Import Mails that have particular label

import_mails_from_a_particular_label.js

/**
 * Retrieves all the rows in the active spreadsheet that contain data and logs the
 * values for each row.
 * For more information on using the Spreadsheet API, see
 * https://developers.google.com/apps-script/service_spreadsheet
 */
function readRows() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var rows = sheet.getDataRange();
  var numRows = rows.getNumRows();
  var values = rows.getValues();

  for (var i = 0; i <= numRows - 1; i++) {
    var row = values[i];
    Logger.log(row);
  }
};

/**
 * Adds a custom menu to the active spreadsheet, containing a single menu item
 * for invoking the readRows() function specified above.
 * The onOpen() function, when defined, is automatically invoked whenever the
 * spreadsheet is opened.
 * For more information on using the Spreadsheet API, see
 * https://developers.google.com/apps-script/service_spreadsheet
 */
function onOpen(e) {
  SpreadsheetApp.getUi().createAddonMenu() // Or DocumentApp.
      .addItem('Import from a Label', 'getMailsForALabel')
      .addToUi();
}

function getMailsForALabel(labelToFetchMailsFor) {
  var sheet = SpreadsheetApp.getActiveSheet();
  var cursorPosition = sheet.getActiveCell();
  var row = cursorPosition.getRow();
  var column = cursorPosition.getColumn();
  //sheet.toast("Importing mails form the thread " + labelToFetchMailsFor);
  //var labelToFetchMailsFor = typeof labelToFetchMailsFor !== 'undefined' ? labelToFetchMailsFor : 'mailmerge';
  var labelToFetchMailsFor = Browser.inputBox("Enter the label you want to import from");
  var selectedLabel = GmailApp.getUserLabelByName(labelToFetchMailsFor);
  var threadsInLabel = selectedLabel.getThreads();
  var messagesArray = [];
  threadsInLabel.forEach(function(thread) {
    thread.getMessages().forEach(function(message){
      Logger.log(message.getPlainBody());
        messagesArray.push([message.getPlainBody()]);
    });
  });
  var destinationRange = sheet.getRange(row, column, messagesArray.length, 1);
  destinationRange.setValues(messagesArray);
  //sheet.toast("Finished importing mails from the label " + labelToFetchMailsFor);
}

function onInstall(e) {
  onOpen(e);
  // Perform additional setup as needed.
}