import type { string_book } from './string_book';
/**
 * Helper for manipulating agent books in-memory.
 *
 * @private internal helper for `@promptbook/core`
 */
export declare class BookEditable {
    private readonly lines;
    /**
     * Creates a mutable view over the supplied book content.
     *
     * @param book - Agent source text to work with.
     */
    constructor(book: string_book);
    /**
     * Creates a new instance from the supplied book text.
     *
     * @param book - Agent source text to work with.
     * @returns Editable view over the book content.
     */
    static from(book: string_book): BookEditable;
    /**
     * Returns the editable content as a string_book.
     *
     * @returns Current book content with original line breaks preserved.
     */
    toString(): string_book;
    /**
     * Checks whether the book contains any non-empty lines.
     *
     * @returns `true` when the book has meaningful content beyond blank lines.
     */
    hasNonEmptyContent(): boolean;
    /**
     * Finds the last line index whose trimmed text matches the commitment name.
     *
     * @param commitment - Commitment keyword to locate (for example `CLOSED`).
     * @returns Zero-based line index or `null` when the commitment is absent.
     */
    findLastCommitmentLineIndex(commitment: string): number | null;
}