gecko-dev/dom/system/NetworkGeolocationProvider.jsm

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

"use strict";

const {XPCOMUtils} = ChromeUtils.import("resource://gre/modules/XPCOMUtils.jsm");
const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");

XPCOMUtils.defineLazyGlobalGetters(this, ["XMLHttpRequest"]);

// PositionError has no interface object, so we can't use that here.
const POSITION_UNAVAILABLE = 2;

var gLoggingEnabled = false;

/*
   The gLocationRequestTimeout controls how long we wait on receiving an update
   from the Wifi subsystem.  If this timer fires, we believe the Wifi scan has
   had a problem and we no longer can use Wifi to position the user this time
   around (we will continue to be hopeful that Wifi will recover).

   This timeout value is also used when Wifi scanning is disabled (see
   gWifiScanningEnabled).  In this case, we use this timer to collect cell/ip
   data and xhr it to the location server.
*/

var gLocationRequestTimeout = 5000;

var gWifiScanningEnabled = true;

function LOG(aMsg) {
  if (gLoggingEnabled) {
    aMsg = "*** WIFI GEO: " + aMsg + "\n";
    Services.console.logStringMessage(aMsg);
    dump(aMsg);
  }
}

function CachedRequest(loc, cellInfo, wifiList) {
  this.location = loc;

  let wifis = new Set();
  if (wifiList) {
    for (let i = 0; i < wifiList.length; i++) {
      wifis.add(wifiList[i].macAddress);
    }
  }

  // Use only these values for equality
  // (the JSON will contain additional values in future)
  function makeCellKey(cell) {
    return "" + cell.radio + ":" + cell.mobileCountryCode + ":" +
    cell.mobileNetworkCode + ":" + cell.locationAreaCode + ":" +
    cell.cellId;
  }

  let cells = new Set();
  if (cellInfo) {
    for (let i = 0; i < cellInfo.length; i++) {
      cells.add(makeCellKey(cellInfo[i]));
    }
  }

  this.hasCells = () => cells.size > 0;

  this.hasWifis = () => wifis.size > 0;

  // if fields match
  this.isCellEqual = function(cellInfo) {
    if (!this.hasCells()) {
      return false;
    }

    let len1 = cells.size;
    let len2 = cellInfo.length;

    if (len1 != len2) {
      LOG("cells not equal len");
      return false;
    }

    for (let i = 0; i < len2; i++) {
      if (!cells.has(makeCellKey(cellInfo[i]))) {
        return false;
      }
    }
    return true;
  };

  // if 50% of the SSIDS match
  this.isWifiApproxEqual = function(wifiList) {
    if (!this.hasWifis()) {
      return false;
    }

    // if either list is a 50% subset of the other, they are equal
    let common = 0;
    for (let i = 0; i < wifiList.length; i++) {
      if (wifis.has(wifiList[i].macAddress)) {
        common++;
      }
    }
    let kPercentMatch = 0.5;
    return common >= (Math.max(wifis.size, wifiList.length) * kPercentMatch);
  };

  this.isGeoip = function() {
    return !this.hasCells() && !this.hasWifis();
  };

  this.isCellAndWifi = function() {
    return this.hasCells() && this.hasWifis();
  };

  this.isCellOnly = function() {
    return this.hasCells() && !this.hasWifis();
  };

  this.isWifiOnly = function() {
    return this.hasWifis() && !this.hasCells();
  };
 }

var gCachedRequest = null;
var gDebugCacheReasoning = ""; // for logging the caching logic

// This function serves two purposes:
// 1) do we have a cached request
// 2) is the cached request better than what newCell and newWifiList will obtain
// If the cached request exists, and we know it to have greater accuracy
// by the nature of its origin (wifi/cell/geoip), use its cached location.
//
// If there is more source info than the cached request had, return false
// In other cases, MLS is known to produce better/worse accuracy based on the
// inputs, so base the decision on that.
function isCachedRequestMoreAccurateThanServerRequest(newCell, newWifiList) {
  gDebugCacheReasoning = "";
  let isNetworkRequestCacheEnabled = true;
  try {
    // Mochitest needs this pref to simulate request failure
    isNetworkRequestCacheEnabled = Services.prefs.getBoolPref("geo.wifi.debug.requestCache.enabled");
    if (!isNetworkRequestCacheEnabled) {
      gCachedRequest = null;
    }
  } catch (e) {}

  if (!gCachedRequest || !isNetworkRequestCacheEnabled) {
    gDebugCacheReasoning = "No cached data";
    return false;
  }

  if (!newCell && !newWifiList) {
    gDebugCacheReasoning = "New req. is GeoIP.";
    return true;
  }

  if (newCell && newWifiList && (gCachedRequest.isCellOnly() || gCachedRequest.isWifiOnly())) {
    gDebugCacheReasoning = "New req. is cell+wifi, cache only cell or wifi.";
    return false;
  }

  if (newCell && gCachedRequest.isWifiOnly()) {
    // In order to know if a cell-only request should trump a wifi-only request
    // need to know if wifi is low accuracy. >5km would be VERY low accuracy,
    // it is worth trying the cell
    var isHighAccuracyWifi = gCachedRequest.location.coords.accuracy < 5000;
    gDebugCacheReasoning = "Req. is cell, cache is wifi, isHigh:" + isHighAccuracyWifi;
    return isHighAccuracyWifi;
  }

  let hasEqualCells = false;
  if (newCell) {
    hasEqualCells = gCachedRequest.isCellEqual(newCell);
  }

  let hasEqualWifis = false;
  if (newWifiList) {
    hasEqualWifis = gCachedRequest.isWifiApproxEqual(newWifiList);
  }

  gDebugCacheReasoning = "EqualCells:" + hasEqualCells + " EqualWifis:" + hasEqualWifis;

  if (gCachedRequest.isCellOnly()) {
    gDebugCacheReasoning += ", Cell only.";
    if (hasEqualCells) {
      return true;
    }
  } else if (gCachedRequest.isWifiOnly() && hasEqualWifis) {
    gDebugCacheReasoning += ", Wifi only.";
    return true;
  } else if (gCachedRequest.isCellAndWifi()) {
     gDebugCacheReasoning += ", Cache has Cell+Wifi.";
    if ((hasEqualCells && hasEqualWifis) ||
        (!newWifiList && hasEqualCells) ||
        (!newCell && hasEqualWifis)) {
     return true;
    }
  }

  return false;
}

function WifiGeoCoordsObject(lat, lon, acc) {
  this.latitude = lat;
  this.longitude = lon;
  this.accuracy = acc;

  // Neither GLS nor MLS return the following properties, so set them to NaN
  // here. nsGeoPositionCoords will convert NaNs to null for optional properties
  // of the JavaScript Coordinates object.
  this.altitude = NaN;
  this.altitudeAccuracy = NaN;
  this.heading = NaN;
  this.speed = NaN;
}

WifiGeoCoordsObject.prototype = {
  QueryInterface:  ChromeUtils.generateQI([Ci.nsIDOMGeoPositionCoords]),
};

function WifiGeoPositionObject(lat, lng, acc) {
  this.coords = new WifiGeoCoordsObject(lat, lng, acc);
  this.address = null;
  this.timestamp = Date.now();
}

WifiGeoPositionObject.prototype = {
  QueryInterface:   ChromeUtils.generateQI([Ci.nsIDOMGeoPosition]),
};

function WifiGeoPositionProvider() {
  gLoggingEnabled = Services.prefs.getBoolPref("geo.wifi.logging.enabled", false);
  gLocationRequestTimeout = Services.prefs.getIntPref("geo.wifi.timeToWaitBeforeSending", 5000);
  gWifiScanningEnabled = Services.prefs.getBoolPref("geo.wifi.scan", true);

  this.wifiService = null;
  this.timer = null;
  this.started = false;
}

WifiGeoPositionProvider.prototype = {
  classID:          Components.ID("{77DA64D3-7458-4920-9491-86CC9914F904}"),
  QueryInterface:   ChromeUtils.generateQI([Ci.nsIGeolocationProvider,
                                            Ci.nsIWifiListener,
                                            Ci.nsITimerCallback,
                                            Ci.nsIObserver]),
  listener: null,

  resetTimer() {
    if (this.timer) {
      this.timer.cancel();
      this.timer = null;
    }
    // wifi thread triggers WifiGeoPositionProvider to proceed, with no wifi, do manual timeout
    this.timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
    this.timer.initWithCallback(this,
                                gLocationRequestTimeout,
                                this.timer.TYPE_REPEATING_SLACK);
  },

  startup() {
    if (this.started)
      return;

    this.started = true;

    if (gWifiScanningEnabled && Cc["@mozilla.org/wifi/monitor;1"]) {
      if (this.wifiService) {
        this.wifiService.stopWatching(this);
      }
      this.wifiService = Cc["@mozilla.org/wifi/monitor;1"].getService(Ci.nsIWifiMonitor);
      this.wifiService.startWatching(this);
    }

    this.resetTimer();
    LOG("startup called.");
  },

  watch(c) {
    this.listener = c;
  },

  shutdown() {
    LOG("shutdown called");
    if (!this.started) {
      return;
    }

    // Without clearing this, we could end up using the cache almost indefinitely
    // TODO: add logic for cache lifespan, for now just be safe and clear it
    gCachedRequest = null;

    if (this.timer) {
      this.timer.cancel();
      this.timer = null;
    }

    if (this.wifiService) {
      this.wifiService.stopWatching(this);
      this.wifiService = null;
    }

    this.listener = null;
    this.started = false;
  },

  setHighAccuracy(enable) {
  },

  onChange(accessPoints) {
    // we got some wifi data, rearm the timer.
    this.resetTimer();

    function isPublic(ap) {
      let mask = "_nomap";
      let result = ap.ssid.indexOf(mask, ap.ssid.length - mask.length);
      if (result != -1) {
        LOG("Filtering out " + ap.ssid + " " + result);
        return false;
      }
      return true;
    }

    function sort(a, b) {
      return b.signal - a.signal;
    }

    function encode(ap) {
      return { "macAddress": ap.mac, "signalStrength": ap.signal };
    }

    let wifiData = null;
    if (accessPoints) {
      wifiData = accessPoints.filter(isPublic).sort(sort).map(encode);
    }
    this.sendLocationRequest(wifiData);
  },

  onError(code) {
    LOG("wifi error: " + code);
    this.sendLocationRequest(null);
  },

  notify(timer) {
    this.sendLocationRequest(null);
  },

  sendLocationRequest(wifiData) {
    let data = { cellTowers: undefined, wifiAccessPoints: undefined };
    if (wifiData && wifiData.length >= 2) {
      data.wifiAccessPoints = wifiData;
    }

    let useCached = isCachedRequestMoreAccurateThanServerRequest(data.cellTowers,
                                                                 data.wifiAccessPoints);

    LOG("Use request cache:" + useCached + " reason:" + gDebugCacheReasoning);

    if (useCached) {
      gCachedRequest.location.timestamp = Date.now();
      if (this.listener) {
        this.listener.update(gCachedRequest.location);
      }
      return;
    }

    // From here on, do a network geolocation request //
    let url = Services.urlFormatter.formatURLPref("geo.wifi.uri");
    LOG("Sending request");

    let xhr = new XMLHttpRequest();
    try {
      xhr.open("POST", url, true);
      xhr.channel.loadFlags = Ci.nsIChannel.LOAD_ANONYMOUS;
    } catch (e) {
      notifyPositionUnavailable(this.listener);
      return;
    }
    xhr.setRequestHeader("Content-Type", "application/json; charset=UTF-8");
    xhr.responseType = "json";
    xhr.mozBackgroundRequest = true;
    xhr.timeout = Services.prefs.getIntPref("geo.wifi.xhr.timeout");
    xhr.ontimeout = () => {
      LOG("Location request XHR timed out.");
      notifyPositionUnavailable(this.listener);
    };
    xhr.onerror = () => {
      notifyPositionUnavailable(this.listener);
    };
    xhr.onload = () => {
      LOG("server returned status: " + xhr.status + " --> " + JSON.stringify(xhr.response));
      if ((xhr.channel instanceof Ci.nsIHttpChannel && xhr.status != 200) ||
          !xhr.response || !xhr.response.location) {
        notifyPositionUnavailable(this.listener);
        return;
      }

      let newLocation = new WifiGeoPositionObject(xhr.response.location.lat,
                                                  xhr.response.location.lng,
                                                  xhr.response.accuracy);

      if (this.listener) {
        this.listener.update(newLocation);
      }
      gCachedRequest = new CachedRequest(newLocation, data.cellTowers, data.wifiAccessPoints);
    };

    var requestData = JSON.stringify(data);
    LOG("sending " + requestData);
    xhr.send(requestData);

    function notifyPositionUnavailable(listener) {
      if (listener) {
        listener.notifyError(POSITION_UNAVAILABLE);
      }
    }
  },
};

var EXPORTED_SYMBOLS = ["WifiGeoPositionProvider"];