Reorder parameters

To match `waku.relay.addObserver`.

src/lib/waku_filter/index.node.spec.ts

@@ -42,10 +42,7 @@ describe("Waku Filter", () => {
       expect(msg.contentTopic).to.eq(TestContentTopic);
       expect(msg.payloadAsUtf8).to.eq(messageText);
     };
-    await waku.filter.subscribe(
-      { contentTopics: [TestContentTopic] },
-      callback
-    );
+    await waku.filter.subscribe(callback, [TestContentTopic]);
     const message = await WakuMessage.fromUtf8String(
       messageText,
       TestContentTopic
@@ -65,10 +62,7 @@ describe("Waku Filter", () => {
       messageCount++;
       expect(msg.contentTopic).to.eq(TestContentTopic);
     };
-    await waku.filter.subscribe(
-      { contentTopics: [TestContentTopic] },
-      callback
-    );
+    await waku.filter.subscribe(callback, [TestContentTopic]);
     await waku.relay.send(
       await WakuMessage.fromUtf8String("Filtering works!", TestContentTopic)
     );
@@ -89,10 +83,9 @@ describe("Waku Filter", () => {
     const callback = (): void => {
       messageCount++;
     };
-    const unsubscribe = await waku.filter.subscribe(
-      { contentTopics: [TestContentTopic] },
-      callback
-    );
+    const unsubscribe = await waku.filter.subscribe(callback, [
+      TestContentTopic,
+    ]);
     await waku.relay.send(
       await WakuMessage.fromUtf8String(
         "This should be received",

src/lib/waku_filter/index.ts

@@ -25,10 +25,6 @@ type FilterSubscriptionOpts = {
    * Optionally specify a PeerId for the subscription. If not included, will use a random peer.
    */
   peerId?: PeerId;
-  /**
-   * Array of ContentTopics to subscribe to. If empty, no messages will be returned from the filter.
-   */
-  contentTopics: string[];
 };
 
 type FilterCallback = (msg: WakuMessage) => void | Promise<void>;
@@ -56,17 +52,18 @@ export class WakuFilter {
   }
 
   /**
-   *
-   * @param opts The FilterSubscriptionOpts used to narrow which messages are returned, and which peer to connect to
-   * @param callback A function that will be called on each message returned by the filter
-   * @returns Unsubscribe function that can be used to end the subscription
+   * @param contentTopics Array of ContentTopics to subscribe to. If empty, no messages will be returned from the filter.
+   * @param callback A function that will be called on each message returned by the filter.
+   * @param opts The FilterSubscriptionOpts used to narrow which messages are returned, and which peer to connect to.
+   * @returns Unsubscribe function that can be used to end the subscription.
    */
   async subscribe(
-    opts: FilterSubscriptionOpts,
-    callback: FilterCallback
+    callback: FilterCallback,
+    contentTopics: string[],
+    opts?: FilterSubscriptionOpts
   ): Promise<UnsubscribeFunction> {
-    const topic = opts.pubsubTopic || DefaultPubSubTopic;
-    const contentFilters = opts.contentTopics.map((contentTopic) => ({
+    const topic = opts?.pubsubTopic || DefaultPubSubTopic;
+    const contentFilters = contentTopics.map((contentTopic) => ({
       contentTopic,
     }));
     const request = FilterRPC.createRequest(
@@ -76,7 +73,7 @@ export class WakuFilter {
       true
     );
 
-    const peer = await this.getPeer(opts.peerId);
+    const peer = await this.getPeer(opts?.peerId);
     const stream = await this.newStream(peer);
 
     try {
@@ -86,7 +83,7 @@ export class WakuFilter {
         "Error subscribing to peer ",
         peer.id.toB58String(),
         "for content topics",
-        opts.contentTopics,
+        contentTopics,
         ": ",
         e
       );