Current File : //lib/node_modules/npm/node_modules/http-cache-semantics/index.js
'use strict';
// rfc7231 6.1
const statusCodeCacheableByDefault = new Set([
200,
203,
204,
206,
300,
301,
404,
405,
410,
414,
501,
]);
// This implementation does not understand partial responses (206)
const understoodStatuses = new Set([
200,
203,
204,
300,
301,
302,
303,
307,
308,
404,
405,
410,
414,
501,
]);
const errorStatusCodes = new Set([
500,
502,
503,
504,
]);
const hopByHopHeaders = {
date: true, // included, because we add Age update Date
connection: true,
'keep-alive': true,
'proxy-authenticate': true,
'proxy-authorization': true,
te: true,
trailer: true,
'transfer-encoding': true,
upgrade: true,
};
const excludedFromRevalidationUpdate = {
// Since the old body is reused, it doesn't make sense to change properties of the body
'content-length': true,
'content-encoding': true,
'transfer-encoding': true,
'content-range': true,
};
function toNumberOrZero(s) {
const n = parseInt(s, 10);
return isFinite(n) ? n : 0;
}
// RFC 5861
function isErrorResponse(response) {
// consider undefined response as faulty
if(!response) {
return true
}
return errorStatusCodes.has(response.status);
}
function parseCacheControl(header) {
const cc = {};
if (!header) return cc;
// TODO: When there is more than one value present for a given directive (e.g., two Expires header fields, multiple Cache-Control: max-age directives),
// the directive's value is considered invalid. Caches are encouraged to consider responses that have invalid freshness information to be stale
const parts = header.trim().split(/\s*,\s*/); // TODO: lame parsing
for (const part of parts) {
const [k, v] = part.split(/\s*=\s*/, 2);
cc[k] = v === undefined ? true : v.replace(/^"|"$/g, ''); // TODO: lame unquoting
}
return cc;
}
function formatCacheControl(cc) {
let parts = [];
for (const k in cc) {
const v = cc[k];
parts.push(v === true ? k : k + '=' + v);
}
if (!parts.length) {
return undefined;
}
return parts.join(', ');
}
module.exports = class CachePolicy {
constructor(
req,
res,
{
shared,
cacheHeuristic,
immutableMinTimeToLive,
ignoreCargoCult,
_fromObject,
} = {}
) {
if (_fromObject) {
this._fromObject(_fromObject);
return;
}
if (!res || !res.headers) {
throw Error('Response headers missing');
}
this._assertRequestHasHeaders(req);
this._responseTime = this.now();
this._isShared = shared !== false;
this._cacheHeuristic =
undefined !== cacheHeuristic ? cacheHeuristic : 0.1; // 10% matches IE
this._immutableMinTtl =
undefined !== immutableMinTimeToLive
? immutableMinTimeToLive
: 24 * 3600 * 1000;
this._status = 'status' in res ? res.status : 200;
this._resHeaders = res.headers;
this._rescc = parseCacheControl(res.headers['cache-control']);
this._method = 'method' in req ? req.method : 'GET';
this._url = req.url;
this._host = req.headers.host;
this._noAuthorization = !req.headers.authorization;
this._reqHeaders = res.headers.vary ? req.headers : null; // Don't keep all request headers if they won't be used
this._reqcc = parseCacheControl(req.headers['cache-control']);
// Assume that if someone uses legacy, non-standard uncecessary options they don't understand caching,
// so there's no point stricly adhering to the blindly copy&pasted directives.
if (
ignoreCargoCult &&
'pre-check' in this._rescc &&
'post-check' in this._rescc
) {
delete this._rescc['pre-check'];
delete this._rescc['post-check'];
delete this._rescc['no-cache'];
delete this._rescc['no-store'];
delete this._rescc['must-revalidate'];
this._resHeaders = Object.assign({}, this._resHeaders, {
'cache-control': formatCacheControl(this._rescc),
});
delete this._resHeaders.expires;
delete this._resHeaders.pragma;
}
// When the Cache-Control header field is not present in a request, caches MUST consider the no-cache request pragma-directive
// as having the same effect as if "Cache-Control: no-cache" were present (see Section 5.2.1).
if (
res.headers['cache-control'] == null &&
/no-cache/.test(res.headers.pragma)
) {
this._rescc['no-cache'] = true;
}
}
now() {
return Date.now();
}
storable() {
// The "no-store" request directive indicates that a cache MUST NOT store any part of either this request or any response to it.
return !!(
!this._reqcc['no-store'] &&
// A cache MUST NOT store a response to any request, unless:
// The request method is understood by the cache and defined as being cacheable, and
('GET' === this._method ||
'HEAD' === this._method ||
('POST' === this._method && this._hasExplicitExpiration())) &&
// the response status code is understood by the cache, and
understoodStatuses.has(this._status) &&
// the "no-store" cache directive does not appear in request or response header fields, and
!this._rescc['no-store'] &&
// the "private" response directive does not appear in the response, if the cache is shared, and
(!this._isShared || !this._rescc.private) &&
// the Authorization header field does not appear in the request, if the cache is shared,
(!this._isShared ||
this._noAuthorization ||
this._allowsStoringAuthenticated()) &&
// the response either:
// contains an Expires header field, or
(this._resHeaders.expires ||
// contains a max-age response directive, or
// contains a s-maxage response directive and the cache is shared, or
// contains a public response directive.
this._rescc['max-age'] ||
(this._isShared && this._rescc['s-maxage']) ||
this._rescc.public ||
// has a status code that is defined as cacheable by default
statusCodeCacheableByDefault.has(this._status))
);
}
_hasExplicitExpiration() {
// 4.2.1 Calculating Freshness Lifetime
return (
(this._isShared && this._rescc['s-maxage']) ||
this._rescc['max-age'] ||
this._resHeaders.expires
);
}
_assertRequestHasHeaders(req) {
if (!req || !req.headers) {
throw Error('Request headers missing');
}
}
satisfiesWithoutRevalidation(req) {
this._assertRequestHasHeaders(req);
// When presented with a request, a cache MUST NOT reuse a stored response, unless:
// the presented request does not contain the no-cache pragma (Section 5.4), nor the no-cache cache directive,
// unless the stored response is successfully validated (Section 4.3), and
const requestCC = parseCacheControl(req.headers['cache-control']);
if (requestCC['no-cache'] || /no-cache/.test(req.headers.pragma)) {
return false;
}
if (requestCC['max-age'] && this.age() > requestCC['max-age']) {
return false;
}
if (
requestCC['min-fresh'] &&
this.timeToLive() < 1000 * requestCC['min-fresh']
) {
return false;
}
// the stored response is either:
// fresh, or allowed to be served stale
if (this.stale()) {
const allowsStale =
requestCC['max-stale'] &&
!this._rescc['must-revalidate'] &&
(true === requestCC['max-stale'] ||
requestCC['max-stale'] > this.age() - this.maxAge());
if (!allowsStale) {
return false;
}
}
return this._requestMatches(req, false);
}
_requestMatches(req, allowHeadMethod) {
// The presented effective request URI and that of the stored response match, and
return (
(!this._url || this._url === req.url) &&
this._host === req.headers.host &&
// the request method associated with the stored response allows it to be used for the presented request, and
(!req.method ||
this._method === req.method ||
(allowHeadMethod && 'HEAD' === req.method)) &&
// selecting header fields nominated by the stored response (if any) match those presented, and
this._varyMatches(req)
);
}
_allowsStoringAuthenticated() {
// following Cache-Control response directives (Section 5.2.2) have such an effect: must-revalidate, public, and s-maxage.
return (
this._rescc['must-revalidate'] ||
this._rescc.public ||
this._rescc['s-maxage']
);
}
_varyMatches(req) {
if (!this._resHeaders.vary) {
return true;
}
// A Vary header field-value of "*" always fails to match
if (this._resHeaders.vary === '*') {
return false;
}
const fields = this._resHeaders.vary
.trim()
.toLowerCase()
.split(/\s*,\s*/);
for (const name of fields) {
if (req.headers[name] !== this._reqHeaders[name]) return false;
}
return true;
}
_copyWithoutHopByHopHeaders(inHeaders) {
const headers = {};
for (const name in inHeaders) {
if (hopByHopHeaders[name]) continue;
headers[name] = inHeaders[name];
}
// 9.1. Connection
if (inHeaders.connection) {
const tokens = inHeaders.connection.trim().split(/\s*,\s*/);
for (const name of tokens) {
delete headers[name];
}
}
if (headers.warning) {
const warnings = headers.warning.split(/,/).filter(warning => {
return !/^\s*1[0-9][0-9]/.test(warning);
});
if (!warnings.length) {
delete headers.warning;
} else {
headers.warning = warnings.join(',').trim();
}
}
return headers;
}
responseHeaders() {
const headers = this._copyWithoutHopByHopHeaders(this._resHeaders);
const age = this.age();
// A cache SHOULD generate 113 warning if it heuristically chose a freshness
// lifetime greater than 24 hours and the response's age is greater than 24 hours.
if (
age > 3600 * 24 &&
!this._hasExplicitExpiration() &&
this.maxAge() > 3600 * 24
) {
headers.warning =
(headers.warning ? `${headers.warning}, ` : '') +
'113 - "rfc7234 5.5.4"';
}
headers.age = `${Math.round(age)}`;
headers.date = new Date(this.now()).toUTCString();
return headers;
}
/**
* Value of the Date response header or current time if Date was invalid
* @return timestamp
*/
date() {
const serverDate = Date.parse(this._resHeaders.date);
if (isFinite(serverDate)) {
return serverDate;
}
return this._responseTime;
}
/**
* Value of the Age header, in seconds, updated for the current time.
* May be fractional.
*
* @return Number
*/
age() {
let age = this._ageValue();
const residentTime = (this.now() - this._responseTime) / 1000;
return age + residentTime;
}
_ageValue() {
return toNumberOrZero(this._resHeaders.age);
}
/**
* Value of applicable max-age (or heuristic equivalent) in seconds. This counts since response's `Date`.
*
* For an up-to-date value, see `timeToLive()`.
*
* @return Number
*/
maxAge() {
if (!this.storable() || this._rescc['no-cache']) {
return 0;
}
// Shared responses with cookies are cacheable according to the RFC, but IMHO it'd be unwise to do so by default
// so this implementation requires explicit opt-in via public header
if (
this._isShared &&
(this._resHeaders['set-cookie'] &&
!this._rescc.public &&
!this._rescc.immutable)
) {
return 0;
}
if (this._resHeaders.vary === '*') {
return 0;
}
if (this._isShared) {
if (this._rescc['proxy-revalidate']) {
return 0;
}
// if a response includes the s-maxage directive, a shared cache recipient MUST ignore the Expires field.
if (this._rescc['s-maxage']) {
return toNumberOrZero(this._rescc['s-maxage']);
}
}
// If a response includes a Cache-Control field with the max-age directive, a recipient MUST ignore the Expires field.
if (this._rescc['max-age']) {
return toNumberOrZero(this._rescc['max-age']);
}
const defaultMinTtl = this._rescc.immutable ? this._immutableMinTtl : 0;
const serverDate = this.date();
if (this._resHeaders.expires) {
const expires = Date.parse(this._resHeaders.expires);
// A cache recipient MUST interpret invalid date formats, especially the value "0", as representing a time in the past (i.e., "already expired").
if (Number.isNaN(expires) || expires < serverDate) {
return 0;
}
return Math.max(defaultMinTtl, (expires - serverDate) / 1000);
}
if (this._resHeaders['last-modified']) {
const lastModified = Date.parse(this._resHeaders['last-modified']);
if (isFinite(lastModified) && serverDate > lastModified) {
return Math.max(
defaultMinTtl,
((serverDate - lastModified) / 1000) * this._cacheHeuristic
);
}
}
return defaultMinTtl;
}
timeToLive() {
const age = this.maxAge() - this.age();
const staleIfErrorAge = age + toNumberOrZero(this._rescc['stale-if-error']);
const staleWhileRevalidateAge = age + toNumberOrZero(this._rescc['stale-while-revalidate']);
return Math.max(0, age, staleIfErrorAge, staleWhileRevalidateAge) * 1000;
}
stale() {
return this.maxAge() <= this.age();
}
_useStaleIfError() {
return this.maxAge() + toNumberOrZero(this._rescc['stale-if-error']) > this.age();
}
useStaleWhileRevalidate() {
return this.maxAge() + toNumberOrZero(this._rescc['stale-while-revalidate']) > this.age();
}
static fromObject(obj) {
return new this(undefined, undefined, { _fromObject: obj });
}
_fromObject(obj) {
if (this._responseTime) throw Error('Reinitialized');
if (!obj || obj.v !== 1) throw Error('Invalid serialization');
this._responseTime = obj.t;
this._isShared = obj.sh;
this._cacheHeuristic = obj.ch;
this._immutableMinTtl =
obj.imm !== undefined ? obj.imm : 24 * 3600 * 1000;
this._status = obj.st;
this._resHeaders = obj.resh;
this._rescc = obj.rescc;
this._method = obj.m;
this._url = obj.u;
this._host = obj.h;
this._noAuthorization = obj.a;
this._reqHeaders = obj.reqh;
this._reqcc = obj.reqcc;
}
toObject() {
return {
v: 1,
t: this._responseTime,
sh: this._isShared,
ch: this._cacheHeuristic,
imm: this._immutableMinTtl,
st: this._status,
resh: this._resHeaders,
rescc: this._rescc,
m: this._method,
u: this._url,
h: this._host,
a: this._noAuthorization,
reqh: this._reqHeaders,
reqcc: this._reqcc,
};
}
/**
* Headers for sending to the origin server to revalidate stale response.
* Allows server to return 304 to allow reuse of the previous response.
*
* Hop by hop headers are always stripped.
* Revalidation headers may be added or removed, depending on request.
*/
revalidationHeaders(incomingReq) {
this._assertRequestHasHeaders(incomingReq);
const headers = this._copyWithoutHopByHopHeaders(incomingReq.headers);
// This implementation does not understand range requests
delete headers['if-range'];
if (!this._requestMatches(incomingReq, true) || !this.storable()) {
// revalidation allowed via HEAD
// not for the same resource, or wasn't allowed to be cached anyway
delete headers['if-none-match'];
delete headers['if-modified-since'];
return headers;
}
/* MUST send that entity-tag in any cache validation request (using If-Match or If-None-Match) if an entity-tag has been provided by the origin server. */
if (this._resHeaders.etag) {
headers['if-none-match'] = headers['if-none-match']
? `${headers['if-none-match']}, ${this._resHeaders.etag}`
: this._resHeaders.etag;
}
// Clients MAY issue simple (non-subrange) GET requests with either weak validators or strong validators. Clients MUST NOT use weak validators in other forms of request.
const forbidsWeakValidators =
headers['accept-ranges'] ||
headers['if-match'] ||
headers['if-unmodified-since'] ||
(this._method && this._method != 'GET');
/* SHOULD send the Last-Modified value in non-subrange cache validation requests (using If-Modified-Since) if only a Last-Modified value has been provided by the origin server.
Note: This implementation does not understand partial responses (206) */
if (forbidsWeakValidators) {
delete headers['if-modified-since'];
if (headers['if-none-match']) {
const etags = headers['if-none-match']
.split(/,/)
.filter(etag => {
return !/^\s*W\//.test(etag);
});
if (!etags.length) {
delete headers['if-none-match'];
} else {
headers['if-none-match'] = etags.join(',').trim();
}
}
} else if (
this._resHeaders['last-modified'] &&
!headers['if-modified-since']
) {
headers['if-modified-since'] = this._resHeaders['last-modified'];
}
return headers;
}
/**
* Creates new CachePolicy with information combined from the previews response,
* and the new revalidation response.
*
* Returns {policy, modified} where modified is a boolean indicating
* whether the response body has been modified, and old cached body can't be used.
*
* @return {Object} {policy: CachePolicy, modified: Boolean}
*/
revalidatedPolicy(request, response) {
this._assertRequestHasHeaders(request);
if(this._useStaleIfError() && isErrorResponse(response)) { // I consider the revalidation request unsuccessful
return {
modified: false,
matches: false,
policy: this,
};
}
if (!response || !response.headers) {
throw Error('Response headers missing');
}
// These aren't going to be supported exactly, since one CachePolicy object
// doesn't know about all the other cached objects.
let matches = false;
if (response.status !== undefined && response.status != 304) {
matches = false;
} else if (
response.headers.etag &&
!/^\s*W\//.test(response.headers.etag)
) {
// "All of the stored responses with the same strong validator are selected.
// If none of the stored responses contain the same strong validator,
// then the cache MUST NOT use the new response to update any stored responses."
matches =
this._resHeaders.etag &&
this._resHeaders.etag.replace(/^\s*W\//, '') ===
response.headers.etag;
} else if (this._resHeaders.etag && response.headers.etag) {
// "If the new response contains a weak validator and that validator corresponds
// to one of the cache's stored responses,
// then the most recent of those matching stored responses is selected for update."
matches =
this._resHeaders.etag.replace(/^\s*W\//, '') ===
response.headers.etag.replace(/^\s*W\//, '');
} else if (this._resHeaders['last-modified']) {
matches =
this._resHeaders['last-modified'] ===
response.headers['last-modified'];
} else {
// If the new response does not include any form of validator (such as in the case where
// a client generates an If-Modified-Since request from a source other than the Last-Modified
// response header field), and there is only one stored response, and that stored response also
// lacks a validator, then that stored response is selected for update.
if (
!this._resHeaders.etag &&
!this._resHeaders['last-modified'] &&
!response.headers.etag &&
!response.headers['last-modified']
) {
matches = true;
}
}
if (!matches) {
return {
policy: new this.constructor(request, response),
// Client receiving 304 without body, even if it's invalid/mismatched has no option
// but to reuse a cached body. We don't have a good way to tell clients to do
// error recovery in such case.
modified: response.status != 304,
matches: false,
};
}
// use other header fields provided in the 304 (Not Modified) response to replace all instances
// of the corresponding header fields in the stored response.
const headers = {};
for (const k in this._resHeaders) {
headers[k] =
k in response.headers && !excludedFromRevalidationUpdate[k]
? response.headers[k]
: this._resHeaders[k];
}
const newResponse = Object.assign({}, response, {
status: this._status,
method: this._method,
headers,
});
return {
policy: new this.constructor(request, newResponse, {
shared: this._isShared,
cacheHeuristic: this._cacheHeuristic,
immutableMinTimeToLive: this._immutableMinTtl,
}),
modified: false,
matches: true,
};
}
};
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