// Copyright (c) 2012 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.

#include "device/geolocation/location_arbitrator.h"

#include <map>
#include <memory>
#include <utility>

#include "base/bind.h"
#include "base/bind_helpers.h"
#include "base/memory/ptr_util.h"
#include "build/build_config.h"
#include "device/geolocation/network_location_provider.h"
#include "device/geolocation/public/cpp/geoposition.h"
#include "device/geolocation/wifi_polling_policy.h"

namespace device {

// To avoid oscillations, set this to twice the expected update interval of a
// a GPS-type location provider (in case it misses a beat) plus a little.
const base::TimeDelta LocationArbitrator::kFixStaleTimeoutTimeDelta =
    base::TimeDelta::FromSeconds(11);

LocationArbitrator::LocationArbitrator(
    const CustomLocationProviderCallback& custom_location_provider_getter,
    GeolocationProvider::RequestContextProducer request_context_producer,
    const std::string& api_key)
    : custom_location_provider_getter_(custom_location_provider_getter),
      request_context_producer_(request_context_producer),
      api_key_(api_key),
      position_provider_(nullptr),
      is_permission_granted_(false),
      is_running_(false) {}

LocationArbitrator::~LocationArbitrator() {
  // Release the global wifi polling policy state.
  WifiPollingPolicy::Shutdown();
}

bool LocationArbitrator::HasPermissionBeenGrantedForTest() const {
  return is_permission_granted_;
}

void LocationArbitrator::OnPermissionGranted() {
  is_permission_granted_ = true;
  for (const auto& provider : providers_)
    provider->OnPermissionGranted();
}

void LocationArbitrator::SetLastNetworkPosition(
    const mojom::Geoposition& position) {
  last_network_position_ = position;
}

const mojom::Geoposition& LocationArbitrator::GetLastNetworkPosition() {
  return last_network_position_;
}

void LocationArbitrator::StartProvider(bool enable_high_accuracy) {
  is_running_ = true;
  enable_high_accuracy_ = enable_high_accuracy;

  if (providers_.empty()) {
    RegisterSystemProvider();

    // Request a URLRequestContextGetter to use for network geolocation.
    if (!request_context_producer_.is_null()) {
      // Note: .Reset() will cancel any previous callback.
      request_context_response_callback_.Reset(
          base::Bind(&LocationArbitrator::OnRequestContextResponse,
                     base::Unretained(this)));
      // Invoke callback to obtain a URL request context.
      request_context_producer_.Run(
          request_context_response_callback_.callback());
      return;
    }
  }
  DoStartProviders();
}

void LocationArbitrator::DoStartProviders() {
  if (providers_.empty()) {
    // If no providers are available, we report an error to avoid
    // callers waiting indefinitely for a reply.
    mojom::Geoposition position;
    position.error_code = mojom::Geoposition::ErrorCode::POSITION_UNAVAILABLE;
    arbitrator_update_callback_.Run(this, position);
    return;
  }
  for (const auto& provider : providers_) {
    provider->StartProvider(enable_high_accuracy_);
  }
}

void LocationArbitrator::StopProvider() {
  // Reset the reference location state (provider+position)
  // so that future starts use fresh locations from
  // the newly constructed providers.
  position_provider_ = nullptr;
  position_ = mojom::Geoposition();

  providers_.clear();
  is_running_ = false;
}

void LocationArbitrator::OnRequestContextResponse(
    scoped_refptr<net::URLRequestContextGetter> context_getter) {
  if (context_getter != nullptr) {
    // Create a NetworkLocationProvider using the provided request context.
    RegisterProvider(
        NewNetworkLocationProvider(std::move(context_getter), api_key_));
  }
  DoStartProviders();
}

void LocationArbitrator::RegisterProvider(
    std::unique_ptr<LocationProvider> provider) {
  if (!provider)
    return;
  provider->SetUpdateCallback(base::Bind(&LocationArbitrator::OnLocationUpdate,
                                         base::Unretained(this)));
  if (is_permission_granted_)
    provider->OnPermissionGranted();
  providers_.push_back(std::move(provider));
}

void LocationArbitrator::RegisterSystemProvider() {
  std::unique_ptr<LocationProvider> provider;
  if (custom_location_provider_getter_)
    provider = custom_location_provider_getter_.Run();

  // Use the default system provider if the custom provider is null.
  if (!provider)
    provider = NewSystemLocationProvider();
  RegisterProvider(std::move(provider));
}

void LocationArbitrator::OnLocationUpdate(
    const LocationProvider* provider,
    const mojom::Geoposition& new_position) {
  DCHECK(ValidateGeoposition(new_position) ||
         new_position.error_code != mojom::Geoposition::ErrorCode::NONE);
  providers_polled_.insert(provider);
  if (IsNewPositionBetter(position_, new_position,
                          provider == position_provider_)) {
    position_provider_ = provider;
    position_ = new_position;
  }
  // Don't fail until all providers had their say.
  if (ValidateGeoposition(position_) || (providers_polled_.size() == providers_.size()))
    arbitrator_update_callback_.Run(this, position_);
}

const mojom::Geoposition& LocationArbitrator::GetPosition() {
  return position_;
}

void LocationArbitrator::SetUpdateCallback(
    const LocationProviderUpdateCallback& callback) {
  DCHECK(!callback.is_null());
  arbitrator_update_callback_ = callback;
}

std::unique_ptr<LocationProvider>
LocationArbitrator::NewNetworkLocationProvider(
    scoped_refptr<net::URLRequestContextGetter> context,
    const std::string& api_key) {
  DCHECK(context != nullptr);
#if defined(OS_ANDROID)
  // Android uses its own SystemLocationProvider.
  return nullptr;
#else
  return std::make_unique<NetworkLocationProvider>(std::move(context), api_key,
                                                   this);
#endif
}

std::unique_ptr<LocationProvider>
LocationArbitrator::NewSystemLocationProvider() {
#if defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_LINUX) || \
    defined(OS_FUCHSIA)
  return nullptr;
#else
  return device::NewSystemLocationProvider();
#endif
}

base::Time LocationArbitrator::GetTimeNow() const {
  return base::Time::Now();
}

bool LocationArbitrator::IsNewPositionBetter(
    const mojom::Geoposition& old_position,
    const mojom::Geoposition& new_position,
    bool from_same_provider) const {
  // Updates location_info if it's better than what we currently have,
  // or if it's a newer update from the same provider.
  if (!ValidateGeoposition(old_position)) {
    // Older location wasn't locked.
    return true;
  }
  if (ValidateGeoposition(new_position)) {
    // New location is locked, let's check if it's any better.
    if (old_position.accuracy >= new_position.accuracy) {
      // Accuracy is better.
      return true;
    } else if (from_same_provider) {
      // Same provider, fresher location.
      return true;
    } else if (GetTimeNow() - old_position.timestamp >
               kFixStaleTimeoutTimeDelta) {
      // Existing fix is stale.
      return true;
    }
  }
  return false;
}

}  // namespace device