Import source: app/backend/src/lib/captcha

Import the existing local project snapshot. This commit organizes existing files; it does not represent newly developed functionality.

app/backend/src/lib/captcha.ts

@@ -0,0 +1,71 @@
+import { randomBytes } from 'node:crypto';
+import { redis } from '../redis.js';
+
+const CAPTCHA_PREFIX = 'captcha:';
+const CAPTCHA_TTL = 120;
+
+function generateCaptchaText(length: number = 5): string {
+  const chars = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789';
+  let result = '';
+  for (let i = 0; i < length; i++) {
+    result += chars.charAt(Math.floor(Math.random() * chars.length));
+  }
+  return result;
+}
+
+function generateCaptchaSVG(text: string): string {
+  const width = 200;
+  const height = 80;
+  const colors = ['#0F6B73', '#D49A2A', '#C76D4A', '#2F8F6B', '#5F6B6D'];
+  const bgColor = '#f0f0f0';
+
+  let noiseSVG = '';
+  for (let i = 0; i < 5; i++) {
+    const x1 = Math.random() * width;
+    const y1 = Math.random() * height;
+    const x2 = Math.random() * width;
+    const y2 = Math.random() * height;
+    const color = colors[Math.floor(Math.random() * colors.length)];
+    noiseSVG += `<line x1="${x1}" y1="${y1}" x2="${x2}" y2="${y2}" stroke="${color}" stroke-width="1.5" opacity="0.3"/>`;
+  }
+
+  let textSVG = '';
+  const charSpacing = width / (text.length + 1);
+
+  for (let i = 0; i < text.length; i++) {
+    const char = text[i];
+    const x = charSpacing * (i + 1) + (Math.random() - 0.5) * 10;
+    const y = height / 2 + (Math.random() - 0.5) * 15;
+    const rotation = (Math.random() - 0.5) * 30;
+    const color = colors[Math.floor(Math.random() * colors.length)];
+    const fontSize = 32 + Math.random() * 8;
+    textSVG += `<text x="${x}" y="${y}" font-size="${fontSize}" font-weight="bold" fill="${color}" transform="rotate(${rotation} ${x} ${y})" font-family="Arial, sans-serif">${char}</text>`;
+  }
+
+  return `<svg xmlns="http://www.w3.org/2000/svg" width="${width}" height="${height}" viewBox="0 0 ${width} ${height}">
+  <rect width="${width}" height="${height}" fill="${bgColor}"/>
+  ${noiseSVG}
+  ${textSVG}
+</svg>`;
+}
+
+export async function createCaptcha() {
+  const id = randomBytes(16).toString('hex');
+  const text = generateCaptchaText(5);
+  const svg = generateCaptchaSVG(text);
+
+  await redis.set(CAPTCHA_PREFIX + id, text.toLowerCase(), 'EX', CAPTCHA_TTL);
+
+  return { id, data: svg };
+}
+
+export async function verifyCaptcha(captchaId: string, userSolution: string): Promise<boolean> {
+  const key = CAPTCHA_PREFIX + captchaId;
+  const stored = await redis.get(key);
+
+  if (!stored) return false;
+
+  await redis.del(key);
+
+  return stored === userSolution.toLowerCase().trim();
+}