feat: add download functionality for upcoming projects report in Excel format

src/app/calendar/page.js

@@ -60,6 +60,7 @@ export default function ProjectCalendarPage() {
 	const [loading, setLoading] = useState(true);
 	const [currentDate, setCurrentDate] = useState(new Date());
 	const [viewMode, setViewMode] = useState('month'); // 'month' or 'upcoming'
+	const [downloading, setDownloading] = useState(false);
 
 	useEffect(() => {
 		fetch("/api/projects")
@@ -131,6 +132,37 @@ export default function ProjectCalendarPage() {
 			});
 	};
 
+	const handleDownloadReport = async () => {
+		setDownloading(true);
+		try {
+			const response = await fetch('/api/reports/upcoming-projects');
+			
+			if (!response.ok) {
+				throw new Error('Failed to download report');
+			}
+
+			// Get the blob from the response
+			const blob = await response.blob();
+			
+			// Create a download link
+			const url = window.URL.createObjectURL(blob);
+			const link = document.createElement('a');
+			link.href = url;
+			link.download = `nadchodzace_projekty_${new Date().toISOString().split('T')[0]}.xlsx`;
+			document.body.appendChild(link);
+			link.click();
+			
+			// Clean up
+			document.body.removeChild(link);
+			window.URL.revokeObjectURL(url);
+		} catch (error) {
+			console.error('Error downloading report:', error);
+			alert('Błąd podczas pobierania raportu');
+		} finally {
+			setDownloading(false);
+		}
+	};
+
 	const renderCalendarGrid = () => {
 		const monthStart = startOfMonth(currentDate);
 		const monthEnd = endOfMonth(currentDate);
@@ -383,6 +415,19 @@ export default function ProjectCalendarPage() {
 				</div>
 			</PageHeader>
 
+			<div className="mb-4 flex justify-end">
+				<button
+					onClick={handleDownloadReport}
+					disabled={downloading}
+					className="p-2 text-gray-600 hover:text-gray-900 hover:bg-gray-100 disabled:opacity-50 disabled:cursor-not-allowed rounded transition-colors"
+					title={downloading ? 'Pobieranie...' : 'Eksportuj raport nadchodzących projektów do Excel'}
+				>
+					<svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24" strokeWidth="2">
+						<path strokeLinecap="round" strokeLinejoin="round" d="M12 10v6m0 0l-3-3m3 3l3-3m2 8H7a2 2 0 01-2-2V5a2 2 0 012-2h5.586a1 1 0 01.707.293l5.414 5.414a1 1 0 01.293.707V19a2 2 0 01-2 2z" />
+					</svg>
+				</button>
+			</div>
+
 			{viewMode === 'month' ? renderCalendarGrid() : renderUpcomingView()}
 		</PageContainer>
 	);