// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SERVICES_DEVICE_GEOLOCATION_GEOLOCATION_PROVIDER_H_
#define SERVICES_DEVICE_GEOLOCATION_GEOLOCATION_PROVIDER_H_

#include "base/callback_list.h"
#include "services/device/public/mojom/geoposition.mojom.h"

namespace device {

// This is the main API to the geolocation subsystem. The application will hold
// a single instance of this class and can register multiple clients to be
// notified of location changes:
// * Callbacks are registered by AddLocationUpdateCallback() and will keep
//   receiving updates until the returned subscription object is destroyed.
// The application must instantiate the GeolocationProvider on the UI thread and
// must communicate with it on the same thread.
// The underlying location arbitrator will only be enabled whilst there is at
// least one registered observer or pending callback (and only after
// mojom::UserDidOptIntoLocationServices() which is implemented by
// GeolocationProviderImpl). The arbitrator and the location providers it uses
// run on a separate Geolocation thread.
class GeolocationProvider {
 public:
  static GeolocationProvider* GetInstance();

  typedef base::RepeatingCallback<void(const mojom::GeopositionResult&)>
      LocationUpdateCallback;

  // |enable_high_accuracy| is used as a 'hint' for the provider preferences for
  // this particular observer, however the observer could receive updates for
  // best available locations from any active provider whilst it is registered.
  virtual base::CallbackListSubscription AddLocationUpdateCallback(
      const LocationUpdateCallback& callback,
      bool enable_high_accuracy) = 0;

  // Returns the current cached position result if available.
  virtual mojom::GeopositionResultPtr GetCachedPosition() = 0;

  // Sets the singleton GeolocationProvider that will be returned by
  // GetInstance().
  static void SetInstanceForTesting(GeolocationProvider* instance_for_testing);

  // Overrides the current location for testing.
  //
  // Overrides the location for automation/testing. Suppresses any further
  // updates from the actual providers and sends an update with the overridden
  // position to all registered clients.
  //
  // Do not use this function in unit tests. The function instantiates the
  // singleton geolocation stack in the background and manipulates it to report
  // a fake location. Neither step can be undone, breaking unit test isolation
  // (https://crbug.com/125931).
  virtual void OverrideLocationForTesting(
      mojom::GeopositionResultPtr result) = 0;

 protected:
  virtual ~GeolocationProvider() = default;

  static GeolocationProvider* instance_for_testing_;
};

}  // namespace device

#endif  // SERVICES_DEVICE_GEOLOCATION_GEOLOCATION_PROVIDER_H_