// durable-payment.ts
  import { Resonate, Context } from "@resonatehq/sdk";
  
  // 1) Initialize Resonate executor
  const resonate = new Resonate();
  
  // 2) Register purchase as a durable async function
  resonate.register("purchase", purchase);
  
  async function purchase(ctx: Context, user: User, song: Song): Promise<Status> {
    const charged = await ctx.run(charge, user, song);
    const granted = await ctx.run(access, user, song);
    return { charged, granted };
  }
  
  // 3) Setup logic for routing to durable async function
  app.post("/purchase", async (req: Request, res: Response) => {
    const user = { id: req.body?.user ?? 1 };
    const song = { id: req.body?.song ?? 1, price: 1.99 };
  
    // 4) uniquely identify the execution
    const id = `purchase-${user.id}-${song.id}`;
    try {
      // 5) Call the purchase function and wait for the result
      res.send(await resonate.run("purchase", id, user, song));
    } catch (err) {
      res.status(500).send("Could not purchase song");
    }
  });