/**
 * The strict tree input format. Must start with a string.
 * This type is exported for testing purposes and advanced usage.
 */
export type TreeInput = Array<string | TreeInput>;
/**
 * Flexible input type that accepts any array.
 * Runtime validation ensures the first element is a string.
 */
type FlexibleTreeInput = readonly (string | unknown[])[];
/**
 * ASCII characters used to render the tree.
 */
export type TreeChars = {
    branch: string;
    lastBranch: string;
    pipe: string;
    space: string;
};
/**
 * @description Creates a text tree representation from a nested array structure using Unicode box-drawing characters.
 *
 * The expected input format is a hierarchical structure where:
 * - The first element must be a string (the root node)
 * - String elements represent nodes at the current level
 * - Array elements following a string represent the children of the previous node
 * - Nested arrays create deeper levels in the tree
 *
 * Examples of supported formats:
 * - `['root', ['child1', 'child2', 'child3']]` creates a root with three children
 * - `['root', 'second', ['child1', 'child2']]` creates multiple root nodes with children
 * - `['root', ['child1', ['grandchild1', 'grandchild2']]]` creates a root with nested children
 * - `['root', ['childA', ['grandchildA'], 'childB']]` creates multiple branches
 *
 * The output uses Unicode box-drawing characters to visualize the tree structure.
 *
 * @param list {FlexibleTreeInput} - An array representing the tree structure. First element must be a string.
 * @param options {Object} - An object containing optional configuration:
 *   - `chars` {TreeChars} - Custom characters for the tree. Defaults to Unicode box-drawing characters.
 *   - `plain` {boolean} - Whether to use plain whitespace characters instead of Unicode box-drawing characters.
 *
 * @returns {string} A string containing the tree representation
 *
 * @example
 * treeify(['root', ['child1', 'child2', ['grandchild']]])
 * //   root
 * //   ├─ child1
 * //   └─ child2
 * //      └─ grandchild
 */
export declare function treeify(list: FlexibleTreeInput, options?: {
    chars?: TreeChars;
    plain?: boolean;
}): string;
export {};