feat: incremental proof of work computing fn

src/index.ts

@@ -4,7 +4,7 @@
  * Copyright © 2021 Aravinth Manivnanan <realaravinth@batsense.net>.
  *
  * Use of this source code is governed by Apache 2.0 or MIT license.
- * You shoud have received a copy of MIT and Apache 2.0 along with
+ * You should have received a copy of MIT and Apache 2.0 along with
  * this program. If not, see <https://spdx.org/licenses/MIT.html> for
  * MIT or <http://www.apache.org/licenses/LICENSE-2.0> for Apache.
  */
@@ -51,7 +51,7 @@ export const digest = async (message: string): Promise<number[]> => {
  * Calculate difficulty of  a hash
  *
  * @param {number[]} hash - hash for which difficulty should be calculated
- * @returns {BigInt} - diffuclty of the given hash
+ * @returns {BigInt} - difficulty of the given hash
  */
 export const score = (hash: number[]): BigInt => {
   let sum = BigInt(0);
@@ -75,7 +75,7 @@ export type WasmWork = {
 };
 
 /**
- * Generate Proof-of-Work(PoW) according to the algorithim used in mCaptcha
+ * Generate Proof-of-Work(PoW) according to the algorithm used in mCaptcha
  *
  * @param {string} salt - salt used in PoW computation. Will be provided in PoW requirement
  * @param {string} phrase - challenge phrase used in PoW computation. Will be provided in PoW requirement
@@ -105,3 +105,46 @@ export const generate_work = async (
   };
   return work;
 };
+
+/**
+ * Generate Proof-of-Work(PoW) according to the algorithm used in mCaptcha incrementally
+ *
+ * @param {string} salt - salt used in PoW computation. Will be provided in PoW requirement
+ * @param {string} phrase - challenge phrase used in PoW computation. Will be provided in PoW requirement
+ * @param {number} difficulty - target difficulty for which PoW should be generated. Will be provided in PoW requirement
+ * @param {number} step - notify progress with nonce after 'n' number of steps
+ * @param {(nonce: number) => void} fn - callback function to notify progress 
+ *
+ * @returns {Promise<WasmWork>} - proof-of-work
+ **/
+export const stepped_generate_work = async (
+  salt: string,
+  phrase: string,
+  difficulty: number,
+  step: number,
+  fn: (nonce: number) => void,
+): Promise<WasmWork> => {
+  const serialized_phrase = decoder.decode(serialize(phrase));
+  const base = salt + serialized_phrase;
+  let nonce = 0;
+  let result: BigInt = BigInt(0);
+  const difficulty_new: BigInt = U128_MAX - U128_MAX / BigInt(difficulty);
+  let count = 0;
+  while (result < difficulty_new) {
+    if (count < step) {
+      nonce += 1;
+      const hash = await digest(base + nonce.toString());
+      result = score(hash);
+      count+=1;
+    } else {
+      fn(nonce);
+      count = 0;
+    }
+  }
+
+  const work: WasmWork = {
+    result: result.toString(),
+    nonce,
+  };
+  return work;
+};

src/test.ts

@@ -1,4 +1,4 @@
-import { digest, score, generate_work } from "./index";
+import { digest, score, generate_work, stepped_generate_work } from "./index";
 import { DATA, DIFFICULTY, SALT } from "./test-data";
 
 ("use strict");
@@ -30,3 +30,33 @@ test("Digest works", async () => {
     }
   }
 });
+
+test("Incremental proof generation works", async () => {
+  for (let i = 0; i < DATA.length; i++) {
+    const d = DATA[i];
+    let last_nonce = 0;
+    const step = 1000;
+    let fnExecuted = false;
+    const fn = (n: number): void => {
+      expect(last_nonce + step).toBe(n);
+      last_nonce = n;
+      fnExecuted = true;
+    };
+
+    try {
+      const proof = await stepped_generate_work(
+        SALT,
+        d.phrase,
+        DIFFICULTY,
+        1000,
+        fn
+      );
+      expect(proof.nonce).toBe(d.pow.nonce);
+      expect(proof.result).toBe(`${d.pow.result}`);
+    } catch (error) {
+      console.log(`${d.pow.nonce}${error}`);
+      throw error;
+    }
+    expect(fnExecuted).toBeTruthy();
+  }
+});