// Host → tenant slug parser for the portal middleware.
//
// In dev we serve at <slug>.localhost:3000 (e.g. acme.localhost:3000). In
// prod we serve at <slug>.breakpilot.com. Backstage lives at the apex —
// no subdomain — and resolves to a fixed `__backstage__` slug.

export type HostMatch =
  | { kind: "tenant"; slug: string }
  | { kind: "backstage" }
  | { kind: "apex" }
  | { kind: "unknown" };

// Longest-first so `stage.breakpilot.com` is matched before `breakpilot.com`.
// Built-ins cover dev (localhost) + the canonical breakpilot.com targets.
// PORTAL_APEX_HOSTS is a comma-separated env override for per-environment
// hosts (e.g. portal-dev.meghsakha.com while breakpilot.com isn't registered).
const APEX_HOSTS = (() => {
  const base = ["stage.breakpilot.com", "breakpilot.com", "localhost"];
  const extra = (process.env.PORTAL_APEX_HOSTS ?? "")
    .split(",")
    .map((h) => h.trim().toLowerCase())
    .filter(Boolean);
  // Longest-first to keep the suffix-strip loop correct.
  return Array.from(new Set([...extra, ...base])).sort(
    (a, b) => b.length - a.length,
  );
})();
const APEX_SET = new Set(APEX_HOSTS);

export function parseHost(host: string | null | undefined): HostMatch {
  if (!host) return { kind: "unknown" };

  const hostNoPort = host.split(":")[0].toLowerCase();

  if (APEX_SET.has(hostNoPort)) return { kind: "apex" };

  // Strip the known apex suffix to extract the subdomain.
  for (const apex of APEX_HOSTS) {
    const suffix = `.${apex}`;
    if (hostNoPort.endsWith(suffix)) {
      const sub = hostNoPort.slice(0, -suffix.length);
      if (!sub) return { kind: "apex" };
      // Backstage is reserved.
      if (sub === "backstage") return { kind: "backstage" };
      // Slugs are [a-z0-9-]{2,40} per the tenant-registry schema check.
      if (/^[a-z0-9-]{2,40}$/.test(sub)) {
        return { kind: "tenant", slug: sub };
      }
      return { kind: "unknown" };
    }
  }

  return { kind: "unknown" };
}