addProduct () {

  if (this.productName === '' || this.category === '' || this.price === 0 || this.contactInformation === '' || this.productDetails === '' || this.files.length === 0) {
    this.$q.notify({
      icon: 'close',
      message: 'Fields can not be empty.',
      timeout: 800,
      color: 'negative',
      textColor: 'white',
      position: 'bottom-left'
    });
  } else {
    this.$q.dialog({
      title: 'Confirm',
      message: 'Are you sure you want to continue?',
      ok: {
        color: 'brown'
      },
      cancel: {
        color: 'brown',
        flat: true
      },
      persistent: true
    })
    .onOk(async () => {

      const docRef = await this.firebase.firestore().collection('products').add({
        productName: this.productName,
        category: this.category,
        price: this.price,
        contactInformation: this.contactInformation,
        productDetails: this.productDetails,
        displayName: this.user.displayName,
        phoneNumber: this.user.phoneNumber,
        uid: this.user.uid,
        createdAt: Date.now()
      });

      const images = [];
      for (const file of files) {
        const storageRef = this.firebase.storage().ref('products/' + this.user.uid + '/' + docRef.id + '/' + file.name);
        const snapshot = await storageRef.put(file);
        const downloadURL = await snapshot.ref.getDownloadURL();
        images.push(downloadURL);
      }

      const data = await this.firebase.firestore().collection('products').doc(docRef.id).update({
        images: images
      });

      this.$refs.uploader.$data.files = [];
      this.productName = ''
      this.category = ''
      this.price = 0
      this.contactInformation = ''
      this.productDetails = ''
      this.$q.notify({
        icon: 'check',
        message: 'You have successfully added.',
        timeout: 800,
        color: 'brown',
        textColor: 'white',
        position: 'bottom-left'
      });

    });
  }

}