add slow pure javascript work function - v1.0.10

work.ts

@@ -1,11 +1,18 @@
+import blake2b from "blake2b";
+import { uint8array_to_hex, int_to_uint8array, hex_to_uint8array } from "./util";
 import type { BlockHash } from "./rpc_types";
 import type { RPC } from "./rpc";
 
+const BANANO_WORK_THRESHOLD = "0xFFFFFE0000000000";
+
+export type WorkFunction = (block_hash: BlockHash) => Promise<string>;
+
 export interface WorkProvider {
-  request_work(block_hash: BlockHash): Promise<string>;
+  request_work: WorkFunction;
 }
 
-export class RPCWorkProvider {
+/** Request work from an RPC provider that supports the `work_generate` RPC call */
+export class RPCWorkProvider implements WorkProvider {
   readonly rpc: RPC;
 
   /** Extra json to send with the rpc payload. Needed for rpc.nano.to's work_generate, unfortunately */
@@ -26,4 +33,17 @@ export class RPCWorkProvider {
   }
 }
 
-//
+/** Use Javascript to slowly generate work for blocks */
+export class SlowJavascriptWorkProvider implements WorkProvider {
+  async request_work(block_hash: BlockHash): Promise<string> {
+    let nonce = 0;
+    while (true) {
+      const nonce_bytes = int_to_uint8array(nonce, 8).reverse();
+      const work = uint8array_to_hex(blake2b(8, undefined, undefined, undefined, true).update(nonce_bytes).update(hex_to_uint8array(block_hash)).digest().reverse()); //noAssert = true so we can have byte of 8 (min for this library is 16 for some reason)
+      if (BigInt(`0x${work}`) > BigInt(BANANO_WORK_THRESHOLD)) {
+        return uint8array_to_hex(nonce_bytes.reverse());
+      }
+      nonce += 1;
+    }
+  }
+}