fixup! Implement ExposedThing functionality

example/exposed_thing/http_server.dart

@@ -3,6 +3,8 @@
 import "package:dart_wot/binding_http.dart";
 import "package:dart_wot/core.dart";
 
+var property = "hi :)";
+
 void main() async {
   final servient =
       Servient.create(servers: [HttpServer(HttpConfig(port: 3000))]);
@@ -25,11 +27,27 @@ void main() async {
     },
   });
 
-  exposedThing.setPropertyReadHandler("status", ({
-    data,
-    formIndex,
-    uriVariables,
-  }) async {
-    return InteractionInput.fromString("Hi :)");
-  });
+  exposedThing
+    ..setPropertyReadHandler("status", ({
+      data,
+      formIndex,
+      uriVariables,
+    }) async {
+      return InteractionInput.fromString(property);
+    })
+    ..setPropertyWriteHandler("status", (
+      interactionOutput, {
+      data,
+      formIndex,
+      uriVariables,
+    }) async {
+      final value = await interactionOutput.value();
+
+      if (value is String) {
+        property = value;
+        return;
+      }
+
+      // TODO: Should an incorrect data type be handled in some way?
+    });
 }

lib/src/binding_http/http_server.dart

@@ -71,17 +71,31 @@ final class HttpServer implements ProtocolServer {
 
     for (final affordance in thingDescription.properties?.entries ??
         <MapEntry<String, Property>>[]) {
-      router.get("/$key/${affordance.key}", (request) async {
-        final content = await thing.handleReadProperty(affordance.key);
-
-        return Response(
-          200,
-          body: content.body,
-          headers: {
-            "Content-Type": content.type,
-          },
-        );
-      });
+      router
+        ..get("/$key/${affordance.key}", (request) async {
+          final content = await thing.handleReadProperty(affordance.key);
+
+          return Response(
+            200,
+            body: content.body,
+            headers: {
+              "Content-Type": content.type,
+            },
+          );
+        })
+        ..post("/$key/${affordance.key}", (request) async {
+          if (request is! Request) {
+            throw Exception();
+          }
+
+          final content =
+              Content(request.mimeType ?? "application/json", request.read());
+          await thing.handleWriteProperty(affordance.key, content);
+
+          return Response(
+            204,
+          );
+        });
     }
 
     _routes[key] = router;

lib/src/core/implementation/exposed_thing.dart

@@ -10,6 +10,7 @@ import "../definitions.dart";
 import "../scripting_api.dart" as scripting_api;
 
 import "content.dart";
+import "interaction_output.dart";
 import "servient.dart";
 
 /// Implementation of the [scripting_api.ExposedThing] interface.
@@ -27,6 +28,9 @@ class ExposedThing implements scripting_api.ExposedThing {
   final Map<String, scripting_api.PropertyReadHandler> _propertyReadHandlers =
       {};
 
+  final Map<String, scripting_api.PropertyWriteHandler> _propertyWriteHandlers =
+      {};
+
   @override
   Future<void> emitPropertyChange(String name) {
     // TODO(JKRhb): implement emitPropertyChange
@@ -38,7 +42,7 @@ class ExposedThing implements scripting_api.ExposedThing {
     String name,
     scripting_api.PropertyWriteHandler handler,
   ) {
-    // TODO(JKRhb): implement setPropertyWriteHandler
+    _propertyWriteHandlers[name] = handler;
   }
 
   @override
@@ -142,4 +146,45 @@ class ExposedThing implements scripting_api.ExposedThing {
       thingDescription.properties?[propertyName],
     );
   }
+
+  /// Handles a `writeproperty` operation triggered by a TD consumer.
+  @internal
+  Future<void> handleWriteProperty(
+    String propertyName,
+    Content input, {
+    int? formIndex,
+    Map<String, Object>? uriVariables,
+    Object? data,
+  }) async {
+    final writeHandler = _propertyWriteHandlers[propertyName];
+
+    if (writeHandler == null) {
+      throw Exception(
+        "Write handler for property $propertyName is not defined.",
+      );
+    }
+
+    final Form form;
+
+    if (formIndex == null) {
+      // FIXME: Returning a form does not really make sense here.
+      form = Form(Uri.parse("hi"));
+    } else {
+      form = thingDescription.properties?[propertyName]?.forms
+              .elementAtOrNull(formIndex) ??
+          Form(Uri.parse("hi"));
+    }
+
+    await writeHandler(
+      InteractionOutput(
+        input,
+        _servient.contentSerdes,
+        form,
+        thingDescription.properties?[propertyName],
+      ),
+      formIndex: formIndex,
+      uriVariables: uriVariables,
+      data: data,
+    );
+  }
 }