import policy from "./backend-url-policy.json";

export interface RuntimeConfig {
  backendBaseUrl?: string;
}

declare global {
  interface Window {
    __THOTHII_CONFIG__?: RuntimeConfig;
  }
}

export function resolveBackendUrl(config: RuntimeConfig | undefined): string {
  const value = config?.backendBaseUrl ?? import.meta.env.VITE_BACKEND_URL ?? "";
  if (policy.relativeBases.includes(value)) return value;
  try {
    if (!new RegExp(policy.absolutePattern).test(value)) throw new Error("syntax");
    const authority = value.replace(/^https?:\/\//, "").split("/", 1)[0];
    const suffix = authority.startsWith("[")
      ? authority.slice(authority.indexOf("]") + 1)
      : authority.slice(authority.lastIndexOf(":"));
    const port = suffix.startsWith(":") ? suffix.slice(1) : "";
    if (port && (port.length > 5 || Number(port) > policy.maxPort)) throw new Error("port");
    return value;
  } catch {
    // Fall through to the single actionable runtime error below.
  }
  throw new Error(
    "Invalid BACKEND_BASE_URL: use empty/root, /api, or a valid http(s) base without credentials, query, or fragment",
  );
}

export function joinBackendPath(base: string, path: string): string {
  const normalizedBase = base === "/" ? "" : base.replace(/\/+$/, "");
  const normalizedPath = path.replace(/^\/+/, "");
  return `${normalizedBase}/${normalizedPath}`;
}

export const backendBaseUrl =
  resolveBackendUrl(typeof window === "undefined" ? undefined : window.__THOTHII_CONFIG__) ||
  "http://localhost:8787";