const FOLDER_ID = ''; // Optional: paste your Drive folder ID here

// Navigate nested path like "Activations/Vendor Name", creating folders as needed
function getOrCreateFolder(root, path, create) {
  var parts = path.split('/').filter(function(p){ return p.trim(); });
  var dest = root;
  for (var i = 0; i < parts.length; i++) {
    var it = dest.getFoldersByName(parts[i]);
    if (it.hasNext()) {
      dest = it.next();
    } else if (create) {
      dest = dest.createFolder(parts[i]);
    } else {
      return null; // folder doesn't exist and we're not creating
    }
  }
  return dest;
}

function doPost(e) {
  try {
    var data = JSON.parse(e.postData.contents);
    var root = FOLDER_ID ? DriveApp.getFolderById(FOLDER_ID) : DriveApp.getRootFolder();

    // LIST FILES (Sync action) 
    if (data.action === 'listFolderFiles') {
      var folder = data.subfolder ? getOrCreateFolder(root, data.subfolder, false) : root;
      if (!folder) {
        return ContentService.createTextOutput(JSON.stringify({
          success: true, files: [], folderUrl: null
        })).setMimeType(ContentService.MimeType.JSON);
      }
      var files = [];
      var it = folder.getFiles();
      while (it.hasNext()) {
        var f = it.next();
        files.push({
          id:   f.getId(),
          name: f.getName(),
          url:  'https://drive.google.com/file/d/' + f.getId() + '/view'
        });
      }
      return ContentService.createTextOutput(JSON.stringify({
        success: true, files: files, folderUrl: folder.getUrl()
      })).setMimeType(ContentService.MimeType.JSON);
    }

    // UPLOAD FILE (default action) 
    var dest = data.subfolder ? getOrCreateFolder(root, data.subfolder, true) : root;
    var parts = data.fileData.split(',');
    var b64   = parts[1] || parts[0];
    var mime  = data.mimeType || 'application/octet-stream';
    var blob  = Utilities.newBlob(Utilities.base64Decode(b64), mime, data.fileName);
    var file  = dest.createFile(blob);
    file.setSharing(DriveApp.Access.ANYONE_WITH_LINK, DriveApp.Permission.VIEW);

    return ContentService.createTextOutput(JSON.stringify({
      success:  true,
      id:       file.getId(),
      name:     file.getName(),
      url:      'https://drive.google.com/file/d/' + file.getId() + '/view',
      preview:  'https://drive.google.com/file/d/' + file.getId() + '/preview',
      download: 'https://drive.google.com/uc?export=download&id=' + file.getId()
    })).setMimeType(ContentService.MimeType.JSON);

  } catch(err) {
    return ContentService.createTextOutput(
      JSON.stringify({ success: false, error: err.toString() })
    ).setMimeType(ContentService.MimeType.JSON);
  }
}