fix(js): use pure JS SHA256 library, refactor (#471)

* fix(js): use pure JS SHA256 library, refactor

Closes #458

Additionally, I made a horrifying discovery: Firefox seems to actively
hinder performance if you are using more than one Worker per page. It
does not spread the load out across cores like I expected. Instead it
seems to make that one Worker thrash and have to constantly context
switch, which caused a lot of slowdown.

The benchmarks in #155 continue to be the best contribution ever made to
Anubis. What clued me into there being a problem here was the fact that
the "slow" algorithm was faster than the "fast" algorithm on my laptop.
This made no intuitive sense to me so I dug further.

Either way I think this is a Firefox bug at its core, but for now we
have to work around it by doing the hacky terrible thing that I hate.

I also swapped the SHA256 operations to @aws-crypto/sha256-js on the
advice of a trusted cryptography expert. I don't know what performance
differences this makes, but I'm getting 150-225 kilohashes per second,
which is pretty dang good.

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

* fix(js): apply suggestions from code review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Signed-off-by: Xe Iaso <me@xeiaso.net>

* fix(js): use fast algo for fast worker

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

---------

Signed-off-by: Xe Iaso <me@xeiaso.net>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

web/js/algorithms/fast.mjs

@@ -0,0 +1,67 @@
+const determineThreadCount = () => {
+  if (navigator.userAgent.includes("Firefox")) {
+    return Math.min(navigator.hardwareConcurrency, 4);
+  }
+
+  if (!!navigator.hardwareConcurrency) {
+    return navigator.hardwareConcurrency;
+  }
+
+  return 1;
+};
+
+export default function process(
+  { basePrefix, version },
+  data,
+  difficulty = 5,
+  signal = null,
+  progressCallback = null,
+  threads = determineThreadCount(),
+) {
+  return new Promise((resolve, reject) => {
+    let webWorkerURL = `${basePrefix}/.within.website/x/cmd/anubis/static/js/worker/fast.mjs?cacheBuster=${version}`;
+
+    const workers = [];
+    const terminate = () => {
+      workers.forEach((w) => w.terminate());
+      if (signal != null) {
+        // clean up listener to avoid memory leak
+        signal.removeEventListener("abort", terminate);
+        if (signal.aborted) {
+          console.log("PoW aborted");
+          reject(false);
+        }
+      }
+    };
+    if (signal != null) {
+      signal.addEventListener("abort", terminate, { once: true });
+    }
+
+    for (let i = 0; i < threads; i++) {
+      let worker = new Worker(webWorkerURL);
+
+      worker.onmessage = (event) => {
+        if (typeof event.data === "number") {
+          progressCallback?.(event.data);
+        } else {
+          terminate();
+          resolve(event.data);
+        }
+      };
+
+      worker.onerror = (event) => {
+        terminate();
+        reject(event);
+      };
+
+      worker.postMessage({
+        data,
+        difficulty,
+        nonce: i,
+        threads,
+      });
+
+      workers.push(worker);
+    }
+  });
+}

web/js/algorithms/slow.mjs

@@ -0,0 +1,48 @@
+// https://dev.to/ratmd/simple-proof-of-work-in-javascript-3kgm
+
+export default function process(
+  { basePrefix, version },
+  data,
+  difficulty = 5,
+  signal = null,
+  progressCallback = null,
+  _threads = 1,
+) {
+  return new Promise((resolve, reject) => {
+    let worker = new Worker(`${basePrefix}/.within.website/x/cmd/anubis/static/js/worker/slow.mjs?cacheBuster=${version}`);
+    const terminate = () => {
+      worker.terminate();
+      if (signal != null) {
+        // clean up listener to avoid memory leak
+        signal.removeEventListener("abort", terminate);
+        if (signal.aborted) {
+          console.log("PoW aborted");
+          reject(false);
+        }
+      }
+    };
+    if (signal != null) {
+      signal.addEventListener("abort", terminate, { once: true });
+    }
+
+    worker.onmessage = (event) => {
+      if (typeof event.data === "number") {
+        progressCallback?.(event.data);
+      } else {
+        terminate();
+        resolve(event.data);
+      }
+    };
+
+    worker.onerror = (event) => {
+      terminate();
+      reject(event);
+    };
+
+    worker.postMessage({
+      data,
+      difficulty
+    });
+  });
+}
+