add helper functions for nip-47

nip47.ts

@@ -0,0 +1,46 @@
+import {finishEvent} from './event.ts'
+import {encrypt} from './nip04.ts'
+import {Kind} from './event'
+
+export function parseConnectionString(connectionString: string) {
+  const {pathname, searchParams} = new URL(connectionString)
+  const pubkey = pathname
+  const relay = searchParams.get('relay')
+  const secret = searchParams.get('secret')
+
+  if (!pubkey || !relay || !secret) {
+    throw new Error('invalid connection string')
+  }
+
+  return {pubkey, relay, secret}
+}
+
+export async function makeNwcRequestEvent({
+  pubkey,
+  secret,
+  invoice
+}: {
+  pubkey: string
+  secret: string
+  invoice: string
+}) {
+  const content = {
+    method: 'pay_invoice',
+    params: {
+      invoice
+    }
+  }
+  const encryptedContent = await encrypt(
+    secret,
+    pubkey,
+    JSON.stringify(content)
+  )
+  const eventTemplate = {
+    kind: Kind.NwcRequest,
+    created_at: Math.round(Date.now() / 1000),
+    content: encryptedContent,
+    tags: [['p', pubkey]]
+  }
+
+  return finishEvent(eventTemplate, secret)
+}