digitalfabrik/integreat-app

import { FeaturedImageModel } from 'shared/api'

const ten = 10
const roundToOneDecimal = (number: number) => Math.round(number * ten) / ten

/**
 * This converts a FeaturedImageModel to a srcset.
 * It's necessary to have a defaultWidth in px of the displayed image tag to compute the ratios for the different
 * screen densities.
 * @param featuredImage
 * @param defaultWidth
 * @returns {string}
 */
const featuredImageToSrcSet = (featuredImage: FeaturedImageModel, defaultWidth: number): string =>
  [featuredImage.thumbnail, featuredImage.medium, featuredImage.large, featuredImage.full]
    .map(({ url, width }) => `${encodeURI(url)} ${roundToOneDecimal(width / defaultWidth)}x`)
    .join(', ')

export default featuredImageToSrcSet