feat: add basic impl

pkgs/shared/package.json

@@ -0,0 +1,13 @@
+{
+	"name": "@pow-captcha/shared",
+	"version": "0.0.0",
+	"module": "dist/lib.js",
+	"types": "dist/lib.d.ts",
+	"scripts": {
+		"build": "tsc -p tsconfig.build.json"
+	},
+	"dependencies": {
+		"base64-js": "^1.5.1",
+		"zod": "^3.25.67"
+	}
+}

pkgs/shared/src/lib.ts

@@ -0,0 +1,2 @@
+export * as wire from "./wire";
+export * as utils from "./utils";

pkgs/shared/src/utils.ts

@@ -0,0 +1,6 @@
+export function createArray<T>(
+	length: number,
+	f: (index: number) => T,
+): Array<T> {
+	return Array.from({ length }, (_, index) => f(index));
+}

pkgs/shared/src/wire.ts

@@ -0,0 +1,72 @@
+import { z } from "zod";
+import {
+	fromByteArray as serializeArray,
+	toByteArray as deserializeArray,
+} from "base64-js";
+
+export { serializeArray, deserializeArray };
+
+export const signedDataSchema = z.object({
+	data: z.string(),
+	hash: z.string(),
+});
+export type SignedData = z.output<typeof signedDataSchema>;
+
+export const challengeEntrySchema = z.tuple([z.string(), z.string()]);
+export type ChallengeEntry = z.output<typeof challengeEntrySchema>;
+
+export const CHALLENGE_MAGIC = "2104f639-ba1b-48f3-9443-889128163f5a";
+
+export const challengeSchema = z.object({
+	magic: z.literal(CHALLENGE_MAGIC),
+	challenges: z.array(challengeEntrySchema),
+});
+export type Challenge = z.output<typeof challengeSchema>;
+
+export const challengeSolutionSchema = z.object({
+	challengesSigned: signedDataSchema,
+	solutions: z.array(z.string()),
+});
+export type ChallengeSolution = z.output<typeof challengeSolutionSchema>;
+
+export const REDEEMED_MAGIC = "90a63087-993a-4376-9532-33c3dc8557c9";
+
+export const redeemedSchema = z.object({
+	magic: z.literal(REDEEMED_MAGIC),
+});
+export type Redeemed = z.output<typeof redeemedSchema>;
+
+export async function serializeAndSignData<T>(
+	data: T,
+	secret: string,
+): Promise<SignedData> {
+	const json = JSON.stringify(data);
+	const arr = utf16StringToArrayBuffer(`${json}:${secret}`);
+	const hash = new Uint8Array(await crypto.subtle.digest("SHA-256", arr));
+	return {
+		data: json,
+		hash: serializeArray(hash),
+	};
+}
+
+export async function verifyAndDeserializeData<T>(
+	signedData: SignedData,
+	schema: z.ZodType<T>,
+	secret: string,
+): Promise<T> {
+	const arr = utf16StringToArrayBuffer(`${signedData.data}:${secret}`);
+	const hash = new Uint8Array(await crypto.subtle.digest("SHA-256", arr));
+	if (hash !== deserializeArray(signedData.hash)) {
+		throw new Error(`Signed data verification failed, hash mismatch`);
+	}
+	const data = JSON.parse(signedData.data);
+	return await schema.parseAsync(data);
+}
+
+export function utf16StringToArrayBuffer(input: string): ArrayBuffer {
+	const arr = new Uint16Array(input.length);
+	for (let i = 0, strLen = input.length; i < strLen; i += 1) {
+		arr[i] = input.charCodeAt(i);
+	}
+	return arr.buffer;
+}

pkgs/shared/tsconfig.build.json

@@ -0,0 +1,8 @@
+{
+	"extends": "../../tsconfig.build.json",
+	"compilerOptions": {
+		"outDir": "dist"
+	},
+	"include": ["src/**/*"],
+	"exclude": ["**/*.spec.ts"]
+}

pkgs/shared/tsconfig.json

@@ -0,0 +1,4 @@
+{
+	"extends": "../../tsconfig.base.json",
+	"include": ["src/**/*"]
+}