add PoW option

index.js

@@ -36,7 +36,7 @@ try {
   }
 
   const pk = getPublicKey(sk);
-  const profileEvent = finalizeEvent(
+  const profileEvent = finalizeEventWithPoW(
     {
       kind: 0,
       content: BOT,
@@ -60,7 +60,7 @@ try {
     const dayOfWeek = today.getUTCDay();
     const message = `${dayOfWeek % 6 === 0 ? "gfy" : "GM"} fiatjaf`;
 
-    const event = finalizeEvent(
+    const event = finalizeEventWithPoW(
       {
         kind: 1,
         content: message,
@@ -90,3 +90,42 @@ try {
   clearInterval(intervalId);
   process.exit(1);
 }
+
+function finalizeEventWithPoW(event, sk, difficulty = 0) {
+  if (difficulty === 0) return finalizeEvent(event, sk);
+
+  const pk = getPublicKey(sk);
+  let nonce = 0;
+  let leadingZeroes = 0;
+  let event = { ...event, pubkey: pk };
+  while (true) {
+    event.tags = [["nonce", nonce.toString(), difficulty.toString()]];
+    event.created_at = Math.floor(Date.now() / 1000);
+
+    const hash = getEventHash(event);
+    leadingZeroes = countLeadingZeroes(hash);
+
+    if (leadingZeroes >= difficulty) {
+      return finalizeEvent(event, sk);
+    }
+
+    nonce++;
+  }
+}
+
+// hex should be a hexadecimal string (with no 0x prefix)
+function countLeadingZeroes(hex) {
+  let count = 0;
+
+  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 count;
+}