fix(flag-evaluation): use js-sha256 which can fall back to pure js (#390)

This solution should fall back to a pure JS based solution is "crypto"
isn't available and doesn't require us to change the public interface of
the package from sync to async.

Author: roncohen

packages/flag-evaluation/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@bucketco/flag-evaluation",
-  "version": "0.2.0",
+  "version": "0.1.1",
   "license": "MIT",
   "repository": {
     "type": "git",
@@ -33,5 +33,8 @@
     "ts-node": "^10.9.2",
     "typescript": "^5.7.3",
     "vitest": "^2.0.5"
+  },
+  "dependencies": {
+    "js-sha256": "0.11.0"
   }
 }

packages/flag-evaluation/src/index.ts

@@ -1,10 +1,4 @@
-try {
-  // crypto not available on globalThis in Node.js v18
-  // eslint-disable-next-line @typescript-eslint/no-require-imports
-  globalThis.crypto ??= require("node:crypto").webcrypto;
-} catch {
-  // ignore
-}
+import { sha256 } from "js-sha256";
 
 /**
  * Represents a filter class with a specific type property.
@@ -271,13 +265,12 @@ export async function hashInt(hashInput: string): Promise<number> {
   // 3. multiply by 100000 to get a number between 0 and 100000 and compare it to the threshold
   //
   // we only need 20 bits to get to 100000 because 2^20 is 1048576
-  const msgUint8 = new TextEncoder().encode(hashInput);
-
-  // Hash the message
-  const hashBuffer = await crypto.subtle.digest("SHA-256", msgUint8);
+  const value =
+    new DataView(sha256.create().update(hashInput).arrayBuffer()).getUint32(
+      0,
+      true,
+    ) & 0xfffff;
 
-  const view = new DataView(hashBuffer);
-  const value = view.getUint32(0, true) & 0xfffff;
   return Math.floor((value / 0xfffff) * 100000);
 }
 

yarn.lock

@@ -560,6 +560,7 @@ __metadata:
     "@bucketco/tsconfig": "workspace:^"
     "@types/node": "npm:^22.12.0"
     eslint: "npm:^9.21.0"
+    js-sha256: "npm:0.11.0"
     prettier: "npm:^3.5.2"
     ts-node: "npm:^10.9.2"
     typescript: "npm:^5.7.3"
@@ -11901,6 +11902,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"js-sha256@npm:0.11.0":
+  version: 0.11.0
+  resolution: "js-sha256@npm:0.11.0"
+  checksum: 10c0/90980fe01ca01fbd166751fb16c4caa09c1ab997e8bf77c0764cc05c772c6044946f4c1b3bad266ce78357280d2131d3dc0cf2dd7646e78272996bd4d590aa4f
+  languageName: node
+  linkType: hard
+
 "js-tokens@npm:^3.0.0 || ^4.0.0, js-tokens@npm:^4.0.0":
   version: 4.0.0
   resolution: "js-tokens@npm:4.0.0"