export const GA_MEASUREMENT_ID = "G-QTT9QT0T3S";
export const CONSENT_STORAGE_KEY = "evandro.analytics-consent.v1";
export const GA_DISABLE_KEY = "ga-disable-G-QTT9QT0T3S";

export type AnalyticsConsent = "granted" | "denied";
export type Gtag = (...args: unknown[]) => void;

declare global {
  interface Window {
    dataLayer?: IArguments[];
    "ga-disable-G-QTT9QT0T3S"?: boolean;
    gtag?: Gtag;
  }
}

export function readConsent(): AnalyticsConsent | null {
  try {
    const value = localStorage.getItem(CONSENT_STORAGE_KEY);
    return value === "granted" || value === "denied" ? value : null;
  } catch {
    return null;
  }
}

function analyticsPagePath(): string {
  const path = window.location.pathname.replace(/\/$/, "") || "/";
  switch (path) {
    case "/":
    case "/servicos":
    case "/cases":
    case "/curriculo":
    case "/privacidade":
      return path;
    default:
      // Route templates keep arbitrary slugs and personal data out of metrics.
      if (path.startsWith("/servicos/")) return "/servicos/[slug]";
      if (path.startsWith("/cases/")) return "/cases/[slug]";
      return "/other";
  }
}

/** Measures an attempted handoff, not an opened app, delivered message or lead.
 * Callers must supply static labels, never form values or destination URLs.
 */
export function trackWhatsAppOpen({
  service,
  placement,
}: {
  service: string;
  placement: string;
}): void {
  if (
    process.env.NODE_ENV !== "production" ||
    typeof window === "undefined" ||
    readConsent() !== "granted" ||
    window[GA_DISABLE_KEY] === true ||
    typeof window.gtag !== "function"
  ) {
    return;
  }

  try {
    const pagePath = analyticsPagePath();
    window.gtag("event", "whatsapp_open", {
      send_to: GA_MEASUREMENT_ID,
      service,
      placement,
      page_path: pagePath,
      // Override gtag's URL defaults so query/hash/referrer data cannot leak.
      page_location: `https://evandro.dev.br${pagePath}`,
      page_referrer: "",
    });
  } catch {
    // Analytics must never interrupt navigation. Dropped events are not replayed.
  }
}