/* global gapi */

const SIZE = {
  UNSPECIFIED: 'THUMBNAIL_SIZE_UNSPECIFIED',
  LARGE: 'LARGE',
  MEDIUM: 'MEDIUM',
  SMALL: 'SMALL',
};

const IMAGE_SIZE = SIZE.SMALL;
const MAX_SLIDE_COUNT = 3;

const getSlideObjects = (presentationId) => {
  return new Promise((resolve, reject) => {
    gapi.client.slides.presentations
      .get({
        presentationId,
        fields: 'slides/objectId',
      })
      .then(({ result }) => {
        const pageObjects = result.slides.map(({ objectId }) => objectId);
        resolve(pageObjects.slice(0, MAX_SLIDE_COUNT));
      })
      .catch((err) => reject(err));
  });
};

const getThumbnailUrl = (presentationId, pageObjectId) => {
  return new Promise((resolve, reject) => {
    gapi.client.slides.presentations.pages
      .getThumbnail({
        presentationId,
        pageObjectId,
        'thumbnailProperties.mimeType': 'PNG',
        'thumbnailProperties.thumbnailSize': IMAGE_SIZE,
      })
      .then(({ result }) => {
        resolve(result.contentUrl);
      })
      .catch((err) => {
        reject(err);
      });
  });
};

const getImageLinks = (presentationId) => {
  return new Promise((resolve, reject) => {
    getSlideObjects(presentationId)
      .then((pageObjects) => {
        return pageObjects.map((pageObjectId) => {
          return getThumbnailUrl(presentationId, pageObjectId);
        });
      })
      .then((thumbnailUrls) => {
        return Promise.all(thumbnailUrls);
      })
      .then((fileUrls) => resolve(fileUrls.filter((url) => url)))
      .catch((err) => reject(err));
  });
};

export default getImageLinks;