feat: add RlnMessage for handy helpers

src/codec.spec.ts

@@ -1,9 +1,5 @@
 import { expect } from "chai";
-import {
-  DecoderV0,
-  EncoderV0,
-  MessageV0,
-} from "js-waku/lib/waku_message/version_0";
+import { DecoderV0, EncoderV0 } from "js-waku/lib/waku_message/version_0";
 
 import { RLNDecoder, RLNEncoder } from "./codec.js";
 
@@ -26,7 +22,10 @@ describe("js-rln: encoder", () => {
       index,
       memKeys
     );
-    const rlnDecoder = new RLNDecoder(new DecoderV0(TestContentTopic));
+    const rlnDecoder = new RLNDecoder(
+      rlnInstance,
+      new DecoderV0(TestContentTopic)
+    );
 
     const bytes = await rlnEncoder.encode({ payload });
     const protoResult = await rlnDecoder.decodeProto(bytes!);
@@ -34,13 +33,11 @@ describe("js-rln: encoder", () => {
     const msg = (await rlnDecoder.decode(protoResult!))!;
 
     // Validate proof
-    const verifResult = rlnInstance.verifyProof(msg.rateLimitProof!);
-    expect(verifResult).to.be.true;
+    expect(msg.verify()).to.be.true;
 
-    const msgV0 = msg as MessageV0;
-    expect(msgV0.contentTopic).to.eq(TestContentTopic);
-    expect(msgV0.version).to.eq(0);
-    expect(msgV0.payload).to.deep.eq(payload);
-    expect(msgV0.timestamp).to.not.be.undefined;
+    expect(msg.contentTopic).to.eq(TestContentTopic);
+    expect(msg.msg.version).to.eq(0);
+    expect(msg.payload).to.deep.eq(payload);
+    expect(msg.timestamp).to.not.be.undefined;
   });
 });

src/codec.ts

@@ -7,6 +7,7 @@ import {
   ProtoMessage,
 } from "js-waku/lib/interfaces";
 
+import { RlnMessage } from "./message.js";
 import { MembershipKey, RLNInstance } from "./rln.js";
 
 const log = debug("waku:message:rln-encoder");
@@ -53,11 +54,11 @@ export class RLNEncoder implements Encoder {
   }
 }
 
-export class RLNDecoder implements Decoder<Message> {
-  public contentTopic: string;
+export class RLNDecoder<T extends Message> implements Decoder<RlnMessage<T>> {
+  constructor(private rlnInstance: RLNInstance, private decoder: Decoder<T>) {}
 
-  constructor(private decoder: Decoder<Message>) {
-    this.contentTopic = decoder.contentTopic;
+  get contentTopic(): string {
+    return this.decoder.contentTopic;
   }
 
   decodeProto(bytes: Uint8Array): Promise<ProtoMessage | undefined> {
@@ -66,12 +67,10 @@ export class RLNDecoder implements Decoder<Message> {
     return Promise.resolve(protoMessage);
   }
 
-  async decode(proto: ProtoMessage): Promise<Message | undefined> {
-    const msg = await this.decoder.decode(proto);
-    if (msg) {
-      msg.rateLimitProof = proto.rateLimitProof;
-    }
-    return msg;
+  async decode(proto: ProtoMessage): Promise<RlnMessage<T> | undefined> {
+    const msg: T | undefined = await this.decoder.decode(proto);
+    if (!msg) return;
+    return new RlnMessage(this.rlnInstance, msg, proto.rateLimitProof);
   }
 }
 

src/message.ts

@@ -0,0 +1,37 @@
+import { Message, RateLimitProof } from "js-waku/lib/interfaces";
+
+import { epochBytesToInt } from "./epoch.js";
+import { RLNInstance } from "./rln.js";
+
+export class RlnMessage<T extends Message> implements Message {
+  constructor(
+    public rlnInstance: RLNInstance,
+    public msg: T,
+    public rateLimitProof?: RateLimitProof
+  ) {}
+
+  public verify(): boolean | undefined {
+    return this.rateLimitProof
+      ? this.rlnInstance.verifyProof(this.rateLimitProof)
+      : undefined;
+  }
+
+  get payload(): Uint8Array | undefined {
+    return this.msg.payload;
+  }
+
+  get contentTopic(): string | undefined {
+    return this.msg.contentTopic;
+  }
+
+  get timestamp(): Date | undefined {
+    return this.msg.timestamp;
+  }
+
+  get epoch(): number | undefined {
+    const bytes = this.msg.rateLimitProof?.epoch;
+    if (!bytes) return;
+
+    return epochBytesToInt(bytes);
+  }
+}