feat(solver-wasm): add basic wasm solver impl

pkgs/solver-wasm/src/lib.rs

@@ -0,0 +1,30 @@
+use sha2::{Digest, Sha256};
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+pub fn solve(nonce: &[u8], target: &[u8]) -> Box<[u8]> {
+    let mut buf = vec![0u8; 8 + nonce.len()];
+    buf[8..].copy_from_slice(nonce);
+
+    for i in 0u64.. {
+        let i_bytes = u64::to_le_bytes(i);
+        buf[0..=7].copy_from_slice(&i_bytes);
+        let hash = Sha256::digest(&buf);
+        if &hash[0..target.len()] == target {
+            return i_bytes.into();
+        }
+    }
+
+    unreachable!();
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn solve() {
+        assert_eq!(
+            super::solve(&[1, 2], &[3, 4]).as_ref(),
+            [45, 176, 0, 0, 0, 0, 0, 0]
+        );
+    }
+}