feat!: add initial support for query parameters to exploreDirectory method

example/directory_discovery.dart

@@ -0,0 +1,29 @@
+// 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_http.dart";
+import "package:dart_wot/core.dart";
+
+Future<void> main(List<String> args) async {
+  final servient = Servient(
+    clientFactories: [
+      HttpClientFactory(),
+    ],
+  );
+
+  final wot = await servient.start();
+  // FIXME(JRKhb): The "things" property currently points to "localhost",
+  //               preventing this example from working
+  final url = Uri.parse("https://zion.vaimee.com/.well-known/wot");
+
+  final thingDiscovery = await wot.exploreDirectory(url);
+
+  await for (final thingDescription in thingDiscovery) {
+    print(thingDescription);
+  }
+}

lib/src/core/implementation/wot.dart

@@ -111,9 +111,17 @@ class WoT implements scripting_api.WoT {
 
   @override
   Future<scripting_api.ThingDiscoveryProcess> exploreDirectory(
-    Uri url, [
+    Uri url, {
     scripting_api.ThingFilter? filter,
-  ]) async {
+    int? offset,
+    int? limit,
+    scripting_api.DirectoryPayloadFormat? format,
+  }) async {
+    // TODO(JKRhb): Add support for the collection format.
+    if (format == scripting_api.DirectoryPayloadFormat.collection) {
+      throw ArgumentError('Format "$format" is currently not supported.');
+    }
+
     final thingDescription = await requestThingDescription(url);
 
     if (!thingDescription.isValidDirectoryThingDescription) {
@@ -124,8 +132,14 @@ class WoT implements scripting_api.WoT {
 
     final consumedDirectoryThing = await consume(thingDescription);
 
-    final interactionOutput =
-        await consumedDirectoryThing.readProperty("things");
+    final interactionOutput = await consumedDirectoryThing.readProperty(
+      "things",
+      uriVariables: {
+        if (offset != null) "offset": offset,
+        if (limit != null) "limit": limit,
+        if (format != null) "format": format.toString(),
+      },
+    );
     final rawThingDescriptions = await interactionOutput.value();
 
     if (rawThingDescriptions is! List<Object?>) {

lib/src/core/scripting_api/wot.dart

@@ -13,6 +13,35 @@ import "discovery/thing_filter.dart";
 import "exposed_thing.dart";
 import "types.dart";
 
+/// Enumeration for specifying the value of the `format` query parameter when
+/// using the `exploreDirectory` discovery method.
+///
+/// See [section 7.3.2.1.5] of the [WoT Discovery] specification for more
+/// information.
+///
+/// [WoT Discovery]: https://www.w3.org/TR/2023/REC-wot-discovery-20231205
+/// [section 7.3.2.1.5]: https://www.w3.org/TR/2023/REC-wot-discovery-20231205/#exploration-directory-api-things-listing
+enum DirectoryPayloadFormat {
+  /// Indicates that an array of Thing Descriptions should be returned.
+  ///
+  /// This is the default value.
+  array,
+
+  /// Indicates that an collection of Thing Descriptions should be returned.
+  collection,
+  ;
+
+  @override
+  String toString() {
+    switch (this) {
+      case array:
+        return "array";
+      case collection:
+        return "collection";
+    }
+  }
+}
+
 /// Interface for a [WoT] runtime.
 ///
 /// See WoT Scripting API specification,
@@ -39,9 +68,12 @@ abstract interface class WoT {
   /// [ThingDescription] objects for Thing Descriptions that match an optional
   /// [filter] argument of type [ThingFilter].
   Future<ThingDiscoveryProcess> exploreDirectory(
-    Uri url, [
+    Uri url, {
     ThingFilter? filter,
-  ]);
+    int? offset,
+    int? limit,
+    DirectoryPayloadFormat? format,
+  });
 
   /// Discovers [ThingDescription]s from a given [url] using the specified
   /// [method].

test/core/discovery_test.dart

@@ -21,6 +21,10 @@ final directoryTestUri2 = Uri.parse("$testUriScheme://[::4]/.well-known/wot");
 final directoryTestThingsUri2 = Uri.parse("$testUriScheme://[::4]/things");
 final directoryTestUri3 = Uri.parse("$testUriScheme://[::5]/.well-known/wot");
 final directoryTestThingsUri3 = Uri.parse("$testUriScheme://[::5]/things");
+final directoryTestUri4 = Uri.parse("$testUriScheme://[::6]/.well-known/wot");
+final directoryTestThingsUri4 = Uri.parse(
+  "$testUriScheme://[::3]/things?offset=2&limit=3&format=array",
+);
 
 const validTestTitle1 = "Test TD 1";
 const validTestThingDescription = '''
@@ -49,6 +53,26 @@ final directoryThingDescription1 = '''
   },
   "properties": {
     "things": {
+      "uriVariables": {
+        "offset": {
+          "title": "Number of TDs to skip before the page",
+          "type": "number",
+          "default": 0
+        },
+        "limit": {
+          "title": "Number of TDs in a page",
+          "type": "number"
+        },
+        "format": {
+          "title": "Payload format",
+          "type": "string",
+          "enum": [
+            "array",
+            "collection"
+          ],
+          "default": "array"
+        }
+      },
       "forms": [
         {
           "href": "$directoryTestThingsUri1"
@@ -128,8 +152,9 @@ class _MockedProtocolClient implements ProtocolClient {
   }
 
   @override
-  Future<Content> readResource(Form form) async {
-    final href = form.href;
+  Future<Content> readResource(AugmentedForm form) async {
+    final href = form.resolvedHref;
+
     if (href == directoryTestThingsUri1) {
       return "[$validTestThingDescription]".toContent("application/td+json");
     }
@@ -142,6 +167,10 @@ class _MockedProtocolClient implements ProtocolClient {
       return invalidTestThingDescription2.toContent("application/td+json");
     }
 
+    if (href == directoryTestThingsUri4) {
+      return "[$validTestThingDescription]".toContent("application/ld+json");
+    }
+
     throw StateError("Encountered an unknown URI $href.");
   }
 
@@ -167,6 +196,10 @@ class _MockedProtocolClient implements ProtocolClient {
       return directoryThingDescription3.toDiscoveryContent(url);
     }
 
+    if (url == directoryTestUri4) {
+      return directoryThingDescription1.toDiscoveryContent(url);
+    }
+
     throw StateError("Encountered invalid URL.");
   }
 
@@ -377,5 +410,44 @@ void main() {
       await thingDiscoveryProcess.stop();
       expect(thingDiscoveryProcess.done, true);
     });
+
+    test("should support the experimental query parameters API", () async {
+      final servient = Servient(
+        clientFactories: [
+          _MockedProtocolClientFactory(),
+        ],
+      );
+
+      final wot = await servient.start();
+      final thingDiscoveryProcess = await wot.exploreDirectory(
+        directoryTestUri4,
+        offset: 2,
+        limit: 3,
+        format: DirectoryPayloadFormat.array,
+      );
+
+      var counter = 0;
+      await for (final thingDescription in thingDiscoveryProcess) {
+        counter++;
+        expect(thingDescription.title, validTestTitle1);
+      }
+      expect(counter, 1);
+      expect(thingDiscoveryProcess.done, true);
+    });
+
+    test(
+        'should currently not support the "collection" format when using the '
+        "experimental query parameters API", () async {
+      final servient = Servient();
+      final wot = await servient.start();
+
+      expect(
+        () async => await wot.exploreDirectory(
+          directoryTestUri4,
+          format: DirectoryPayloadFormat.collection,
+        ),
+        throwsArgumentError,
+      );
+    });
   });
 }