/**
 * LayoutEngine
 *
 * Manages document layouts (headers, footers, wrappers) for PDF/document generation.
 *
 * Features:
 * - Load layouts from filesystem (JSON format)
 * - Locale-based layout resolution with fallback
 * - Header/footer/wrapper support
 * - Handlebars variable support in layouts
 * - Layout caching for performance
 * - Integrates with TemplateEngine
 *
 * Layout Structure:
 * ```
 * templates/layouts/
 *   ├── en/
 *   │   ├── headers/
 *   │   │   ├── default.html
 *   │   │   └── invoice.html
 *   │   ├── footers/
 *   │   │   ├── default.html
 *   │   │   └── invoice.html
 *   │   ├── wrappers/
 *   │   │   ├── default.html
 *   │   │   └── invoice.html
 *   │   ├── default.html (shorthand for full layout)
 *   │   └── invoice.md (can be .md or .html)
 * ```
 *
 * Template Frontmatter Options:
 * ```yaml
 * # Option 1: Full wrapper layout
 * layout: invoice  # Uses templates/layouts/{locale}/invoice.html
 *
 * # Option 2: Separate header/footer
 * header: invoice  # Uses templates/layouts/{locale}/headers/invoice.html
 * footer: default  # Uses templates/layouts/{locale}/footers/default.html
 *
 * # Option 3: Custom wrapper with header/footer
 * wrapper: custom  # Uses templates/layouts/{locale}/wrappers/custom.html
 * header: invoice
 * footer: invoice
 *
 * # Option 4: Mix and match
 * header: invoice
 * footer: default
 * # No wrapper, just header + content + footer
 * ```
 */
import type { StorageLayoutEngineConfig, StorageAppliedLayout } from '@plyaz/types/storage';
/**
 * LayoutEngine
 *
 * Manages document layouts (headers, footers, wrappers).
 *
 * @example
 * ```typescript
 * const layoutEngine = new LayoutEngine({
 *   basePath: './layouts',
 *   defaultLocale: 'en',
 * });
 *
 * // Apply layout to content
 * const result = await layoutEngine.applyLayout(
 *   htmlContent,
 *   'invoice',
 *   { companyName: 'Acme Corp', pageNumber: 1 },
 *   'en'
 * );
 * ```
 */
export declare class LayoutEngine {
    private readonly basePath;
    private readonly defaultLocale;
    private readonly cacheEnabled;
    private readonly cacheTTL;
    private readonly logger?;
    private readonly layoutCache;
    constructor(config?: StorageLayoutEngineConfig);
    /**
     * Apply layout to content
     *
     * @param content - HTML content to wrap
     * @param layoutName - Layout name (e.g., 'invoice', 'default')
     * @param data - Data for Handlebars variables
     * @param locale - Locale for layout resolution (default: engine's defaultLocale)
     * @returns Applied layout result
     */
    applyLayout(content: string, layoutName: string, data?: Record<string, unknown>, locale?: string): Promise<StorageAppliedLayout>;
    /**
     * Apply layout from template frontmatter (flexible mode)
     *
     * Supports multiple layout modes:
     * 1. layout: Full wrapper template
     * 2. header + footer: Separate components
     * 3. wrapper + header + footer: All three
     * 4. wrapper only: Just wrap content
     *
     * @param content - HTML content to wrap
     * @param frontmatter - Template frontmatter with layout specifications
     * @param data - Data for Handlebars variables
     * @param locale - Locale for layout resolution
     * @returns Applied layout result
     */
    applyLayoutFromFrontmatter(content: string, frontmatter: {
        layout?: string;
        header?: string;
        footer?: string;
        wrapper?: string;
        styling?: Record<string, string>;
        css?: string;
        [key: string]: unknown;
    }, data?: Record<string, unknown>, locale?: string): Promise<StorageAppliedLayout>;
    /**
     * Load layout component from filesystem with caching
     *
     * Supports both .html and .md files
     * Tries: {locale}/{type}/{name}.html then {locale}/{type}/{name}.md
     * Falls back to base locale and default locale
     *
     * @param componentName - Component name
     * @param componentType - Component type (header/footer/wrapper)
     * @param locale - Locale
     * @returns Cached layout component
     * @private
     */
    private loadLayoutComponent;
    /**
     * Load layout from filesystem with caching (for full layout templates)
     *
     * @param layoutName - Layout name
     * @param locale - Locale
     * @returns Cached layout entry
     * @private
     */
    private loadLayout;
    /**
     * Resolve layout component path with locale fallback
     *
     * Supports both .html and .md files
     * Tries in order:
     * 1. Exact locale with .html (e.g., en-US/headers/invoice.html)
     * 2. Exact locale with .md (e.g., en-US/headers/invoice.md)
     * 3. Base locale with .html (e.g., en/headers/invoice.html)
     * 4. Base locale with .md
     * 5. Default locale with .html
     * 6. Default locale with .md
     *
     * @param componentName - Component name
     * @param componentType - Component type (layout/header/footer/wrapper)
     * @param locale - Requested locale
     * @returns Resolved path and file type
     * @private
     */
    private resolveLayoutComponentPath;
    /**
     * Read layout file from filesystem
     *
     * @param path - Absolute path to layout file
     * @returns Layout JSON content
     * @private
     */
    private readLayoutFile;
    /**
     * Check if file exists
     *
     * @param path - File path
     * @returns True if file exists
     * @private
     */
    private fileExists;
    /**
     * Clear layout cache
     */
    clearCache(): void;
    /**
     * Get cache statistics
     */
    getCacheStats(): {
        size: number;
        entries: string[];
    };
    /**
     * Helper: Log locale fallback when using different locale than requested
     */
    private logLocaleFallback;
    /**
     * Inject custom CSS from frontmatter into HTML
     *
     * Inserts CSS block before </head>, before <body>, or prepends to content
     *
     * @param html - HTML content
     * @param css - CSS string from frontmatter
     * @returns HTML with injected CSS (or original if no CSS)
     * @private
     */
    private injectCustomCSS;
}