feat: improve DataSchemaValue handling

example/coap_discovery.dart

@@ -21,10 +21,16 @@ Future<void> handleThingDescription(
   ThingDescription thingDescription,
 ) async {
   final consumedThing = await wot.consume(thingDescription);
-  await consumedThing.writeProperty(propertyName, 'Hello World!');
+  await consumedThing.writeProperty(
+    propertyName,
+    'Hello World'.asInteractionInput(),
+  );
   var output = await consumedThing.readProperty(propertyName);
   await output.printValue();
-  await consumedThing.writeProperty(propertyName, 'Bye World!');
+  await consumedThing.writeProperty(
+    propertyName,
+    'Bye Value'.asInteractionInput(),
+  );
   output = await consumedThing.readProperty(propertyName);
   await output.printValue();
 }

example/mqtt_example.dart

@@ -85,13 +85,15 @@ Future<void> main(List<String> args) async {
     },
   );
 
-  await consumedThing.invokeAction('toggle', input: 'Hello World!');
-  await consumedThing.invokeAction('toggle', input: 'Hello World!');
-  await consumedThing.invokeAction('toggle', input: 'Hello World!');
-  await consumedThing.invokeAction('toggle', input: 'Hello World!');
+  final actionInput = 'Hello World'.asInteractionInput();
+
+  await consumedThing.invokeAction('toggle', input: actionInput);
+  await consumedThing.invokeAction('toggle', input: actionInput);
+  await consumedThing.invokeAction('toggle', input: actionInput);
+  await consumedThing.invokeAction('toggle', input: actionInput);
   await subscription.stop();
 
-  await consumedThing.invokeAction('toggle', input: 'Bye World!');
+  await consumedThing.invokeAction('toggle', input: actionInput);
   await consumedThing.readAndPrintProperty('status');
   print('Done!');
 }

lib/scripting_api.dart

@@ -11,10 +11,12 @@
 library scripting_api;
 
 export 'src/scripting_api/consumed_thing.dart';
+export 'src/scripting_api/data_schema_value.dart';
 export 'src/scripting_api/discovery/discovery_method.dart';
 export 'src/scripting_api/discovery/thing_discovery.dart';
 export 'src/scripting_api/discovery/thing_filter.dart';
 export 'src/scripting_api/exposed_thing.dart';
+export 'src/scripting_api/interaction_input.dart';
 export 'src/scripting_api/interaction_output.dart';
 export 'src/scripting_api/subscription.dart';
 export 'src/scripting_api/types.dart';

lib/src/core/codecs/cbor_codec.dart

@@ -7,26 +7,34 @@
 import 'package:cbor/cbor.dart' as cbor;
 
 import '../../definitions/data_schema.dart';
+import '../../scripting_api/data_schema_value.dart';
 import 'content_codec.dart';
 
 /// A [ContentCodec] that encodes and decodes CBOR data.
 class CborCodec extends ContentCodec {
   @override
   List<int> valueToBytes(
-    Object? value,
+    DataSchemaValue? dataSchemaValue,
     DataSchema? dataSchema,
     Map<String, String>? parameters,
   ) {
-    return cbor.cborEncode(cbor.CborValue(value));
+    if (dataSchemaValue == null) {
+      return [];
+    }
+
+    final cborValue = cbor.CborValue(dataSchemaValue.value);
+
+    return cbor.cborEncode(cborValue);
   }
 
   @override
-  Object? bytesToValue(
+  DataSchemaValue? bytesToValue(
     List<int> bytes,
     DataSchema? dataSchema,
     Map<String, String>? parameters,
   ) {
-    // TODO(JKRhb): Use dataSchema for validation
-    return cbor.cborDecode(bytes).toObject();
+    final cborObject = cbor.cborDecode(bytes).toObject();
+
+    return DataSchemaValue.tryParse(cborObject);
   }
 }

lib/src/core/codecs/content_codec.dart

@@ -5,18 +5,19 @@
 // SPDX-License-Identifier: BSD-3-Clause
 
 import '../../definitions/data_schema.dart';
+import '../../scripting_api/data_schema_value.dart';
 
 /// Interface for providing a codec for a specific media type.
 abstract class ContentCodec {
   /// Converts an [Object] to its byte representation in the given media type.
   List<int> valueToBytes(
-    Object? value,
+    DataSchemaValue<Object?> value,
     DataSchema? dataSchema,
     Map<String, String>? parameters,
   );
 
   /// Converts a payload of the given media type to an [Object].
-  Object? bytesToValue(
+  DataSchemaValue<Object?>? bytesToValue(
     List<int> bytes,
     DataSchema? dataSchema,
     Map<String, String>? parameters,

lib/src/core/codecs/json_codec.dart

@@ -8,27 +8,38 @@ import 'dart:convert';
 
 import '../../definitions/data_schema.dart';
 
+import '../../scripting_api/data_schema_value.dart';
 import 'content_codec.dart';
 
 /// A [ContentCodec] that encodes and decodes JSON data.
 class JsonCodec extends ContentCodec {
   @override
   List<int> valueToBytes(
-    Object? value,
+    DataSchemaValue? dataSchemaValue,
     DataSchema? dataSchema,
     Map<String, String>? parameters,
   ) {
-    return utf8.encode(jsonEncode(value));
+    if (dataSchemaValue == null) {
+      return [];
+    }
+
+    return utf8.encode(jsonEncode(dataSchemaValue.value));
   }
 
   @override
-  Object? bytesToValue(
+  DataSchemaValue? bytesToValue(
     List<int> bytes,
     DataSchema? dataSchema,
     Map<String, String>? parameters,
   ) {
     // TODO(JKRhb): Use dataSchema for validation
 
-    return jsonDecode(utf8.decoder.convert(bytes));
+    if (bytes.isEmpty) {
+      return null;
+    }
+
+    final decodedJson = jsonDecode(utf8.decoder.convert(bytes));
+
+    return DataSchemaValue.tryParse(decodedJson);
   }
 }

lib/src/core/codecs/text_codec.dart

@@ -0,0 +1,63 @@
+// Copyright 2023 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 'dart:convert';
+
+import '../../definitions/data_schema.dart';
+
+import '../../scripting_api/data_schema_value.dart';
+import 'content_codec.dart';
+
+const _utf8Coding = 'utf-8';
+
+/// A [ContentCodec] that encodes and decodes plain text data.
+class TextCodec extends ContentCodec {
+  @override
+  List<int> valueToBytes(
+    DataSchemaValue? dataSchemaValue,
+    DataSchema? dataSchema,
+    Map<String, String>? parameters,
+  ) {
+    if (dataSchemaValue == null) {
+      return [];
+    }
+
+    final rawValue = dataSchemaValue.value.toString();
+
+    final coding = parameters.coding;
+
+    switch (coding) {
+      case _utf8Coding:
+        return utf8.encode(rawValue);
+      default:
+        throw FormatException('Encountered unsupported text coding $coding');
+    }
+  }
+
+  @override
+  DataSchemaValue? bytesToValue(
+    List<int> bytes,
+    DataSchema? dataSchema,
+    Map<String, String>? parameters,
+  ) {
+    if (bytes.isEmpty) {
+      return null;
+    }
+
+    final coding = parameters.coding;
+
+    switch (coding) {
+      case _utf8Coding:
+        return DataSchemaValue.fromString(utf8.decoder.convert(bytes));
+      default:
+        throw FormatException('Encountered unsupported text coding $coding');
+    }
+  }
+}
+
+extension _ParametersExtension on Map<String, String>? {
+  String get coding => this?['charset']?.toLowerCase() ?? _utf8Coding;
+}

lib/src/core/consumed_thing.dart

@@ -11,6 +11,7 @@ import '../definitions/form.dart';
 import '../definitions/interaction_affordances/interaction_affordance.dart';
 import '../definitions/operation_type.dart';
 import '../definitions/thing_description.dart';
+import 'content.dart';
 import 'interaction_output.dart';
 import 'protocol_interfaces/protocol_client.dart';
 import 'servient.dart';
@@ -153,7 +154,7 @@ class ConsumedThing implements scripting_api.ConsumedThing {
   @override
   Future<void> writeProperty(
     String propertyName,
-    InteractionInput input, {
+    InteractionInput? input, {
     int? formIndex,
     Map<String, Object>? uriVariables,
     Object? data,
@@ -179,15 +180,21 @@ class ConsumedThing implements scripting_api.ConsumedThing {
 
     final form = clientAndForm.form;
     final client = clientAndForm.client;
-    final content = servient.contentSerdes
-        .valueToContent(input, property, form.contentType);
+
+    final content = Content.fromInteractionInput(
+      input,
+      form.contentType,
+      servient.contentSerdes,
+      property,
+    );
+
     await client.writeResource(form, content);
   }
 
   @override
   Future<InteractionOutput> invokeAction(
     String actionName, {
-    InteractionInput input,
+    InteractionInput? input,
     Object? data,
     int? formIndex,
     Map<String, Object>? uriVariables,
@@ -213,8 +220,13 @@ class ConsumedThing implements scripting_api.ConsumedThing {
 
     final form = clientAndForm.form;
     final client = clientAndForm.client;
-    final content = servient.contentSerdes
-        .valueToContent(input, action.input, form.contentType);
+
+    final content = Content.fromInteractionInput(
+      input,
+      form.contentType,
+      servient.contentSerdes,
+      action.input,
+    );
 
     final output = await client.invokeResource(form, content);
 

lib/src/core/content.dart

@@ -8,12 +8,45 @@ import 'dart:typed_data';
 
 import 'package:typed_data/typed_data.dart';
 
+import '../definitions/data_schema.dart';
+import '../scripting_api/interaction_input.dart';
+import 'content_serdes.dart';
+
 /// This class contains binary input or output data and indicates the media
 /// type this data is encoded in.
 class Content {
   /// Creates a new [Content] object from a media [type] and a [body].
   Content(this.type, this.body);
 
+  /// Creates a new [Content] object from an [interactionInput].
+  ///
+  /// If the [interactionInput] is not a [StreamInput], it will be converted to
+  /// a [Stream] by the referenced [contentSerdes] if it supports the specified
+  /// [contentType].
+  /// In this case, the optional [dataSchema] will be used for validation before
+  /// the conversion.
+  factory Content.fromInteractionInput(
+    InteractionInput? interactionInput,
+    String contentType,
+    ContentSerdes contentSerdes,
+    DataSchema? dataSchema,
+  ) {
+    if (interactionInput == null) {
+      return Content(contentType, const Stream.empty());
+    }
+
+    switch (interactionInput) {
+      case DataSchemaValueInput():
+        return contentSerdes.valueToContent(
+          interactionInput.dataSchemaValue,
+          dataSchema,
+          contentType,
+        );
+      case StreamInput():
+        return Content(contentType, interactionInput.byteStream);
+    }
+  }
+
   /// The media type corresponding with this [Content] object.
   ///
   /// Examples would be `application/json` or `application/cbor`.