Google Script - Auto signature

var signature = '';

//enter your label names here.
var labelForInboundEmails = 'New Inbound Email';
var labelToApplyAfterCreatingDraft = 'Waiting for your reply';
var yourEmailAddress = 'you@domain.com';

//-------------------------------------------------------------------------------------------------------------------//
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//    PURPOSE:                                                                                                       //
//    Automatically adds your signature to Gmail incoming emails, and sorts your inbox using a couple of labels      //
//    As Android gmail doesn't support HTML signatures, creating a draft via a google script is a workaround.        //
//                                                                                                                   //
//                                                                                                                   //
//    SETUP GUIDE:                                                                                                   //
//    1. Create the two labels on line 4 and 5 in your gmail (customise as you want), and set your email in line 6   //
//    2. Create a draft email, with the signature you want to apply, subject 'signature' (lowercase)                 //
//    3. Run 'getGmailSignature', and copy the entire output of the console "Info" to line 1's variable              //
//    4. Set up a gmail filter for "Includes the words: label:unread"                                                //
//    5. Have this filer apply the label you selected on line 4                                                      //
//    6. Set this script to run every x minutes in your "Triggers" tab on google scripts                             //
//    7. ??? emails will automatically get a new Draft                                                               //
//-------------------------------------------------------------------------------------------------------------------//
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//can run this if signature is changed, then paste the console output into the above var
function getGmailSignature() {
  //find a draft email with the subject 'signature'
  var draft = GmailApp.search("subject:signature label:draft", 0, 1);
  //print the body of that email to the console for copy/paste into line 1 var
  console.log(draft[0].getMessages()[0].getBody());
}

function createEmailDraft() {
  //find threads with the label
  const inboundThreads = GmailApp.search('label:"'+labelForInboundEmails+'"');
  //for each thread with that label, find all messages
  for (const thread of inboundThreads) {
    //get all messages in thread
    const messages = thread.getMessages();
    messageNum = 1;
    for (message of messages) {
      //if messageNum is the same as current count of messages create a draft
      if (messageNum === thread.getMessageCount()) {
        message.createDraftReply(
          '', //body
          {
            //set the htmlBody of the email to the var signature
            htmlBody: signature,
            from: yourEmailAddress
          }
        );
        //remove that label from this thread
        var inboundLabel = GmailApp.getUserLabelByName(labelForInboundEmails);
        thread.removeLabel(inboundLabel);
        var outboundLabel = GmailApp.getUserLabelByName(labelToApplyAfterCreatingDraft);
        thread.addLabel(outboundLabel);
      }
      messageNum = messageNum + 1;
    }
  }
  //this section removes the "labelToApplyAfterCreatingDraft" after replying
  const outboundThreads = GmailApp.search('label:"'+labelToApplyAfterCreatingDraft+'"');
  for (const thread of outboundThreads) {
    const messages = thread.getMessages();
    messageNum = 1;
    for (message of messages) {
      if (messageNum === thread.getMessageCount()) {
        if(message.getFrom().includes(yourEmailAddress) && !message.isDraft()) {
          var outboundLabel = GmailApp.getUserLabelByName(labelToApplyAfterCreatingDraft);
          thread.removeLabel(outboundLabel);
        }
      }
      messageNum = messageNum + 1;
    }
  }
}