/**
 * Environment variable utility to handle Firebase configuration
 * Framework-agnostic approach to configuration
 */
import { FirebaseConfig } from '../types';
declare global {
    interface Window {
        __FIREBASE_CONFIG__?: Record<string, string>;
        __ENV__?: Record<string, string>;
    }
}
/**
 * Get a configuration value from various sources
 * Priority:
 * 1. Window.__FIREBASE_CONFIG__
 * 2. Window.__ENV__
 * 3. process.env
 */
export declare function getConfigValue(key: string): string | undefined;
/**
 * Get Firebase configuration from various sources
 */
export declare function getFirebaseConfig(providedConfig?: FirebaseConfig): FirebaseConfig | null;
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