ketting/dist/middlewares/cache.js

Opinionated HATEOAS / Rest client.

import { isSafeMethod } from '../http/util.js';
import LinkHeader from 'http-link-header';
import { resolve } from '../util/uri.js';
/**
 * This middleware manages the cache based on information in requests
 * and responses.
 *
 * It expires items from the cache and updates the cache if `Content-Location`
 * appeared in the response.
 *
 * It's also responsible for emitting 'stale' events.
 */
export default function (client) {
    return async (request, next) => {
        /**
         * Prevent a 'stale' event from being emitted, but only for the main
         * uri
         */
        let noStaleEvent = false;
        if (request.headers.has('X-KETTING-NO-STALE')) {
            noStaleEvent = true;
            request.headers.delete('X-KETTING-NO-STALE');
        }
        const response = await next(request);
        if (isSafeMethod(request.method)) {
            return response;
        }
        if (!response.ok) {
            // There was an error, no cache changes
            return response;
        }
        // We just processed an unsafe method, lets notify all subsystems.
        const stale = [];
        const deleted = [];
        if (request.method === 'DELETE') {
            deleted.push(request.url);
        }
        else if (!noStaleEvent) {
            stale.push(request.url);
        }
        // If the response had a Link: rel=invalidate header, we want to
        // expire those too.
        if (response.headers.has('Link')) {
            for (const httpLink of LinkHeader.parse(response.headers.get('Link')).rel('invalidates')) {
                const uri = resolve(request.url, httpLink.uri);
                stale.push(uri);
            }
        }
        // Location headers should also expire
        if (response.headers.has('Location')) {
            stale.push(resolve(request.url, response.headers.get('Location')));
        }
        client.clearResourceCache(stale, deleted);
        // If the response had a 'Content-Location' header, it means that the
        // response body is the _new_ state for the url in the content-location
        // header, so we store it!
        if (request.cache !== 'no-store' && response.headers.has('Content-Location')) {
            const cl = resolve(request.url, response.headers.get('Content-Location'));
            const clState = await client.getStateForResponse(cl, response.clone());
            client.cacheState(clState);
        }
        return response;
    };
}
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