Index: node_modules/http-cache-semantics/index.js =================================================================== --- node_modules/http-cache-semantics/index.js (revision 81bc7da776d8cda42939ef4ab350c88d13b4941f) +++ node_modules/http-cache-semantics/index.js (revision 81bc7da776d8cda42939ef4ab350c88d13b4941f) @@ -0,0 +1,928 @@ +'use strict'; + +/** + * @typedef {Object} HttpRequest + * @property {Record} headers - Request headers + * @property {string} [method] - HTTP method + * @property {string} [url] - Request URL + */ + +/** + * @typedef {Object} HttpResponse + * @property {Record} headers - Response headers + * @property {number} [status] - HTTP status code + */ + +/** + * Set of default cacheable status codes per RFC 7231 section 6.1. + * @type {Set} + */ +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} + */ +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} + */ +const errorStatusCodes = new Set([ + 500, + 502, + 503, + 504, +]); + +/** + * Object representing hop-by-hop headers that should be removed. + * @type {Record} + */ +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} + */ +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} An object representing Cache-Control directives. + */ +function parseCacheControl(header) { + /** @type {Record} */ + 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} 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} Response headers */ + this._resHeaders = res.headers; + /** @type {Record} 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|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} 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, synchronous: boolean}|undefined} revalidation - Revalidation information, if any. + * @returns {{response: {headers: Record}, revalidation: {headers: Record, 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, 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, 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}|undefined, revalidation: {headers: Record, synchronous: boolean}|undefined}} An object containing keys: + * - revalidation: { headers: Record, synchronous: boolean } Set if you should send this to the origin server + * - response: { headers: Record } 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} inHeaders - old headers from the cached response + * @returns {Record} A new headers object without hop-by-hop headers. + */ + _copyWithoutHopByHopHeaders(inHeaders) { + /** @type {Record} */ + 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} 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} 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, + }; + } +};