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node-fetch-cache/index.js

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const fetch = require('node-fetch');
const fs = require('fs');
const crypto = require('crypto');
const path = require('path');
function md5(str) {
return crypto.createHash('md5').update(str).digest('hex');
}
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class Headers {
constructor(rawHeaders) {
this.rawHeaders = rawHeaders;
}
* entries() {
for (let entry of Object.entries(this.rawHeaders)) {
yield entry;
}
}
* keys() {
for (let key of Object.keys(this.rawHeaders)) {
yield key;
}
}
* values() {
for (let value of Object.values(this.rawHeaders)) {
yield value;
}
}
get(name) {
return this.rawHeaders[name.toLowerCase()] || null;
}
has(name) {
return !!this.get(name);
}
}
class Response {
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constructor(raw, cacheFilePath, fromCache) {
Object.assign(this, raw);
this.cacheFilePath = cacheFilePath;
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this.headers = new Headers(raw.headers);
this.fromCache = fromCache;
if (this.bodyBuffer.type === 'Buffer') {
this.bodyBuffer = Buffer.from(this.bodyBuffer);
}
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}
text() {
return this.bodyBuffer.toString();
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}
json() {
return JSON.parse(this.bodyBuffer.toString());
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}
buffer() {
return this.bodyBuffer;
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}
ejectFromCache() {
return fs.promises.unlink(this.cacheFilePath);
}
}
async function createRawResponse(fetchRes) {
const buffer = await fetchRes.buffer();
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const rawHeaders = Array.from(fetchRes.headers.entries())
.reduce((aggregate, entry) => ({ ...aggregate, [entry[0]]: entry[1] }), {});
return {
status: fetchRes.status,
statusText: fetchRes.statusText,
type: fetchRes.type,
url: fetchRes.url,
ok: fetchRes.ok,
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headers: rawHeaders,
redirected: fetchRes.redirected,
bodyBuffer: buffer,
};
}
async function getResponse(cacheDirPath, requestArguments) {
const [url, requestInit, ...rest] = requestArguments;
const requestParams = requestInit.body
? ({ ...requestInit, body: typeof requestInit.body === 'object' ? requestInit.body.toString() : requestInit.body })
: requestInit;
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const cacheHash = md5(JSON.stringify([url, requestParams, ...rest]));
const cachedFilePath = path.join(cacheDirPath, `${cacheHash}.json`);
try {
const rawResponse = JSON.parse(await fs.promises.readFile(cachedFilePath));
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return new Response(rawResponse, cachedFilePath, true);
} catch (err) {
const fetchResponse = await fetch(...requestArguments);
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const rawResponse = await createRawResponse(fetchResponse);
await fs.promises.writeFile(cachedFilePath, JSON.stringify(rawResponse));
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return new Response(rawResponse, cachedFilePath, false);
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}
}
function createFetch(cacheDirPath) {
let madeDir = false;
return async (...args) => {
if (!madeDir) {
await fs.promises.mkdir(cacheDirPath, { recursive: true });
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madeDir = true;
}
return getResponse(cacheDirPath, args);
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};
}
module.exports = createFetch;