initial import from /x/ monorepo

Signed-off-by: Xe Iaso <me@xeiaso.net>

cmd/anubis/js/proof-of-work.mjs

@@ -0,0 +1,62 @@
+// https://dev.to/ratmd/simple-proof-of-work-in-javascript-3kgm
+
+export function process(data, difficulty = 5) {
+  return new Promise((resolve, reject) => {
+    let webWorkerURL = URL.createObjectURL(new Blob([
+      '(', processTask(), ')()'
+    ], { type: 'application/javascript' }));
+
+    let worker = new Worker(webWorkerURL);
+
+    worker.onmessage = (event) => {
+      worker.terminate();
+      resolve(event.data);
+    };
+
+    worker.onerror = (event) => {
+      worker.terminate();
+      reject();
+    };
+
+    worker.postMessage({
+      data,
+      difficulty
+    });
+
+    URL.revokeObjectURL(webWorkerURL);
+  });
+}
+
+function processTask() {
+  return function () {
+    const sha256 = (text) => {
+      const encoded = new TextEncoder().encode(text);
+      return crypto.subtle.digest("SHA-256", encoded.buffer).then((result) =>
+        Array.from(new Uint8Array(result))
+          .map((c) => c.toString(16).padStart(2, "0"))
+          .join(""),
+      );
+    };
+
+    addEventListener('message', async (event) => {
+      let data = event.data.data;
+      let difficulty = event.data.difficulty;
+
+      let hash;
+      let nonce = 0;
+      do {
+        hash = await sha256(data + nonce++);
+      } while (hash.substring(0, difficulty) !== Array(difficulty + 1).join('0'));
+
+      nonce -= 1; // last nonce was post-incremented
+
+      postMessage({
+        hash,
+        data,
+        difficulty,
+        nonce,
+      });
+    });
+  }.toString();
+}
+