/**
 * Umami (self-hosted) analytics configuration and payload redaction.
 *
 * Two deliberate choices are encoded here:
 *
 * 1. The tracker is served same-origin through a rewrite (see `ANALYTICS_PROXY_PATH`
 *    and next.config.mjs) rather than from the Umami host directly. That keeps the
 *    strict CSP in middleware.ts untouched — `script-src`/`connect-src` stay
 *    `'self'` — and stops content blockers from dropping the request.
 *
 * 2. Nothing that identifies a user's content ever reaches the analytics database.
 *    See `redactUrl` / `redactTitle`.
 */

/** Same-origin prefix the tracker and its beacon are proxied through. */
export const ANALYTICS_PROXY_PATH = "/_a";

export interface UmamiConfig {
  /** Origin of the Umami instance, e.g. "https://analytics.example.com". */
  hostUrl: string;
  websiteId: string;
}

/**
 * Resolve the Umami config from the environment. Returns null when either value
 * is absent, which disables analytics entirely (the default in development).
 *
 * Both are read at build time for statically rendered pages, so they must be
 * present as build args in Docker — see the Dockerfile.
 */
export function umamiConfig(): UmamiConfig | null {
  const hostUrl = process.env.UMAMI_HOST_URL?.trim().replace(/\/+$/, "");
  const websiteId = process.env.UMAMI_WEBSITE_ID?.trim();
  if (!hostUrl || !websiteId) return null;
  return { hostUrl, websiteId };
}

/**
 * Path segments that are opaque identifiers rather than page names.
 *
 * Sending them would put episode IDs, series IDs and — worst — unlisted share
 * IDs into the analytics database. Share links are secret by design, so leaking
 * one there effectively publishes it. Collapsing them also makes the reports
 * useful: one "/episodes/[id]" row instead of thousands of singletons.
 */
export function redactPath(pathname: string): string {
  const seg = pathname.split("/").filter(Boolean);

  // "/episodes/new" is a real page; "/episodes/<cuid>" is not.
  if (seg[0] === "episodes" && seg[1] && seg[1] !== "new") seg[1] = "[id]";
  else if (seg[0] === "series" && seg[1]) seg[1] = "[id]";
  else if (seg[0] === "p" && seg[1]) seg[1] = "[shareId]";
  else if (seg[0] === "admin" && seg[1] === "users" && seg[2]) seg[2] = "[id]";

  return `/${seg.join("/")}`;
}

/**
 * Redact a full URL: collapse identifier segments and drop the query string and
 * hash outright.
 *
 * The query string is the sharper hazard — /reset-password carries a live
 * password-reset token in `?token=`, and /sign-in carries the visitor's intended
 * destination in `?redirect=`. `data-exclude-search` already strips it; this is
 * the second line of defence, and it also covers the referrer field, which the
 * tracker fills from the previous URL.
 */
export function redactUrl(raw: string): string {
  if (!raw) return raw;
  try {
    // Bare paths are the common case; the base only matters for absolute URLs.
    const url = new URL(raw, "http://localhost");
    const path = redactPath(url.pathname);
    return url.origin === "http://localhost" && !raw.startsWith("http")
      ? path
      : `${url.origin}${path}`;
  } catch {
    // Unparseable — return just the redacted path portion, never the raw value.
    return redactPath(raw.split(/[?#]/)[0]);
  }
}

/** Whether a path carries user content that its <title> would expose. */
function isRedacted(pathname: string): boolean {
  return redactPath(pathname) !== pathname;
}

/**
 * Page titles on detail routes are the user's own content — `generateMetadata`
 * returns the episode or series title verbatim. Swap those for the route name so
 * the reports stay readable without storing anyone's content.
 */
export function redactTitle(title: string, url: string): string {
  let pathname: string;
  try {
    pathname = new URL(url, "http://localhost").pathname;
  } catch {
    pathname = url.split(/[?#]/)[0];
  }
  return isRedacted(pathname) ? `${redactPath(pathname)} · Podcast Distribution AI` : title;
}

/** The Umami event payload we are allowed to inspect and rewrite. */
export interface UmamiPayload {
  url?: string;
  referrer?: string;
  title?: string;
  [key: string]: unknown;
}

/** Apply every redaction rule to one outgoing event payload. */
export function redactPayload(payload: UmamiPayload): UmamiPayload {
  const url = payload.url ? redactUrl(payload.url) : payload.url;
  return {
    ...payload,
    ...(url !== undefined ? { url } : {}),
    ...(payload.referrer ? { referrer: redactUrl(payload.referrer) } : {}),
    ...(payload.title && payload.url
      ? { title: redactTitle(payload.title, payload.url) }
      : {}),
  };
}