storage.js

const conf = require('./config.js');
const fs = require('fs');
const AWS = require('aws-sdk');

if (conf.s3_bucket) {
  const bucket = new AWS.S3({ params: { Bucket: conf.s3_bucket } });
  module.exports = {
    length: function(id) {
      return bucket.headObject({ Key: id }).promise();
    },
    get: function(id) {
      return bucket.getObject({ Key: id }).createReadStream();
    },
    set: function(id, stream) {
      return bucket.upload({ Key: id, Body: stream }).promise();
    },
    del: function(id) {
      return bucket.deleteObject({ Key: id }).promise();
    }
  };
} else {
  module.exports = {
    length: function(id) {},
    get: function(id) {},
    set: function(id, stream) {},
    del: function(id) {}
  };
}