114 lines
3.2 KiB
JavaScript
114 lines
3.2 KiB
JavaScript
const fetch = require('node-fetch');
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const fs = require('fs');
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const { URLSearchParams } = require('url');
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const crypto = require('crypto');
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const Response = require('./classes/response.js');
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const MemoryCache = require('./classes/caching/memory_cache.js');
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const CACHE_VERSION = 2;
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function md5(str) {
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return crypto.createHash('md5').update(str).digest('hex');
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}
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// Since the bounday in FormData is random,
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// we ignore it for purposes of calculating
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// the cache key.
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function getFormDataCacheKey(formData) {
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const cacheKey = { ...formData };
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if (typeof formData.getBoundary === 'function') {
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const boundary = formData.getBoundary();
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// eslint-disable-next-line no-underscore-dangle
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delete cacheKey._boundary;
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// eslint-disable-next-line no-underscore-dangle
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if (Array.isArray(cacheKey._streams)) {
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const boundaryReplaceRegex = new RegExp(boundary, 'g');
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// eslint-disable-next-line no-underscore-dangle
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cacheKey._streams = cacheKey._streams.map((s) => {
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if (typeof s === 'string') {
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return s.replace(boundaryReplaceRegex, '');
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}
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return s;
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});
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}
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}
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return cacheKey;
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}
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function getBodyCacheKeyJson(body) {
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if (!body) {
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return body;
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} if (typeof body === 'string') {
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return body;
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} if (body instanceof URLSearchParams) {
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return body.toString();
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} if (body instanceof fs.ReadStream) {
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return body.path;
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} if (body.toString && body.toString() === '[object FormData]') {
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return getFormDataCacheKey(body);
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}
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throw new Error('Unsupported body type');
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}
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function getCacheKey(requestArguments) {
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const resource = requestArguments[0];
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const init = requestArguments[1] || {};
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const resourceCacheKeyJson = typeof resource === 'string' ? { url: resource } : { ...resource };
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const initCacheKeyJson = { ...init };
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resourceCacheKeyJson.body = getBodyCacheKeyJson(resourceCacheKeyJson.body);
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initCacheKeyJson.body = getBodyCacheKeyJson(initCacheKeyJson.body);
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return md5(JSON.stringify([resourceCacheKeyJson, initCacheKeyJson, CACHE_VERSION]));
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}
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async function createRawResponse(fetchRes) {
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const buffer = await fetchRes.buffer();
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const rawHeaders = Array.from(fetchRes.headers.entries())
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.reduce((aggregate, entry) => ({ ...aggregate, [entry[0]]: entry[1] }), {});
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return {
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status: fetchRes.status,
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statusText: fetchRes.statusText,
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type: fetchRes.type,
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url: fetchRes.url,
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ok: fetchRes.ok,
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headers: rawHeaders,
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redirected: fetchRes.redirected,
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bodyBuffer: buffer,
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};
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}
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async function getResponse(cache, requestArguments) {
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const cacheKey = getCacheKey(requestArguments);
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const cachedValue = await cache.get(cacheKey);
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const ejectSelfFromCache = () => cache.remove(cacheKey);
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if (cachedValue) {
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return new Response(cachedValue, ejectSelfFromCache, true);
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}
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const fetchResponse = await fetch(...requestArguments);
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const rawResponse = await createRawResponse(fetchResponse);
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await cache.set(cacheKey, rawResponse);
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return new Response(rawResponse, ejectSelfFromCache, false);
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}
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function createFetchWithCache(cache) {
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const fetchCache = (...args) => getResponse(cache, args);
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fetchCache.withCache = createFetchWithCache;
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return fetchCache;
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}
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module.exports = createFetchWithCache(new MemoryCache());
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