script.js

const excelFile = document.getElementById('excelFile');
const errorDiv = document.getElementById('error');
const successDiv = document.getElementById('success');
const downloadBtn = document.getElementById('downloadBtn');
let generatedCSV = "";

excelFile.addEventListener('change', function (e) {
  clearMessages();
  generatedCSV = "";
  downloadBtn.disabled = true;

  const file = e.target.files[0];
  if (!file) return;

  const reader = new FileReader();

  reader.onload = function (evt) {
    try {
      const data = new Uint8Array(evt.target.result);
      const workbook = XLSX.read(data, { type: 'array' });
      const firstSheet = workbook.Sheets[workbook.SheetNames[0]];
      const rows = XLSX.utils.sheet_to_json(firstSheet, { header: 1 });

      if (rows.length < 2) throw new Error("Excel must have headers and at least one row.");

      function normalized(str) {
        return str.toString().replace(/\s+/g, "").toLowerCase();
      }
      const headers = rows[0].map(h => normalized(h));

      const emailIdx = headers.findIndex(h => h.includes("email"));
      const nameIdx = headers.findIndex(h => h.includes("name"));

      if (emailIdx === -1 || nameIdx === -1)
        throw new Error('Headers "email" and "name" are required.');

      const attrHeaders = headers
        .map((h, i) => ({ h, i }))
        .filter(x => x.i !== emailIdx && x.i !== nameIdx)
        .map(x => x.h);

      let csvLines = [];
      csvLines.push('email,name,attributes');

      for (let i = 1; i < rows.length; i++) {
        const row = rows[i];
        while (row.length < headers.length) row.push("");

        const email = (row[emailIdx] || "").toString().replace(/"/g, '""');
        const name = (row[nameIdx] || "").toString().replace(/"/g, '""');

        const attrsObj = {};
        attrHeaders.forEach(hdr => {
          const idx = headers.indexOf(hdr);
          let val = "";
          if (row[idx] !== undefined && row[idx] !== null) {
            val = row[idx].toString();
          }
          attrsObj[hdr] = val;
        });

        const attrPairs = Object.entries(attrsObj).map(([k, v]) =>
          `"${k}": "${v.replace(/"/g, '\\"')}"`
        );
        const attrJSONString = `{${attrPairs.join(", ")}}`.replace(/"/g, '""');

        csvLines.push(`"${email}","${name}","${attrJSONString}"`);
      }

      generatedCSV = csvLines.join("\r\n");
      downloadBtn.disabled = false;
      showSuccess("");
    } catch (err) {
      showError("Processing error: " + err.message);
    }
  };

  reader.onerror = function () {
    showError("Failed to read file.");
  };

  reader.readAsArrayBuffer(file);
});

downloadBtn.addEventListener('click', function () {
  if (!generatedCSV) return;

  try {
    const blob = new Blob([generatedCSV], { type: 'text/csv' });
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = "processed.csv";
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
    showSuccess("");
  } catch (err) {
    showError("Download error: " + err.message);
  }
});

function showError(msg) {
  errorDiv.textContent = msg;
  errorDiv.classList.remove('hidden');
  successDiv.classList.add('hidden');
}

function showSuccess(msg) {
  successDiv.textContent = msg;
  successDiv.classList.remove('hidden');
  errorDiv.classList.add('hidden');
}

function clearMessages() {
  errorDiv.textContent = "";
  successDiv.textContent = "";
  errorDiv.classList.add('hidden');
  successDiv.classList.add('hidden');
}