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'use strict'
const assert = require('node:assert')
/**
* This takes care of revalidation requests we send to the origin. If we get
* a response indicating that what we have is cached (via a HTTP 304), we can
* continue using the cached value. Otherwise, we'll receive the new response
* here, which we then just pass on to the next handler (most likely a
* CacheHandler). Note that this assumes the proper headers were already
* included in the request to tell the origin that we want to revalidate the
* response (i.e. if-modified-since or if-none-match).
*
* @see https://www.rfc-editor.org/rfc/rfc9111.html#name-validation
*
* @implements {import('../../types/dispatcher.d.ts').default.DispatchHandler}
*/
class CacheRevalidationHandler {
#successful = false
/**
* @type {((boolean, any) => void) | null}
*/
#callback
/**
* @type {(import('../../types/dispatcher.d.ts').default.DispatchHandler)}
*/
#handler
#context
/**
* @type {boolean}
*/
#allowErrorStatusCodes
/**
* @param {(boolean) => void} callback Function to call if the cached value is valid
* @param {import('../../types/dispatcher.d.ts').default.DispatchHandlers} handler
* @param {boolean} allowErrorStatusCodes
*/
constructor (callback, handler, allowErrorStatusCodes) {
if (typeof callback !== 'function') {
throw new TypeError('callback must be a function')
}
this.#callback = callback
this.#handler = handler
this.#allowErrorStatusCodes = allowErrorStatusCodes
}
onRequestStart (_, context) {
this.#successful = false
this.#context = context
}
onRequestUpgrade (controller, statusCode, headers, socket) {
this.#handler.onRequestUpgrade?.(controller, statusCode, headers, socket)
}
onResponseStart (
controller,
statusCode,
headers,
statusMessage
) {
assert(this.#callback != null)
// https://www.rfc-editor.org/rfc/rfc9111.html#name-handling-a-validation-respo
// https://datatracker.ietf.org/doc/html/rfc5861#section-4
this.#successful = statusCode === 304 ||
(this.#allowErrorStatusCodes && statusCode >= 500 && statusCode <= 504)
this.#callback(this.#successful, this.#context)
this.#callback = null
if (this.#successful) {
return true
}
this.#handler.onRequestStart?.(controller, this.#context)
this.#handler.onResponseStart?.(
controller,
statusCode,
headers,
statusMessage
)
}
onResponseData (controller, chunk) {
if (this.#successful) {
return
}
return this.#handler.onResponseData?.(controller, chunk)
}
onResponseEnd (controller, trailers) {
if (this.#successful) {
return
}
this.#handler.onResponseEnd?.(controller, trailers)
}
onResponseError (controller, err) {
if (this.#successful) {
return
}
if (this.#callback) {
this.#callback(false)
this.#callback = null
}
if (typeof this.#handler.onResponseError === 'function') {
this.#handler.onResponseError(controller, err)
} else {
throw err
}
}
}
module.exports = CacheRevalidationHandler
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