Backend logic in TypeScript.

import { mutation, v } from "@pylonsync/functions";
 
export default mutation({
  args: { roomId: v.id("Room"), body: v.string() },
  async handler(ctx, args) {
    if (!ctx.auth.userId) throw ctx.error("UNAUTHENTICATED", "log in first");
    const id = await ctx.db.insert("Message", {
      roomId: args.roomId,
      authorId: ctx.auth.userId,
      body: args.body.trim(),
      createdAt: new Date().toISOString(),
    });
    return ctx.db.get("Message", id);   // broadcasts to subscribers
  },
});