fix(coap-server): add missing cov:observe subprotocol

packages/binding-coap/src/coap-server.ts

@@ -35,6 +35,7 @@ import { MdnsIntroducer } from "./mdns-introducer";
 import { PropertyElement, DataSchema, ActionElement, EventElement } from "wot-thing-description-types";
 import { CoapServerConfig } from "./coap";
 import { DataSchemaValue } from "wot-typescript-definitions";
+import { filterPropertyObserveOperations, getPropertyOpValues } from "./util";
 
 const { debug, warn, info, error } = createLoggers("binding-coap", "coap-server");
 
@@ -233,27 +234,42 @@ export default class CoapServer implements ProtocolServer {
     private addFormToAffordance(form: TD.Form, affordance: AffordanceElement): void {
         const affordanceForms = affordance.forms;
         if (affordanceForms == null) {
-            affordance.forms ??= [form];
+            affordance.forms = [form];
         } else {
             affordanceForms.push(form);
         }
     }
 
     private fillInPropertyBindingData(thing: ExposedThing, base: string, offeredMediaType: string) {
         for (const [propertyName, property] of Object.entries(thing.properties)) {
-            const opValues = ProtocolHelpers.getPropertyOpValues(property);
-            const form = this.createAffordanceForm(
-                base,
-                this.PROPERTY_DIR,
-                offeredMediaType,
-                opValues,
-                thing.uriVariables,
-                propertyName,
-                property.uriVariables
-            );
+            const [readWriteOpValues, observeOpValues] = getPropertyOpValues(property);
+            for (const formOpValues of [observeOpValues, readWriteOpValues]) {
+                if (formOpValues.length === 0) {
+                    continue;
+                }
 
-            this.addFormToAffordance(form, property);
-            this.logHrefAssignment(form, "Property", propertyName);
+                let subprotocol: string | undefined;
+
+                const observeOpValues = filterPropertyObserveOperations(formOpValues);
+
+                if (observeOpValues.length > 0) {
+                    subprotocol = "cov:observe";
+                }
+
+                const form = this.createAffordanceForm(
+                    base,
+                    this.PROPERTY_DIR,
+                    offeredMediaType,
+                    formOpValues,
+                    thing.uriVariables,
+                    propertyName,
+                    property.uriVariables,
+                    subprotocol
+                );
+
+                this.addFormToAffordance(form, property);
+                this.logHrefAssignment(form, "Property", propertyName);
+            }
         }
     }
 
@@ -283,7 +299,8 @@ export default class CoapServer implements ProtocolServer {
                 ["subscribeevent", "unsubscribeevent"],
                 thing.uriVariables,
                 eventName,
-                event.uriVariables
+                event.uriVariables,
+                "cov:observe"
             );
 
             this.addFormToAffordance(form, event);
@@ -298,7 +315,8 @@ export default class CoapServer implements ProtocolServer {
         opValues: string | string[],
         thingUriVariables: PropertyElement["uriVariables"],
         affordanceName?: string,
-        affordanceUriVariables?: PropertyElement["uriVariables"]
+        affordanceUriVariables?: PropertyElement["uriVariables"],
+        subprotocol?: string
     ): TD.Form {
         const affordanceNamePattern = Helpers.updateInteractionNameWithUriVariablePattern(
             affordanceName ?? "",
@@ -314,6 +332,7 @@ export default class CoapServer implements ProtocolServer {
 
         const form = new TD.Form(href, offeredMediaType);
         form.op = opValues;
+        form.subprotocol = subprotocol;
 
         return form;
     }

packages/binding-coap/src/util.ts

@@ -0,0 +1,69 @@
+/********************************************************************************
+ * Copyright (c) 2018 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0, or the W3C Software Notice and
+ * Document License (2015-05-13) which is available at
+ * https://www.w3.org/Consortium/Legal/2015/copyright-software-and-document.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR W3C-20150513
+ ********************************************************************************/
+
+import { ProtocolHelpers } from "@node-wot/core";
+import { PropertyElement } from "wot-thing-description-types";
+
+const observeOpFilter = ["observeproperty", "unobserveproperty"];
+const readWriteOpFilter = ["readproperty", "writeproperty"];
+
+function filterOpValues(opValues: string[], filterValues: string[]) {
+    return opValues.filter((opValue) => filterValues.includes(opValue));
+}
+
+/**
+ * Convenience function to filter out the `op` values "observeproperty" and
+ * "unobserveproperty" from a string array.
+ *
+ * @param opValues The `op` values to be filtered.
+ * @returns A filtered array that might be empty.
+ */
+export function filterPropertyObserveOperations(opValues: string[]) {
+    return filterOpValues(opValues, observeOpFilter);
+}
+
+/**
+ * Convenience function to filter out the `op` values "readproperty" and
+ * "writeproperty" from a string array.
+ *
+ * @param opValues The `op` values to be filtered.
+ * @returns A filtered array that might be empty.
+ */
+function filterPropertyReadWriteOperations(opValues: string[]) {
+    return filterOpValues(opValues, readWriteOpFilter);
+}
+
+/**
+ * Function to (potentially) generate two arrays of `op` values: One with the
+ * values "readproperty" and "writeproperty", and one with
+ * "observerproperty" and "unobserveproperty".
+ *
+ * This CoAP-specific distinction is made to be able to generate
+ * separate forms for the observe-related operations, where the addition
+ * of a `subprotocol` field with a value of `cov:observe` has to be added.
+ *
+ * @param property The property for which the forms are going to be
+ *                 generated.
+ * @returns A tuple consisting of two op value arrays (one for read and
+ *          write operations, one for observe-related operations).
+ */
+export function getPropertyOpValues(property: PropertyElement) {
+    const opValues = ProtocolHelpers.getPropertyOpValues(property);
+
+    const readWriteOpValues = filterPropertyReadWriteOperations(opValues);
+    const observeOpValues = filterPropertyObserveOperations(opValues);
+
+    return [readWriteOpValues, observeOpValues];
+}