export declare const SECONDS_PER_HOUR: number;
/**
 * In milliseconds
 */
export declare const SECONDS = 1000;
/**
 * In milliseconds
 */
export declare const MINUTES: number;
/**
 * In milliseconds
 */
export declare const HOURS: number;
/**
 * In milliseconds
 */
export declare const DAYS: number;
/**
 * Ensure an env var exists and return the contents if it does
 */
export declare const requiredVar: (varName: string | string[]) => string;
/**
 * Fetches the contents of an env var if it exists and is not empty, otherwise returning the specified default value,
 * this means that if no default is specified then `''` will be normalized to `undefined`
 */
export declare function optionalVar<R>(varName: string | string[], defaultValue: R): string | R;
export declare function optionalVar(varName: string | string[], defaultValue?: undefined): string | undefined;
/**
 * Checks that a string is a valid int and returns the number if so
 */
export declare const checkInt: (s: string) => number | undefined;
/**
 * Fetches the contents of an env var, ensuring it is a valid integer if set,
 * if it is not set then instead it returns the specified default value
 */
export declare function intVar(varName: string | string[]): number;
export declare function intVar<R>(varName: string | string[], defaultValue: R): number | R;
/**
 * Fetches the contents of an env var, ensuring it is a valid boolean (`'true'`/`'false'`) if set,
 * if it is not set then instead it returns the specified default value
 */
export declare function boolVar(varName: string | string[]): boolean;
export declare function boolVar<R>(varName: string | string[], defaultValue: R): boolean | R;
/**
 * Fetches the contents of an env var, ensuring it is one of the valid values if set,
 * if it is not set then instead it returns the specified default value
 */
export declare function enumVar<T extends string>(varName: string | string[], validValues: readonly T[]): T;
export declare function enumVar<T extends string>(varName: string | string[], validValues: readonly T[], defaultValue: T): T;
/**
 * Splits an env var using the provided delimiter (defaults to ',') into an array of individual string values.
 * Optionally accepts an array of allowed values for the array.
 */
export declare const arrayVar: <S extends string>(name: string, { delimiter, allowedValues, }?: {
    delimiter?: string | RegExp;
    allowedValues?: S[];
}) => S[] | undefined;
export type HostPort = {
    host: string;
    port: number;
};
/**
 * Splits an env var in the format of `${host1}:${port1}, ${host2}:${port2}, ...`
 * into an array of individual host/port pairings
 */
export declare const hostPortsVar: (varName: string | string[], defaultHosts?: HostPort[]) => HostPort[];
/**
 * Parses a "trust proxy" env var designed for use with express' trust proxy setting,
 * ie it will parse 'true'/'false' into a boolean for express and '123'/etc into a number
 * so that express will be able to handle those correctly
 */
export declare const trustProxyVar: <R>(varName: string | string[], defaultValue?: R) => boolean | string | number | R;