export type StepValidator = () => string[];
/** Reducer state: current step, the furthest validly reached step, and the blocking messages. */
export type WizardState = {
    /** Zero-based index of the current step. */
    index: number;
    /** Furthest step the user has validly reached; stages beyond it stay locked. */
    furthest: number;
    /** Messages blocking the current step; [] when none. */
    errors: string[];
};
/** Actions `wizardTransition` understands. */
export type WizardAction = 
/** Validates the current step, then advances; failing keeps the step and stores its errors. */
{
    type: "next";
}
/** Steps back one, clearing errors. */
 | {
    type: "back";
}
/** Jumps to `index` if it is at or before `furthest`; otherwise ignored. */
 | {
    type: "goto";
    index: number;
}
/** Moves to `index` and shows `errors`, used when finishing finds an invalid step. */
 | {
    type: "fail";
    index: number;
    errors: string[];
}
/** Returns to the first step with nothing reached beyond it. */
 | {
    type: "reset";
};
export declare const INITIAL_WIZARD_STATE: WizardState;
/** Pure step reducer: `next` validates the current step, `goto` only reaches steps up to `furthest`. */
export declare function wizardTransition(state: WizardState, action: WizardAction, validators: (StepValidator | undefined)[]): WizardState;
/** First step whose validator reports errors, or null when every step is valid. */
export declare function firstInvalidStep(validators: (StepValidator | undefined)[]): {
    index: number;
    errors: string[];
} | null;