function getFilesDataTransferItems(dataTransferItems) {
    function traverseFileTreePromise(item, path = "", folder) {
        return new Promise(resolve => {
            if (item.isFile) {
                item.file(file => {
                    file.filepath = path + "/" + file.name; //save full path
                    folder.push(file);
                    resolve(file);
                });
            } else if (item.isDirectory) {
                let dirReader = item.createReader();
                dirReader.readEntries(entries => {
                    let entriesPromises = [];
                    let subfolder = [];
                    folder.push({ name: item.name, subfolder: subfolder });
                    for (let entry of entries)
                        entriesPromises.push(
                            traverseFileTreePromise(entry, path + "/" + item.name, subfolder)
                        );
                    resolve(Promise.all(entriesPromises));
                });
            }
        });
    }

    let files = [];
    return new Promise((resolve, reject) => {
        let entriesPromises = [];
        for (let it of dataTransferItems)
            entriesPromises.push(
                traverseFileTreePromise(it.webkitGetAsEntry(), "", files)
            );
        Promise.all(entriesPromises).then(entries => {
            resolve(files);
        });
    });
}

export function get_files_data_transfer_items(data_transfer_items) {
    return getFilesDataTransferItems(data_transfer_items);
}