/**
 * The **Theme History Service** — a bounded undo/redo stack of applied themes.
 * A linear history with a cursor: pushing after an undo truncates the redo tail
 * (standard editor semantics). Undoing past the first entry returns `null`,
 * meaning "revert to the base mode/variant".
 *
 * @packageDocumentation
 */
import type { GeneratedTheme, ThemeHistoryEntry } from '../../types/theme-ai.types';
/** Default maximum number of retained history entries. */
export declare const DEFAULT_THEME_HISTORY_LIMIT = 50;
/** Undo/redo/restore stack for applied themes. */
export declare class ThemeHistoryService {
    private readonly limit;
    private entries;
    /** Index of the current entry, or -1 when at the base (no theme). */
    private cursor;
    private seq;
    constructor(limit?: number);
    /** Record a newly applied theme as the current state (truncates any redo tail). */
    push(theme: GeneratedTheme): void;
    /** The current theme, or `null` at the base. */
    current(): GeneratedTheme | null;
    /** Step back one entry. Returns the now-current theme, or `null` if it reached the base. */
    undo(): GeneratedTheme | null;
    /** Step forward one entry. Returns the now-current theme, or `null` if already at the newest. */
    redo(): GeneratedTheme | null;
    /** Restore a specific entry by its monotonic index. */
    restore(index: number): GeneratedTheme | null;
    /** Clear the entire history (back to base). */
    reset(): void;
    /** The full history stack, oldest first. */
    getAll(): readonly ThemeHistoryEntry[];
}
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