Add NIP-13 (proof-of-work) module

index.ts

@@ -9,6 +9,7 @@ export * as nip04 from './nip04'
 export * as nip05 from './nip05'
 export * as nip06 from './nip06'
 export * as nip10 from './nip10'
+export * as nip13 from './nip13'
 export * as nip19 from './nip19'
 export * as nip26 from './nip26'
 export * as nip39 from './nip39'

nip13.test.js

@@ -0,0 +1,8 @@
+/* eslint-env jest */
+const {nip13} = require('./lib/nostr.cjs')
+
+test('identifies proof-of-work difficulty', async () => {
+  const id = '000006d8c378af1779d2feebc7603a125d99eca0ccf1085959b307f64e5dd358'
+  const difficulty = nip13.getPow(id)
+  expect(difficulty).toEqual(21)
+})

nip13.ts

@@ -0,0 +1,42 @@
+import * as secp256k1 from '@noble/secp256k1'
+
+/** Get POW difficulty from a Nostr hex ID. */
+export function getPow(id: string): number {
+  return getLeadingZeroBits(secp256k1.utils.hexToBytes(id))
+}
+
+/**
+ * Get number of leading 0 bits. Adapted from nostream.
+ * https://github.com/Cameri/nostream/blob/fb6948fd83ca87ce552f39f9b5eb780ea07e272e/src/utils/proof-of-work.ts
+ */
+function getLeadingZeroBits(hash: Uint8Array): number {
+  let total: number, i: number, bits: number
+
+  for (i = 0, total = 0; i < hash.length; i++) {
+    bits = msb(hash[i])
+    total += bits
+    if (bits !== 8) {
+      break
+    }
+  }
+  return total
+}
+
+/**
+ * Adapted from nostream.
+ * https://github.com/Cameri/nostream/blob/fb6948fd83ca87ce552f39f9b5eb780ea07e272e/src/utils/proof-of-work.ts
+ */
+function msb(b: number) {
+  let n = 0
+
+  if (b === 0) {
+    return 8
+  }
+
+  // eslint-disable-next-line no-cond-assign
+  while (b >>= 1) {
+    n++
+  }
+
+  return 7 - n
+}