export declare type ValidationError = TypeError | MissingKey | UnexpectedKey | MissingTypeTag | UnexpectedTypeTag | InvalidIntegerString;
export interface TypeError {
    errorType: 'type-error';
    expectedType: string;
    actualType: string;
}
export interface MissingKey {
    errorType: 'missing-key';
    expectedKey: string;
    expectedType: string;
}
export interface UnexpectedKey {
    errorType: 'unexpected-key';
    key: string;
}
export interface MissingTypeTag {
    errorType: 'missing-type-tag';
    expectedTypeTags: string[];
}
export interface UnexpectedTypeTag {
    errorType: 'unexpected-type-tag';
    expectedTypeTags: string[];
    actualTypeTag: string;
}
export interface InvalidIntegerString {
    errorType: 'invalid-integer-string';
    actualValue: string;
}
export interface ValidationTree {
    errors: ValidationError[];
    children: Record<string, ValidationTree>;
}
export declare function isValid(tree: ValidationTree): boolean;
export interface Validation {
    type: string;
    validate(value: any): ValidationTree;
    validate(value: any, key: string, validation: ValidationTree): ValidationTree;
}
export interface UnionValidation<Tag extends string, A extends {
    [_ in Tag]: string;
}> extends Validation {
    tag: Tag;
    values(): {
        [_ in A[Tag]]: Validation;
    };
}
export interface ObjectValidation<A extends object> extends Validation {
    required(): RequiredFieldsValidators<A>;
    optional(): OptionalFieldsValidators<A>;
}
export declare const noFields: () => {};
export declare function init(key?: string, validation?: ValidationTree): ValidationTree;
export declare function typeOf(value: any): 'string' | 'number' | 'bigint' | 'boolean' | 'symbol' | 'undefined' | 'null' | 'object' | 'function' | 'array';
/**
 * Extracts required keys as a string type union
 */
export declare type RequiredKeys<T> = {
    [K in keyof T]: {} extends Pick<T, K> ? never : K;
} extends {
    [_ in keyof T]: infer U;
} ? {} extends U ? never : U : never;
/**
 * Extracts optional keys as a string type union
 */
export declare type OptionalKeys<T> = {
    [K in keyof T]: T extends Record<K, T[K]> ? never : K;
} extends {
    [_ in keyof T]: infer U;
} ? {} extends U ? never : U : never;
export declare type RequiredFields<K extends object, V> = Record<RequiredKeys<K>, V>;
export declare type RequiredFieldsValidators<K extends object> = RequiredFields<K, Validation>;
export declare type OptionalFields<K extends object, V> = Record<OptionalKeys<K>, V>;
export declare type OptionalFieldsValidators<K extends object> = OptionalFields<K, Validation>;