/*
 * L.MarkerClusterGroup extends L.FeatureGroup by clustering the markers contained within
 */

L.MarkerClusterGroup = L.FeatureGroup.extend({

	options: {
		maxClusterRadius: 80, //A cluster will cover at most this many pixels from its center
		iconCreateFunction: null,

		spiderfyOnMaxZoom: true,
		showCoverageOnHover: true,
		zoomToBoundsOnClick: true,
		singleMarkerMode: false,

		disableClusteringAtZoom: null,

		// Setting this to false prevents the removal of any clusters outside of the viewpoint, which
		// is the default behaviour for performance reasons.
		removeOutsideVisibleBounds: true,

		// Set to false to disable all animations (zoom and spiderfy).
		// If false, option animateAddingMarkers below has no effect.
		// If L.DomUtil.TRANSITION is falsy, this option has no effect.
		animate: true,

		//Whether to animate adding markers after adding the MarkerClusterGroup to the map
		// If you are adding individual markers set to true, if adding bulk markers leave false for massive performance gains.
		animateAddingMarkers: false,

		//Increase to increase the distance away that spiderfied markers appear from the center
		spiderfyDistanceMultiplier: 1,

		// Make it possible to specify a polyline options on a spider leg
		spiderLegPolylineOptions: { weight: 1.5, color: '#222', opacity: 0.5 },

		// When bulk adding layers, adds markers in chunks. Means addLayers may not add all the layers in the call, others will be loaded during setTimeouts
		chunkedLoading: false,
		chunkInterval: 200, // process markers for a maximum of ~ n milliseconds (then trigger the chunkProgress callback)
		chunkDelay: 50, // at the end of each interval, give n milliseconds back to system/browser
		chunkProgress: null, // progress callback: function(processed, total, elapsed) (e.g. for a progress indicator)

		//Options to pass to the L.Polygon constructor
		polygonOptions: {}
	},

	initialize: function (options) {
		L.Util.setOptions(this, options);
		if (!this.options.iconCreateFunction) {
			this.options.iconCreateFunction = this._defaultIconCreateFunction;
		}

		this._featureGroup = L.featureGroup();
		this._featureGroup.addEventParent(this);

		this._nonPointGroup = L.featureGroup();
		this._nonPointGroup.addEventParent(this);

		this._inZoomAnimation = 0;
		this._needsClustering = [];
		this._needsRemoving = []; //Markers removed while we aren't on the map need to be kept track of
		//The bounds of the currently shown area (from _getExpandedVisibleBounds) Updated on zoom/move
		this._currentShownBounds = null;

		this._queue = [];

		// Hook the appropriate animation methods.
		var animate = L.DomUtil.TRANSITION && this.options.animate;
		L.extend(this, animate ? this._withAnimation : this._noAnimation);
		// Remember which MarkerCluster class to instantiate (animated or not).
		this._markerCluster = animate ? L.MarkerCluster : L.MarkerClusterNonAnimated;
	},

	addLayer: function (layer) {

		if (layer instanceof L.LayerGroup) {
			return this.addLayers([layer]);
		}

		//Don't cluster non point data
		if (!layer.getLatLng) {
			this._nonPointGroup.addLayer(layer);
			return this;
		}

		if (!this._map) {
			this._needsClustering.push(layer);
			return this;
		}

		if (this.hasLayer(layer)) {
			return this;
		}


		//If we have already clustered we'll need to add this one to a cluster

		if (this._unspiderfy) {
			this._unspiderfy();
		}

		this._addLayer(layer, this._maxZoom);

		// Refresh bounds and weighted positions.
		this._topClusterLevel._recalculateBounds();

		this._refreshClustersIcons();

		//Work out what is visible
		var visibleLayer = layer,
		    currentZoom = this._zoom;
		if (layer.__parent) {
			while (visibleLayer.__parent._zoom >= currentZoom) {
				visibleLayer = visibleLayer.__parent;
			}
		}

		if (this._currentShownBounds.contains(visibleLayer.getLatLng())) {
			if (this.options.animateAddingMarkers) {
				this._animationAddLayer(layer, visibleLayer);
			} else {
				this._animationAddLayerNonAnimated(layer, visibleLayer);
			}
		}
		return this;
	},

	removeLayer: function (layer) {

		if (layer instanceof L.LayerGroup) {
			return this.removeLayers([layer]);
		}

		//Non point layers
		if (!layer.getLatLng) {
			this._nonPointGroup.removeLayer(layer);
			return this;
		}

		if (!this._map) {
			if (!this._arraySplice(this._needsClustering, layer) && this.hasLayer(layer)) {
				this._needsRemoving.push(layer);
			}
			return this;
		}

		if (!layer.__parent) {
			return this;
		}

		if (this._unspiderfy) {
			this._unspiderfy();
			this._unspiderfyLayer(layer);
		}

		//Remove the marker from clusters
		this._removeLayer(layer, true);

		// Refresh bounds and weighted positions.
		this._topClusterLevel._recalculateBounds();

		this._refreshClustersIcons();

		layer.off('move', this._childMarkerMoved, this);

		if (this._featureGroup.hasLayer(layer)) {
			this._featureGroup.removeLayer(layer);
			if (layer.clusterShow) {
				layer.clusterShow();
			}
		}

		return this;
	},

	//Takes an array of markers and adds them in bulk
	addLayers: function (layersArray) {
		if (!L.Util.isArray(layersArray)) {
			return this.addLayer(layersArray);
		}

		var fg = this._featureGroup,
		    npg = this._nonPointGroup,
		    chunked = this.options.chunkedLoading,
		    chunkInterval = this.options.chunkInterval,
		    chunkProgress = this.options.chunkProgress,
		    l = layersArray.length,
		    offset = 0,
		    originalArray = true,
		    m;

		if (this._map) {
			var started = (new Date()).getTime();
			var process = L.bind(function () {
				var start = (new Date()).getTime();
				for (; offset < l; offset++) {
					if (chunked && offset % 200 === 0) {
						// every couple hundred markers, instrument the time elapsed since processing started:
						var elapsed = (new Date()).getTime() - start;
						if (elapsed > chunkInterval) {
							break; // been working too hard, time to take a break :-)
						}
					}

					m = layersArray[offset];

					// Group of layers, append children to layersArray and skip.
					// Side effects:
					// - Total increases, so chunkProgress ratio jumps backward.
					// - Groups are not included in this group, only their non-group child layers (hasLayer).
					// Changing array length while looping does not affect performance in current browsers:
					// http://jsperf.com/for-loop-changing-length/6
					if (m instanceof L.LayerGroup) {
						if (originalArray) {
							layersArray = layersArray.slice();
							originalArray = false;
						}
						this._extractNonGroupLayers(m, layersArray);
						l = layersArray.length;
						continue;
					}

					//Not point data, can't be clustered
					if (!m.getLatLng) {
						npg.addLayer(m);
						continue;
					}

					if (this.hasLayer(m)) {
						continue;
					}

					this._addLayer(m, this._maxZoom);

					//If we just made a cluster of size 2 then we need to remove the other marker from the map (if it is) or we never will
					if (m.__parent) {
						if (m.__parent.getChildCount() === 2) {
							var markers = m.__parent.getAllChildMarkers(),
							    otherMarker = markers[0] === m ? markers[1] : markers[0];
							fg.removeLayer(otherMarker);
						}
					}
				}

				if (chunkProgress) {
					// report progress and time elapsed:
					chunkProgress(offset, l, (new Date()).getTime() - started);
				}

				// Completed processing all markers.
				if (offset === l) {

					// Refresh bounds and weighted positions.
					this._topClusterLevel._recalculateBounds();

					this._refreshClustersIcons();

					this._topClusterLevel._recursivelyAddChildrenToMap(null, this._zoom, this._currentShownBounds);
				} else {
					setTimeout(process, this.options.chunkDelay);
				}
			}, this);

			process();
		} else {
			var needsClustering = this._needsClustering;

			for (; offset < l; offset++) {
				m = layersArray[offset];

				// Group of layers, append children to layersArray and skip.
				if (m instanceof L.LayerGroup) {
					if (originalArray) {
						layersArray = layersArray.slice();
						originalArray = false;
					}
					this._extractNonGroupLayers(m, layersArray);
					l = layersArray.length;
					continue;
				}

				//Not point data, can't be clustered
				if (!m.getLatLng) {
					npg.addLayer(m);
					continue;
				}

				if (this.hasLayer(m)) {
					continue;
				}

				needsClustering.push(m);
			}
		}
		return this;
	},

	//Takes an array of markers and removes them in bulk
	removeLayers: function (layersArray) {
		var i, m,
		    l = layersArray.length,
		    fg = this._featureGroup,
		    npg = this._nonPointGroup,
		    originalArray = true;

		if (!this._map) {
			for (i = 0; i < l; i++) {
				m = layersArray[i];

				// Group of layers, append children to layersArray and skip.
				if (m instanceof L.LayerGroup) {
					if (originalArray) {
						layersArray = layersArray.slice();
						originalArray = false;
					}
					this._extractNonGroupLayers(m, layersArray);
					l = layersArray.length;
					continue;
				}

				this._arraySplice(this._needsClustering, m);
				npg.removeLayer(m);
				if (this.hasLayer(m)) {
					this._needsRemoving.push(m);
				}
			}
			return this;
		}

		if (this._unspiderfy) {
			this._unspiderfy();

			// Work on a copy of the array, so that next loop is not affected.
			var layersArray2 = layersArray.slice(),
			    l2 = l;
			for (i = 0; i < l2; i++) {
				m = layersArray2[i];

				// Group of layers, append children to layersArray and skip.
				if (m instanceof L.LayerGroup) {
					this._extractNonGroupLayers(m, layersArray2);
					l2 = layersArray2.length;
					continue;
				}

				this._unspiderfyLayer(m);
			}
		}

		for (i = 0; i < l; i++) {
			m = layersArray[i];

			// Group of layers, append children to layersArray and skip.
			if (m instanceof L.LayerGroup) {
				if (originalArray) {
					layersArray = layersArray.slice();
					originalArray = false;
				}
				this._extractNonGroupLayers(m, layersArray);
				l = layersArray.length;
				continue;
			}

			if (!m.__parent) {
				npg.removeLayer(m);
				continue;
			}

			this._removeLayer(m, true, true);

			if (fg.hasLayer(m)) {
				fg.removeLayer(m);
				if (m.clusterShow) {
					m.clusterShow();
				}
			}
		}

		// Refresh bounds and weighted positions.
		this._topClusterLevel._recalculateBounds();

		this._refreshClustersIcons();

		//Fix up the clusters and markers on the map
		this._topClusterLevel._recursivelyAddChildrenToMap(null, this._zoom, this._currentShownBounds);

		return this;
	},

	//Removes all layers from the MarkerClusterGroup
	clearLayers: function () {
		//Need our own special implementation as the LayerGroup one doesn't work for us

		//If we aren't on the map (yet), blow away the markers we know of
		if (!this._map) {
			this._needsClustering = [];
			delete this._gridClusters;
			delete this._gridUnclustered;
		}

		if (this._noanimationUnspiderfy) {
			this._noanimationUnspiderfy();
		}

		//Remove all the visible layers
		this._featureGroup.clearLayers();
		this._nonPointGroup.clearLayers();

		this.eachLayer(function (marker) {
			marker.off('move', this._childMarkerMoved, this);
			delete marker.__parent;
		});

		if (this._map) {
			//Reset _topClusterLevel and the DistanceGrids
			this._generateInitialClusters();
		}

		return this;
	},

	//Override FeatureGroup.getBounds as it doesn't work
	getBounds: function () {
		var bounds = new L.LatLngBounds();

		if (this._topClusterLevel) {
			bounds.extend(this._topClusterLevel._bounds);
		}

		for (var i = this._needsClustering.length - 1; i >= 0; i--) {
			bounds.extend(this._needsClustering[i].getLatLng());
		}

		bounds.extend(this._nonPointGroup.getBounds());

		return bounds;
	},

	//Overrides LayerGroup.eachLayer
	eachLayer: function (method, context) {
		var markers = this._needsClustering.slice(),
			needsRemoving = this._needsRemoving,
			i;

		if (this._topClusterLevel) {
			this._topClusterLevel.getAllChildMarkers(markers);
		}

		for (i = markers.length - 1; i >= 0; i--) {
			if (needsRemoving.indexOf(markers[i]) === -1) {
				method.call(context, markers[i]);
			}
		}

		this._nonPointGroup.eachLayer(method, context);
	},

	//Overrides LayerGroup.getLayers
	getLayers: function () {
		var layers = [];
		this.eachLayer(function (l) {
			layers.push(l);
		});
		return layers;
	},

	//Overrides LayerGroup.getLayer, WARNING: Really bad performance
	getLayer: function (id) {
		var result = null;
		
		id = parseInt(id, 10);

		this.eachLayer(function (l) {
			if (L.stamp(l) === id) {
				result = l;
			}
		});

		return result;
	},

	//Returns true if the given layer is in this MarkerClusterGroup
	hasLayer: function (layer) {
		if (!layer) {
			return false;
		}

		var i, anArray = this._needsClustering;

		for (i = anArray.length - 1; i >= 0; i--) {
			if (anArray[i] === layer) {
				return true;
			}
		}

		anArray = this._needsRemoving;
		for (i = anArray.length - 1; i >= 0; i--) {
			if (anArray[i] === layer) {
				return false;
			}
		}

		return !!(layer.__parent && layer.__parent._group === this) || this._nonPointGroup.hasLayer(layer);
	},

	//Zoom down to show the given layer (spiderfying if necessary) then calls the callback
	zoomToShowLayer: function (layer, callback) {
		
		if (typeof callback !== 'function') {
			callback = function () {};
		}

		var showMarker = function () {
			if ((layer._icon || layer.__parent._icon) && !this._inZoomAnimation) {
				this._map.off('moveend', showMarker, this);
				this.off('animationend', showMarker, this);

				if (layer._icon) {
					callback();
				} else if (layer.__parent._icon) {
					this.once('spiderfied', callback, this);
					layer.__parent.spiderfy();
				}
			}
		};

		if (layer._icon && this._map.getBounds().contains(layer.getLatLng())) {
			//Layer is visible ond on screen, immediate return
			callback();
		} else if (layer.__parent._zoom < Math.round(this._map._zoom)) {
			//Layer should be visible at this zoom level. It must not be on screen so just pan over to it
			this._map.on('moveend', showMarker, this);
			this._map.panTo(layer.getLatLng());
		} else {
			var moveStart = function () {
				this._map.off('movestart', moveStart, this);
				moveStart = null;
			};

			this._map.on('movestart', moveStart, this);
			this._map.on('moveend', showMarker, this);
			this.on('animationend', showMarker, this);
			layer.__parent.zoomToBounds();

			if (moveStart) {
				//Never started moving, must already be there, probably need clustering however
				showMarker.call(this);
			}
		}
	},

	//Overrides FeatureGroup.onAdd
	onAdd: function (map) {
		this._map = map;
		var i, l, layer;

		if (!isFinite(this._map.getMaxZoom())) {
			throw "Map has no maxZoom specified";
		}

		this._featureGroup.addTo(map);
		this._nonPointGroup.addTo(map);

		if (!this._gridClusters) {
			this._generateInitialClusters();
		}

		this._maxLat = map.options.crs.projection.MAX_LATITUDE;

		for (i = 0, l = this._needsRemoving.length; i < l; i++) {
			layer = this._needsRemoving[i];
			this._removeLayer(layer, true);
		}
		this._needsRemoving = [];

		//Remember the current zoom level and bounds
		this._zoom = Math.round(this._map._zoom);
		this._currentShownBounds = this._getExpandedVisibleBounds();

		this._map.on('zoomend', this._zoomEnd, this);
		this._map.on('moveend', this._moveEnd, this);

		if (this._spiderfierOnAdd) { //TODO FIXME: Not sure how to have spiderfier add something on here nicely
			this._spiderfierOnAdd();
		}

		this._bindEvents();

		//Actually add our markers to the map:
		l = this._needsClustering;
		this._needsClustering = [];
		this.addLayers(l);
	},

	//Overrides FeatureGroup.onRemove
	onRemove: function (map) {
		map.off('zoomend', this._zoomEnd, this);
		map.off('moveend', this._moveEnd, this);

		this._unbindEvents();

		//In case we are in a cluster animation
		this._map._mapPane.className = this._map._mapPane.className.replace(' leaflet-cluster-anim', '');

		if (this._spiderfierOnRemove) { //TODO FIXME: Not sure how to have spiderfier add something on here nicely
			this._spiderfierOnRemove();
		}

		delete this._maxLat;

		//Clean up all the layers we added to the map
		this._hideCoverage();
		this._featureGroup.remove();
		this._nonPointGroup.remove();

		this._featureGroup.clearLayers();

		this._map = null;
	},

	getVisibleParent: function (marker) {
		var vMarker = marker;
		while (vMarker && !vMarker._icon) {
			vMarker = vMarker.__parent;
		}
		return vMarker || null;
	},

	//Remove the given object from the given array
	_arraySplice: function (anArray, obj) {
		for (var i = anArray.length - 1; i >= 0; i--) {
			if (anArray[i] === obj) {
				anArray.splice(i, 1);
				return true;
			}
		}
	},

	/**
	 * Removes a marker from all _gridUnclustered zoom levels, starting at the supplied zoom.
	 * @param marker to be removed from _gridUnclustered.
	 * @param z integer bottom start zoom level (included)
	 * @private
	 */
	_removeFromGridUnclustered: function (marker, z) {
		var map             = this._map,
		    gridUnclustered = this._gridUnclustered;

		for (; z >= 0; z--) {
			if (!gridUnclustered[z].removeObject(marker, map.project(marker.getLatLng(), z))) {
				break;
			}
		}
	},

	_childMarkerMoved: function (e) {
		if (!this._ignoreMove) {
			e.target._latlng = e.oldLatLng;
			this.removeLayer(e.target);

			e.target._latlng = e.latlng;
			this.addLayer(e.target);
		}
	},

	//Internal function for removing a marker from everything.
	//dontUpdateMap: set to true if you will handle updating the map manually (for bulk functions)
	_removeLayer: function (marker, removeFromDistanceGrid, dontUpdateMap) {
		var gridClusters = this._gridClusters,
			gridUnclustered = this._gridUnclustered,
			fg = this._featureGroup,
			map = this._map;

		//Remove the marker from distance clusters it might be in
		if (removeFromDistanceGrid) {
			this._removeFromGridUnclustered(marker, this._maxZoom);
		}

		//Work our way up the clusters removing them as we go if required
		var cluster = marker.__parent,
			markers = cluster._markers,
			otherMarker;

		//Remove the marker from the immediate parents marker list
		this._arraySplice(markers, marker);

		while (cluster) {
			cluster._childCount--;
			cluster._boundsNeedUpdate = true;

			if (cluster._zoom < 0) {
				//Top level, do nothing
				break;
			} else if (removeFromDistanceGrid && cluster._childCount <= 1) { //Cluster no longer required
				//We need to push the other marker up to the parent
				otherMarker = cluster._markers[0] === marker ? cluster._markers[1] : cluster._markers[0];

				//Update distance grid
				gridClusters[cluster._zoom].removeObject(cluster, map.project(cluster._cLatLng, cluster._zoom));
				gridUnclustered[cluster._zoom].addObject(otherMarker, map.project(otherMarker.getLatLng(), cluster._zoom));

				//Move otherMarker up to parent
				this._arraySplice(cluster.__parent._childClusters, cluster);
				cluster.__parent._markers.push(otherMarker);
				otherMarker.__parent = cluster.__parent;

				if (cluster._icon) {
					//Cluster is currently on the map, need to put the marker on the map instead
					fg.removeLayer(cluster);
					if (!dontUpdateMap) {
						fg.addLayer(otherMarker);
					}
				}
			} else {
				cluster._iconNeedsUpdate = true;
			}

			cluster = cluster.__parent;
		}

		delete marker.__parent;
	},

	_isOrIsParent: function (el, oel) {
		while (oel) {
			if (el === oel) {
				return true;
			}
			oel = oel.parentNode;
		}
		return false;
	},

	//Override L.Evented.fire
	fire: function (type, data, propagate) {
		if (data && data.layer instanceof L.MarkerCluster) {
			//Prevent multiple clustermouseover/off events if the icon is made up of stacked divs (Doesn't work in ie <= 8, no relatedTarget)
			if (data.originalEvent && this._isOrIsParent(data.layer._icon, data.originalEvent.relatedTarget)) {
				return;
			}
			type = 'cluster' + type;
		}

		L.FeatureGroup.prototype.fire.call(this, type, data, propagate);
	},

	//Override L.Evented.listens
	listens: function (type, propagate) {
		return L.FeatureGroup.prototype.listens.call(this, type, propagate) || L.FeatureGroup.prototype.listens.call(this, 'cluster' + type, propagate);
	},

	//Default functionality
	_defaultIconCreateFunction: function (cluster) {
		var childCount = cluster.getChildCount();

		var c = ' marker-cluster-';
		if (childCount < 10) {
			c += 'small';
		} else if (childCount < 100) {
			c += 'medium';
		} else {
			c += 'large';
		}

		return new L.DivIcon({ html: '<div><span>' + childCount + '</span></div>', className: 'marker-cluster' + c, iconSize: new L.Point(40, 40) });
	},

	_bindEvents: function () {
		var map = this._map,
		    spiderfyOnMaxZoom = this.options.spiderfyOnMaxZoom,
		    showCoverageOnHover = this.options.showCoverageOnHover,
		    zoomToBoundsOnClick = this.options.zoomToBoundsOnClick;

		//Zoom on cluster click or spiderfy if we are at the lowest level
		if (spiderfyOnMaxZoom || zoomToBoundsOnClick) {
			this.on('clusterclick', this._zoomOrSpiderfy, this);
		}

		//Show convex hull (boundary) polygon on mouse over
		if (showCoverageOnHover) {
			this.on('clustermouseover', this._showCoverage, this);
			this.on('clustermouseout', this._hideCoverage, this);
			map.on('zoomend', this._hideCoverage, this);
		}
	},

	_zoomOrSpiderfy: function (e) {
		var cluster = e.layer,
		    bottomCluster = cluster;

		while (bottomCluster._childClusters.length === 1) {
			bottomCluster = bottomCluster._childClusters[0];
		}

		if (bottomCluster._zoom === this._maxZoom &&
			bottomCluster._childCount === cluster._childCount &&
			this.options.spiderfyOnMaxZoom) {

			// All child markers are contained in a single cluster from this._maxZoom to this cluster.
			cluster.spiderfy();
		} else if (this.options.zoomToBoundsOnClick) {
			cluster.zoomToBounds();
		}

		// Focus the map again for keyboard users.
		if (e.originalEvent && e.originalEvent.keyCode === 13) {
			this._map._container.focus();
		}
	},

	_showCoverage: function (e) {
		var map = this._map;
		if (this._inZoomAnimation) {
			return;
		}
		if (this._shownPolygon) {
			map.removeLayer(this._shownPolygon);
		}
		if (e.layer.getChildCount() > 2 && e.layer !== this._spiderfied) {
			this._shownPolygon = new L.Polygon(e.layer.getConvexHull(), this.options.polygonOptions);
			map.addLayer(this._shownPolygon);
		}
	},

	_hideCoverage: function () {
		if (this._shownPolygon) {
			this._map.removeLayer(this._shownPolygon);
			this._shownPolygon = null;
		}
	},

	_unbindEvents: function () {
		var spiderfyOnMaxZoom = this.options.spiderfyOnMaxZoom,
			showCoverageOnHover = this.options.showCoverageOnHover,
			zoomToBoundsOnClick = this.options.zoomToBoundsOnClick,
			map = this._map;

		if (spiderfyOnMaxZoom || zoomToBoundsOnClick) {
			this.off('clusterclick', this._zoomOrSpiderfy, this);
		}
		if (showCoverageOnHover) {
			this.off('clustermouseover', this._showCoverage, this);
			this.off('clustermouseout', this._hideCoverage, this);
			map.off('zoomend', this._hideCoverage, this);
		}
	},

	_zoomEnd: function () {
		if (!this._map) { //May have been removed from the map by a zoomEnd handler
			return;
		}
		this._mergeSplitClusters();

		this._zoom = Math.round(this._map._zoom);
		this._currentShownBounds = this._getExpandedVisibleBounds();
	},

	_moveEnd: function () {
		if (this._inZoomAnimation) {
			return;
		}

		var newBounds = this._getExpandedVisibleBounds();

		this._topClusterLevel._recursivelyRemoveChildrenFromMap(this._currentShownBounds, this._zoom, newBounds);
		this._topClusterLevel._recursivelyAddChildrenToMap(null, Math.round(this._map._zoom), newBounds);

		this._currentShownBounds = newBounds;
		return;
	},

	_generateInitialClusters: function () {
		var maxZoom = this._map.getMaxZoom(),
			radius = this.options.maxClusterRadius,
			radiusFn = radius;
	
		//If we just set maxClusterRadius to a single number, we need to create
		//a simple function to return that number. Otherwise, we just have to
		//use the function we've passed in.
		if (typeof radius !== "function") {
			radiusFn = function () { return radius; };
		}

		if (this.options.disableClusteringAtZoom) {
			maxZoom = this.options.disableClusteringAtZoom - 1;
		}
		this._maxZoom = maxZoom;
		this._gridClusters = {};
		this._gridUnclustered = {};
	
		//Set up DistanceGrids for each zoom
		for (var zoom = maxZoom; zoom >= 0; zoom--) {
			this._gridClusters[zoom] = new L.DistanceGrid(radiusFn(zoom));
			this._gridUnclustered[zoom] = new L.DistanceGrid(radiusFn(zoom));
		}

		// Instantiate the appropriate L.MarkerCluster class (animated or not).
		this._topClusterLevel = new this._markerCluster(this, -1);
	},

	//Zoom: Zoom to start adding at (Pass this._maxZoom to start at the bottom)
	_addLayer: function (layer, zoom) {
		var gridClusters = this._gridClusters,
		    gridUnclustered = this._gridUnclustered,
		    markerPoint, z;

		if (this.options.singleMarkerMode) {
			this._overrideMarkerIcon(layer);
		}

		layer.on('move', this._childMarkerMoved, this);

		//Find the lowest zoom level to slot this one in
		for (; zoom >= 0; zoom--) {
			markerPoint = this._map.project(layer.getLatLng(), zoom); // calculate pixel position

			//Try find a cluster close by
			var closest = gridClusters[zoom].getNearObject(markerPoint);
			if (closest) {
				closest._addChild(layer);
				layer.__parent = closest;
				return;
			}

			//Try find a marker close by to form a new cluster with
			closest = gridUnclustered[zoom].getNearObject(markerPoint);
			if (closest) {
				var parent = closest.__parent;
				if (parent) {
					this._removeLayer(closest, false);
				}

				//Create new cluster with these 2 in it

				var newCluster = new this._markerCluster(this, zoom, closest, layer);
				gridClusters[zoom].addObject(newCluster, this._map.project(newCluster._cLatLng, zoom));
				closest.__parent = newCluster;
				layer.__parent = newCluster;

				//First create any new intermediate parent clusters that don't exist
				var lastParent = newCluster;
				for (z = zoom - 1; z > parent._zoom; z--) {
					lastParent = new this._markerCluster(this, z, lastParent);
					gridClusters[z].addObject(lastParent, this._map.project(closest.getLatLng(), z));
				}
				parent._addChild(lastParent);

				//Remove closest from this zoom level and any above that it is in, replace with newCluster
				this._removeFromGridUnclustered(closest, zoom);

				return;
			}

			//Didn't manage to cluster in at this zoom, record us as a marker here and continue upwards
			gridUnclustered[zoom].addObject(layer, markerPoint);
		}

		//Didn't get in anything, add us to the top
		this._topClusterLevel._addChild(layer);
		layer.__parent = this._topClusterLevel;
		return;
	},

	/**
	 * Refreshes the icon of all "dirty" visible clusters.
	 * Non-visible "dirty" clusters will be updated when they are added to the map.
	 * @private
	 */
	_refreshClustersIcons: function () {
		this._featureGroup.eachLayer(function (c) {
			if (c instanceof L.MarkerCluster && c._iconNeedsUpdate) {
				c._updateIcon();
			}
		});
	},

	//Enqueue code to fire after the marker expand/contract has happened
	_enqueue: function (fn) {
		this._queue.push(fn);
		if (!this._queueTimeout) {
			this._queueTimeout = setTimeout(L.bind(this._processQueue, this), 300);
		}
	},
	_processQueue: function () {
		for (var i = 0; i < this._queue.length; i++) {
			this._queue[i].call(this);
		}
		this._queue.length = 0;
		clearTimeout(this._queueTimeout);
		this._queueTimeout = null;
	},

	//Merge and split any existing clusters that are too big or small
	_mergeSplitClusters: function () {
		var mapZoom = Math.round(this._map._zoom);

		//In case we are starting to split before the animation finished
		this._processQueue();

		if (this._zoom < mapZoom && this._currentShownBounds.intersects(this._getExpandedVisibleBounds())) { //Zoom in, split
			this._animationStart();
			//Remove clusters now off screen
			this._topClusterLevel._recursivelyRemoveChildrenFromMap(this._currentShownBounds, this._zoom, this._getExpandedVisibleBounds());

			this._animationZoomIn(this._zoom, mapZoom);

		} else if (this._zoom > mapZoom) { //Zoom out, merge
			this._animationStart();

			this._animationZoomOut(this._zoom, mapZoom);
		} else {
			this._moveEnd();
		}
	},

	//Gets the maps visible bounds expanded in each direction by the size of the screen (so the user cannot see an area we do not cover in one pan)
	_getExpandedVisibleBounds: function () {
		if (!this.options.removeOutsideVisibleBounds) {
			return this._mapBoundsInfinite;
		} else if (L.Browser.mobile) {
			return this._checkBoundsMaxLat(this._map.getBounds());
		}

		return this._checkBoundsMaxLat(this._map.getBounds().pad(1)); // Padding expands the bounds by its own dimensions but scaled with the given factor.
	},

	/**
	 * Expands the latitude to Infinity (or -Infinity) if the input bounds reach the map projection maximum defined latitude
	 * (in the case of Web/Spherical Mercator, it is 85.0511287798 / see https://en.wikipedia.org/wiki/Web_Mercator#Formulas).
	 * Otherwise, the removeOutsideVisibleBounds option will remove markers beyond that limit, whereas the same markers without
	 * this option (or outside MCG) will have their position floored (ceiled) by the projection and rendered at that limit,
	 * making the user think that MCG "eats" them and never displays them again.
	 * @param bounds L.LatLngBounds
	 * @returns {L.LatLngBounds}
	 * @private
	 */
	_checkBoundsMaxLat: function (bounds) {
		var maxLat = this._maxLat;

		if (maxLat !== undefined) {
			if (bounds.getNorth() >= maxLat) {
				bounds._northEast.lat = Infinity;
			}
			if (bounds.getSouth() <= -maxLat) {
				bounds._southWest.lat = -Infinity;
			}
		}

		return bounds;
	},

	//Shared animation code
	_animationAddLayerNonAnimated: function (layer, newCluster) {
		if (newCluster === layer) {
			this._featureGroup.addLayer(layer);
		} else if (newCluster._childCount === 2) {
			newCluster._addToMap();

			var markers = newCluster.getAllChildMarkers();
			this._featureGroup.removeLayer(markers[0]);
			this._featureGroup.removeLayer(markers[1]);
		} else {
			newCluster._updateIcon();
		}
	},

	/**
	 * Extracts individual (i.e. non-group) layers from a Layer Group.
	 * @param group to extract layers from.
	 * @param output {Array} in which to store the extracted layers.
	 * @returns {*|Array}
	 * @private
	 */
	_extractNonGroupLayers: function (group, output) {
		var layers = group.getLayers(),
		    i = 0,
		    layer;

		output = output || [];

		for (; i < layers.length; i++) {
			layer = layers[i];

			if (layer instanceof L.LayerGroup) {
				this._extractNonGroupLayers(layer, output);
				continue;
			}

			output.push(layer);
		}

		return output;
	},

	/**
	 * Implements the singleMarkerMode option.
	 * @param layer Marker to re-style using the Clusters iconCreateFunction.
	 * @returns {L.Icon} The newly created icon.
	 * @private
	 */
	_overrideMarkerIcon: function (layer) {
		var icon = layer.options.icon = this.options.iconCreateFunction({
			getChildCount: function () {
				return 1;
			},
			getAllChildMarkers: function () {
				return [layer];
			}
		});

		return icon;
	}
});

// Constant bounds used in case option "removeOutsideVisibleBounds" is set to false.
L.MarkerClusterGroup.include({
	_mapBoundsInfinite: new L.LatLngBounds(new L.LatLng(-Infinity, -Infinity), new L.LatLng(Infinity, Infinity))
});

L.MarkerClusterGroup.include({
	_noAnimation: {
		//Non Animated versions of everything
		_animationStart: function () {
			//Do nothing...
		},
		_animationZoomIn: function (previousZoomLevel, newZoomLevel) {
			this._topClusterLevel._recursivelyRemoveChildrenFromMap(this._currentShownBounds, previousZoomLevel);
			this._topClusterLevel._recursivelyAddChildrenToMap(null, newZoomLevel, this._getExpandedVisibleBounds());

			//We didn't actually animate, but we use this event to mean "clustering animations have finished"
			this.fire('animationend');
		},
		_animationZoomOut: function (previousZoomLevel, newZoomLevel) {
			this._topClusterLevel._recursivelyRemoveChildrenFromMap(this._currentShownBounds, previousZoomLevel);
			this._topClusterLevel._recursivelyAddChildrenToMap(null, newZoomLevel, this._getExpandedVisibleBounds());

			//We didn't actually animate, but we use this event to mean "clustering animations have finished"
			this.fire('animationend');
		},
		_animationAddLayer: function (layer, newCluster) {
			this._animationAddLayerNonAnimated(layer, newCluster);
		}
	},

	_withAnimation: {
		//Animated versions here
		_animationStart: function () {
			this._map._mapPane.className += ' leaflet-cluster-anim';
			this._inZoomAnimation++;
		},

		_animationZoomIn: function (previousZoomLevel, newZoomLevel) {
			var bounds = this._getExpandedVisibleBounds(),
			    fg     = this._featureGroup,
			    i;

			this._ignoreMove = true;

			//Add all children of current clusters to map and remove those clusters from map
			this._topClusterLevel._recursively(bounds, previousZoomLevel, 0, function (c) {
				var startPos = c._latlng,
				    markers  = c._markers,
				    m;

				if (!bounds.contains(startPos)) {
					startPos = null;
				}

				if (c._isSingleParent() && previousZoomLevel + 1 === newZoomLevel) { //Immediately add the new child and remove us
					fg.removeLayer(c);
					c._recursivelyAddChildrenToMap(null, newZoomLevel, bounds);
				} else {
					//Fade out old cluster
					c.clusterHide();
					c._recursivelyAddChildrenToMap(startPos, newZoomLevel, bounds);
				}

				//Remove all markers that aren't visible any more
				//TODO: Do we actually need to do this on the higher levels too?
				for (i = markers.length - 1; i >= 0; i--) {
					m = markers[i];
					if (!bounds.contains(m._latlng)) {
						fg.removeLayer(m);
					}
				}

			});

			this._forceLayout();

			//Update opacities
			this._topClusterLevel._recursivelyBecomeVisible(bounds, newZoomLevel);
			//TODO Maybe? Update markers in _recursivelyBecomeVisible
			fg.eachLayer(function (n) {
				if (!(n instanceof L.MarkerCluster) && n._icon) {
					n.clusterShow();
				}
			});

			//update the positions of the just added clusters/markers
			this._topClusterLevel._recursively(bounds, previousZoomLevel, newZoomLevel, function (c) {
				c._recursivelyRestoreChildPositions(newZoomLevel);
			});

			this._ignoreMove = false;

			//Remove the old clusters and close the zoom animation
			this._enqueue(function () {
				//update the positions of the just added clusters/markers
				this._topClusterLevel._recursively(bounds, previousZoomLevel, 0, function (c) {
					fg.removeLayer(c);
					c.clusterShow();
				});

				this._animationEnd();
			});
		},

		_animationZoomOut: function (previousZoomLevel, newZoomLevel) {
			this._animationZoomOutSingle(this._topClusterLevel, previousZoomLevel - 1, newZoomLevel);

			//Need to add markers for those that weren't on the map before but are now
			this._topClusterLevel._recursivelyAddChildrenToMap(null, newZoomLevel, this._getExpandedVisibleBounds());
			//Remove markers that were on the map before but won't be now
			this._topClusterLevel._recursivelyRemoveChildrenFromMap(this._currentShownBounds, previousZoomLevel, this._getExpandedVisibleBounds());
		},

		_animationAddLayer: function (layer, newCluster) {
			var me = this,
			    fg = this._featureGroup;

			fg.addLayer(layer);
			if (newCluster !== layer) {
				if (newCluster._childCount > 2) { //Was already a cluster

					newCluster._updateIcon();
					this._forceLayout();
					this._animationStart();

					layer._setPos(this._map.latLngToLayerPoint(newCluster.getLatLng()));
					layer.clusterHide();

					this._enqueue(function () {
						fg.removeLayer(layer);
						layer.clusterShow();

						me._animationEnd();
					});

				} else { //Just became a cluster
					this._forceLayout();

					me._animationStart();
					me._animationZoomOutSingle(newCluster, this._map.getMaxZoom(), this._zoom);
				}
			}
		}
	},

	// Private methods for animated versions.
	_animationZoomOutSingle: function (cluster, previousZoomLevel, newZoomLevel) {
		var bounds = this._getExpandedVisibleBounds();

		//Animate all of the markers in the clusters to move to their cluster center point
		cluster._recursivelyAnimateChildrenInAndAddSelfToMap(bounds, previousZoomLevel + 1, newZoomLevel);

		var me = this;

		//Update the opacity (If we immediately set it they won't animate)
		this._forceLayout();
		cluster._recursivelyBecomeVisible(bounds, newZoomLevel);

		//TODO: Maybe use the transition timing stuff to make this more reliable
		//When the animations are done, tidy up
		this._enqueue(function () {

			//This cluster stopped being a cluster before the timeout fired
			if (cluster._childCount === 1) {
				var m = cluster._markers[0];
				//If we were in a cluster animation at the time then the opacity and position of our child could be wrong now, so fix it
				this._ignoreMove = true;
				m.setLatLng(m.getLatLng());
				this._ignoreMove = false;
				if (m.clusterShow) {
					m.clusterShow();
				}
			} else {
				cluster._recursively(bounds, newZoomLevel, 0, function (c) {
					c._recursivelyRemoveChildrenFromMap(bounds, previousZoomLevel + 1);
				});
			}
			me._animationEnd();
		});
	},

	_animationEnd: function () {
		if (this._map) {
			this._map._mapPane.className = this._map._mapPane.className.replace(' leaflet-cluster-anim', '');
		}
		this._inZoomAnimation--;
		this.fire('animationend');
	},

	//Force a browser layout of stuff in the map
	// Should apply the current opacity and location to all elements so we can update them again for an animation
	_forceLayout: function () {
		//In my testing this works, infact offsetWidth of any element seems to work.
		//Could loop all this._layers and do this for each _icon if it stops working

		L.Util.falseFn(document.body.offsetWidth);
	}
});

L.markerClusterGroup = function (options) {
	return new L.MarkerClusterGroup(options);
};
