import { computed, effect, isSignal, signal, type Signal } from '@angular/core';
import type { SQLocal } from '../client.js';
import type { ReactiveQueryStatus, StatementInput } from '../types.js';

/**
 * A signal function for using reactive SQL queries in Angular components.
 * @see {@link https://sqlocal.dev/api/reactivequery#angular}
 */
export function useReactiveQuery<Result extends Record<string, any>>(
	db: SQLocal | Signal<SQLocal>,
	query: StatementInput<Result> | Signal<StatementInput<Result>>
): {
	data: Signal<Result[]>;
	error: Signal<Error | undefined>;
	status: Signal<ReactiveQueryStatus>;
} {
	const data = signal<Result[]>([]);
	const error = signal<Error | undefined>(undefined);
	const pending = signal<boolean>(true);

	const dbValue = computed(() => (isSignal(db) ? db() : db));
	const queryValue = computed(() => (isSignal(query) ? query() : query));

	effect(
		(onCleanup) => {
			const db = dbValue();
			const query = queryValue();

			pending.set(true);

			const subscription = db.reactiveQuery(query).subscribe(
				(results) => {
					data.set(results);
					error.set(undefined);
					pending.set(false);
				},
				(err) => {
					error.set(err);
				}
			);

			onCleanup(() => {
				subscription.unsubscribe();
			});
		},
		{ allowSignalWrites: true }
	);

	const status = computed<ReactiveQueryStatus>(() => {
		const hasError = !!error();
		const isPending = pending();
		if (hasError) return 'error';
		if (isPending) return 'pending';
		return 'ok';
	});

	return {
		data: data.asReadonly(),
		error: error.asReadonly(),
		status,
	};
}