export declare abstract class BaseResource<T = any> {
    protected resource: T;
    protected additionalData: Record<string, any>;
    constructor(resource: T);
    /**
     * Transform the resource into a plain object.
     * Must be implemented by child classes.
     */
    abstract toArray(): Record<string, any>;
    /**
     * Convert the resource to JSON, merging additional data.
     */
    toJSON(): Record<string, any>;
    /**
     * Conditionally include a value if condition is true.
     */
    protected when(condition: boolean, value: any, defaultValue?: any): any;
    /**
     * Include related resource only if relation is loaded (exists).
     * Handles both single object and array of objects.
     */
    protected whenLoaded<R>(relation: string, ResourceClass: new (resource: any) => BaseResource<R>): object | object[] | null;
    /**
     * Add extra data to merge into final output.
     */
    additional(data: Record<string, any>): this;
}