var crypto = require('crypto');
var FormData = require('form-data');
var fetch = require('node-fetch');

function getFilename (req, file, cb) {
  crypto.pseudoRandomBytes(16, function (err, raw) {
    cb(err, err ? undefined : raw.toString('hex'));
  });
}

function getBucketTmp (req, file, cb) {
  cb(null, 'tmp');
}

function TalariaStorage(opts) {
  this.serviceUrl = opts.serviceUrl;
  if (!this.serviceUrl) {
    throw new Error('Missing `serviceUrl` options');
  }

  this.getFilename = (opts.filename || getFilename);
  if (typeof opts.bucket === 'string') {
    this.getBucket = ($0, $1, cb) => cb(null, opts.bucket);
  } else {
    this.getBucket = (opts.bucket || getBucketTmp);
  }
}

TalariaStorage.prototype._handleFile = function _handleFile (req, file, cb) {
  this.getBucket(req, file, (err, bucket) => {
    if (err) return cb(err);

    this.getFilename(req, file, (err, filename) => {
      if (err) return cb(err);

      var form = new FormData();
      form.append('bucket', bucket);
      form.append('file', file.stream, filename);

      fetch(this.serviceUrl, {
        method: 'POST',
        body: form,
      }).then(res => res.json())
        .then(result => cb(null, {
          bucket,
          filename,
          key: result.key,
          location: result.url,
        }))
        .catch(cb);
    });
  });
};

TalariaStorage.prototype._removeFile = function _removeFile (req, file, cb) {
  cb(null);
};

module.exports = function (opts) {
  return new TalariaStorage(opts);
};