feat(core): add JSON schema validation of values

lib/src/core/content_serdes.dart

@@ -8,6 +8,7 @@ import 'dart:convert';
 import 'dart:typed_data';
 
 import 'package:http_parser/http_parser.dart';
+import 'package:json_schema2/json_schema2.dart';
 
 import '../definitions/data_schema.dart';
 import 'codecs/cbor_codec.dart';
@@ -28,6 +29,16 @@ const jsonLdContentType = 'application/ld+json';
 /// Defines `application/json` as the default content type.
 const defaultContentType = jsonContentType;
 
+/// Custom [Exception] that is thrown when Serialization or Deserialization
+/// fails.
+class ContentSerdesException implements Exception {
+  /// The error message of this [ContentSerdesException].
+  String? message;
+
+  /// Constructor.
+  ContentSerdesException(this.message);
+}
+
 /// Class providing serializing and deserializing capabilities.
 ///
 // TODO(JKRhb): Decide if a class-based approach is the right way to go.
@@ -151,12 +162,25 @@ class ContentSerdes {
     return _supportedCodecs[codecName];
   }
 
+  void _validateValue(Object? value, DataSchema? dataSchema) {
+    final dataSchemaJson = dataSchema?.rawJson;
+    if (dataSchemaJson == null) {
+      return;
+    }
+    final schema = JsonSchema.createSchema(dataSchemaJson);
+    if (!schema.validate(value)) {
+      throw ContentSerdesException("JSON Schema validation failed.");
+    }
+  }
+
   /// Converts an [Object] to a byte representation based on its [contentType].
   ///
   /// A [dataSchema] can be passed for validating the input [value] before the
   /// conversion.
   Content valueToContent(
       Object? value, DataSchema? dataSchema, String? contentType) {
+    _validateValue(value, dataSchema);
+
     contentType ??= defaultContentType;
 
     final parsedMediaType = MediaType.parse(contentType);
@@ -194,7 +218,9 @@ class ContentSerdes {
 
     final codec = _getCodecFromMediaType(mimeType);
     if (codec != null) {
-      return codec.bytesToValue(bytes, dataSchema, parameters);
+      final value = codec.bytesToValue(bytes, dataSchema, parameters);
+      _validateValue(value, dataSchema);
+      return value;
     } else {
       // TODO(JKRhb): Should unsupported data be returned as a String?
       return utf8.decode(bytes.asUint8List());

lib/src/definitions/data_schema.dart

@@ -70,8 +70,12 @@ class DataSchema {
   /// or null.
   String? type;
 
+  /// The original JSON object that was parsed when creating this [DataSchema].
+  Map<String, dynamic>? rawJson;
+
   /// Creates a new [DataSchema] from a [json] object.
   DataSchema.fromJson(Map<String, dynamic> json) {
     parseDataSchemaJson(this, json);
+    rawJson = json;
   }
 }

lib/src/definitions/interaction_affordances/property.dart

@@ -40,12 +40,16 @@ class Property extends InteractionAffordance implements DataSchema {
   @override
   bool? writeOnly;
 
+  @override
+  Map<String, dynamic>? rawJson;
+
   /// Default constructor that creates a [Property] from a [List] of [forms].
   Property(List<Form> forms) : super(forms);
 
   /// Creates a new [Property] from a [json] object.
   Property.fromJson(Map<String, dynamic> json) : super([]) {
     parseAffordanceFields(json);
     parseDataSchemaJson(this, json);
+    rawJson = json;
   }
 }