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index.js
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155 lines (135 loc) · 4.43 KB
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'use strict';
const EventEmitter = require('events');
const urlLib = require('url');
const normalizeUrl = require('normalize-url');
const getStream = require('get-stream');
const CachePolicy = require('http-cache-semantics');
const Response = require('responselike');
const lowercaseKeys = require('lowercase-keys');
const cloneResponse = require('clone-response');
const Keyv = require('keyv');
class CacheableRequest {
constructor(request, cacheAdapter) {
if (typeof request !== 'function') {
throw new TypeError('Parameter `request` must be a function');
}
this.cache = new Keyv({
uri: typeof cacheAdapter === 'string' && cacheAdapter,
store: typeof cacheAdapter !== 'string' && cacheAdapter,
namespace: 'cacheable-request'
});
return this.createCacheableRequest(request);
}
createCacheableRequest(request) {
return (opts, cb) => {
if (typeof opts === 'string') {
opts = urlLib.parse(opts);
}
opts = Object.assign({
headers: {},
method: 'GET',
cache: true,
strictTtl: false,
automaticFailover: false
}, opts);
opts.headers = lowercaseKeys(opts.headers);
const ee = new EventEmitter();
const url = normalizeUrl(urlLib.format(opts));
const key = `${opts.method}:${url}`;
let revalidate = false;
let madeRequest = false;
const makeRequest = opts => {
madeRequest = true;
const handler = response => {
if (revalidate) {
const revalidatedPolicy = CachePolicy.fromObject(revalidate.cachePolicy).revalidatedPolicy(opts, response);
if (!revalidatedPolicy.modified) {
const headers = revalidatedPolicy.policy.responseHeaders();
response = new Response(response.statusCode, headers, revalidate.body, revalidate.url);
response.cachePolicy = revalidatedPolicy.policy;
response.fromCache = true;
}
}
if (!response.fromCache) {
response.cachePolicy = new CachePolicy(opts, response);
response.fromCache = false;
}
let clonedResponse;
if (opts.cache && response.cachePolicy.storable()) {
clonedResponse = cloneResponse(response);
getStream.buffer(response)
.then(body => {
const value = {
cachePolicy: response.cachePolicy.toObject(),
url: response.url,
statusCode: response.fromCache ? revalidate.statusCode : response.statusCode,
body
};
const ttl = opts.strictTtl ? response.cachePolicy.timeToLive() : undefined;
return this.cache.set(key, value, ttl);
})
.catch(err => ee.emit('error', new CacheableRequest.CacheError(err)));
} else if (opts.cache && revalidate) {
this.cache.delete(key)
.catch(err => ee.emit('error', new CacheableRequest.CacheError(err)));
}
ee.emit('response', clonedResponse || response);
if (typeof cb === 'function') {
cb(clonedResponse || response);
}
};
try {
const req = request(opts, handler);
ee.emit('request', req);
} catch (err) {
ee.emit('error', new CacheableRequest.RequestError(err));
}
};
const get = opts => Promise.resolve()
.then(() => opts.cache ? this.cache.get(key) : undefined)
.then(cacheEntry => {
if (typeof cacheEntry === 'undefined') {
return makeRequest(opts);
}
const policy = CachePolicy.fromObject(cacheEntry.cachePolicy);
if (policy.satisfiesWithoutRevalidation(opts)) {
const headers = policy.responseHeaders();
const response = new Response(cacheEntry.statusCode, headers, cacheEntry.body, cacheEntry.url);
response.cachePolicy = policy;
response.fromCache = true;
ee.emit('response', response);
if (typeof cb === 'function') {
cb(response);
}
} else {
revalidate = cacheEntry;
opts.headers = policy.revalidationHeaders(opts);
makeRequest(opts);
}
});
this.cache.on('error', err => ee.emit('error', new CacheableRequest.CacheError(err)));
get(opts).catch(err => {
if (opts.automaticFailover && !madeRequest) {
makeRequest(opts);
}
ee.emit('error', new CacheableRequest.CacheError(err));
});
return ee;
};
}
}
CacheableRequest.RequestError = class extends Error {
constructor(err) {
super(err.message);
this.name = 'RequestError';
Object.assign(this, err);
}
};
CacheableRequest.CacheError = class extends Error {
constructor(err) {
super(err.message);
this.name = 'CacheError';
Object.assign(this, err);
}
};
module.exports = CacheableRequest;