1 files changed, 115 insertions, 0 deletions
diff --git a/devtools/shared/platform/CacheEntry.sys.mjs b/devtools/shared/platform/CacheEntry.sys.mjs
new file mode 100644
index 0000000000..761f0d2946
--- /dev/null
+++ b/devtools/shared/platform/CacheEntry.sys.mjs
@@ -0,0 +1,115 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  NetworkHelper:
+    "resource://devtools/shared/network-observer/NetworkHelper.sys.mjs",
+});
+
+/**
+ * Global cache session object.
+ */
+let gCacheSession = null;
+
+/**
+ * Get (and create if necessary) a cache session / cache storage session.
+ *
+ * @param {nsIRequest} request
+ */
+function getCacheSession(request) {
+  if (!gCacheSession) {
+    try {
+      const cacheService = Services.cache2;
+      if (cacheService) {
+        let loadContext = lazy.NetworkHelper.getRequestLoadContext(request);
+        if (!loadContext) {
+          // Get default load context if we can't fetch.
+          loadContext = Services.loadContextInfo.default;
+        }
+        gCacheSession = cacheService.diskCacheStorage(loadContext);
+      }
+    } catch (e) {
+      gCacheSession = null;
+    }
+  }
+
+  return gCacheSession;
+}
+
+/**
+ * Parses a cache entry returned from the backend to build a response cache
+ * object.
+ *
+ * @param {nsICacheEntry} cacheEntry
+ *     The cache entry from the backend.
+ *
+ * @returns {Object}
+ *     A responseCache object expected by RDP.
+ */
+function buildResponseCacheObject(cacheEntry) {
+  const cacheObject = {};
+  try {
+    if (cacheEntry.storageDataSize) {
+      cacheObject.storageDataSize = cacheEntry.storageDataSize;
+    }
+  } catch (e) {
+    // We just need to handle this in case it's a js file of 0B.
+  }
+  if (cacheEntry.expirationTime) {
+    cacheObject.expirationTime = cacheEntry.expirationTime;
+  }
+  if (cacheEntry.fetchCount) {
+    cacheObject.fetchCount = cacheEntry.fetchCount;
+  }
+  if (cacheEntry.lastFetched) {
+    cacheObject.lastFetched = cacheEntry.lastFetched;
+  }
+  if (cacheEntry.lastModified) {
+    cacheObject.lastModified = cacheEntry.lastModified;
+  }
+  if (cacheEntry.deviceID) {
+    cacheObject.deviceID = cacheEntry.deviceID;
+  }
+  return cacheObject;
+}
+
+/**
+ * Does the fetch for the cache entry from the session.
+ *
+ * @param {nsIRequest} request
+ *     The request object.
+ *
+ * @returns {Promise}
+ *     Promise which resolve a response cache object object, or null if none
+ *     was available.
+ */
+export function getResponseCacheObject(request) {
+  const cacheSession = getCacheSession(request);
+  if (!cacheSession) {
+    return null;
+  }
+
+  return new Promise(resolve => {
+    cacheSession.asyncOpenURI(
+      request.URI,
+      "",
+      Ci.nsICacheStorage.OPEN_SECRETLY,
+      {
+        onCacheEntryCheck: entry => {
+          return Ci.nsICacheEntryOpenCallback.ENTRY_WANTED;
+        },
+        onCacheEntryAvailable: (cacheEntry, isnew, status) => {
+          if (cacheEntry) {
+            const cacheObject = buildResponseCacheObject(cacheEntry);
+            resolve(cacheObject);
+          } else {
+            resolve(null);
+          }
+        },
+      }
+    );
+  });
+}