/**
 * Ion access token configuration.
 *
 * Accepts:
 * - A plain `string` — same token in every environment
 * - A `Record<string, string>` — keyed by Vite `mode`
 * - A callback `(mode: string) => string | Promise<string>` — resolved at
 *   build start, useful for secrets managers or async vault lookups
 *
 * When omitted, the plugin looks for `CESIUM_ION_TOKEN` (or
 * `CESIUM_ION_TOKEN_<MODE>`) in the Vite env automatically.
 *
 * @example plain string
 * ```ts
 * ionToken: "eyJhbGci..."
 * ```
 *
 * @example per-environment map
 * ```ts
 * ionToken: {
 *   development: "eyJhbGci...",
 *   production:  "eyJhbGci...",
 * }
 * ```
 *
 * @example async callback (e.g. AWS Secrets Manager)
 * ```ts
 * ionToken: async (mode) => {
 *   const secret = await getSecret(`cesium-ion-token-${mode}`);
 *   return secret.value;
 * }
 * ```
 */
export type IonTokenCallback = (mode: string) => string | Promise<string>;
export type IonTokenConfig = string | Record<string, string> | IonTokenCallback;
export declare function validateToken(token: string, mode: string): void;
export declare function resolveToken(tokenConfig: IonTokenConfig | undefined, mode: string, env: Record<string, string>): Promise<string | undefined>;
export declare function logResolvedToken(token: string | undefined, config: IonTokenConfig | undefined, mode: string, env: Record<string, string>): void;