const EventEmitter = require('events');
const { arrayToHex } = require('./utils');

class FileSender extends EventEmitter {
  constructor(file) {
    super();
    this.file = file;
    this.iv = window.crypto.getRandomValues(new Uint8Array(12));
    this.uploadXHR = new XMLHttpRequest();
  }

  static delete(fileId, token) {
    return new Promise((resolve, reject) => {
      if (!fileId || !token) {
        return reject();
      }
      const xhr = new XMLHttpRequest();
      xhr.open('post', '/delete/' + fileId, true);
      xhr.setRequestHeader('Content-Type', 'application/json');

      xhr.onreadystatechange = () => {
        if (xhr.readyState === XMLHttpRequest.DONE) {
          resolve();
        }
      };

      xhr.send(JSON.stringify({ delete_token: token }));
    });
  }

  cancel() {
    this.uploadXHR.abort();
  }

  upload() {
    const self = this;
    self.emit('loading');
    return Promise.all([
      window.crypto.subtle.generateKey(
        {
          name: 'AES-GCM',
          length: 128
        },
        true,
        ['encrypt', 'decrypt']
      ),
      new Promise((resolve, reject) => {
        const reader = new FileReader();
        reader.readAsArrayBuffer(this.file);
        reader.onload = function(event) {
          const plaintext = new Uint8Array(this.result);
          resolve(plaintext);
        };
        reader.onerror = function(err) {
          reject(err);
        };
      })
    ])
      .then(([secretKey, plaintext]) => {
        self.emit('encrypting');
        return Promise.all([
          window.crypto.subtle.encrypt(
            {
              name: 'AES-GCM',
              iv: this.iv,
              tagLength: 128
            },
            secretKey,
            plaintext
          ),
          window.crypto.subtle.exportKey('jwk', secretKey)
        ]);
      })
      .then(([encrypted, keydata]) => {
        return new Promise((resolve, reject) => {
          const file = this.file;
          const fileId = arrayToHex(this.iv);
          const dataView = new DataView(encrypted);
          const blob = new Blob([dataView], { type: file.type });
          const fd = new FormData();
          fd.append('data', blob, file.name);

          const xhr = self.uploadXHR;

          xhr.upload.addEventListener('progress', e => {
            if (e.lengthComputable) {
              self.emit('progress', [e.loaded, e.total]);
            }
          });

          xhr.onreadystatechange = () => {
            if (xhr.readyState === XMLHttpRequest.DONE) {
              if (xhr.status === 200) {
                const responseObj = JSON.parse(xhr.responseText);
                return resolve({
                  url: responseObj.url,
                  fileId: responseObj.id,
                  secretKey: keydata.k,
                  deleteToken: responseObj.delete
                });
              }
              reject(xhr.status);
            }
          };

          xhr.open('post', '/upload', true);
          xhr.setRequestHeader(
            'X-File-Metadata',
            JSON.stringify({
              id: fileId,
              filename: encodeURIComponent(file.name)
            })
          );
          xhr.send(fd);
        });
      });
  }
}

module.exports = FileSender;