/**
 * Client for PdfService (issue #14) — renders a PO's export page to a real PDF.
 *
 * The app's own /api/po/:id/export?format=pdf produces a print-styled HTML page;
 * PdfService (headless Chromium) navigates to it and returns PDF bytes. We pass a
 * short-lived service token so the export route serves the page without a user
 * session. Configured via:
 *   PDF_SERVICE_URL    — e.g. http://localhost:3005
 *   PDF_SERVICE_TOKEN  — shared secret echoed by the export route
 *   APP_INTERNAL_URL   — base URL PdfService can reach the app at (falls back to NEXTAUTH_URL)
 */
export class PdfServiceError extends Error {}

export function isPdfServiceConfigured(): boolean {
  return !!process.env.PDF_SERVICE_URL && !!process.env.PDF_SERVICE_TOKEN;
}

/** Render a PO to a PDF buffer via PdfService. Throws PdfServiceError on failure. */
export async function renderPoPdf(poId: string): Promise<Buffer> {
  const serviceUrl = process.env.PDF_SERVICE_URL;
  const token = process.env.PDF_SERVICE_TOKEN;
  if (!serviceUrl || !token) {
    throw new PdfServiceError("PDF service is not configured.");
  }

  const appBase = (process.env.APP_INTERNAL_URL ?? process.env.NEXTAUTH_URL ?? "http://localhost:3000").replace(/\/$/, "");
  const exportUrl = `${appBase}/api/po/${poId}/export?format=pdf&pdf=1&svc=${encodeURIComponent(token)}`;

  let res: Response;
  try {
    res = await fetch(`${serviceUrl.replace(/\/$/, "")}/pdf`, {
      method: "POST",
      headers: { "Content-Type": "application/json", "x-pdf-token": token },
      body: JSON.stringify({ url: exportUrl }),
    });
  } catch (e) {
    throw new PdfServiceError(`PDF service unreachable: ${String(e)}`);
  }

  if (!res.ok) {
    throw new PdfServiceError(`PDF service returned ${res.status}`);
  }
  return Buffer.from(await res.arrayBuffer());
}