File: //lib/node_modules/npm/node_modules/http-cache-semantics/index.js
'use strict';
/**
* @typedef {Object} HttpRequest
* @property {Record<string, string>} headers - Request headers
* @property {string} [method] - HTTP method
* @property {string} [url] - Request URL
*/
/**
* @typedef {Object} HttpResponse
* @property {Record<string, string>} headers - Response headers
* @property {number} [status] - HTTP status code
*/
/**
* Set of default cacheable status codes per RFC 7231 section 6.1.
* @type {Set<number>}
*/
const statusCodeCacheableByDefault = new Set([
200,
203,
204,
206,
300,
301,
308,
404,
405,
410,
414,
501,
]);
/**
* Set of HTTP status codes that the cache implementation understands.
* Note: This implementation does not understand partial responses (206).
* @type {Set<number>}
*/
const understoodStatuses = new Set([
200,
203,
204,
300,
301,
302,
303,
307,
308,
404,
405,
410,
414,
501,
]);
/**
* Set of HTTP error status codes.
* @type {Set<number>}
*/
const errorStatusCodes = new Set([
500,
502,
503,
504,
]);
/**
* Object representing hop-by-hop headers that should be removed.
* @type {Record<string, boolean>}
*/
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,
};
/**
* Headers that are excluded from revalidation update.
* @type {Record<string, boolean>}
*/
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,
};
/**
* Converts a string to a number or returns zero if the conversion fails.
* @param {string} s - The string to convert.
* @returns {number} The parsed number or 0.
*/
function toNumberOrZero(s) {
const n = parseInt(s, 10);
return isFinite(n) ? n : 0;
}
/**
* Determines if the given response is an error response.
* Implements RFC 5861 behavior.
* @param {HttpResponse|undefined} response - The HTTP response object.
* @returns {boolean} true if the response is an error or undefined, false otherwise.
*/
function isErrorResponse(response) {
// consider undefined response as faulty
if (!response) {
return true;
}
return errorStatusCodes.has(response.status);
}
/**
* Parses a Cache-Control header string into an object.
* @param {string} [header] - The Cache-Control header value.
* @returns {Record<string, string|boolean>} An object representing Cache-Control directives.
*/
function parseCacheControl(header) {
/** @type {Record<string, string|boolean>} */
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(/,/);
for (const part of parts) {
const [k, v] = part.split(/=/, 2);
cc[k.trim()] = v === undefined ? true : v.trim().replace(/^"|"$/g, '');
}
return cc;
}
/**
* Formats a Cache-Control directives object into a header string.
* @param {Record<string, string|boolean>} cc - The Cache-Control directives.
* @returns {string|undefined} A formatted Cache-Control header string or undefined if empty.
*/
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 {
/**
* Creates a new CachePolicy instance.
* @param {HttpRequest} req - Incoming client request.
* @param {HttpResponse} res - Received server response.
* @param {Object} [options={}] - Configuration options.
* @param {boolean} [options.shared=true] - Is the cache shared (a public proxy)? `false` for personal browser caches.
* @param {number} [options.cacheHeuristic=0.1] - Fallback heuristic (age fraction) for cache duration.
* @param {number} [options.immutableMinTimeToLive=86400000] - Minimum TTL for immutable responses in milliseconds.
* @param {boolean} [options.ignoreCargoCult=false] - Detect nonsense cache headers, and override them.
* @param {any} [options._fromObject] - Internal parameter for deserialization. Do not use.
*/
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);
/** @type {number} Timestamp when the response was received */
this._responseTime = this.now();
/** @type {boolean} Indicates if the cache is shared */
this._isShared = shared !== false;
/** @type {boolean} Indicates if legacy cargo cult directives should be ignored */
this._ignoreCargoCult = !!ignoreCargoCult;
/** @type {number} Heuristic cache fraction */
this._cacheHeuristic =
undefined !== cacheHeuristic ? cacheHeuristic : 0.1; // 10% matches IE
/** @type {number} Minimum TTL for immutable responses in ms */
this._immutableMinTtl =
undefined !== immutableMinTimeToLive
? immutableMinTimeToLive
: 24 * 3600 * 1000;
/** @type {number} HTTP status code */
this._status = 'status' in res ? res.status : 200;
/** @type {Record<string, string>} Response headers */
this._resHeaders = res.headers;
/** @type {Record<string, string|boolean>} Parsed Cache-Control directives from response */
this._rescc = parseCacheControl(res.headers['cache-control']);
/** @type {string} HTTP method (e.g., GET, POST) */
this._method = 'method' in req ? req.method : 'GET';
/** @type {string} Request URL */
this._url = req.url;
/** @type {string} Host header from the request */
this._host = req.headers.host;
/** @type {boolean} Whether the request does not include an Authorization header */
this._noAuthorization = !req.headers.authorization;
/** @type {Record<string, string>|null} Request headers used for Vary matching */
this._reqHeaders = res.headers.vary ? req.headers : null; // Don't keep all request headers if they won't be used
/** @type {Record<string, string|boolean>} Parsed Cache-Control directives from request */
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 (
this._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;
}
}
/**
* You can monkey-patch it for testing.
* @returns {number} Current time in milliseconds.
*/
now() {
return Date.now();
}
/**
* Determines if the response is storable in a cache.
* @returns {boolean} `false` if can never be cached.
*/
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))
);
}
/**
* @returns {boolean} true if expiration is explicitly defined.
*/
_hasExplicitExpiration() {
// 4.2.1 Calculating Freshness Lifetime
return !!(
(this._isShared && this._rescc['s-maxage']) ||
this._rescc['max-age'] ||
this._resHeaders.expires
);
}
/**
* @param {HttpRequest} req - a request
* @throws {Error} if the headers are missing.
*/
_assertRequestHasHeaders(req) {
if (!req || !req.headers) {
throw Error('Request headers missing');
}
}
/**
* Checks if the request matches the cache and can be satisfied from the cache immediately,
* without having to make a request to the server.
*
* This doesn't support `stale-while-revalidate`. See `evaluateRequest()` for a more complete solution.
*
* @param {HttpRequest} req - The new incoming HTTP request.
* @returns {boolean} `true`` if the cached response used to construct this cache policy satisfies the request without revalidation.
*/
satisfiesWithoutRevalidation(req) {
const result = this.evaluateRequest(req);
return !result.revalidation;
}
/**
* @param {{headers: Record<string, string>, synchronous: boolean}|undefined} revalidation - Revalidation information, if any.
* @returns {{response: {headers: Record<string, string>}, revalidation: {headers: Record<string, string>, synchronous: boolean}|undefined}} An object with a cached response headers and revalidation info.
*/
_evaluateRequestHitResult(revalidation) {
return {
response: {
headers: this.responseHeaders(),
},
revalidation,
};
}
/**
* @param {HttpRequest} request - new incoming
* @param {boolean} synchronous - whether revalidation must be synchronous (not s-w-r).
* @returns {{headers: Record<string, string>, synchronous: boolean}} An object with revalidation headers and a synchronous flag.
*/
_evaluateRequestRevalidation(request, synchronous) {
return {
synchronous,
headers: this.revalidationHeaders(request),
};
}
/**
* @param {HttpRequest} request - new incoming
* @returns {{response: undefined, revalidation: {headers: Record<string, string>, synchronous: boolean}}} An object indicating no cached response and revalidation details.
*/
_evaluateRequestMissResult(request) {
return {
response: undefined,
revalidation: this._evaluateRequestRevalidation(request, true),
};
}
/**
* Checks if the given request matches this cache entry, and how the cache can be used to satisfy it. Returns an object with:
*
* ```
* {
* // If defined, you must send a request to the server.
* revalidation: {
* headers: {}, // HTTP headers to use when sending the revalidation response
* // If true, you MUST wait for a response from the server before using the cache
* // If false, this is stale-while-revalidate. The cache is stale, but you can use it while you update it asynchronously.
* synchronous: bool,
* },
* // If defined, you can use this cached response.
* response: {
* headers: {}, // Updated cached HTTP headers you must use when responding to the client
* },
* }
* ```
* @param {HttpRequest} req - new incoming HTTP request
* @returns {{response: {headers: Record<string, string>}|undefined, revalidation: {headers: Record<string, string>, synchronous: boolean}|undefined}} An object containing keys:
* - revalidation: { headers: Record<string, string>, synchronous: boolean } Set if you should send this to the origin server
* - response: { headers: Record<string, string> } Set if you can respond to the client with these cached headers
*/
evaluateRequest(req) {
this._assertRequestHasHeaders(req);
// In all circumstances, a cache MUST NOT ignore the must-revalidate directive
if (this._rescc['must-revalidate']) {
return this._evaluateRequestMissResult(req);
}
if (!this._requestMatches(req, false)) {
return this._evaluateRequestMissResult(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 this._evaluateRequestMissResult(req);
}
if (requestCC['max-age'] && this.age() > toNumberOrZero(requestCC['max-age'])) {
return this._evaluateRequestMissResult(req);
}
if (requestCC['min-fresh'] && this.maxAge() - this.age() < toNumberOrZero(requestCC['min-fresh'])) {
return this._evaluateRequestMissResult(req);
}
// the stored response is either:
// fresh, or allowed to be served stale
if (this.stale()) {
// If a value is present, then the client is willing to accept a response that has
// exceeded its freshness lifetime by no more than the specified number of seconds
const allowsStaleWithoutRevalidation = 'max-stale' in requestCC &&
(true === requestCC['max-stale'] || requestCC['max-stale'] > this.age() - this.maxAge());
if (allowsStaleWithoutRevalidation) {
return this._evaluateRequestHitResult(undefined);
}
if (this.useStaleWhileRevalidate()) {
return this._evaluateRequestHitResult(this._evaluateRequestRevalidation(req, false));
}
return this._evaluateRequestMissResult(req);
}
return this._evaluateRequestHitResult(undefined);
}
/**
* @param {HttpRequest} req - check if this is for the same cache entry
* @param {boolean} allowHeadMethod - allow a HEAD method to match.
* @returns {boolean} `true` if the request matches.
*/
_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)
);
}
/**
* Determines whether storing authenticated responses is allowed.
* @returns {boolean} `true` if allowed.
*/
_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']
);
}
/**
* Checks whether the Vary header in the response matches the new request.
* @param {HttpRequest} req - incoming HTTP request
* @returns {boolean} `true` if the vary headers match.
*/
_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;
}
/**
* Creates a copy of the given headers without any hop-by-hop headers.
* @param {Record<string, string>} inHeaders - old headers from the cached response
* @returns {Record<string, string>} A new headers object without hop-by-hop headers.
*/
_copyWithoutHopByHopHeaders(inHeaders) {
/** @type {Record<string, string>} */
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;
}
/**
* Returns the response headers adjusted for serving the cached response.
* Removes hop-by-hop headers and updates the Age and Date headers.
* @returns {Record<string, string>} The adjusted response 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;
}
/**
* Returns the Date header value from the response or the current time if invalid.
* @returns {number} Timestamp (in milliseconds) representing the Date header or response time.
*/
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.
* @returns {number} The age in seconds.
*/
age() {
let age = this._ageValue();
const residentTime = (this.now() - this._responseTime) / 1000;
return age + residentTime;
}
/**
* @returns {number} The Age header value as a number.
*/
_ageValue() {
return toNumberOrZero(this._resHeaders.age);
}
/**
* Possibly outdated value of applicable max-age (or heuristic equivalent) in seconds.
* This counts since response's `Date`.
*
* For an up-to-date value, see `timeToLive()`.
*
* Returns the maximum age (freshness lifetime) of the response in seconds.
* @returns {number} The max-age value in seconds.
*/
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;
}
/**
* Remaining time this cache entry may be useful for, in *milliseconds*.
* You can use this as an expiration time for your cache storage.
*
* Prefer this method over `maxAge()`, because it includes other factors like `age` and `stale-while-revalidate`.
* @returns {number} Time-to-live in milliseconds.
*/
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.round(Math.max(0, age, staleIfErrorAge, staleWhileRevalidateAge) * 1000);
}
/**
* If true, this cache entry is past its expiration date.
* Note that stale cache may be useful sometimes, see `evaluateRequest()`.
* @returns {boolean} `false` doesn't mean it's fresh nor usable
*/
stale() {
return this.maxAge() <= this.age();
}
/**
* @returns {boolean} `true` if `stale-if-error` condition allows use of a stale response.
*/
_useStaleIfError() {
return this.maxAge() + toNumberOrZero(this._rescc['stale-if-error']) > this.age();
}
/** See `evaluateRequest()` for a more complete solution
* @returns {boolean} `true` if `stale-while-revalidate` is currently allowed.
*/
useStaleWhileRevalidate() {
const swr = toNumberOrZero(this._rescc['stale-while-revalidate']);
return swr > 0 && this.maxAge() + swr > this.age();
}
/**
* Creates a `CachePolicy` instance from a serialized object.
* @param {Object} obj - The serialized object.
* @returns {CachePolicy} A new CachePolicy instance.
*/
static fromObject(obj) {
return new this(undefined, undefined, { _fromObject: obj });
}
/**
* @param {any} obj - The serialized object.
* @throws {Error} If already initialized or if the object is invalid.
*/
_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._ignoreCargoCult = !!obj.icc;
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;
}
/**
* Serializes the `CachePolicy` instance into a JSON-serializable object.
* @returns {Object} The serialized object.
*/
toObject() {
return {
v: 1,
t: this._responseTime,
sh: this._isShared,
ch: this._cacheHeuristic,
imm: this._immutableMinTtl,
icc: this._ignoreCargoCult,
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.
* @param {HttpRequest} incomingReq - The incoming HTTP request.
* @returns {Record<string, string>} The headers for the revalidation 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.
*
* @param {HttpRequest} request - The latest HTTP request asking for the cached entry.
* @param {HttpResponse} response - The latest revalidation HTTP response from the origin server.
* @returns {{policy: CachePolicy, modified: boolean, matches: boolean}} The updated policy and modification status.
* @throws {Error} If the response headers are missing.
*/
revalidatedPolicy(request, response) {
this._assertRequestHasHeaders(request);
if (this._useStaleIfError() && isErrorResponse(response)) {
return {
policy: this,
modified: false,
matches: true,
};
}
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;
}
}
const optionsCopy = {
shared: this._isShared,
cacheHeuristic: this._cacheHeuristic,
immutableMinTimeToLive: this._immutableMinTtl,
ignoreCargoCult: this._ignoreCargoCult,
};
if (!matches) {
return {
policy: new this.constructor(request, response, optionsCopy),
// 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, optionsCopy),
modified: false,
matches: true,
};
}
};