astro/dist/assets/build/remote.js

Astro is a modern site builder with web best practices, performance, and DX front-of-mind.

import CachePolicy from "http-cache-semantics";
import { fetchWithRedirects } from "../utils/redirectValidation.js";
export async function loadRemoteImage(src, fetchFn = globalThis.fetch, imageConfig = {
	remotePatterns: [],
	domains: []
}) {
	const res = await fetchWithRedirects({
		url: src,
		fetchFn,
		imageConfig
	});
	if (!res.ok) {
		throw new Error(`Failed to load remote image ${src}. The request did not return a 200 OK response. (received ${res.status}))`);
	}
	// calculate an expiration date based on the response's TTL
	const req = new Request(src);
	const policy = new CachePolicy(webToCachePolicyRequest(req), webToCachePolicyResponse(res));
	const expires = policy.storable() ? policy.timeToLive() : 0;
	return {
		data: Buffer.from(await res.arrayBuffer()),
		expires: Date.now() + expires,
		etag: res.headers.get("Etag") ?? undefined,
		lastModified: res.headers.get("Last-Modified") ?? undefined
	};
}
/**
* Revalidate a cached remote asset using its entity-tag or modified date.
* Uses the [If-None-Match](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/If-None-Match) and [If-Modified-Since](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/If-Modified-Since)
* headers to check with the remote server if the cached version of a remote asset is still up to date.
* The remote server may respond that the cached asset is still up-to-date if the entity-tag or modification time matches (304 Not Modified), or respond with an updated asset (200 OK)
* @param src - url to remote asset
* @param revalidationData - an object containing the stored Entity-Tag of the cached asset and/or the Last Modified time
* @returns An object containing the refreshed expiry time and cache headers. `data` will be a `Buffer` of the new image if the asset was modified (200 OK), or `null` if the cached version is still valid (304 Not Modified).
*/
export async function revalidateRemoteImage(src, revalidationData, fetchFn = globalThis.fetch, imageConfig = {
	remotePatterns: [],
	domains: []
}) {
	const headers = {
		...revalidationData.etag && { "If-None-Match": revalidationData.etag },
		...revalidationData.lastModified && { "If-Modified-Since": revalidationData.lastModified }
	};
	const req = new Request(src, {
		headers,
		cache: "no-cache"
	});
	const res = await fetchWithRedirects({
		url: src,
		headers: new Headers(headers),
		imageConfig,
		fetchFn
	});
	// Allow 304 Not Modified: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/304
	if (!res.ok && res.status !== 304) {
		if (res.status >= 300 && res.status < 400) {
			throw new Error(`Failed to revalidate cached remote image ${src}. The request was redirected.`);
		}
		throw new Error(`Failed to revalidate cached remote image ${src}. The request did not return a 200 OK / 304 NOT MODIFIED response. (received ${res.status} ${res.statusText})`);
	}
	const data = Buffer.from(await res.arrayBuffer());
	if (res.ok && !data.length) {
		// Server did not include body but indicated cache was stale
		return await loadRemoteImage(src, fetchFn, imageConfig);
	}
	// calculate an expiration date based on the response's TTL
	const policy = new CachePolicy(webToCachePolicyRequest(req), webToCachePolicyResponse(res.ok ? res : new Response(null, {
		status: 200,
		headers: res.headers
	})));
	const expires = policy.storable() ? policy.timeToLive() : 0;
	return {
		data: res.ok ? data : null,
		expires: Date.now() + expires,
		// While servers should respond with the same headers as a 200 response, if they don't we should reuse the stored value
		etag: res.headers.get("Etag") ?? (res.ok ? undefined : revalidationData.etag),
		lastModified: res.headers.get("Last-Modified") ?? (res.ok ? undefined : revalidationData.lastModified)
	};
}
function webToCachePolicyRequest({ url, method, headers }) {
	return {
		method,
		url,
		headers: Object.fromEntries(headers.entries())
	};
}
function webToCachePolicyResponse({ status, headers }) {
	return {
		status,
		headers: Object.fromEntries(headers.entries())
	};
}