Leaflet Bing layer

TileLayer.Bing.js

var bounds_intersects = function(a, b) {
    return (
        a.contains(b._northEast) || 
        a.contains(b._southWest) ||
        b.contains(a._northEast) ||
        b.contains(a._southWest)
    );
};
L.TileLayer.Bing = L.TileLayer.extend({
  
  supportedTypes: ['Road', 'Aerial', 'AerialWithLabels'],
  
  attributionTemplate: '<span style="display:inline-block">' +
       '<a target="_blank" href="http://www.bing.com/maps/">' +
       '<img src="{logo}" /></a><br><span>{copyrights}' +
       '<a style="white-space: nowrap" target="_blank" '+
       'href="http://www.microsoft.com/maps/product/terms.html">' +
       'Terms of Use</a></span></span>',
  
  initialize: function(/*String*/ apiKey, /*String*/ mapType, /*Object*/ options) {
    
    this._apiKey = apiKey;
    this._mapType = mapType;
    
    this._loadMetadata();
    
    L.Util.setOptions(this, options);
  },
  
  _loadMetadata: function() {
    
    this._callbackId = "_l_tilelayer_bing_" + (L.TileLayer.Bing._callbackId++);
    window[this._callbackId] = L.Util.bind(L.TileLayer.Bing.processMetadata, this);
    
    var params = {
      key: this._apiKey,
      jsonp: this._callbackId,
      include: 'ImageryProviders'
    },
        url = "http://dev.virtualearth.net/REST/v1/Imagery/Metadata/" +
              this._mapType + L.Util.getParamString(params),
        script = document.createElement("script");
        
    script.type = "text/javascript";
    script.src = url;
    script.id = this._callbackId;
    document.getElementsByTagName("head")[0].appendChild(script);
  },
  
  _onMetadataLoaded: function() {},
  
  onAdd: function(map, insertAtTheBottom) {
    if (!this.metadata) {
      this._onMetadataLoaded = L.Util.bind(function() {
        L.TileLayer.prototype.onAdd.call(this, map, insertAtTheBottom);
        map.on('moveend', this._updateAttribution, this);
        this._updateAttribution();
      }, this);
    } else {
      L.TileLayer.prototype.onAdd.call(this, map, insertAtTheBottom);
      map.on('moveend', this._updateAttribution, this);
      this._updateAttribution();
    }
  },
  
  onRemove: function(map) {
    if (this._map.attributionControl) {
      this._map.attributionControl.removeAttribution(this.attribution);
    }
    this._map.off('moveend', this._updateAttribution, this);
    L.TileLayer.prototype.onRemove.call(this, map);
  },
  
  getTileUrl: function(xy, z) {
    var subdomains = this.options.subdomains,
                        quadDigits = [],
                        i = z,
                        digit,
                        mask,
                        quadKey;
// borrowed directly from OpenLayers
    for (; i > 0; --i) {
        digit = '0';
        mask = 1 << (i - 1);
        if ((xy.x & mask) != 0) {
            digit++;
        }
        if ((xy.y & mask) != 0) {
            digit++;
            digit++;
        }
        quadDigits.push(digit);
    }

        return this._url
                        .replace('{subdomain}', subdomains[(xy.x + xy.y) % subdomains.length])
                        .replace('{quadkey}', quadDigits.join(""));
  },
  
  _updateAttribution: function() {
    if (this._map.attributionControl) {
      var metadata = this.metadata;
      var res = metadata.resourceSets[0].resources[0];
      var bounds = this._map.getBounds();
      var providers = res.imageryProviders, zoom = this._map.getZoom() + 1,
          copyrights = "", provider, i, ii, j, jj, bbox, coverage;
      for (i=0,ii=providers.length; i<ii; ++i) {
          provider = providers[i];
          for (j=0,jj=provider.coverageAreas.length; j<jj; ++j) {
              coverage = provider.coverageAreas[j];
              if (zoom <= coverage.zoomMax && zoom >= coverage.zoomMin && bounds_intersects(coverage.bbox, bounds)) {
                  copyrights += provider.attribution + " ";
                  j = jj;
              }
          }
      }
      this._map.attributionControl.removeAttribution(this.attribution);
      this.attribution = this.attributionTemplate
        .replace('{logo}', metadata.brandLogoUri)
        .replace('{copyrights}', copyrights);
      this._map.attributionControl.addAttribution(this.attribution);
    }
  }
});

L.TileLayer.Bing._callbackId = 0;

L.TileLayer.Bing.processMetadata = function(metadata) {
  if (metadata.authenticationResultCode != 'ValidCredentials') {
    throw "Invalid Bing Maps API Key"
  }
  
  if (!metadata.resourceSets.length || !metadata.resourceSets[0].resources.length) {
    throw "No resources returned, perhaps " + this._mapType + " is an invalid map type?";
  }
  
  if (metadata.statusCode != 200) {
    throw "Bing Maps API request failed with status code " + metadata.statusCode;
  }
  
  this.metadata = metadata;
  var res = metadata.resourceSets[0].resources[0],
      providers = res.imageryProviders,
      i = 0,
      j,
      provider,
      bbox,
      script = document.getElementById(this._callbackId);
  
  for (; i<providers.length; i++) {
    provider = providers[i];
    for (j=0; j<provider.coverageAreas.length; j++) {
      bbox = provider.coverageAreas[j].bbox;
      provider.coverageAreas[j].bbox = new L.LatLngBounds(new L.LatLng(bbox[0],bbox[1],true),new L.LatLng(bbox[2],bbox[3], true));
    }
  }
  
  this._url = res.imageUrl.replace('{culture}','en-US');
  this.options.subdomains = [].concat(res.imageUrlSubdomains);
  script.parentNode.removeChild(script);
  window[this._callbackId] = undefined; // cannot delete from window in IE
  delete this._callbackId;
  this._onMetadataLoaded();
}