More detailed implementation of the RequestPicker

components/offline_pages/background/request_picker.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_PICKER_H_
 #define COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_PICKER_H_
 
+#include <memory>
+
 #include "base/memory/weak_ptr.h"
+#include "components/offline_pages/background/device_conditions.h"
+#include "components/offline_pages/background/offliner_policy.h"
 #include "components/offline_pages/background/request_coordinator.h"
 #include "components/offline_pages/background/request_queue.h"
 
 namespace offline_pages {
+
+typedef bool (RequestPicker::*RequestCompareFunction)(
+    const SavePageRequest* left, const SavePageRequest* right);
+
 class RequestPicker {
  public:
-  RequestPicker(RequestQueue* requestQueue);
+  RequestPicker(RequestQueue* requestQueue, OfflinerPolicy* policy);
 
   ~RequestPicker();
 
   // Choose which request we should process next based on the current
   // conditions, and call back to the RequestCoordinator when we have one.
   void ChooseNextRequest(
       RequestCoordinator::RequestPickedCallback picked_callback,
-      RequestCoordinator::RequestQueueEmptyCallback empty_callback);
+      RequestCoordinator::RequestQueueEmptyCallback empty_callback,
+      DeviceConditions* device_conditions);
 
  private:
   // Callback for the GetRequest results to be delivered.
   void GetRequestResultCallback(RequestQueue::GetRequestsResult result,
                                 const std::vector<SavePageRequest>& results);
 
+  // Filter out requests that don't meet the current conditions.  For instance,
+  // if this is a predictive request, and we are not on WiFi, it should be
+  // ignored this round.
+  bool RequestConditionsSatisfied(const SavePageRequest& request);
+
+  // Using policies, decide if the new request is preferable to the best we have
+  // so far.
+  bool IsNewRequestBetter(const SavePageRequest* oldRequest,
+                          const SavePageRequest* newRequest,
+                          RequestCompareFunction comparator);
+
+  // Is the new request preferable from the retry count first standpoint?
+  bool RetryCountFirstCompareFunction(const SavePageRequest* left,
+                                      const SavePageRequest* right);
+
+  // Is the new request better from the recency first standpoint?
+  bool RecencyFirstCompareFunction(const SavePageRequest* left,
+                                   const SavePageRequest* right);
+
+  // Does the new request have better retry count?
+  int CompareRetryCount(const SavePageRequest* left,
+                        const SavePageRequest* right);
+
+  // Does the new request have better creation time?
+  int CompareCreationTime(const SavePageRequest* left,
+                          const SavePageRequest* right);
+
   // unowned pointer to the request queue.
   RequestQueue* queue_;
+  // unowned pointer to the policy object.
+  OfflinerPolicy* policy_;
+  // Current conditions on the device
+  std::unique_ptr<DeviceConditions> current_conditions_;
+  // True if we prefer less-tried requests
+  bool fewer_retries_better_;
+  // True if we prefer requests submitted more recently
+  bool earlier_requests_better_;
   // Callback for when we are done picking a request to do next.
   RequestCoordinator::RequestPickedCallback picked_callback_;
   // Callback for when there are no more reqeusts to pick.
   RequestCoordinator::RequestQueueEmptyCallback empty_callback_;
   // Allows us to pass a weak pointer to callbacks.
   base::WeakPtrFactory<RequestPicker> weak_ptr_factory_;
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_PICKER_H_