feat(auth): svg captcha challenge factory

Made-with: Cursor

server/service/captcha/challenge.test.ts

@@ -0,0 +1,13 @@
+import { describe, expect, test } from "bun:test";
+import { createCaptchaChallenge } from "./challenge";
+
+describe("createCaptchaChallenge", () => {
+    test("returns captchaId and non-empty svg", () => {
+        const { captchaId, imageSvg } = createCaptchaChallenge();
+        expect(captchaId).toMatch(
+            /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i,
+        );
+        expect(imageSvg.length).toBeGreaterThan(50);
+        expect(imageSvg.includes("svg")).toBe(true);
+    });
+});

server/service/captcha/challenge.ts

@@ -0,0 +1,18 @@
+import svgCaptcha from "svg-captcha";
+import { captchaCreate } from "./store";
+
+/** 易混淆字符已剔除，长度 5 */
+const CHAR_PRESET = "abcdefghjkmnpqrstuvwxyz23456789";
+
+export function createCaptchaChallenge(): { captchaId: string; imageSvg: string } {
+    const { data: imageSvg, text } = svgCaptcha.create({
+        size: 5,
+        noise: 2,
+        color: true,
+        charPreset: CHAR_PRESET,
+        background: "#f4f4f5",
+    });
+    const answerNormalized = text.toLowerCase();
+    const { captchaId } = captchaCreate(answerNormalized);
+    return { captchaId, imageSvg };
+}