refactor: centralize group sender identity

src/auto-reply/reply/inbound-sender-meta.ts

@@ -0,0 +1,38 @@
+import type { MsgContext } from "../templating.js";
+
+export function formatInboundBodyWithSenderMeta(params: {
+  body: string;
+  ctx: MsgContext;
+}): string {
+  const body = params.body;
+  if (!body.trim()) return body;
+  const chatType = params.ctx.ChatType?.trim().toLowerCase();
+  if (!chatType || chatType === "direct") return body;
+  if (hasSenderMetaLine(body)) return body;
+
+  const senderLabel = formatSenderLabel(params.ctx);
+  if (!senderLabel) return body;
+
+  const lineBreak = resolveBodyLineBreak(body);
+  return `${body}${lineBreak}[from: ${senderLabel}]`;
+}
+
+function resolveBodyLineBreak(body: string): string {
+  const hasEscaped = body.includes("\\n");
+  const hasNewline = body.includes("\n");
+  if (hasEscaped && !hasNewline) return "\\n";
+  return "\n";
+}
+
+function hasSenderMetaLine(body: string): boolean {
+  return /(^|\n|\\n)\[from:/i.test(body);
+}
+
+function formatSenderLabel(ctx: MsgContext): string | null {
+  const senderName = ctx.SenderName?.trim();
+  const senderId = (ctx.SenderE164?.trim() || ctx.SenderId?.trim()) ?? "";
+  if (senderName && senderId && senderName !== senderId) {
+    return `${senderName} (${senderId})`;
+  }
+  return senderName ?? (senderId || null);
+}