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'use strict';
// rfc7231 6.1
function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }
var statusCodeCacheableByDefault = [200, 203, 204, 206, 300, 301, 404, 405, 410, 414, 501];
// This implementation does not understand partial responses (206)
var understoodStatuses = [200, 203, 204, 300, 301, 302, 303, 307, 308, 404, 405, 410, 414, 501];
var hopByHopHeaders = { 'connection': true, 'keep-alive': true, 'proxy-authenticate': true, 'proxy-authorization': true, 'te': true, 'trailer': true, 'transfer-encoding': true, 'upgrade': true };
var 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 parseCacheControl(header) {
var 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
var parts = header.trim().split(/\s*,\s*/); // TODO: lame parsing
for (var _iterator = parts, _isArray = Array.isArray(_iterator), _i = 0, _iterator = _isArray ? _iterator : _iterator[Symbol.iterator]();;) {
var _ref;
if (_isArray) {
if (_i >= _iterator.length) break;
_ref = _iterator[_i++];
} else {
_i = _iterator.next();
if (_i.done) break;
_ref = _i.value;
}
var part = _ref;
var _part$split = part.split(/\s*=\s*/, 2),
k = _part$split[0],
v = _part$split[1];
cc[k] = v === undefined ? true : v.replace(/^"|"$/g, ''); // TODO: lame unquoting
}
return cc;
}
function formatCacheControl(cc) {
var parts = [];
for (var k in cc) {
var v = cc[k];
parts.push(v === true ? k : k + '=' + v);
}
if (!parts.length) {
return undefined;
}
return parts.join(', ');
}
module.exports = function () {
function CachePolicy(req, res) {
var _ref2 = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : {},
shared = _ref2.shared,
cacheHeuristic = _ref2.cacheHeuristic,
immutableMinTimeToLive = _ref2.immutableMinTimeToLive,
ignoreCargoCult = _ref2.ignoreCargoCult,
_fromObject = _ref2._fromObject;
_classCallCheck(this, CachePolicy);
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'] && /no-cache/.test(res.headers.pragma)) {
this._rescc['no-cache'] = true;
}
}
CachePolicy.prototype.now = function now() {
return Date.now();
};
CachePolicy.prototype.storable = function 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.indexOf(this._status) !== -1 &&
// 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.public || this._rescc['max-age'] || this._rescc['s-maxage'] ||
// has a status code that is defined as cacheable by default
statusCodeCacheableByDefault.indexOf(this._status) !== -1));
};
CachePolicy.prototype._hasExplicitExpiration = function _hasExplicitExpiration() {
// 4.2.1 Calculating Freshness Lifetime
return this._isShared && this._rescc['s-maxage'] || this._rescc['max-age'] || this._resHeaders.expires;
};
CachePolicy.prototype._assertRequestHasHeaders = function _assertRequestHasHeaders(req) {
if (!req || !req.headers) {
throw Error("Request headers missing");
}
};
CachePolicy.prototype.satisfiesWithoutRevalidation = function 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
var 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()) {
var 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);
};
CachePolicy.prototype._requestMatches = function _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);
};
CachePolicy.prototype._allowsStoringAuthenticated = function _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'];
};
CachePolicy.prototype._varyMatches = function _varyMatches(req) {
if (!this._resHeaders.vary) {
return true;
}
// A Vary header field-value of "*" always fails to match
if (this._resHeaders.vary === '*') {
return false;
}
var fields = this._resHeaders.vary.trim().toLowerCase().split(/\s*,\s*/);
for (var _iterator2 = fields, _isArray2 = Array.isArray(_iterator2), _i2 = 0, _iterator2 = _isArray2 ? _iterator2 : _iterator2[Symbol.iterator]();;) {
var _ref3;
if (_isArray2) {
if (_i2 >= _iterator2.length) break;
_ref3 = _iterator2[_i2++];
} else {
_i2 = _iterator2.next();
if (_i2.done) break;
_ref3 = _i2.value;
}
var name = _ref3;
if (req.headers[name] !== this._reqHeaders[name]) return false;
}
return true;
};
CachePolicy.prototype._copyWithoutHopByHopHeaders = function _copyWithoutHopByHopHeaders(inHeaders) {
var headers = {};
for (var name in inHeaders) {
if (hopByHopHeaders[name]) continue;
headers[name] = inHeaders[name];
}
// 9.1. Connection
if (inHeaders.connection) {
var tokens = inHeaders.connection.trim().split(/\s*,\s*/);
for (var _iterator3 = tokens, _isArray3 = Array.isArray(_iterator3), _i3 = 0, _iterator3 = _isArray3 ? _iterator3 : _iterator3[Symbol.iterator]();;) {
var _ref4;
if (_isArray3) {
if (_i3 >= _iterator3.length) break;
_ref4 = _iterator3[_i3++];
} else {
_i3 = _iterator3.next();
if (_i3.done) break;
_ref4 = _i3.value;
}
var _name = _ref4;
delete headers[_name];
}
}
if (headers.warning) {
var warnings = headers.warning.split(/,/).filter(function (warning) {
return !/^\s*1[0-9][0-9]/.test(warning);
});
if (!warnings.length) {
delete headers.warning;
} else {
headers.warning = warnings.join(',').trim();
}
}
return headers;
};
CachePolicy.prototype.responseHeaders = function responseHeaders() {
var headers = this._copyWithoutHopByHopHeaders(this._resHeaders);
var 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)}`;
return headers;
};
/**
* Value of the Date response header or current time if Date was demed invalid
* @return timestamp
*/
CachePolicy.prototype.date = function date() {
var dateValue = Date.parse(this._resHeaders.date);
var maxClockDrift = 8 * 3600 * 1000;
if (Number.isNaN(dateValue) || dateValue < this._responseTime - maxClockDrift || dateValue > this._responseTime + maxClockDrift) {
return this._responseTime;
}
return dateValue;
};
/**
* Value of the Age header, in seconds, updated for the current time.
* May be fractional.
*
* @return Number
*/
CachePolicy.prototype.age = function age() {
var age = Math.max(0, (this._responseTime - this.date()) / 1000);
if (this._resHeaders.age) {
var ageValue = this._ageValue();
if (ageValue > age) age = ageValue;
}
var residentTime = (this.now() - this._responseTime) / 1000;
return age + residentTime;
};
CachePolicy.prototype._ageValue = function _ageValue() {
var ageValue = parseInt(this._resHeaders.age);
return isFinite(ageValue) ? ageValue : 0;
};
/**
* 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
*/
CachePolicy.prototype.maxAge = function 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 parseInt(this._rescc['s-maxage'], 10);
}
}
// 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 parseInt(this._rescc['max-age'], 10);
}
var defaultMinTtl = this._rescc.immutable ? this._immutableMinTtl : 0;
var dateValue = this.date();
if (this._resHeaders.expires) {
var 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 < dateValue) {
return 0;
}
return Math.max(defaultMinTtl, (expires - dateValue) / 1000);
}
if (this._resHeaders['last-modified']) {
var lastModified = Date.parse(this._resHeaders['last-modified']);
if (isFinite(lastModified) && dateValue > lastModified) {
return Math.max(defaultMinTtl, (dateValue - lastModified) / 1000 * this._cacheHeuristic);
}
}
return defaultMinTtl;
};
CachePolicy.prototype.timeToLive = function timeToLive() {
return Math.max(0, this.maxAge() - this.age()) * 1000;
};
CachePolicy.prototype.stale = function stale() {
return this.maxAge() <= this.age();
};
CachePolicy.fromObject = function fromObject(obj) {
return new this(undefined, undefined, { _fromObject: obj });
};
CachePolicy.prototype._fromObject = function _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;
};
CachePolicy.prototype.toObject = function 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.
*/
CachePolicy.prototype.revalidationHeaders = function revalidationHeaders(incomingReq) {
this._assertRequestHasHeaders(incomingReq);
var 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.
var 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']) {
var etags = headers['if-none-match'].split(/,/).filter(function (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}
*/
CachePolicy.prototype.revalidatedPolicy = function revalidatedPolicy(request, response) {
this._assertRequestHasHeaders(request);
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.
var 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),
modified: true
};
}
// use other header fields provided in the 304 (Not Modified) response to replace all instances
// of the corresponding header fields in the stored response.
var headers = {};
for (var k in this._resHeaders) {
headers[k] = k in response.headers && !excludedFromRevalidationUpdate[k] ? response.headers[k] : this._resHeaders[k];
}
var newResponse = Object.assign({}, response, {
status: this._status,
method: this._method,
headers
});
return {
policy: new this.constructor(request, newResponse),
modified: false
};
};
return CachePolicy;
}();