/* Based on https://gist.github.com/Ferrari/9678772 */

function parseEmailMessages(start) {
  start = start || 0;

  var threads = GmailApp.getInboxThreads(start, 100);
  var sheet = SpreadsheetApp.getActiveSheet();

  for (var i = 0; i < threads.length; i++) {
    // Get the first email message of a threads
    var tmp,
      message = threads[i].getMessages()[0],
      subject = message.getSubject(),
      content = message.getPlainBody();

    // Get the plain text body of the email message
    // You may also use getRawContent() for parsing HTML

    // Implement Parsing rules using regular expressions
    if (content) {
      tmp = content.match(/Name:\s*([A-Za-z0-9\s]+)(\r?\n)/);
      var username = tmp && tmp[1] ? tmp[1].trim() : 'No username';

      tmp = content.match(/Email:\s*([A-Za-z0-9@.]+)/);
      var email = tmp && tmp[1] ? tmp[1].trim() : 'No email';

      tmp = content.match(/Comments:\s*([\s\S]+)/);
      var comment = tmp && tmp[1] ? tmp[1] : 'No comment';

      sheet.appendRow([username, email, subject, comment]);
    } // End if
  } // End for loop
}