Angularjs - downloading a file in a specific location - angularjs

Question

here is the situation.
I have an angular app that need to be used via a machine on wich you can put an USB key.
Several exports are possible from the corresponding backend and thoses exports (pdf, csv or rtf) need to be downloaded directly on the key, without asking the user.
Furthermore I need to be able to detect if the key is not present and show an error.
I don't think that it is doable using only angular with chromium.
I was thinking of making a local nodejs server on each machine that could access the filesystem for that. It works when using postman with form-data, but I don't know how I can pass a file donwloaded in angular to the nodejs server as a formdata, I keep getting incorrect pdf files.
TLDR :
I need to be able to have a chain like this :
get file from backend in angular
post a request to local (nodejs) server with the downloaded file
receive the file in nodejs to save it on disk
I am open to other ideas if this one doesn't work, as long as I can download this file I am happy.
current nodejs code, that works when i post the file using postman :
router.post('/save', function(req, res, next) {
console.log('savexvbxc');
var fstream;
//test if USB key is available
fs.stat(basePath, function(err, stats) {
if (err) {
console.log('error, key not present');
res.send(412, 'FAILURE');
}
var filename = basePath + 'toti.pdf';
console.log('filename is ' + filename);
if (req.busboy) {
console.log('busboy loaded');
req.busboy.on('file', function(fieldName, fileStream, fileName, encoding, mimeType) {
console.log('Saving: ' + filename + ' ' + fileName);
fstream = fs.createWriteStream(filename);
fileStream.pipe(fstream);
fstream.on('close', function() {
console.log('successfully saved ' + filename);
res.status(200).send('SUCCESS');
});
fstream.on('error', function(error) {
console.log('failed saved ' + filename);
console.log(error);
res.send(500, 'FAILURE');
});
});
req.busboy.on('error', function(error) {
console.log('failed saved ' + filename);
console.log(error);
res.send(500, 'FAILURE');
});
return req.pipe(req.busboy);
} else {
console.log('error, busboy not loaded');
res.send(500, 'FAILURE');
}
});
});
current angular code that do not work:
var dlReq = {
method: 'GET',
url: '/fep/documents/TVFI_FEP_0015_SFS_Specifications_Fonctionnelles_Detaillees_V00.9.pdf',
headers: {
'Content-Type': 'application/pdf',
'Accept': 'http://localhost:4000/fep/documents/TVFI_FEP_0015_SFS_Specifications_Fonctionnelles_Detaillees_V00.9.pdf'
},
responseType: 'arraybuffer'
};
$http(dlReq).then(function(data, status, headers, config) {
console.log(resp);
var file = new Blob([(resp)], {type: 'application/pdf'});
var formdata = new FormData();
formdata.append('file', file);
var request = {
method: 'POST',
url: 'http://localhost:4080/save',
data: formdata,
headers: {
'Content-Type': undefined,
'Accept': '*/*'
}
};
// SEND THE FILES.
$http(request)
.success(function(d) {
console.log('ok', d);
})
.error(function() {
console.log('fail');
});
});
Thank you