fix: Notification Templates

+ Notifications are identified by UUIDs.
+ Turtle notification template has the same fields as JSON-LD.
+ `notify:state` transmits Event-ID (which uniquely identifies a resource's state) and not E-Tag (which identify representations of the resource).
+ Parent reuses the generated Event-ID.

Author: CxRes

lib/handlers/notify.js

@@ -88,8 +88,6 @@ function handler (req, res, next) {
               object,
               target,
               date: eventDate,
-              // We use eTag as a proxy for state for now
-              state: res.getHeader('ETag'),
               mediaType
             })}`
           } else {
@@ -110,7 +108,10 @@ function handler (req, res, next) {
   // POST in Solid creates a child resource
   const parent = getParent(path)
   if (parent && method !== 'POST') {
-    const parentID = res.setEventID(parent)
+    res.setEventID({
+      path: parent,
+      id: eventID
+    })
     const parentUrl = new URL(parent, fullUrl)
     try {
       trigger({
@@ -125,11 +126,10 @@ function handler (req, res, next) {
           if (ALLOWED_RDF_MIME_TYPES.includes(mediaType?.[0])) {
             return `${headerTemplate(negotiatedFields)}\r\n${solidRDFTemplate({
               activity,
-              eventID: parentID,
+              eventID,
               date: eventDate,
               object,
               target,
-              eTag: undefined,
               mediaType
             })}`
           }

lib/rdf-notification-template.js

@@ -1,10 +1,12 @@
+const uuid = require('uuid')
+
 const CONTEXT_ACTIVITYSTREAMS = 'https://www.w3.org/ns/activitystreams'
 const CONTEXT_NOTIFICATION = 'https://www.w3.org/ns/solid/notification/v1'
 const CONTEXT_XML_SCHEMA = 'http://www.w3.org/2001/XMLSchema'
 
 function generateJSONNotification ({
   activity: type,
-  eventId: id,
+  eventID,
   date: published,
   object,
   target,
@@ -13,30 +15,40 @@ function generateJSONNotification ({
   return {
     published,
     type,
-    id,
+    id: `urn:uuid:${uuid.v4()}`,
+    ...(eventID) && { state: eventID },
     object,
     ...(type === 'Add') && { target },
-    ...(type === 'Remove') && { origin: target },
-    ...(state) && { state }
+    ...(type === 'Remove') && { origin: target }
   }
 }
 
 function generateTurtleNotification ({
   activity,
-  eventId,
+  eventID,
   date,
   object,
-  target,
-  state = undefined
+  target
 }) {
-  const stateLine = `\n    notify:state "${state}" ;`
+  let targetLine = ''
+  let stateLine = ''
+
+  if (activity === 'Add') {
+    targetLine = `\n    as:target ${target} ;`
+  }
+  if (activity === 'Remove') {
+    targetLine = `\n    as:origin ${target} ;`
+  }
+  if (eventID) {
+    stateLine = `\n    notify:state "${eventID}" ;`
+  }
 
   return `@prefix as: <${CONTEXT_ACTIVITYSTREAMS}#> .
 @prefix notify: <${CONTEXT_NOTIFICATION}#> .
 @prefix xsd: <${CONTEXT_XML_SCHEMA}#> .
 
-<${eventId}> a as:${activity} ;${state && stateLine}
-    as:object ${object} ;
+<urn:uuid:${uuid.v4()}> a as:${activity} ;
+    as:object ${object} ;${targetLine}${stateLine}
     as:published "${date}"^^xsd:dateTime .`.replaceAll('\n', '\r\n')
 }