DWN

DWN Client

1. Install

npm i @extrimian/dwn-client

2. Init DWN Client

When we wants to intance a DWN it has to be config passing a DID, to pull messages from that DID, inboxURL that is the endpoint of our DWN service, and a storage to save messages.

const dwnClient = new DWNClient({
  did : "did:example";
  inboxURL : "dwnURL";
  storage : MessageStorage;
});

For this test case you can create a storage that saves the data in memory.

export const storageMock: MessageStorage = {
  async getMessages(): Promise<Entry[]> {
    return messagesStorage;
  },
  async getLastPullDate(): Promise<Date> {
    return lastPullDate;
  },
  async saveMessages(messages: Entry[]): Promise<void> {
    messagesStorage.push(...messages);
  },
  async updateLastPullDate(date: Date): Promise<void> {
    lastPullDate = date;
  },
};

3. Send a message to the DWN

const sendMsg = await dwnClient.sendMessage({
  targetDID: "did:example", //Recipient's DID
  targetInboxURL: "dwnURL", // Recipient's DWN service, obtained by resolving the DID Document
  message: {
    data: packedMessage, //message packed with Didcomm
    descriptor: {
      method: ThreadMethod.Create,
      dateCreated: new Date(),
      dataFormat: "application/json",
    },
  },
});

DWN Types

The message structure is already defined in the protocol so would be as the following.

export type Entry = {
  descriptor: MessageDescriptor;
  data?: any;
};

export type MessageDescriptor = {
  method: ThreadMethod;
  // UUIDv4
  objectId?: string;
  // Content-Type header (e.g. application/json)
  dataFormat?: string;
  // content id
  cid?: {
    codec: string;
    version: number;
    hash: any;
  };
  // Creation date in UNIX timestamp format
  dateCreated?: number;
  // Data Schema URL
  schema?: string;
  // Initial thread message id
  root?: string;
  // Parent (replying to) message id
  parent?: string;
};

DWN Scheduler to pull messages

1. Install

npm i @extrimian/dwn-client-scheduler

2. Init DwnClientScheduler

const dwnClientScheduler = new DWNClientScheduler(dwnClient, cronExpression);

dwnClientScheduler.start();

dwnClient.addSubscriber(async (messages) => {
  console.log(`Found ${messages.length} messages`);
  console.log(messages);
});

const cronExpression = "*/10 * * * * *";