import { goto } from '$app/navigation';

/**
 * Resolve-callback factory for `use:enhance`.
 *
 * Follows `result.type === 'redirect'` automatically (actions like login,
 * billing portal, and logged-out pricing choose throw redirects), then hands
 * everything else to the optional handler — falling back to the default
 * `update()` when none is given.
 *
 * Usage:
 *   <form method="POST" use:enhance={handleResult(({ result }) => {...})}>
 *   <form method="POST" use:enhance={handleResult()}>
 */
export function handleResult(
	handler?: (ctx: { result: any; update: () => Promise<void> }) => Promise<void>
) {
	return async ({ result, update }: any) => {
		if (result?.type === 'redirect') {
			const target = String(result.location);
			const isExternal = /^https?:\/\//i.test(target) && !target.startsWith(window.location.origin);
			if (isExternal) {
				window.location.assign(target);
			} else {
				await goto(target);
			}
			return;
		}
		if (result?.type === 'error') {
			// Unhandled server exception — never let these vanish silently.
			const { notices } = await import('$lib/stores/notices.svelte');
			notices.error('Something went wrong', result.error?.message || 'Internal error.');
			return;
		}
		if (handler) await handler({ result, update });
		else await update();
	};
}