1 files changed, 81 insertions, 0 deletions
diff --git a/node_modules/fresh/index.js b/node_modules/fresh/index.js
new file mode 100644
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+++ b/node_modules/fresh/index.js
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+/*!
+ * fresh
+ * Copyright(c) 2012 TJ Holowaychuk
+ * Copyright(c) 2016-2017 Douglas Christopher Wilson
+ * MIT Licensed
+ */
+
+'use strict'
+
+/**
+ * RegExp to check for no-cache token in Cache-Control.
+ * @private
+ */
+
+var CACHE_CONTROL_NO_CACHE_REGEXP = /(?:^|,)\s*?no-cache\s*?(?:,|$)/
+
+/**
+ * Simple expression to split token list.
+ * @private
+ */
+
+var TOKEN_LIST_REGEXP = / *, */
+
+/**
+ * Module exports.
+ * @public
+ */
+
+module.exports = fresh
+
+/**
+ * Check freshness of the response using request and response headers.
+ *
+ * @param {Object} reqHeaders
+ * @param {Object} resHeaders
+ * @return {Boolean}
+ * @public
+ */
+
+function fresh (reqHeaders, resHeaders) {
+  // fields
+  var modifiedSince = reqHeaders['if-modified-since']
+  var noneMatch = reqHeaders['if-none-match']
+
+  // unconditional request
+  if (!modifiedSince && !noneMatch) {
+    return false
+  }
+
+  // Always return stale when Cache-Control: no-cache
+  // to support end-to-end reload requests
+  // https://tools.ietf.org/html/rfc2616#section-14.9.4
+  var cacheControl = reqHeaders['cache-control']
+  if (cacheControl && CACHE_CONTROL_NO_CACHE_REGEXP.test(cacheControl)) {
+    return false
+  }
+
+  // if-none-match
+  if (noneMatch && noneMatch !== '*') {
+    var etag = resHeaders['etag']
+    var etagStale = !etag || noneMatch.split(TOKEN_LIST_REGEXP).every(function (match) {
+      return match !== etag && match !== 'W/' + etag && 'W/' + match !== etag
+    })
+
+    if (etagStale) {
+      return false
+    }
+  }
+
+  // if-modified-since
+  if (modifiedSince) {
+    var lastModified = resHeaders['last-modified']
+    var modifiedStale = !lastModified || Date.parse(lastModified) > Date.parse(modifiedSince)
+
+    if (modifiedStale) {
+      return false
+    }
+  }
+
+  return true
+}