exportGmailMessage

/**
 * Exports a Gmail message as PDF (and optionally attachments)
 * @param {int} recordNum Internal tracking number (to group messages and attachments together)
 * @param {String} messageID GmailMessage id
 * @param {String} userAccount Email address of person exporting
 * @param {String} userAccountName Full name of person exporting
 * @param {boolean} [includeAttachments=true] Whether to also save attachments (in original format)
 * @param {Folder} [targetFolder] Folder to save PDF and attachments to.  By default root folder ('My Drive')
 * @return {File[]} resultArray Files generated
 *
 *     Files will be created in targetFolder
 *     <recordNum>-0 <date>.pdf - GmailMessage body & headers
 *     <recordNum>-N <filename>.<ext> - attachments
 *
 */ 
function exportGmailMessage(recordNum,messageID,userAccount,userAccountName,includeAttachments,targetFolder){
  targetFolder = targetFolder || DriveApp.getRootFolder(); // targetFolder should be required, but putting this here until I figure out a better error response
  includeAttachments = includeAttachments || true;
  
  var resultArray = [];
  
  var htmlT = HtmlService.createTemplateFromFile("ToFile_GmailPrintTemplate");
  htmlT.gmailAccount = userAccount;
  htmlT.gmailAccountName = userAccountName;
  
  var originalMessageObject = GmailApp.getMessageById(messageID);

  var preppedMessageObject = prepMessageObject(originalMessageObject);
  /* prepMessageObject() basically does a few things the Gmail WebUI does intuitively - subject is (no subject) and in-line images are in body of message instead of an attachment */

  htmlT.retrievedMessageObject = preppedMessageObject;

  if(includeAttachments){
    var atts = preppedMessageObject.cleanAttachments;
    for(var i=0;i<atts.length;i++){
       var result = DriveApp.createFile(atts[i]);
      targetFolder.addFile(result);
      resultArray.push(result);
    var originalName = result.getName();
    result.setName(recordNum + "-" + (i+1) + " - " + originalName);
    result.setDescription("Exported from Gmail, user " + userAccountName + "(" + userAccount + ")");
    }
  }
  var htmlFile = htmlT.evaluate().getAs("text/html");

  
  var rf = htmlFile.getAs("application/pdf");
  var result = DriveApp.createFile(rf);
  targetFolder.addFile(result);
  resultArray.push(result);
  result.setName(recordNum + "-0 - " + preppedMessageObject.messageObject.getDate() + ".pdf");
  result.setDescription("Exported from Gmail, user " + userAccountName + "(" + userAccount + ")");
  
  return resultArray;
  
}