import * as XLSX from "xlsx";

/**
 * Parse an Excel (.xlsx, .xls) or CSV file to an array of row objects.
 * Keys come from the first row (headers).
 */
export function parseSpreadsheet(file: File): Promise<Record<string, string>[]> {
  return new Promise((resolve, reject) => {
    const reader = new FileReader();
    reader.onload = (e) => {
      try {
        const data = new Uint8Array(e.target!.result as ArrayBuffer);
        const workbook = XLSX.read(data, { type: "array" });
        const sheetName = workbook.SheetNames[0];
        if (!sheetName) {
          resolve([]);
          return;
        }
        const sheet = workbook.Sheets[sheetName];
        if (!sheet) {
          resolve([]);
          return;
        }
        const rows = XLSX.utils.sheet_to_json<Record<string, string>>(sheet, {
          raw: false,
          defval: "",
        });
        resolve(rows);
      } catch (err) {
        reject(err);
      }
    };
    reader.onerror = () => reject(reader.error);
    reader.readAsArrayBuffer(file);
  });
}

export function isSpreadsheetFile(file: File): boolean {
  return (
    file.type === "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" ||
    file.type === "application/vnd.ms-excel" ||
    file.name.endsWith(".xlsx") ||
    file.name.endsWith(".xls") ||
    file.name.endsWith(".csv")
  );
}