fix: add download csv function

app/lib/download.ts

@@ -0,0 +1,72 @@
+/**
+ * Download data as CSV file.
+ *
+ * @param headers - Array of header names. If omitted and data is array of objects, keys will be taken from first object.
+ * @param data - Array of rows. Each row can be either an object (key -> value) or an array of values.
+ * @param filename - optional file name to use for downloaded file
+ * @param delimiter - csv delimiter (default is comma)
+ * @param addBOM - add UTF-8 BOM to the file to make Excel detect UTF-8 correctly
+ */
+export function downloadCsv(
+	headers: string[] | null,
+	data: Array<Record<string, any> | any[]>,
+	filename = 'data.csv',
+	delimiter = ',',
+	addBOM = true,
+) {
+	if (!Array.isArray(data) || data.length === 0) {
+		// still create an empty CSV containing only headers
+		const csvHeader = headers ? headers.join(delimiter) : '';
+		const csvString = addBOM ? '\uFEFF' + csvHeader : csvHeader;
+		const blob = new Blob([csvString], { type: 'text/csv;charset=utf-8;' });
+		const link = document.createElement('a');
+		link.href = URL.createObjectURL(blob);
+		link.setAttribute('download', filename);
+		document.body.appendChild(link);
+		link.click();
+		document.body.removeChild(link);
+		return;
+	}
+
+	// if headers not provided and rows are objects, take keys from first object
+	let _headers: string[] | null = headers;
+	if (!_headers) {
+		const firstRow = data[0];
+		if (typeof firstRow === 'object' && !Array.isArray(firstRow)) {
+			_headers = Object.keys(firstRow);
+		} else if (Array.isArray(firstRow)) {
+			// if rows are arrays and no headers provided, we won't add header row
+			_headers = null;
+		}
+	}
+
+	const escape = (val: unknown) => {
+		if (val === null || typeof val === 'undefined') return '';
+		const str = String(val);
+		const needsQuoting = str.includes(delimiter) || str.includes('\n') || str.includes('\r') || str.includes('"');
+		if (!needsQuoting) return str;
+		return '"' + str.replace(/"/g, '""') + '"';
+	};
+
+	const rows: string[] = data.map((row) => {
+		if (Array.isArray(row)) {
+			return row.map(escape).join(delimiter);
+		}
+		// object row - map using headers if available, otherwise use object values
+		if (_headers && Array.isArray(_headers)) {
+			return _headers.map(h => escape((row as Record<string, any>)[h])).join(delimiter);
+		}
+		return Object.values(row).map(escape).join(delimiter);
+	});
+
+	const headerRow = _headers ? _headers.join(delimiter) : null;
+	const csvString = (addBOM ? '\uFEFF' : '') + [headerRow, ...rows].filter(Boolean).join('\r\n');
+
+	const blob = new Blob([csvString], { type: 'text/csv;charset=utf-8;' });
+	const link = document.createElement('a');
+	link.href = URL.createObjectURL(blob);
+	link.setAttribute('download', filename);
+	document.body.appendChild(link);
+	link.click();
+	document.body.removeChild(link);
+}