a few changes to make A/B testing easier

frontend/src/fileReceiver.js

@@ -1,80 +0,0 @@
-import EventEmitter from 'events';
-import { hexToArray } from './utils';
-
-export default class FileReceiver extends EventEmitter {
-  constructor(url, k) {
-    super();
-    this.key = window.crypto.subtle.importKey(
-      'jwk',
-      {
-        k,
-        kty: 'oct',
-        alg: 'A128GCM',
-        ext: true
-      },
-      {
-        name: 'AES-GCM'
-      },
-      false,
-      ['decrypt']
-    );
-    this.url = url;
-  }
-
-  downloadFile() {
-    return new Promise((resolve, reject) => {
-      const xhr = new XMLHttpRequest();
-
-      xhr.onprogress = event => {
-        if (event.lengthComputable && event.target.status !== 404) {
-          this.emit('progress', [event.loaded, event.total]);
-        }
-      };
-
-      xhr.onload = function(event) {
-        if (xhr.status === 404) {
-          reject(new Error('notfound'));
-          return;
-        }
-
-        const blob = new Blob([this.response]);
-        const meta = JSON.parse(xhr.getResponseHeader('X-File-Metadata'));
-        const fileReader = new FileReader();
-        fileReader.onload = function() {
-          resolve({
-            data: this.result,
-            name: meta.filename,
-            type: meta.mimeType,
-            iv: meta.id
-          });
-        };
-
-        fileReader.readAsArrayBuffer(blob);
-      };
-
-      xhr.open('get', this.url);
-      xhr.responseType = 'blob';
-      xhr.send();
-    });
-  }
-
-  async download() {
-    const key = await this.key;
-    const file = await this.downloadFile();
-    this.emit('decrypting');
-    const plaintext = await window.crypto.subtle.decrypt(
-      {
-        name: 'AES-GCM',
-        iv: hexToArray(file.iv),
-        tagLength: 128
-      },
-      key,
-      file.data
-    );
-    return {
-      plaintext,
-      name: decodeURIComponent(file.name),
-      type: file.type
-    };
-  }
-}