// 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`.
const APEX_HOSTS = ["stage.breakpilot.com", "breakpilot.com", "localhost"];
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" };
}