import { useEffect } from 'react';
import { toast } from 'react-toastify';
import { useAuth } from '../app/context/AuthProvider';
import { downloadExport, getExportFilename, startExportUpdates, subscribeExports } from '../api/exports';
import { downloadFile } from '../utils/downloadFile';
import { getApiErrorMessage } from '../utils/getApiErrorMessage';

export default function ExportJobs() {
	const { user, isAuthenticated } = useAuth();
	useEffect(() => {
		if (!isAuthenticated || !user?.id) return;
		let stopped = false;
		const processing = new Set();
		const handled = new Set();
		const toastIds = new Set();
		const key = (id) => `export-handled:${user.id}:${id}`;
		const wasHandled = (id) => {
			try { return handled.has(id) || Boolean(localStorage.getItem(key(id))); }
			catch { return handled.has(id); }
		};
		const markHandled = (id) => {
			handled.add(id);
			try { localStorage.setItem(key(id), String(Date.now())); } catch { /* Memory fallback. */ }
		};
		const showLoading = (id, message) => {
			toastIds.add(id);
			if (!toast.isActive(id)) toast.loading(message, { toastId: id, autoClose: false });
			else toast.update(id, { render: message, isLoading: true, autoClose: false });
		};
		const observe = async (job) => {
			if (stopped || wasHandled(job.id) || processing.has(job.id)) return;
			const toastId = `export:${user.id}:${job.id}`;
			if (['queued', 'processing'].includes(job.status)) {
				showLoading(toastId, 'Идёт формирование файла…');
				return;
			}
			processing.add(job.id);
			showLoading(toastId, 'Скачивание файла…');
			try {
				if (job.status === 'failed') throw new Error(job.error || 'Ошибка экспорта');
				const response = await downloadExport(job.id);
				if (stopped) return;
				await downloadFile(response, getExportFilename(job), 'xlsx');
				markHandled(job.id);
				toast.update(toastId, { render: 'Файл сформирован, скачивание началось', type: 'success', isLoading: false, autoClose: 3000 });
			} catch (error) {
				if (stopped) return;
				if (job.status === 'failed' || error?.response?.status === 410) markHandled(job.id);
				const message = await getApiErrorMessage(error, 'Не удалось скачать файл');
				if (!stopped) toast.update(toastId, { render: message, type: 'error', isLoading: false, autoClose: 5000 });
			} finally { processing.delete(job.id); }
		};
		const unsubscribe = subscribeExports((jobs) => { for (const job of jobs) void observe(job); });
		const stop = startExportUpdates();
		return () => {
			stopped = true;
			unsubscribe();
			stop();
			for (const id of toastIds) toast.dismiss(id);
		};
	}, [isAuthenticated, user?.id]);
	return null;
}