How to use Google App Script to send a file using POST request

I want to use Google Apps Script to integrate a Google Sheets with an API

This is the documentation from the API service:

curl --location --request POST 'https://apinew.socialhub.pro/api/sendMessage' \
--form 'api_token="SEU API_TOKEN AQUI"' \
--form 'phone="NUMERO DESTINO"' \
--form 'file=@"DIRETÓRIO DO ARQUIVO"' \
--form 'message="MENSAGEM"'

I have manage to create a script in Google App Script that works perfectly:

function send_message_teste(telephone,message) {
  var url = "https://apinew.socialhub.pro/api/sendMessage";
  
  telephone = telephone.toString();
  
  let request = {
                  "api_token":"MY_TOKEN",
                  "phone":telephone,
                  "message":message
                };
                
  let resquest_body = JSON.stringify(request);

  let config = {
    muteHttpExceptions: true,
    method: "post",
    headers: {
      "Content-Type": "application/json"
    },
    payload:resquest_body
  };
               

  let response = UrlFetchApp.fetch(url, config);
  var data = JSON.parse(response.getContentText());
  
  return response
}

My problem is that I can not make this work with a file. The API documentation has only the curl example. I have manage to translate this example to Google App Script, but I got stuck when trying to send a file through the API. Can anyone help me?

I believe your goal is as follows.

• You want to convert the following curl command to Google Apps Script.

  curl --location --request POST 'https://apinew.socialhub.pro/api/sendMessage' \
  --form 'api_token="SEU API_TOKEN AQUI"' \
  --form 'phone="NUMERO DESTINO"' \
  --form 'file=@"DIRETÓRIO DO ARQUIVO"' \
  --form 'message="MENSAGEM"'
  

I thought that when I saw your curl command, the request is multipart/form-data. But, in your showing script, it seems that the value is sent ad JSON data. I thought that this might be the reason for your current issue. When this is reflected in a sample script, how about the following sample script?

Sample script:

Please set the file ID of your file on Google Drive to fileId.

function send_message_teste(telephone,message) {
  const fileId = "###"; // Please set your file ID of the file you want to upload.

  var url = "https://apinew.socialhub.pro/api/sendMessage";
  telephone = telephone.toString();
  let request = {
    "api_token": "MY_TOKEN",
    "phone": telephone,
    "message": message
  };
  const payload = { ...request, file: DriveApp.getFileById(fileId).getBlob() };
  let config = { muteHttpExceptions: true, payload };
  let response = UrlFetchApp.fetch(url, config);
  var data = JSON.parse(response.getContentText());
  return response;
}

• When payload is included, the POST method is automatically used.

Note:

• I think that the request of this modified script is the same with the above curl command. But, if an error occurs, please confirm your values of request and fileId, again.

• If the structure of multipart/form-data of this modified script cannot be used in your API, this Google Apps Script library might be able to be used. Ref (Author: me)

Reference:

• fetch(url, params)