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#### Adding Middleware
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You can add middleware using the `addMiddleware` method:
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```dart
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db.addMiddleware((method, params, next) async {
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// Do something before the request
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print('Before request: $method with params: $params');
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// Execute the request
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final result = await next();
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// Do something after the request
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print('After request: $method with result: $result');
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return result;
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});
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```
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Multiple middleware functions can be added, and they will be executed in the order they were added.
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#### Token Refresh Example
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Here's how you can implement token refresh using middleware:
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```dart
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db.addMiddleware((method, params, next) async {
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try {
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// Try to execute the request normally
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return await next();
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} catch (e) {
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// If we get an authentication error
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if (e.toString().contains('authentication invalid')) {
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// Refresh the token (implement your token refresh logic)
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final newToken = await refreshToken();
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// Re-authenticate with the new token
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await db.authenticate(newToken);
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// Retry the original request
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return await next();
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}
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// For other errors, just rethrow
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rethrow;
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}
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});
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```
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This middleware will catch authentication errors, refresh the token, and retry the original request automatically.
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### Basic Queries
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SurrealDB allows executing a variety of commands, including CRUD operations (Create, Read, Update, Delete) via queries. Here's how you can perform simple database operations.
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‎lib/src/surrealdb.dart‎

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Original file line numberDiff line numberDiff line change
@@ -4,6 +4,53 @@ import 'package:surrealdb/src/pinger.dart';
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import 'package:surrealdb/src/ws.dart';
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import 'package:surrealdb/surrealdb.dart';
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/// Type definition for middleware function
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/// [method] - The method being called
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/// [params] - The parameters passed to the method
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/// [next] - The function to call to continue the middleware chain
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typedef Middleware = Future<Object?> Function(
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String method,
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List<Object?> params,
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Future<Object?> Function() next,
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);
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/// SurrealDB client for Dart & Flutter
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///
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/// This client provides an interface to interact with SurrealDB via WebSockets.
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/// It supports authentication, database operations, and middleware for request
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/// manipulation.
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///
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/// Example usage with token refresh middleware:
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/// ```dart
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/// final db = SurrealDB('ws://localhost:8000');
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/// db.connect();
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/// await db.wait();
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///
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/// // Add a token refresh middleware
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/// db.addMiddleware((method, params, next) async {
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/// try {
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/// // Try to execute the request normally
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/// return await next();
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/// } catch (e) {
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/// // If we get an authentication error
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/// if (e.toString().contains('authentication invalid')) {
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/// // Refresh the token
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/// final newToken = await refreshToken(); // Your token refresh logic
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///
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/// // Re-authenticate with the new token
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/// await db.authenticate(newToken);
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///
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/// // Retry the original request
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/// return await next();
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/// }
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/// // For other errors, just rethrow
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/// rethrow;
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/// }
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/// });
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///
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/// // Now all requests will automatically refresh the token if needed
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/// final results = await db.select('users');
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/// ```
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class SurrealDB {
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SurrealDB(
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this.url, {
@@ -18,6 +65,9 @@ class SurrealDB {
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Pinger? _pinger;
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late final WSService _wsService;
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final SurrealDBOptions options;
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/// List of middleware functions to execute before each request
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final List<Middleware> _middlewares = [];
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/// Connects to a local or remote database endpoint.
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void connect() {
@@ -127,6 +177,25 @@ class SurrealDB {
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return _wsService.rpc(Methods.invalidate);
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}
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/// Adds a middleware function to be executed before each request
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///
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/// Middleware functions are executed in the order they are added.
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/// Each middleware function must call the next function to continue the chain.
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///
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/// Example:
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/// ```dart
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/// db.addMiddleware((method, params, next) async {
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/// print('Before request: $method');
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/// final result = await next();
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/// print('After request: $method');
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/// return result;
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/// });
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/// ```
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void addMiddleware(Middleware middleware) {
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_middlewares.add(middleware);
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_wsService.setMiddlewares(_middlewares);
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}
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130199
/// Authenticates the current connection with a JWT [token].
131200
Future<void> authenticate(String token) {
132201
return _wsService.rpc(Methods.authenticate, [token]);

‎lib/src/ws.dart‎

Lines changed: 68 additions & 30 deletions
Original file line numberDiff line numberDiff line change
@@ -11,6 +11,12 @@ import 'package:web_socket_channel/web_socket_channel.dart';
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typedef WsFunctionParam = Map<String, dynamic>;
1212
typedef WsFunction = void Function(WsFunctionParam);
1313

14+
typedef Middleware = Future<Object?> Function(
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String method,
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List<Object?> params,
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Future<Object?> Function() next,
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);
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1420
class WSService {
1521
WSService(this.url, this.options);
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final String url;
@@ -23,6 +29,14 @@ class WSService {
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var _shouldReconnect = false;
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2531
var _reconnectDuration = const Duration(milliseconds: 100);
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final List<Middleware> _middlewares = [];
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void setMiddlewares(List<Middleware> middlewares) {
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_middlewares
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..clear()
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..addAll(middlewares);
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}
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Future<void> connect() async {
2842
_shouldReconnect = true;
@@ -87,47 +101,71 @@ class WSService {
87101
String method, [
88102
List<Object?> data = const [],
89103
Duration? timeout,
90-
]) {
91-
final completer = Completer<Object?>();
92-
104+
]) async {
93105
final ws = _ws;
94106

95107
if (ws == null) {
96-
return (completer..completeError('websocket not connected')).future;
108+
throw Exception('websocket not connected');
97109
}
98110

99-
final id = getNextId();
100-
101-
ws.sink.add(
102-
jsonEncode(
103-
{
104-
'method': method,
105-
'id': id,
106-
'params': data,
107-
},
108-
),
109-
);
110-
111-
if (timeout != Duration.zero) {
112-
Future.delayed(
113-
options.timeoutDuration,
114-
() {
115-
if (completer.isCompleted) return;
116-
completer.completeError(TimeoutException('timeout', timeout));
117-
},
111+
// Function to execute the actual RPC call without middleware
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Future<Object?> executeActualRpc() async {
113+
final id = getNextId();
114+
final completer = Completer<Object?>();
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116+
ws.sink.add(
117+
jsonEncode(
118+
{
119+
'method': method,
120+
'id': id,
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'params': data,
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},
123+
),
118124
);
125+
126+
if (timeout != Duration.zero) {
127+
Future.delayed(
128+
options.timeoutDuration,
129+
() {
130+
if (completer.isCompleted) return;
131+
completer.completeError(TimeoutException('timeout', timeout));
132+
},
133+
);
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}
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_methodBus.once<RpcResponse>(id, (rpcResponse) {
137+
if (completer.isCompleted) return;
138+
if (rpcResponse.error != null) {
139+
completer.completeError(rpcResponse.error!);
140+
} else {
141+
completer.complete(rpcResponse.data);
142+
}
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});
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return completer.future;
119146
}
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121-
_methodBus.once<RpcResponse>(id, (rpcResponse) {
122-
if (completer.isCompleted) return;
123-
if (rpcResponse.error != null) {
124-
completer.completeError(rpcResponse.error!);
148+
// If there are no middlewares, just execute the RPC call directly
149+
if (_middlewares.isEmpty) {
150+
return executeActualRpc();
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}
152+
153+
// Build the middleware chain
154+
var index = 0;
155+
156+
Future<Object?> executeMiddlewareChain() async {
157+
if (index < _middlewares.length) {
158+
final middleware = _middlewares[index++];
159+
// Execute the middleware and pass the next middleware in the chain
160+
return middleware(method, data, executeMiddlewareChain);
125161
} else {
126-
completer.complete(rpcResponse.data);
162+
// All middlewares executed, perform the actual RPC call
163+
return executeActualRpc();
127164
}
128-
});
165+
}
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130-
return completer.future;
167+
// Start executing the middleware chain
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return executeMiddlewareChain();
131169
}
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133171
Future<void> _handleMessage(Map<String, dynamic> data) async {

‎pubspec.yaml‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,10 +1,10 @@
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name: surrealdb
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description: SurrealDB client written in pure dart. Auto reconnect, Typed functions
3-
version: 1.0.2
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version: 1.1.0
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repository: https://github.com/duhanbalci/surrealdb_flutter
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environment:
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sdk: '>=3.0.0 <4.0.0'
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sdk: ">=3.0.0 <4.0.0"
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dependencies:
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uuid: ^4.5.0

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