From 4463c4afabc09b2cd09f1ea64b0fa59957457954 Mon Sep 17 00:00:00 2001
From: "fryorcraken.eth" <git@fryorcraken.xyz>
Date: Wed, 28 Sep 2022 13:05:10 +1000
Subject: [PATCH] refactor: extract helper functions

---
 src/byte_utils.ts | 39 +++++++++++++++++++++++++++++++++
 src/epoch.ts      | 11 ++++++++++
 src/rln.ts        | 56 ++++-------------------------------------------
 3 files changed, 54 insertions(+), 52 deletions(-)
 create mode 100644 src/byte_utils.ts
 create mode 100644 src/epoch.ts

diff --git a/src/byte_utils.ts b/src/byte_utils.ts
new file mode 100644
index 0000000..99c9671
--- /dev/null
+++ b/src/byte_utils.ts
@@ -0,0 +1,39 @@
+// Adapted from https://github.com/feross/buffer
+
+function checkInt(
+  buf: Uint8Array,
+  value: number,
+  offset: number,
+  ext: number,
+  max: number,
+  min: number
+): void {
+  if (value > max || value < min)
+    throw new RangeError('"value" argument is out of bounds');
+  if (offset + ext > buf.length) throw new RangeError("Index out of range");
+}
+
+export function writeUIntLE(
+  buf: Uint8Array,
+  value: number,
+  offset: number,
+  byteLength: number,
+  noAssert?: boolean
+): Uint8Array {
+  value = +value;
+  offset = offset >>> 0;
+  byteLength = byteLength >>> 0;
+  if (!noAssert) {
+    const maxBytes = Math.pow(2, 8 * byteLength) - 1;
+    checkInt(buf, value, offset, byteLength, maxBytes, 0);
+  }
+
+  let mul = 1;
+  let i = 0;
+  buf[offset] = value & 0xff;
+  while (++i < byteLength && (mul *= 0x100)) {
+    buf[offset + i] = (value / mul) & 0xff;
+  }
+
+  return buf;
+}
diff --git a/src/epoch.ts b/src/epoch.ts
new file mode 100644
index 0000000..3a14bd2
--- /dev/null
+++ b/src/epoch.ts
@@ -0,0 +1,11 @@
+import { writeUIntLE } from "./byte_utils.js";
+
+const DefaultEpochUnitSeconds = 10; // the rln-relay epoch length in seconds
+
+export function dateToEpoch(
+  timestamp: Date,
+  epochUnitSeconds: number = DefaultEpochUnitSeconds
+): Uint8Array {
+  const unix = Math.floor(timestamp.getTime() / 1000 / epochUnitSeconds);
+  return writeUIntLE(new Uint8Array(32), unix, 0, 8);
+}
diff --git a/src/rln.ts b/src/rln.ts
index 1140daf..d82931d 100644
--- a/src/rln.ts
+++ b/src/rln.ts
@@ -1,6 +1,8 @@
 import init, * as zerokitRLN from "@waku/zerokit-rln-wasm";
 import { RateLimitProof } from "js-waku/lib/interfaces";
 
+import { writeUIntLE } from "./byte_utils.js";
+import { dateToEpoch } from "./epoch.js";
 import verificationKey from "./resources/verification_key.js";
 import * as wc from "./witness_calculator.js";
 import { WitnessCalculator } from "./witness_calculator.js";
@@ -67,56 +69,6 @@ export class MembershipKey {
   }
 }
 
-// Adapted from https://github.com/feross/buffer
-
-function checkInt(
-  buf: Uint8Array,
-  value: number,
-  offset: number,
-  ext: number,
-  max: number,
-  min: number
-): void {
-  if (value > max || value < min)
-    throw new RangeError('"value" argument is out of bounds');
-  if (offset + ext > buf.length) throw new RangeError("Index out of range");
-}
-
-const writeUIntLE = function writeUIntLE(
-  buf: Uint8Array,
-  value: number,
-  offset: number,
-  byteLength: number,
-  noAssert?: boolean
-): Uint8Array {
-  value = +value;
-  offset = offset >>> 0;
-  byteLength = byteLength >>> 0;
-  if (!noAssert) {
-    const maxBytes = Math.pow(2, 8 * byteLength) - 1;
-    checkInt(buf, value, offset, byteLength, maxBytes, 0);
-  }
-
-  let mul = 1;
-  let i = 0;
-  buf[offset] = value & 0xff;
-  while (++i < byteLength && (mul *= 0x100)) {
-    buf[offset + i] = (value / mul) & 0xff;
-  }
-
-  return buf;
-};
-
-const DefaultEpochUnitSeconds = 10; // the rln-relay epoch length in seconds
-
-export function toEpoch(
-  timestamp: Date,
-  epochUnitSeconds: number = DefaultEpochUnitSeconds
-): Uint8Array {
-  const unix = Math.floor(timestamp.getTime() / 1000 / epochUnitSeconds);
-  return writeUIntLE(new Uint8Array(32), unix, 0, 8);
-}
-
 const proofOffset = 128;
 const rootOffset = proofOffset + 32;
 const epochOffset = rootOffset + 32;
@@ -200,9 +152,9 @@ export class RLNInstance {
     idKey: Uint8Array
   ): Promise<RateLimitProof> {
     if (epoch == undefined) {
-      epoch = toEpoch(new Date());
+      epoch = dateToEpoch(new Date());
     } else if (epoch instanceof Date) {
-      epoch = toEpoch(epoch);
+      epoch = dateToEpoch(epoch);
     }
 
     if (epoch.length != 32) throw "invalid epoch";