Add client ALTCHA proof-of-work and Vite env flags for uploads.

Expose enabled/max-number settings and wire altcha-lib for per-upload challenges.

frontend/src/config/index.ts

@@ -10,10 +10,16 @@ const env = (key: string): string => {
 
 const envInt = (key: string): number => parseInt(env(key), 10);
 
+const isEnabled = (key: string): boolean => env(key) === 'true';
+
 export const config = {
     baseUrl: env('VITE_API_BASE_URL'),
     clearnetDomain: env('VITE_CLEARNET_DOMAIN'),
     onionHostname: env('VITE_ONION_HOSTNAME'),
+    altcha: {
+        enabled: isEnabled('VITE_ALTCHA_ENABLED'),
+        maxNumber: envInt('VITE_ALTCHA_MAX_NUMBER')
+    },
     validation: {
         upload: {
             maxQueueSize: envInt('VITE_UPLOAD_MAX_QUEUE_SIZE'),

frontend/src/stores/altcha.ts

@@ -0,0 +1,70 @@
+import { solveChallengeWorkers } from 'altcha-lib/v1';
+import type { Challenge, Payload } from 'altcha-lib/v1/types';
+import { defineStore } from 'pinia';
+import { config } from '@/config';
+import { api } from '@/plugins/axios';
+import { bytesToBase64 } from '@/utils/encoding/bytesToBase64';
+import AltchaSolveWorker from 'altcha-lib/v1/worker?worker';
+
+export const useAltchaStore = defineStore('altcha', () => {
+    const runProofOfWork = async (): Promise<string | undefined> => {
+        if (!config.altcha.enabled) {
+            return undefined;
+        }
+
+        const challenge = await fetchChallenge();
+
+        return encodeSolvedChallenge(challenge);
+    };
+
+    const fetchChallenge = async (): Promise<Challenge> => {
+        const { data } = await api.get<Challenge>('/altcha/challenge');
+
+        return data;
+    };
+
+    const encodeSolvedChallenge = async ({
+        algorithm,
+        challenge: challengeValue,
+        salt,
+        signature,
+        maxnumber
+    }: Challenge): Promise<string> => {
+        const { maxNumber: fallbackMaxNumber } = config.altcha;
+
+        const maxNumber = maxnumber ?? fallbackMaxNumber;
+        const cuncurrency = Math.min(8, Math.max(1, navigator.hardwareConcurrency ?? 4));
+
+        const solution = await solveChallengeWorkers(
+            () => new AltchaSolveWorker(),
+            cuncurrency,
+            challengeValue,
+            salt,
+            algorithm,
+            maxNumber
+        );
+
+        if (!solution) {
+            throw new Error('ALTCHA proof of work could not be solved');
+        }
+
+        const payload: Payload = {
+            algorithm,
+            challenge: challengeValue,
+            number: solution.number,
+            salt,
+            signature
+        };
+
+        const json = JSON.stringify(payload);
+
+        const textEncoder = new TextEncoder();
+        const bytes = textEncoder.encode(json);
+
+        return bytesToBase64(bytes);
+    };
+
+    return {
+        runProofOfWork
+    };
+});

frontend/src/vite-env.d.ts

@@ -4,6 +4,8 @@ interface ImportMetaEnv {
     readonly VITE_API_BASE_URL: string;
     readonly VITE_CLEARNET_DOMAIN: string;
     readonly VITE_ONION_HOSTNAME: string;
+    readonly VITE_ALTCHA_ENABLED: string;
+    readonly VITE_ALTCHA_MAX_NUMBER: string;
     readonly VITE_UPLOAD_MAX_QUEUE_SIZE: string;
     readonly VITE_VALIDATION_UPLOAD_MAX_VIEWS_MAX: string;
     readonly VITE_VALIDATION_UPLOAD_MAX_IMAGE_BYTES: string;