function sendMessage() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var setupSheet = ss.getSheetByName('setup_freshchat');

  // Fetch sheet names from column H on the "setup_freshchat" sheet
  var sheetNames = setupSheet.getRange('H2:H' + setupSheet.getLastRow()).getValues().flat().filter(String);

  var reportSheet = ss.getSheetByName('wa_blast_report');

  // Fetch template and language settings
  var languageCode = setupSheet.getRange('B1').getValue();
  var headerType = setupSheet.getRange('B2').getValue();
  var customParamsConditions = setupSheet.getRange('B3:B7').getValues().flat();
  var bodyParamsKeys = setupSheet.getRange('C3:C7').getValues().flat();

  // Fetch column letters from setup_freshchat
  var phoneNumberColumn = setupSheet.getRange('O2').getValue();
  var statusColumn = setupSheet.getRange('L2').getValue();
  var templateNameColumn = setupSheet.getRange('M2').getValue();
  var mediaUrlColumn = setupSheet.getRange('N2').getValue();

  // Log the column letters
  Logger.log('Phone Number Column: ' + phoneNumberColumn);
  Logger.log('Status Column: ' + statusColumn);
  Logger.log('Template Name Column: ' + templateNameColumn);
  Logger.log('Media URL Column: ' + mediaUrlColumn);

  // Convert column letters to zero-based indices
  var phoneNumberIndex = letterToColumnIndex(phoneNumberColumn);
  var statusIndex = letterToColumnIndex(statusColumn);
  var templateNameIndex = letterToColumnIndex(templateNameColumn);
  var mediaUrlIndex = letterToColumnIndex(mediaUrlColumn);

  // Log the column indices
  Logger.log('Phone Number Index: ' + phoneNumberIndex);
  Logger.log('Status Index: ' + statusIndex);
  Logger.log('Template Name Index: ' + templateNameIndex);
  Logger.log('Media URL Index: ' + mediaUrlIndex);

  var reportRows = [];

  sheetNames.forEach(function(sheetName) {
    var sheet = ss.getSheetByName(sheetName);
    if (!sheet) return;

    var lastRow = sheet.getLastRow();
    var columns = [phoneNumberIndex, statusIndex, templateNameIndex, mediaUrlIndex];
    var minColumn = Math.min.apply(null, columns) + 1;
    var maxColumn = Math.max.apply(null, columns) + 1;

    // Log the range details
    Logger.log('Sheet Name: ' + sheetName);
    Logger.log('Last Row: ' + lastRow);
    Logger.log('Min Column: ' + minColumn);
    Logger.log('Max Column: ' + maxColumn);

    var dataRange = sheet.getRange(2, minColumn, lastRow - 1, maxColumn - minColumn + 1);
    var dataValues = dataRange.getValues();

    var statusUpdates = dataValues.map(row => [row[statusIndex - minColumn + 1]]);

    dataValues.forEach((row, index) => {
      var phoneNumber = row[phoneNumberIndex - minColumn + 1];
      var status = row[statusIndex - minColumn + 1];
      var templateName = row[templateNameIndex - minColumn + 1];
      var mediaUrl = row[mediaUrlIndex - minColumn + 1];

      if (status === "Ready") {
        try {
          // Construct bodyParams based on "Custom" condition
          var bodyParams = constructBodyParams(bodyParamsKeys, customParamsConditions, index + 2, sheet);

          var payload = {
            "from": { "phone_number": "[YOUR PHONE NUMBER]" },
            "provider": "whatsapp",
            "to": [{ "phone_number": "+" + String(phoneNumber).trim() }],
            "data": {
              "message_template": {
                "storage": "none",
                "template_name": templateName,
                "namespace": "[YOUR NAMESPACE]",
                "language": {
                  "policy": "deterministic",
                  "code": languageCode
                },
                "rich_template_data": {}
              }
            }
          };

          // Add header only if headerType is not empty
          if (headerType) {
            payload.data.message_template.rich_template_data.header = {
              "type": headerType,
              "media_url": mediaUrl
            };
          }

          // Add body params only if they exist
          if (bodyParams.length > 0) {
            payload.data.message_template.rich_template_data.body = {
              "params": bodyParams
            };
          }

          var options = {
            "method": "post",
            "contentType": "application/json",
            "headers": {
              "Authorization": "[YOUR API KEY]"
            },
            "payload": JSON.stringify(payload),
            "muteHttpExceptions": true
          };

          var response = UrlFetchApp.fetch("https://api.freshchat.com/v2/outbound-messages/whatsapp", options);
          var result = JSON.parse(response.getContentText());

          Logger.log(result); // Log the full result to understand the response structure

          if (result.request_id) {
            reportRows.push([new Date(), phoneNumber, templateName, "Success"]);
            statusUpdates[index] = ["Done"];
          } else {
            reportRows.push([new Date(), phoneNumber, templateName, "Failed"]);
            statusUpdates[index] = ["Failed"];
            Logger.log("Error: " + result.error_message || "Undefined error message");
          }
        } catch (e) {
          reportRows.push([new Date(), phoneNumber, templateName, "Failed"]);
          statusUpdates[index] = ["Failed"];
          Logger.log("Error: " + e.toString());
        }
      }
    });

    if (reportRows.length > 0) {
      reportSheet.getRange(reportSheet.getLastRow() + 1, 1, reportRows.length, 4).setValues(reportRows);
    }

    sheet.getRange('I2:I' + lastRow).setValues(statusUpdates);
  });
}

function constructBodyParams(bodyParamsKeys, customParamsConditions, rowIndex, sheet) {
  var bodyParams = [];
  bodyParamsKeys.forEach((key, index) => {
    if (customParamsConditions[index] === "Custom") {
      bodyParams.push({ "data": key });
    } else {
      var columnLetter = customParamsConditions[index].split(' ')[1]; // Extracts column letter
      if(columnLetter) {
        try {
          var value = sheet.getRange(columnLetter + rowIndex).getValue();
          if (value) {
            bodyParams.push({ "data": value });
          }
        } catch(e) {
          Logger.log('Error accessing cell for column ' + columnLetter + ' in row ' + rowIndex + ': ' + e.toString());
        }
      }
    }
  });
  return bodyParams;
}

function letterToColumnIndex(letter) {
  var columnIndex = 0;
  var letters = letter.replace('Column ', '').toUpperCase();
  for (var i = 0; i < letters.length; i++) {
    columnIndex = columnIndex * 26 + (letters.charCodeAt(i) - 'A'.charCodeAt(0)) + 1;
  }
  return columnIndex - 1; // Convert to zero-based index
}