1 files changed, 124 insertions, 0 deletions
diff --git a/vanilla/node_modules/undici/lib/handler/cache-revalidation-handler.js b/vanilla/node_modules/undici/lib/handler/cache-revalidation-handler.js
new file mode 100644
index 0000000..393d16d
--- /dev/null
+++ b/vanilla/node_modules/undici/lib/handler/cache-revalidation-handler.js
@@ -0,0 +1,124 @@
+'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