// The PayPal JS SDK is injected at runtime by the script tag below, so there is
// no package to import types from. This declares the sliver of it this app
// actually uses, rather than repeating `(window as any).paypal` at each call
// site — three casts that each silently opted out of type checking.
//
// Deliberately narrow: it describes what is called here, not the whole SDK. A
// wider guess would be fiction, and a wrong shape typed confidently is worse
// than an honest `unknown`.
export interface PaypalButtonsConfig {
  createOrder: () => Promise<string>;
  onApprove: (data: { orderID: string }) => Promise<void> | void;
  onError: (err: unknown) => void;
}

export interface PaypalSdk {
  Buttons: (config: PaypalButtonsConfig) => { render: (selector: string) => void };
}

declare global {
  interface Window {
    // Absent until the SDK script has loaded, which is what loadPaypalSdk and
    // every caller has to check before using it.
    paypal?: PaypalSdk;
  }
}

let loadPromise: Promise<void> | null = null;

export function loadPaypalSdk(clientId: string, currency: string): Promise<void> {
  if (window.paypal) return Promise.resolve();
  if (loadPromise) return loadPromise;
  loadPromise = new Promise((resolve, reject) => {
    const script = document.createElement('script');
    script.src = `https://www.paypal.com/sdk/js?client-id=${encodeURIComponent(clientId)}&currency=${currency}`;
    script.onload = () => resolve();
    script.onerror = () => reject(new Error('failed to load paypal sdk'));
    document.head.appendChild(script);
  });
  return loadPromise;
}