import { queryClient } from '$shared/api/queryClient';
import {
    QueryObserver,
    type QueryObserverOptions,
    type QueryObserverResult,
} from '@tanstack/query-core';

/**
 * Abstract base class for reactive Svelte 5 stores backed by TanStack Query.
 *
 * Provides a unified way to use TanStack Query observers within Svelte 5 classes
 * using runes for reactivity. Handles subscription lifecycle automatically.
 *
 * @template TData - The type of data returned by the query.
 * @template TError - The type of error that can be thrown.
 */
export abstract class BaseQueryStore<TData, TError = Error> {
    #result = $state<QueryObserverResult<TData, TError>>({} as QueryObserverResult<TData, TError>);
    #observer: QueryObserver<TData, TError>;
    #unsubscribe: () => void;

    constructor(options: QueryObserverOptions<TData, TError, TData, any, any>) {
        this.#observer = new QueryObserver(queryClient, options);
        this.#unsubscribe = this.#observer.subscribe(result => {
            this.#result = result;
        });
    }

    /**
     * Current query result (reactive)
     */
    protected get result(): QueryObserverResult<TData, TError> {
        return this.#result;
    }

    /**
     * Updates observer options dynamically.
     * Use this when query parameters or dependencies change.
     */
    protected updateOptions(options: QueryObserverOptions<TData, TError, TData, any, any>): void {
        this.#observer.setOptions(options);
    }

    /**
     * Cleans up the observer subscription.
     * Should be called when the store is no longer needed.
     */
    destroy(): void {
        this.#unsubscribe();
    }
}