feat(automation): support public reply variations (#31)

scripts/test-unit.ts

@@ -12,7 +12,11 @@ import { FREE_ATTEMPTS, lockRemaining, lockSecondsFor } from '../src/throttle.ts
 import type { Env } from '../src/types.ts';
 import { authorizeUrl, oauthRedirectUri } from '../src/meta.ts';
 import { isSelfComment } from '../src/guard.ts';
-import { parseWebhookPayload } from '../src/process.ts';
+import {
+  parsePublicReplyVariations,
+  parseWebhookPayload,
+  selectPublicReply,
+} from '../src/process.ts';
 import {
   escapeRegex,
   findMatchingRule,
@@ -363,3 +367,54 @@ describe('login throttle', () => {
     assert.equal(lockRemaining({ fails: 0, lockedUntil: 0 }, 1_000), 0);
   });
 });
+
+describe('public reply variations', () => {
+  it('handles null, undefined, or empty string gracefully', () => {
+    assert.deepEqual(parsePublicReplyVariations(null), []);
+    assert.deepEqual(parsePublicReplyVariations(undefined), []);
+    assert.deepEqual(parsePublicReplyVariations(''), []);
+    assert.deepEqual(parsePublicReplyVariations('   \n  \n  '), []);
+    assert.equal(selectPublicReply(null), null);
+    assert.equal(selectPublicReply(''), null);
+  });
+
+  it('keeps backward compatibility with existing single-value reply text', () => {
+    const single = 'Sent you a DM with the details! Check your inbox.';
+    assert.deepEqual(parsePublicReplyVariations(single), [single]);
+    assert.equal(selectPublicReply(single), single);
+  });
+
+  it('parses multiple newline-delimited variations ignoring blank lines', () => {
+    const multiline = `
+      Check your DM!
+
+      Sent to your inbox!
+
+      Check your message request folder!
+    `;
+    const variations = parsePublicReplyVariations(multiline);
+    assert.deepEqual(variations, [
+      'Check your DM!',
+      'Sent to your inbox!',
+      'Check your message request folder!',
+    ]);
+  });
+
+  it('supports JSON array format if stored as json', () => {
+    const jsonStr = JSON.stringify(['Variation 1', 'Variation 2', 'Variation 3']);
+    assert.deepEqual(parsePublicReplyVariations(jsonStr), [
+      'Variation 1',
+      'Variation 2',
+      'Variation 3',
+    ]);
+  });
+
+  it('picks variations at random using random generator function', () => {
+    const text = 'Option A\nOption B\nOption C';
+    assert.equal(selectPublicReply(text, () => 0), 'Option A');
+    assert.equal(selectPublicReply(text, () => 1), 'Option B');
+    assert.equal(selectPublicReply(text, () => 2), 'Option C');
+    assert.equal(selectPublicReply(text, () => 3), 'Option A'); // modulo wrapping
+  });
+});
+

src/process.ts

@@ -57,6 +57,43 @@ export function parseWebhookPayload(raw: string): unknown {
   }
 }
 
+export function parsePublicReplyVariations(raw: string | null | undefined): string[] {
+  if (!raw) return [];
+  const trimmed = raw.trim();
+  if (!trimmed) return [];
+
+  if (trimmed.startsWith('[')) {
+    try {
+      const parsed = JSON.parse(trimmed);
+      if (Array.isArray(parsed)) {
+        return parsed.map((s) => String(s).trim()).filter((s) => s.length > 0);
+      }
+    } catch {
+      // Fall through if not valid JSON
+    }
+  }
+
+  return trimmed
+    .split(/\r?\n/)
+    .map((s) => s.trim())
+    .filter((s) => s.length > 0);
+}
+
+export function selectPublicReply(
+  raw: string | null | undefined,
+  randomFn: (max: number) => number = (max) => {
+    const arr = new Uint32Array(1);
+    crypto.getRandomValues(arr);
+    return arr[0] % max;
+  }
+): string | null {
+  const variations = parsePublicReplyVariations(raw);
+  if (variations.length === 0) return null;
+  if (variations.length === 1) return variations[0];
+  const idx = Math.abs(randomFn(variations.length)) % variations.length;
+  return variations[idx];
+}
+
 function commentIdOf(value: CommentValue): string | undefined {
   return asId(value.id) || asId(value.comment_id);
 }
@@ -170,7 +207,7 @@ export async function processComment(
 
   if (!dm.ok) errors.push(`DM: ${dm.body}`);
 
-  const publicText = rule.public_reply_text?.trim();
+  const publicText = selectPublicReply(rule.public_reply_text);
   if (publicText) {
     const reply = await sendPublicReply(commentId, token, publicText);
     replyStatus = reply.ok ? 'ok' : 'failed';

src/routes/admin.ts

@@ -588,7 +588,7 @@ function ruleForm(opts: {
       <p class="muted">${String(dmLen)}/1,000 characters</p>
       <label for="public_reply_text">Public reply under the comment (optional)</label>
       <textarea id="public_reply_text" name="public_reply_text">${v.public_reply_text}</textarea>
-      <p class="muted">Leave blank to only send the private message, with no public reply.</p>
+      <p class="muted">One reply per line (one chosen at random per send). Leave blank to only send the private message, with no public reply.</p>
       <div class="row"><button type="submit">Save rule</button></div>
     </form>
   `;