/**
 * Client-side environment variable access for Next.js applications.
 *
 * This module provides a function to read runtime environment variables
 * that were injected by the PublicEnvScript server component.
 *
 * @remarks
 * This is part of the simplified Next.js API. For advanced configuration loading
 * with custom loaders or direct AWS SDK integration, import from `@dyanet/config-aws` directly:
 *
 * ```typescript
 * import { ConfigManager, EnvironmentLoader } from '@dyanet/config-aws';
 * ```
 *
 * @example
 * ```tsx
 * 'use client';
 *
 * import { env } from '@dyanet/nextjs-config-aws';
 *
 * function MyComponent() {
 *   const apiUrl = env('API_URL');
 *   const appName = env('APP_NAME', 'Default App');
 *
 *   return <div>API: {apiUrl}, App: {appName}</div>;
 * }
 * ```
 */
/**
 * Type declaration for the global window object with environment variables.
 */
declare global {
    interface Window {
        __ENV?: Record<string, string>;
        [key: string]: unknown;
    }
}
/**
 * Retrieves a runtime environment variable value.
 *
 * This function reads from the global window object where environment
 * variables were injected by the PublicEnvScript component.
 *
 * @param key - The environment variable name
 * @returns The value of the environment variable, or undefined if not found
 *
 * @example
 * ```ts
 * const apiUrl = env('API_URL');
 * if (apiUrl) {
 *   // Use the API URL
 * }
 * ```
 */
export declare function env(key: string): string | undefined;
/**
 * Retrieves a runtime environment variable value with a default.
 *
 * @param key - The environment variable name
 * @param defaultValue - The default value to return if the variable is not found
 * @returns The value of the environment variable, or the default value
 *
 * @example
 * ```ts
 * const apiUrl = env('API_URL', 'http://localhost:3000');
 * // apiUrl is guaranteed to be a string
 * ```
 */
export declare function env<T>(key: string, defaultValue: T): string | T;
/**
 * Retrieves a runtime environment variable from a custom variable name.
 *
 * Use this when you've configured PublicEnvScript with a custom variableName.
 *
 * @param variableName - The global variable name to read from
 * @param key - The environment variable name
 * @returns The value of the environment variable, or undefined if not found
 *
 * @example
 * ```ts
 * // If PublicEnvScript was configured with variableName="__MY_ENV"
 * const apiUrl = envFrom('__MY_ENV', 'API_URL');
 * ```
 */
export declare function envFrom(variableName: string, key: string): string | undefined;
/**
 * Retrieves a runtime environment variable from a custom variable name with a default.
 *
 * @param variableName - The global variable name to read from
 * @param key - The environment variable name
 * @param defaultValue - The default value to return if the variable is not found
 * @returns The value of the environment variable, or the default value
 */
export declare function envFrom<T>(variableName: string, key: string, defaultValue: T): string | T;
/**
 * Gets all runtime environment variables.
 *
 * @param variableName - The global variable name to read from (default: '__ENV')
 * @returns A copy of all environment variables
 *
 * @example
 * ```ts
 * const allEnv = getAllEnv();
 * console.log(allEnv); // { API_URL: '...', APP_NAME: '...' }
 * ```
 */
export declare function getAllEnv(variableName?: string): Record<string, string>;
/**
 * Checks if a runtime environment variable exists.
 *
 * @param key - The environment variable name
 * @param variableName - The global variable name to read from (default: '__ENV')
 * @returns True if the variable exists, false otherwise
 *
 * @example
 * ```ts
 * if (hasEnv('FEATURE_FLAG')) {
 *   // Feature is enabled
 * }
 * ```
 */
export declare function hasEnv(key: string, variableName?: string): boolean;
export default env;
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