nip13: use a simpler implementation

nip13.ts

@@ -1,42 +1,16 @@
-import { hexToBytes } from '@noble/hashes/utils'
-
 /** Get POW difficulty from a Nostr hex ID. */
-export function getPow(id: string): number {
-  return getLeadingZeroBits(hexToBytes(id))
-}
+export function getPow(hex: string): number {
+  let count = 0
 
-/**
- * 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) {
+  for (let i = 0; i < hex.length; i++) {
+    const nibble = parseInt(hex[i], 16)
+    if (nibble === 0) {
+      count += 4
+    } else {
+      count += Math.clz32(nibble) - 28
       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
+
+  return count
 }