feat: add getbalance to nwc provider

examples/nostr-wallet-connect.js

@@ -15,8 +15,10 @@ rl.close();
 
 const webln = new providers.NostrWebLNProvider({ nostrWalletConnectUrl: nwcUrl });
 await webln.enable();
-const response = await webln.sendPayment(invoice);
+const sendPaymentResponse = await webln.sendPayment(invoice);
+console.log(sendPaymentResponse);
 
-console.log(response);
+const getBalanceResponse = await webln.getBalance();
+console.log(getBalanceResponse);
 
 webln.close();

src/webln/NostrWeblnProvider.ts

@@ -23,6 +23,13 @@ const NWCs: Record<string,NostrWebLNOptions> = {
   }
 };
 
+// TODO: fetch this from @webbtc/webln-types
+interface GetBalanceResponse {
+  balance: number;
+  max_amount?: number;
+  budget_renewal?: string;
+}
+
 interface NostrWebLNOptions {
   authorizationUrl?: string; // the URL to the NWC interface for the user to confirm the session
   relayUrl: string;
@@ -175,6 +182,84 @@ export class NostrWebLNProvider implements WebLNProvider, Nip07Provider {
     }
   }
 
+  // TODO: refactor code in getBalance and sendPayment
+  getBalance() {
+    this.checkConnected();
+
+    return new Promise<GetBalanceResponse>(async (resolve, reject) => {
+      const command = {
+        "method": "get_balance"
+      };
+      const encryptedCommand = await this.encrypt(this.walletPubkey, JSON.stringify(command));
+      const unsignedEvent: UnsignedEvent = {
+        kind: 23194 as Kind,
+        created_at: Math.floor(Date.now() / 1000),
+        tags: [['p', this.walletPubkey]],
+        content: encryptedCommand,
+        pubkey: this.publicKey
+      };
+
+      const event = await this.signEvent(unsignedEvent);
+      // subscribe to NIP_47_SUCCESS_RESPONSE_KIND and NIP_47_ERROR_RESPONSE_KIND
+      // that reference the request event (NIP_47_REQUEST_KIND)
+      let sub = this.relay.sub([
+        {
+          kinds: [23195],
+          authors: [this.walletPubkey],
+          "#e": [event.id],
+        }
+      ]);
+
+      function replyTimeout() {
+        sub.unsub();
+        //console.error(`Reply timeout: event ${event.id} `);
+        reject({error: `reply timeout: event ${event.id}`, code: "INTERNAL"});
+      }
+
+      let replyTimeoutCheck = setTimeout(replyTimeout, 60000);
+
+      sub.on('event', async (event) => {
+        //console.log(`Received reply event: `, event);
+        clearTimeout(replyTimeoutCheck);
+        sub.unsub();
+        const decryptedContent = await this.decrypt(this.walletPubkey, event.content);
+        let response;
+        try {
+          response = JSON.parse(decryptedContent);
+        } catch(e) {
+          reject({ error: "invalid response", code: "INTERNAL" });
+          return;
+        }
+        // @ts-ignore // event is still unknown in nostr-tools
+        if (event.kind == 23195 && response.result?.balance) {
+          resolve(response.result);
+          this.notify('getBalance', response.result);
+        } else {
+          reject({ error: response.error?.message, code: response.error?.code });
+        }
+      });
+
+      let pub = this.relay.publish(event);
+
+      function publishTimeout() {
+        //console.error(`Publish timeout: event ${event.id}`);
+        reject({ error: `Publish timeout: event ${event.id}` });
+      }
+      let publishTimeoutCheck = setTimeout(publishTimeout, 5000);
+
+      pub.on('failed', (reason: unknown) => {
+        //console.debug(`failed to publish to ${this.relay.url}: ${reason}`)
+        clearTimeout(publishTimeoutCheck)
+        reject({ error: `Failed to publish request: ${reason}` });
+      });
+
+      pub.on('ok', () => {
+        //console.debug(`Event ${event.id} for ${invoice} published`);
+        clearTimeout(publishTimeoutCheck);
+      });
+    });
+  }
+
   sendPayment(invoice: string) {
     this.checkConnected();