Add prepaid credits

import { credits, memoryBalance, payPerCall } from "tollstile";
import { tollstile } from "@tollstile/hono";

const balance = memoryBalance({ acct_1: "$5.00" }); // implement Balance on your database in production

app.post(
  "/v1/generate",
  tollstile(
    toll.price("$0.02", { access: [credits({ balance }), payPerCall()] }),
    { principal: (c) => (c.get("user") ? { id: c.get("user").id } : null) },
  ),
  generate,
);

import type { Balance } from "tollstile";

export const balance: Balance = {
  async reserve(account, amount, key) {
    // In one transaction: if a reservation with `key` exists, return "reserved".
    // Otherwise, if available >= amount, subtract and insert (key, account, amount, "reserved").
    return "reserved"; // or "insufficient"
  },
  async commit(key) { /* reserved → committed */ },
  async release(key) { /* reserved → released, and add the amount back */ },
  async status(key) { return "committed"; /* reserved | committed | released | none */ },
};