components/offline_pages/background/request_queue.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_QUEUE_H_
#define COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_QUEUE_H_

#include <stdint.h>

#include <memory>
#include <vector>

#include "base/callback.h"
#include "base/macros.h"

namespace offline_pages {

class RequestQueueStore;
class SavePageRequest;

// Class responsible for managing save page requests.
class RequestQueue {
 public:
  enum class GetRequestsResult {
    kSuccess,
    kStoreFailure,
  };

  enum class AddRequestResult {
    kSuccess,
    kStoreFailure,
    kRequestQuotaHit,  // Cannot add a request with this namespace, as it has
                       // reached a quota of active requests.
  };

  enum class UpdateRequestResult {
    kSuccess,
    kStoreFailure,
    kRequestDoesNotExist,  // Failed to delete the request because it does not
                           // exist.
  };

  // Callback used for |GetRequests|.
  typedef base::Callback<void(GetRequestsResult,
                              const std::vector<SavePageRequest>&)>
      GetRequestsCallback;

  // Callback used for |AddRequest|.
  typedef base::Callback<void(AddRequestResult, const SavePageRequest& request)>
      AddRequestCallback;

  // Callback used by |UdpateRequest| and |RemoveRequest|.
  typedef base::Callback<void(UpdateRequestResult)> UpdateRequestCallback;

  explicit RequestQueue(std::unique_ptr<RequestQueueStore> store);
  ~RequestQueue();

  // Gets all of the active requests from the store. Calling this method may
  // schedule purging of the request queue.
  void GetRequests(const GetRequestsCallback& callback);

  // Adds |request| to the request queue. Result is returned through |callback|.
  // In case adding the request violates policy, the result will fail with
  // appropriate result. Callback will also return a copy of a request with all
  // fields set.
  void AddRequest(const SavePageRequest& request,
                  const AddRequestCallback& callback);

  // Updates a request in the request queue if a request with matching ID
  // exists. Does nothing otherwise. Result is returned through |callback|.
  void UpdateRequest(const SavePageRequest& request,
                     const UpdateRequestCallback& callback);

  // Removes the request matching the |request_id|. Result is returned through
  // |callback|.
  void RemoveRequest(int64_t request_id, const UpdateRequestCallback& callback);

 private:
  // Callback used by |PurgeRequests|.
  typedef base::Callback<void(UpdateRequestResult,
                              int /* removed requests count */)>
      PurgeRequestsCallback;

  // Purges the queue, removing the requests that are no longer relevant, e.g.
  // expired request. Result is returned through |callback| carries the number
  // of removed requests.
  void PurgeRequests(const PurgeRequestsCallback& callback);

  std::unique_ptr<RequestQueueStore> store_;

  DISALLOW_COPY_AND_ASSIGN(RequestQueue);
};

}  // namespace offline_pages

#endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_QUEUE_H_