import { type NotificationItem, parseNotificationEvent } from '$lib/utils/notifications';

export type { NotificationItem };

export function createNotificationStream() {
	let notifications = $state<NotificationItem[]>([]);
	let unreadCount = $state(0);
	let eventSource: EventSource | null = null;

	async function fetchNotifications(): Promise<void> {
		try {
			const res = await fetch('/api/notifications?size=10');
			if (res.ok) {
				const data = await res.json();
				notifications = data.content ?? [];
			}
		} catch (e) {
			console.error('Failed to fetch notifications', e);
		}
	}

	async function fetchUnreadCount(): Promise<void> {
		try {
			const res = await fetch('/api/notifications/unread-count');
			if (res.ok) {
				const data = await res.json();
				unreadCount = data.count;
			}
		} catch (e) {
			console.error('Failed to fetch unread count', e);
		}
	}

	async function markRead(notification: NotificationItem): Promise<void> {
		if (!notification.read) {
			try {
				await fetch(`/api/notifications/${notification.id}/read`, { method: 'PATCH' });
				notification.read = true;
				unreadCount = Math.max(0, unreadCount - 1);
			} catch (e) {
				console.error('Failed to mark notification as read', e);
			}
		}
	}

	async function markAllRead(): Promise<void> {
		try {
			await fetch('/api/notifications/read-all', { method: 'POST' });
			for (const n of notifications) {
				n.read = true;
			}
			unreadCount = 0;
		} catch (e) {
			console.error('Failed to mark all notifications as read', e);
		}
	}

	function init(): void {
		fetchUnreadCount();
		eventSource = new EventSource('/api/notifications/stream');
		eventSource.addEventListener('notification', (e) => {
			const notification = parseNotificationEvent(e.data);
			if (!notification) return;
			notifications = [notification, ...notifications];
			if (!notification.read) unreadCount += 1;
		});
		eventSource.onopen = () => {
			fetchUnreadCount();
		};
		eventSource.onerror = () => {
			// Close on error to avoid repeated reconnect noise
			eventSource?.close();
		};
	}

	function destroy(): void {
		eventSource?.close();
		eventSource = null;
	}

	return {
		get notifications() {
			return notifications;
		},
		get unreadCount() {
			return unreadCount;
		},
		fetchNotifications,
		fetchUnreadCount,
		markRead,
		markAllRead,
		init,
		destroy
	};
}