작성 작업으로 Compose UI 확장

    /**
     * Compose trigger function that fires when the compose UI is
     * requested. Builds and returns a compose UI for inserting images.
     *
     * @param {event} e The compose trigger event object. Not used in
     *         this example.
     * @return {Card[]}
     */
    function getComposeUI(e) {
      return [buildComposeCard()];
    }

    /**
     * Build a card to display interactive buttons to allow the user to
     * update the subject, and To, Cc, Bcc recipients.
     *
     * @return {Card}
     */
    function buildComposeCard() {

      var card = CardService.newCardBuilder();
      var cardSection = CardService.newCardSection().setHeader('Update email');
      cardSection.addWidget(
          CardService.newTextButton()
              .setText('Update subject')
              .setOnClickAction(CardService.newAction()
                  .setFunctionName('applyUpdateSubjectAction')));
      cardSection.addWidget(
          CardService.newTextButton()
              .setText('Update To recipients')
              .setOnClickAction(CardService.newAction()
                  .setFunctionName('updateToRecipients')));
      cardSection.addWidget(
          CardService.newTextButton()
              .setText('Update Cc recipients')
              .setOnClickAction(CardService.newAction()
                  .setFunctionName('updateCcRecipients')));
      cardSection.addWidget(
          CardService.newTextButton()
              .setText('Update Bcc recipients')
              .setOnClickAction(CardService.newAction()
                  .setFunctionName('updateBccRecipients')));
      return card.addSection(cardSection).build();
    }

    /**
     * Updates the subject field of the current email when the user clicks
     * on "Update subject" in the compose UI.
     *
     * Note: This is not the compose action that builds a compose UI, but
     * rather an action taken when the user interacts with the compose UI.
     *
     * @return {UpdateDraftActionResponse}
     */
    function applyUpdateSubjectAction() {
      // Get the new subject field of the email.
      // This function is not shown in this example.
      var subject = getSubject();
      var response = CardService.newUpdateDraftActionResponseBuilder()
          .setUpdateDraftSubjectAction(CardService.newUpdateDraftSubjectAction()
              .addUpdateSubject(subject))
          .build();
      return response;
    }

    /**
     * Updates the To recipients of the current email when the user clicks
     * on "Update To recipients" in the compose UI.
     *
     * Note: This is not the compose action that builds a compose UI, but
     * rather an action taken when the user interacts with the compose UI.
     *
     * @return {UpdateDraftActionResponse}
     */
    function applyUpdateToRecipientsAction() {
      // Get the new To recipients of the email.
      // This function is not shown in this example.
      var toRecipients = getToRecipients();
      var response = CardService.newUpdateDraftActionResponseBuilder()
          .setUpdateDraftToRecipientsAction(CardService.newUpdateDraftToRecipientsAction()
              .addUpdateToRecipients(toRecipients))
          .build();
      return response;
    }

    /**
     * Updates the Cc recipients  of the current email when the user clicks
     * on "Update Cc recipients" in the compose UI.
     *
     * Note: This is not the compose action that builds a compose UI, but
     * rather an action taken when the user interacts with the compose UI.
     *
     * @return {UpdateDraftActionResponse}
     */
    function applyUpdateCcRecipientsAction() {
      // Get the new Cc recipients of the email.
      // This function is not shown in this example.
      var ccRecipients = getCcRecipients();
      var response = CardService.newUpdateDraftActionResponseBuilder()
          .setUpdateDraftCcRecipientsAction(CardService.newUpdateDraftCcRecipientsAction()
              .addUpdateToRecipients(ccRecipients))
          .build();
      return response;
    }

    /**
     * Updates the Bcc recipients  of the current email when the user clicks
     * on "Update Bcc recipients" in the compose UI.
     *
     * Note: This is not the compose action that builds a compose UI, but
     * rather an action taken when the user interacts with the compose UI.
     *
     * @return {UpdateDraftActionResponse}
     */
    function applyUpdateBccRecipientsAction() {
      // Get the new Bcc recipients of the email.
      // This function is not shown in this example.
      var bccRecipients = getBccRecipients();
      var response = CardService.newUpdateDraftActionResponseBuilder()
          .setUpdateDraftBccRecipientsAction(CardService.newUpdateDraftBccRecipientsAction()
              .addUpdateToRecipients(bccRecipients))
          .build();
      return response;
    }

    /**
     * Compose trigger function that fires when the compose UI is
     * requested. Builds and returns a compose UI for inserting images.
     *
     * @param {event} e The compose trigger event object. Not used in
     *         this example.
     * @return {Card[]}
     */
    function getInsertImageComposeUI(e) {
      return [buildImageComposeCard()];
    }

    /**
     * Build a card to display images from a third-party source.
     *
     * @return {Card}
     */
    function buildImageComposeCard() {
      // Get a short list of image URLs to display in the UI.
      // This function is not shown in this example.
      var imageUrls = getImageUrls();

      var card = CardService.newCardBuilder();
      var cardSection = CardService.newCardSection().setHeader('My Images');
      for (var i = 0; i < imageUrls.length; i++) {
        var imageUrl = imageUrls[i];
        cardSection.addWidget(
            CardService.newImage()
                .setImageUrl(imageUrl)
                .setOnClickAction(CardService.newAction()
                      .setFunctionName('applyInsertImageAction')
                      .setParameters({'url' : imageUrl})));
      }
      return card.addSection(cardSection).build();
    }

    /**
     * Adds an image to the current draft email when the image is clicked
     * in the compose UI. The image is inserted at the current cursor
     * location. If any content of the email draft is currently selected,
     * it is deleted and replaced with the image.
     *
     * Note: This is not the compose action that builds a compose UI, but
     * rather an action taken when the user interacts with the compose UI.
     *
     * @param {event} e The incoming event object.
     * @return {UpdateDraftActionResponse}
     */
    function applyInsertImageAction(e) {
      var imageUrl = e.parameters.url;
      var imageHtmlContent = '<img style=\"display: block\" src=\"'
           + imageUrl + '\"/>';
      var response = CardService.newUpdateDraftActionResponseBuilder()
          .setUpdateDraftBodyAction(CardService.newUpdateDraftBodyAction()
              .addUpdateContent(
                  imageHtmlContent,
                  CardService.ContentType.MUTABLE_HTML)
              .setUpdateType(
                  CardService.UpdateDraftBodyType.IN_PLACE_INSERT))
          .build();
      return response;
    }