feat: create initial NDN binding implementation

example/ndn/client_example.dart

@@ -0,0 +1,52 @@
+// Copyright 2024 Contributors to the Eclipse Foundation. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+// ignore_for_file: avoid_print
+
+import "package:dart_wot/binding_ndn.dart";
+import "package:dart_wot/core.dart";
+import "package:dart_wot/src/binding_ndn/ndn_config.dart";
+
+Future<void> main() async {
+  final faceUri = Uri.parse("tcp4://localhost:6363");
+  final ndnConfig = NdnConfig(
+    faceUri: faceUri,
+  );
+
+  final servient = Servient(
+    clientFactories: [NdnClientFactory(ndnConfig: ndnConfig)],
+  );
+
+  final wot = await servient.start();
+
+  final thingDescription = {
+    "@context": "https://www.w3.org/2022/wot/td/v1.1",
+    "title": "NDN Thing",
+    "id": "urn:test",
+    "securityDefinitions": {
+      "nosec_sc": {"scheme": "nosec"},
+    },
+    "security": "nosec_sc",
+    "properties": {
+      "ping": {
+        "forms": [
+          {
+            "contentType": "text/plain",
+            "href": "ndn:///ndn/ping/9001",
+          },
+        ],
+      },
+    },
+  }.toThingDescription();
+
+  final consumedThing = await wot.consume(thingDescription);
+
+  final result = await consumedThing.readProperty("ping");
+
+  print(await result.value());
+
+  await servient.shutdown();
+}

lib/binding_ndn.dart

@@ -0,0 +1,13 @@
+// Copyright 2024 Contributors to the Eclipse Foundation. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+/// Protocol binding for Named Data Networking (NDN). Follows
+/// an experimental [NDN Protocol Binding specification].
+///
+/// [NDN Protocol Binding specification]: https://github.com/JKRhb/wot-binding-templates/tree/ndn-binding
+library binding_ndn;
+
+export "src/binding_ndn/ndn_consumer_factory.dart";

lib/src/binding_coap/coap_client.dart

@@ -438,11 +438,6 @@ final class CoapClient implements ProtocolClient {
     return CoapSubscription(coapClient, null, complete);
   }
 
-  @override
-  Future<void> start() async {
-    // Do nothing
-  }
-
   @override
   Future<void> stop() async {}
 

lib/src/binding_coap/coap_client_factory.dart

@@ -36,7 +36,7 @@ final class CoapClientFactory implements ProtocolClientFactory {
   }
 
   @override
-  ProtocolClient createClient() => CoapClient(
+  Future<ProtocolClient> createClient() async => CoapClient(
         coapConfig: coapConfig,
         pskCredentialsCallback: _pskCredentialsCallback,
         aceSecurityCallback: _aceSecurityCallback,

lib/src/binding_http/http_client.dart

@@ -263,11 +263,6 @@ final class HttpClient implements ProtocolClient {
     return _contentFromResponse(form, response);
   }
 
-  @override
-  Future<void> start() async {
-    // Do nothing
-  }
-
   @override
   Future<void> stop() async {
     _client.close();

lib/src/binding_http/http_client_factory.dart

@@ -33,7 +33,7 @@ final class HttpClientFactory implements ProtocolClientFactory {
   }
 
   @override
-  ProtocolClient createClient() => HttpClient(
+  Future<ProtocolClient> createClient() async => HttpClient(
         basicCredentialsCallback: _basicCredentialsCallback,
         bearerCredentialsCallback: _bearerCredentialsCallback,
       );

lib/src/binding_mqtt/mqtt_client.dart

@@ -166,11 +166,6 @@ final class MqttClient implements ProtocolClient {
       ..disconnect();
   }
 
-  @override
-  Future<void> start() async {
-    // Do nothing
-  }
-
   @override
   Future<void> stop() async {
     // Do nothing

lib/src/binding_mqtt/mqtt_client_factory.dart

@@ -25,7 +25,7 @@ final class MqttClientFactory implements ProtocolClientFactory {
       _basicCredentialsCallback;
 
   @override
-  ProtocolClient createClient() => MqttClient(
+  Future<ProtocolClient> createClient() async => MqttClient(
         mqttConfig: _mqttConfig,
         basicCredentialsCallback: _basicCredentialsCallback,
       );

lib/src/binding_ndn/ndn_config.dart

@@ -0,0 +1,25 @@
+// Copyright 2024 Contributors to the Eclipse Foundation. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+import "package:meta/meta.dart";
+
+import "ndn_consumer.dart";
+
+@immutable
+
+/// Configuration class used by [NdnClient]s.
+class NdnConfig {
+  ///
+  const NdnConfig({
+    this.faceUri,
+  });
+
+  /// [Uri] of the local NDN Forwarding Daemon (NFD).
+  ///
+  /// If `null`, then the default [Uri] will be used, connecting the
+  /// [NdnClient] to the NFD via a Unix Socket.
+  final Uri? faceUri;
+}

lib/src/binding_ndn/ndn_consumer.dart

@@ -0,0 +1,92 @@
+// Copyright 2024 Contributors to the Eclipse Foundation. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+import "package:dart_ndn/dart_ndn.dart";
+import "package:meta/meta.dart";
+
+import "../../core.dart";
+import "ndn_config.dart";
+
+/// A WoT [ProtocolClient] acting as an NDN consumer.
+@immutable
+class NdnClient implements ProtocolClient {
+  /// Creates a new [NdnClient] from an NDN [_consumer].
+  const NdnClient(this._consumer);
+
+  /// Asynchronously creates a new [NdnClient] from an [NdnConfig].
+  static Future<NdnClient> create(NdnConfig config) async {
+    final consumer = await Consumer.create(config.faceUri);
+    return NdnClient(consumer);
+  }
+
+  final Consumer _consumer;
+
+  @override
+  Stream<DiscoveryContent> discoverDirectly(
+    Uri uri, {
+    bool disableMulticast = false,
+  }) {
+    // TODO: implement discoverDirectly
+    throw UnimplementedError();
+  }
+
+  @override
+  Stream<DiscoveryContent> discoverWithCoreLinkFormat(Uri uri) {
+    // TODO: implement discoverWithCoreLinkFormat
+    throw UnimplementedError();
+  }
+
+  @override
+  Future<Content> invokeResource(AugmentedForm form, Content content) {
+    // TODO: implement invokeResource
+    throw UnimplementedError();
+  }
+
+  @override
+  Future<Content> readResource(AugmentedForm form) async {
+    // TODO: Add Name.fromUri
+    final name = Name.fromString(form.href.path);
+
+    final result = await _consumer.expressInterest(name);
+
+    switch (result) {
+      case DataReceived(:final data):
+        final iterable = [data.content ?? <int>[]];
+
+        return Content(form.contentType, Stream.fromIterable(iterable));
+      default:
+        throw Exception("TODO");
+    }
+  }
+
+  @override
+  Future<Content> requestThingDescription(Uri url) {
+    // TODO: implement requestThingDescription
+    throw UnimplementedError();
+  }
+
+  @override
+  Future<void> stop() async {
+    await _consumer.shutdown();
+  }
+
+  @override
+  Future<Subscription> subscribeResource(
+    AugmentedForm form, {
+    required void Function(Content content) next,
+    void Function(Exception error)? error,
+    required void Function() complete,
+  }) {
+    // TODO: implement subscribeResource
+    throw UnimplementedError();
+  }
+
+  @override
+  Future<void> writeResource(AugmentedForm form, Content content) {
+    // TODO: implement writeResource
+    throw UnimplementedError();
+  }
+}

lib/src/binding_ndn/ndn_consumer_factory.dart

@@ -0,0 +1,46 @@
+// Copyright 2024 Contributors to the Eclipse Foundation. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+import "package:meta/meta.dart";
+
+import "../../core.dart";
+import "ndn_config.dart";
+import "ndn_consumer.dart";
+
+/// A [ProtocolClientFactory] that produces
+@immutable
+class NdnClientFactory implements ProtocolClientFactory {
+  /// Creates a new [ProtocolClientFactory] from an [ndnConfig].
+  const NdnClientFactory({
+    this.ndnConfig = const NdnConfig(),
+  });
+
+  /// The [NdnConfig] acting as the blueprint for creating
+  final NdnConfig ndnConfig;
+
+  @override
+  Future<ProtocolClient> createClient() async {
+    return NdnClient.create(ndnConfig);
+  }
+
+  @override
+  bool destroy() {
+    return true;
+  }
+
+  @override
+  bool init() {
+    return true;
+  }
+
+  @override
+  Set<String> get schemes => {"ndn"};
+
+  @override
+  bool supportsOperation(OperationType operationType, String? subprotocol) {
+    return operationType == OperationType.readproperty && subprotocol == null;
+  }
+}

lib/src/core/implementation/consumed_thing.dart

@@ -35,13 +35,13 @@ class ConsumedThing implements scripting_api.ConsumedThing {
   /// Determines the id of this [ConsumedThing].
   String get identifier => thingDescription.identifier;
 
-  (ProtocolClient client, AugmentedForm form) _getClientFor(
+  Future<(ProtocolClient client, AugmentedForm form)> _getClientFor(
     List<Form> forms,
     OperationType operationType,
     InteractionAffordance interactionAffordance, {
     required int? formIndex,
     required Map<String, Object>? uriVariables,
-  }) {
+  }) async {
     final augmentedForms = forms
         .map(
           (form) => AugmentedForm.new(
@@ -59,7 +59,7 @@ class ConsumedThing implements scripting_api.ConsumedThing {
       if (formIndex >= 0 && formIndex < forms.length) {
         foundForm = augmentedForms[formIndex];
         final scheme = foundForm.href.scheme;
-        client = servient.clientFor(scheme);
+        client = await servient.createClient(scheme);
       } else {
         throw ArgumentError(
           'ConsumedThing "$title" missing formIndex for '
@@ -86,7 +86,7 @@ class ConsumedThing implements scripting_api.ConsumedThing {
         orElse: () => throw Exception("No matching form found!"),
       );
       final scheme = foundForm.href.scheme;
-      client = servient.clientFor(scheme);
+      client = await servient.createClient(scheme);
     }
 
     return (client, foundForm);
@@ -108,7 +108,7 @@ class ConsumedThing implements scripting_api.ConsumedThing {
       );
     }
 
-    final (ProtocolClient client, AugmentedForm form) = _getClientFor(
+    final (ProtocolClient client, AugmentedForm form) = await _getClientFor(
       property.forms,
       OperationType.readproperty,
       property,
@@ -117,6 +117,8 @@ class ConsumedThing implements scripting_api.ConsumedThing {
     );
 
     final content = await client.readResource(form);
+    // FIXME: Clients should be reusable
+    await client.stop();
     return InteractionOutput(content, servient.contentSerdes, form, property);
   }
 
@@ -137,7 +139,7 @@ class ConsumedThing implements scripting_api.ConsumedThing {
       );
     }
 
-    final (client, form) = _getClientFor(
+    final (client, form) = await _getClientFor(
       property.forms,
       OperationType.writeproperty,
       property,
@@ -173,7 +175,7 @@ class ConsumedThing implements scripting_api.ConsumedThing {
       );
     }
 
-    final (client, form) = _getClientFor(
+    final (client, form) = await _getClientFor(
       action.forms,
       OperationType.invokeaction,
       action,
@@ -269,7 +271,7 @@ class ConsumedThing implements scripting_api.ConsumedThing {
         subscriptions = _subscribedEvents;
     }
 
-    final (client, form) = _getClientFor(
+    final (client, form) = await _getClientFor(
       affordance.forms,
       operationType,
       affordance,

lib/src/core/implementation/protocol_interfaces/protocol_client.dart

@@ -10,9 +10,6 @@ import "../content.dart";
 
 /// Base class for a Protocol Client.
 abstract interface class ProtocolClient {
-  /// Starts this [ProtocolClient].
-  Future<void> start();
-
   /// Stops this [ProtocolClient].
   Future<void> stop();
 

lib/src/core/implementation/protocol_interfaces/protocol_client_factory.dart

@@ -26,7 +26,7 @@ abstract interface class ProtocolClientFactory {
 
   /// Creates a new [ProtocolClient] with that supports one or more of the given
   /// [schemes].
-  ProtocolClient createClient();
+  Future<ProtocolClient> createClient();
 
   /// Indicates whether this [ProtocolClientFactory] supports a given
   /// [operationType] and subprotocol.