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network_location_provider.cc

// Copyright (c) 2010 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 "chrome/browser/geolocation/network_location_provider.h"

#include "base/time.h"
#include "chrome/browser/geolocation/access_token_store.h"

namespace {
// The maximum period of time we'll wait for a complete set of device data
// before sending the request.
const int kDataCompleteWaitPeriod = 1000 * 2;  // 2 seconds

// The maximum size of the cache of positions for previously requested device
// data.
const size_t kMaximumCacheSize = 10;
}  // namespace

// The PositionCache handles caching and retrieving a position returned by a
// network location provider. It is not thread safe. It's methods are called on
// multiple threads by NetworkLocationProvider, but the timing is such that
// thread safety is not required.
class NetworkLocationProvider::PositionCache {
 public:
  // Caches the current position response for the current set of cell ID and
  // WiFi data. Returns true on success, false otherwise.
  bool CachePosition(const RadioData& radio_data,
                     const WifiData& wifi_data,
                     const Geoposition& position) {
    // Check that we can generate a valid key for the device data.
    string16 key;
    if (!MakeKey(radio_data, wifi_data, &key)) {
      return false;
    }
    // If the cache is full, remove the oldest entry.
    if (cache_.size() == kMaximumCacheSize) {
      DCHECK(cache_times_.size() == kMaximumCacheSize);
      CacheTimesMap::iterator oldest_entry = cache_times_.begin();
      DCHECK(oldest_entry != cache_times_.end());
      cache_.erase(oldest_entry->second);
      cache_times_.erase(oldest_entry);
    }
    // Insert the position into the cache.
    std::pair<CacheMap::iterator, bool> result =
        cache_.insert(std::make_pair(key, position));
    DCHECK(result.second);
    cache_times_[position.timestamp] = result.first;
    DCHECK(cache_.size() == cache_times_.size());
    return true;
  }

  // Searches for a cached position response for the current set of cell ID and
  // WiFi data. Returns the cached position if available, NULL otherwise.
  const Geoposition *FindPosition(const RadioData &radio_data,
                                  const WifiData &wifi_data) {
    string16 key;
    if (!MakeKey(radio_data, wifi_data, &key)) {
      return NULL;
    }
    CacheMap::const_iterator iter = cache_.find(key);
    return iter == cache_.end() ? NULL : &iter->second;
  }

  // Makes the key for the map of cached positions, using a set of
  // device data. Returns true if a good key was generated, false otherwise.
  static bool MakeKey(const RadioData& /*radio_data*/,
                      const WifiData& wifi_data,
                      string16* key) {
    // Currently we use only the WiFi data, and base the key only on the MAC
    // addresses.
    // TODO(steveblock): Make use of radio_data.
    DCHECK(key);
    key->clear();
    key->reserve(wifi_data.access_point_data.size() * 19);
    const string16 separator(ASCIIToUTF16("|"));
    for (WifiData::AccessPointDataSet::const_iterator iter =
         wifi_data.access_point_data.begin();
         iter != wifi_data.access_point_data.end();
         iter++) {
      *key += separator;
      *key += iter->mac_address;
      *key += separator;
    }
    // If the key is the empty string, return false, as we don't want to cache a
    // position for such a set of device data.
    return !key->empty();
  }

 private:
  // The cache of positions. This is stored using two maps. One map is keyed on
  // a string that represents a set of device data, the other is keyed on the
  // timestamp of the position.
  typedef std::map<string16, Geoposition> CacheMap;
  CacheMap cache_;
  typedef std::map<base::Time, CacheMap::iterator> CacheTimesMap;
  CacheTimesMap cache_times_;
};

// NetworkLocationProvider factory function
LocationProviderBase* NewNetworkLocationProvider(
    AccessTokenStore* access_token_store,
    URLRequestContextGetter* context,
    const GURL& url,
    const string16& access_token) {
  return new NetworkLocationProvider(
      access_token_store, context, url, access_token);
}

// NetworkLocationProvider
NetworkLocationProvider::NetworkLocationProvider(
    AccessTokenStore* access_token_store,
    URLRequestContextGetter* url_context_getter,
    const GURL& url,
    const string16& access_token)
    : access_token_store_(access_token_store),
      radio_data_provider_(NULL),
      wifi_data_provider_(NULL),
      is_radio_data_complete_(false),
      is_wifi_data_complete_(false),
      access_token_(access_token),
      is_new_data_available_(false),
      ALLOW_THIS_IN_INITIALIZER_LIST(delayed_start_task_(this)) {
  // Create the position cache.
  position_cache_.reset(new PositionCache());

  request_.reset(new NetworkLocationRequest(url_context_getter, url, this));
}

NetworkLocationProvider::~NetworkLocationProvider() {
  StopProvider();
}

// LocationProviderBase implementation
void NetworkLocationProvider::GetPosition(Geoposition *position) {
  DCHECK(position);
  *position = position_;
}

void NetworkLocationProvider::UpdatePosition() {
  // TODO(joth): When called via the public (base class) interface, this should
  // poke each data provider to get them to expedite their next scan.
  // Whilst in the delayed start, only send request if all data is ready.
  if (delayed_start_task_.empty() ||
      (is_radio_data_complete_ && is_wifi_data_complete_)) {
    RequestPosition();
  }
}

void NetworkLocationProvider::OnPermissionGranted(
    const GURL& requesting_frame) {
  const bool host_was_empty = most_recent_authorized_host_.empty();
  most_recent_authorized_host_ = requesting_frame.host();
  if (host_was_empty && !most_recent_authorized_host_.empty()
      && IsStarted()) {
    UpdatePosition();
  }
}

// DeviceDataProviderInterface::ListenerInterface implementation.
void NetworkLocationProvider::DeviceDataUpdateAvailable(
    RadioDataProvider* provider) {
  DCHECK(provider == radio_data_provider_);
  is_radio_data_complete_ = radio_data_provider_->GetData(&radio_data_);
  OnDeviceDataUpdated();
}

void NetworkLocationProvider::DeviceDataUpdateAvailable(
    WifiDataProvider* provider) {
  DCHECK(provider == wifi_data_provider_);
  is_wifi_data_complete_ = wifi_data_provider_->GetData(&wifi_data_);
  OnDeviceDataUpdated();
}

// NetworkLocationRequest::ListenerInterface implementation.
void NetworkLocationProvider::LocationResponseAvailable(
    const Geoposition& position,
    bool server_error,
    const string16& access_token,
    const RadioData& radio_data,
    const WifiData& wifi_data) {
  DCHECK(CalledOnValidThread());
  // Record the position and update our cache.
  position_ = position;
  if (position.IsValidFix()) {
    position_cache_->CachePosition(radio_data, wifi_data, position);
  }

  // Record access_token if it's set.
  if (!access_token.empty() && access_token_ != access_token) {
    access_token_ = access_token;
    access_token_store_->SaveAccessToken(request_->url(), access_token);
  }

  // Let listeners know that we now have a position available.
  UpdateListeners();
}

bool NetworkLocationProvider::StartProvider(bool high_accuracy) {
  DCHECK(CalledOnValidThread());
  if (IsStarted())
    return true;
  DCHECK(wifi_data_provider_ == NULL);
  if (!request_->url().is_valid()) {
    LOG(WARNING) << "StartProvider() : Failed, Bad URL: "
                 << request_->url().possibly_invalid_spec();
    return false;
  }

  // Get the device data providers. The first call to Register will create the
  // provider and it will be deleted by ref counting.
  radio_data_provider_ = RadioDataProvider::Register(this);
  wifi_data_provider_ = WifiDataProvider::Register(this);

  MessageLoop::current()->PostDelayedTask(
      FROM_HERE,
      delayed_start_task_.NewRunnableMethod(
          &NetworkLocationProvider::RequestPosition),
      kDataCompleteWaitPeriod);
  // Get the device data.
  is_radio_data_complete_ = radio_data_provider_->GetData(&radio_data_);
  is_wifi_data_complete_ = wifi_data_provider_->GetData(&wifi_data_);
  if (is_radio_data_complete_ || is_wifi_data_complete_)
    OnDeviceDataUpdated();
  return true;
}

void NetworkLocationProvider::StopProvider() {
  DCHECK(CalledOnValidThread());
  if (IsStarted()) {
    radio_data_provider_->Unregister(this);
    wifi_data_provider_->Unregister(this);
  }
  radio_data_provider_ = NULL;
  wifi_data_provider_ = NULL;
  delayed_start_task_.RevokeAll();
}

// Other methods
void NetworkLocationProvider::RequestPosition() {
  DCHECK(CalledOnValidThread());
  if (!is_new_data_available_)
    return;

  const Geoposition* cached_position =
      position_cache_->FindPosition(radio_data_, wifi_data_);
  DCHECK(!device_data_updated_timestamp_.is_null()) <<
      "Timestamp must be set before looking up position";
  if (cached_position) {
    DCHECK(cached_position->IsValidFix());
    // Record the position and update its timestamp.
    position_ = *cached_position;
    // The timestamp of a position fix is determined by the timestamp
    // of the source data update. (The value of position_.timestamp from
    // the cache could be from weeks ago!)
    position_.timestamp = device_data_updated_timestamp_;
    is_new_data_available_ = false;
    // Let listeners know that we now have a position available.
    UpdateListeners();
    return;
  }
  // Don't send network requests until authorized. http://crbug.com/39171
  if (most_recent_authorized_host_.empty())
    return;

  delayed_start_task_.RevokeAll();
  is_new_data_available_ = false;

  // TODO(joth): Rather than cancel pending requests, we should create a new
  // NetworkLocationRequest for each and hold a set of pending requests.
  if (request_->is_request_pending()) {
    LOG(INFO) << "NetworkLocationProvider - pre-empting pending network request"
              << "with new data. Wifi APs: "
              << wifi_data_.access_point_data.size();
  }
  // The hostname sent in the request is just to give a first-order
  // approximation of usage. We do not need to guarantee that this network
  // request was triggered by an API call from this specific host.
  request_->MakeRequest(most_recent_authorized_host_, access_token_,
                        radio_data_, wifi_data_,
                        device_data_updated_timestamp_);
}

void NetworkLocationProvider::OnDeviceDataUpdated() {
  DCHECK(CalledOnValidThread());
  device_data_updated_timestamp_ = base::Time::Now();

  is_new_data_available_ = is_radio_data_complete_ || is_wifi_data_complete_;
  UpdatePosition();
}

bool NetworkLocationProvider::IsStarted() const {
  DCHECK_EQ(!!radio_data_provider_, !!wifi_data_provider_);
  return wifi_data_provider_ != NULL;
}

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