/**
 * Open-tracking pixel injector (Phase 4b). Appends a 1×1 transparent
 * image pointing at /api/public/email-pixel/[sendId] to outbound HTML
 * emails. The pixel endpoint records the open + cross-posts the event
 * to Umami.
 *
 * Sites that want to opt out of tracking simply don't call this helper.
 * The pixel URL is unguessable per-send (UUID), but a `track_opens=false`
 * row in `document_sends` makes the endpoint a no-op even if someone
 * does guess one.
 *
 * Privacy: respects EMAIL_REDIRECT_TO (no pixel injected when dev
 * redirect is active) so a re-routed message doesn't fire a fake open.
 */

import { env } from '@/lib/env';

interface InjectOptions {
  /** Public base URL of the CRM (e.g. https://crm.portnimara.com).
   *  Required so the pixel link is absolute - relative URLs break in
   *  email clients. */
  appBaseUrl: string;
  /** UUID of the row in `document_sends`. */
  sendId: string;
}

/**
 * Append a 1×1 tracking pixel just before `</body>` (or at the end of the
 * document if no `</body>` is present). Returns the HTML unchanged when
 * EMAIL_REDIRECT_TO is set so dev-mode re-routing doesn't generate
 * misleading open events.
 */
export function injectTrackingPixel(html: string, opts: InjectOptions): string {
  if (env.EMAIL_REDIRECT_TO) return html;

  const base = opts.appBaseUrl.replace(/\/$/, '');
  const pixelUrl = `${base}/api/public/email-pixel/${opts.sendId}`;
  const pixelTag =
    `<img src="${pixelUrl}" width="1" height="1" alt="" ` +
    `style="display:block;border:0;margin:0;padding:0" />`;

  if (html.includes('</body>')) {
    return html.replace('</body>', `${pixelTag}</body>`);
  }
  return html + pixelTag;
}