/** One piped answer is at most this long (an email address is at most 254 bytes). */
export declare const MAX_ANSWER_BYTES = 256;
export type PromptIO = {
    stdin?: NodeJS.ReadableStream;
    stderr: NodeJS.WritableStream;
};
export declare function hasInteractiveInput(stdin: NodeJS.ReadableStream | undefined): boolean;
/**
 * A visible one-line prompt on a TTY (account picker, confirmations): the
 * trimmed answer, or null when the input ended (Ctrl-D) before one.
 */
export declare function promptLine(io: PromptIO, label: string): Promise<string | null>;
/**
 * One line of piped input, without consuming the next one: whatever follows
 * the newline is pushed back onto the stream for the next prompt. Bytes past
 * `MAX_ANSWER_BYTES` are dropped up to the newline, so an overlong line comes
 * back too long and fails validation. Null at the end of the input.
 */
export declare function readPipedLine(stdin: NodeJS.ReadableStream): Promise<string | null>;
/**
 * A visible prompt for the email verification. On a terminal it is
 * `promptLine`; without one the label still goes to stderr and the answer is
 * one line of piped stdin. Null when the input ended without an answer.
 */
export declare function promptAnswer(io: PromptIO, label: string): Promise<string | null>;
/**
 * `[y/N]` upload confirmation: an explicit `y` is required. `--yes` (or its
 * alias `--confirm`) answers yes; without a terminal and without them it is
 * CONFIRMATION_REQUIRED.
 */
export declare function confirmUpload(io: PromptIO, question: string, options: {
    isConfirmed: boolean;
    flag?: string;
}): Promise<boolean>;
/**
 * `[Y/n]` question where Enter means yes (installing cf). The caller handles
 * `--yes` and the no-terminal case; an input that ends before an answer is
 * CONFIRMATION_REQUIRED.
 */
export declare function confirmDefaultYes(io: PromptIO, question: string): Promise<boolean>;