[discovery] first draft of DiscoveryClient

packages/discovery/package.json

@@ -37,5 +37,9 @@
     "jest": "^29.5.0",
     "solid-test-utils": "^0.0.0",
     "ts-jest": "^29.1.0"
+  },
+  "dependencies": {
+    "@janeirodigital/interop-utils": "^1.0.0-rc.20",
+    "n3": "^1.16.4"
   }
 }

packages/discovery/src/client.ts

@@ -0,0 +1,81 @@
+import { DataFactory } from 'n3'
+import { parseTurtle, getDescriptionResource, getOneMatchingQuad, getAllMatchingQuads, NOTIFY } from '@janeirodigital/interop-utils'
+import type { DatasetCore } from '@rdfjs/types'
+import { ChannelType, SubscriptionService } from '@solid-notifications/types'
+
+// TODO remove once fetching from CSS
+const snippet = `
+  @prefix notify: <http://www.w3.org/ns/solid/notifications#>.
+
+  <http://localhost:3000/.well-known/solid>
+      a                   <http://www.w3.org/ns/pim/space#Storage> ;
+      notify:subscription <http://localhost:3000/.notifications/WebSocketChannel2023/> ,
+                          <http://localhost:3000/.notifications/WebhookChannel2023/> .
+  <http://localhost:3000/.notifications/WebSocketChannel2023/>
+      notify:channelType  notify:WebSocketChannel2023 ;
+      notify:feature      notify:accept ,
+                          notify:endAt ,
+                          notify:rate ,
+                          notify:startAt ,
+                          notify:state .
+  <http://localhost:3000/.notifications/WebhookChannel2023/>
+      notify:channelType  notify:WebhookChannel2023;
+      notify:feature      notify:accept ,
+                          notify:endAt ,
+                          notify:rate ,
+                          notify:startAt ,
+                          notify:state . 
+`
+
+export class DiscoveryClient {
+
+  private parser: {
+    contentType: 'text/turtle' | 'application/ld+json',
+    parse: typeof parseTurtle
+  }
+  constructor(private authnFetch: typeof fetch) {
+    // TODO pass Turtle or JSON-LD parser and set accordignly
+    this.parser = {
+      contentType: 'text/turtle',
+      parse: parseTurtle
+    }
+  }
+
+  async findService(resourceUri: string, channelType: ChannelType): Promise<SubscriptionService | null> {
+
+    // const storageDescription = this.fetchStorageDescription(resourceUri)
+
+    const storageDescription = await parseTurtle(snippet)
+
+    // TODO handle multiple matching services
+    const serviceNode = getOneMatchingQuad(storageDescription, null, NOTIFY.channelType, DataFactory.namedNode(channelType))?.subject
+    if (!serviceNode) return null
+    const features = getAllMatchingQuads(storageDescription, serviceNode, NOTIFY.feature).map(quad => quad.object.value)
+    return {
+      id: serviceNode.value,
+      channelType,
+      feature: features
+    }
+  }
+
+  // TODO use some rdf-fetch util
+  async fetchStorageDescription(resourceUri): Promise<DatasetCore> {
+    const storageDescriptionUri = await this.discoverStorageDescription(resourceUri)
+    const response = await this.authnFetch(storageDescriptionUri, {
+      headers: {
+        'Accept': this.parser.contentType
+      }
+    })
+    return this.parser.parse(await response.text(), response.url)
+  }
+
+  async discoverStorageDescription(resourceUri: string): Promise<string> {
+    const response = await this.authnFetch(resourceUri, { method: 'head' })
+    return getDescriptionResource(response.headers.get('Link')) // TODO add getStorageDescription to utils
+  }
+
+  async discoverResourceDescription(resourceUri: string): Promise<string> {
+    const response = await this.authnFetch(resourceUri, { method: 'head' })
+    return getDescriptionResource(response.headers.get('Link'))
+  }
+}

packages/discovery/src/index.ts

@@ -1 +1 @@
-export * from "./getDescribedByUri";
+export * from "./client";

packages/types/src/NotificationChannel.ts

@@ -1,6 +1,11 @@
+export enum ChannelType {
+  WebhookChannel2023 = 'http://www.w3.org/ns/solid/notifications#WebhookChannel2023',
+  WebSocketChannel2023 = 'http://www.w3.org/ns/solid/notifications#WebSocketChannel2023',
+}
+
 export interface NotificationChannel {
   id: string;
-  type: string;
+  type: ChannelType; // TODO channel types should be extendible
   topic: string | string[];
   receiveFrom: string;
   sendTo?: string;