apps/newsletters-api/src/services/image/image-signer.ts

import { format } from '@guardian/image';
import type {
	NewsletterData,
	NewsletterDataWithoutMeta,
} from '@newsletters-nx/newsletters-data-client';
import { getConfigValue } from '@newsletters-nx/util';

interface Props {
	dpr?: number;
	width: number;
}

export const signImage = async (
	src: string,
	{ width = 650, dpr = 2 }: Props,
): Promise<string> => {
	const salt = await getConfigValue('imageSalt');
	if (!salt) throw new Error(`imageSalt not found`);

	return format(src, salt, {
		quality: 85,
		dpr,
		width,
	});
};

export const signTemplateImages = async (
	newsletterData: NewsletterDataWithoutMeta,
): Promise<NewsletterData> => {
	let signedImages = {};
	const { renderingOptions } = newsletterData;
	if (!renderingOptions) return newsletterData;
	const { mainBannerUrl, subheadingBannerUrl, darkSubheadingBannerUrl } =
		renderingOptions;
	const imageKeyValueMapping = [
		{ key: 'mainBannerUrl', imageUrl: mainBannerUrl },
		{ key: 'subheadingBannerUrl', imageUrl: subheadingBannerUrl },
		{ key: 'darkSubheadingBannerUrl', imageUrl: darkSubheadingBannerUrl },
	];
	for await (const image of imageKeyValueMapping) {
		const { key, imageUrl } = image;
		if (imageUrl) {
			signedImages = shouldSignImage(imageUrl)
				? {
						...signedImages,
						[key]: await signImage(imageUrl, { dpr: 2, width: 650 }),
				  }
				: { ...signedImages, [key]: imageUrl };
		}
	}
	return {
		...newsletterData,
		renderingOptions: {
			...renderingOptions,
			...signedImages,
		},
	};
};

const supportedSigningDomains = ['uploads.guim.co.uk'];
export const shouldSignImage = (imageUrl: string): boolean => {
	const asUrl = new URL(imageUrl);
	return supportedSigningDomains.includes(asUrl.hostname);
};