import type { PlanInterface, PlanItemInterface } from "./interfaces/index.js";
import type { ContentProviderInterface } from "./contentProviders/ContentProvider.js";
import { LessonsContentProvider } from "./contentProviders/LessonsContentProvider.js";
export declare class PlanHelper {
    private static providers;
    static registerProvider(provider: ContentProviderInterface): void;
    static replaceProvider(provider: ContentProviderInterface): void;
    static populate(plan: PlanInterface, planItems: PlanItemInterface[]): Promise<PlanItemInterface[]>;
    private static flattenItems;
    private static attachContent;
    static getLessonsProvider(): LessonsContentProvider;
    /** Format seconds as MM:SS string. */
    static formatTime(seconds: number): string;
    /** Calculate total duration of a section's children. */
    static getSectionDuration(section: PlanItemInterface): number;
}
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