// Based on https://github.com/shramov/leaflet-plugins
// GridLayer like https://avinmathew.com/leaflet-and-google-maps/ , but using MutationObserver instead of jQuery


// 🍂class GridLayer.GoogleMutant
// 🍂extends GridLayer
L.GridLayer.GoogleMutant = L.GridLayer.extend({
	options: {
		minZoom: 0,
		maxZoom: 21, // can be 23, but ugly if more than maxNativeZoom
		tileSize: 256,
		subdomains: 'abc',
		errorTileUrl: '',
		attribution: '',	// The mutant container will add its own attribution anyways.
		opacity: 1,
		continuousWorld: false,
		noWrap: false,
		// 🍂option type: String = 'roadmap'
		// Google's map type. Valid values are 'roadmap', 'satellite' or 'terrain'. 'hybrid' is not really supported.
		type: 'roadmap',
		maxNativeZoom: 21
	},

	initialize: function (options) {
		L.GridLayer.prototype.initialize.call(this, options);

		this._ready = !!window.google && !!window.google.maps && !!window.google.maps.Map;
		this._isMounted = true;

		this._GAPIPromise = this._ready ? Promise.resolve(window.google) : new Promise(function (resolve, reject) {
			var checkCounter = 0,
			    intervalId = null;

			intervalId = setInterval(function () {
				if (checkCounter >= 10) {
					clearInterval(intervalId);
					return reject(new Error('window.google not found after 10 attempts'));
				}
				if (!!window.google && !!window.google.maps && !!window.google.maps.Map) {
					clearInterval(intervalId);
					return resolve(window.google);
				}
				++checkCounter;
			}, 500);
		});

		// Couple data structures indexed by tile key
		this._tileCallbacks = {};	// Callbacks for promises for tiles that are expected
		this._freshTiles = {};	// Tiles from the mutant which haven't been requested yet

		this._imagesPerTile = (this.options.type === 'hybrid') ? 2 : 1;

		this._boundOnMutatedImage = this._onMutatedImage.bind(this);
	},

	onAdd: function (map) {
		L.GridLayer.prototype.onAdd.call(this, map);
		this._initMutantContainer();

		this._GAPIPromise.then(function () {
			if (!this._isMounted) {
				return;
			}
			this._ready = true;
			this._map = map;

			this._initMutant();

			map.on('viewreset', this._reset, this);
			if (this.options.updateWhenIdle) {
				map.on('moveend', this._update, this);
			} else {
				map.on('move', this._update, this);
			}
			map.on('zoomend', this._handleZoomAnim, this);
			map.on('resize', this._resize, this);

			//handle layer being added to a map for which there are no Google tiles at the given zoom
			google.maps.event.addListenerOnce(this._mutant, 'idle', function () {
				this._checkZoomLevels();
				this._mutantIsReady = true;
			}.bind(this));

			//20px instead of 1em to avoid a slight overlap with google's attribution
			map._controlCorners.bottomright.style.marginBottom = '20px';
			map._controlCorners.bottomleft.style.marginBottom = '20px';

			this._reset();
			this._update();

			if (this._subLayers) {
				//restore previously added google layers
				for (var layerName in this._subLayers) {
					this._subLayers[layerName].setMap(this._mutant);
				}
			}
		}.bind(this));
	},

	onRemove: function (map) {
		L.GridLayer.prototype.onRemove.call(this, map);
		this._observer.disconnect();
		map._container.removeChild(this._mutantContainer);

		google.maps.event.clearListeners(map, 'idle');
		if (this._mutant) {
			google.maps.event.clearListeners(this._mutant, 'idle');
		}
		map.off('viewreset', this._reset, this);
		map.off('move', this._update, this);
		map.off('moveend', this._update, this);
		map.off('zoomend', this._handleZoomAnim, this);
		map.off('resize', this._resize, this);

		if (map._controlCorners) {
			map._controlCorners.bottomright.style.marginBottom = 0;
			map._controlCorners.bottomleft.style.marginBottom = 0;
		}
		this._isMounted = false;
	},

	getAttribution: function () {
		return this.options.attribution;
	},

	setElementSize: function (e, size) {
		e.style.width = size.x + 'px';
		e.style.height = size.y + 'px';
	},


	addGoogleLayer: function (googleLayerName, options) {
		if (!this._subLayers) this._subLayers = {};
		return this._GAPIPromise.then(function () {
			var Constructor = google.maps[googleLayerName],
			    googleLayer = new Constructor(options);

			googleLayer.setMap(this._mutant);
			this._subLayers[googleLayerName] = googleLayer;
			return googleLayer;
		}.bind(this));
	},

	removeGoogleLayer: function (googleLayerName) {
		var googleLayer = this._subLayers && this._subLayers[googleLayerName];
		if (!googleLayer) return;

		googleLayer.setMap(null);
		delete this._subLayers[googleLayerName];
	},


	_initMutantContainer: function () {
		if (!this._mutantContainer) {
			this._mutantContainer = L.DomUtil.create('div', 'leaflet-google-mutant leaflet-top leaflet-left');
			this._mutantContainer.id = '_MutantContainer_' + L.Util.stamp(this._mutantContainer);
			this._mutantContainer.style.zIndex = 800; //leaflet map pane at 400, controls at 1000
			this._mutantContainer.style.pointerEvents = 'none';

			L.DomEvent.off(this._mutantContainer);

		}
		this._map.getContainer().appendChild(this._mutantContainer);

		this.setOpacity(this.options.opacity);
		this.setElementSize(this._mutantContainer, this._map.getSize());

		this._attachObserver(this._mutantContainer);
	},

	_initMutant: function () {
		if (!this._ready || !this._mutantContainer) return;

		if (this._mutant) {
			// reuse old _mutant, just make sure it has the correct size
			this._resize();
			return;
		}

		this._mutantCenter = new google.maps.LatLng(0, 0);

		var map = new google.maps.Map(this._mutantContainer, {
			center: this._mutantCenter,
			zoom: 0,
			tilt: 0,
			mapTypeId: this.options.type,
			disableDefaultUI: true,
			keyboardShortcuts: false,
			draggable: false,
			disableDoubleClickZoom: true,
			scrollwheel: false,
			streetViewControl: false,
			styles: this.options.styles || {},
			backgroundColor: 'transparent'
		});

		this._mutant = map;

		google.maps.event.addListenerOnce(map, 'idle', function () {
			var nodes = this._mutantContainer.querySelectorAll('a');
			for (var i = 0; i < nodes.length; ++i) {
				nodes[i].style.pointerEvents = 'auto';
			}
		}.bind(this));

		// 🍂event spawned
		// Fired when the mutant has been created.
		this.fire('spawned', {mapObject: map});
	},

	_attachObserver: function _attachObserver (node) {
// 		console.log('Gonna observe', node);

		if (!this._observer)
			this._observer = new MutationObserver(this._onMutations.bind(this));

		// pass in the target node, as well as the observer options
		this._observer.observe(node, { childList: true, subtree: true });

		// if we are reusing an old _mutantContainer, we must manually detect
		// all existing tiles in it
		Array.prototype.forEach.call(
			node.querySelectorAll('img'),
			this._boundOnMutatedImage
		);
	},

	_onMutations: function _onMutations (mutations) {
		for (var i = 0; i < mutations.length; ++i) {
			var mutation = mutations[i];
			for (var j = 0; j < mutation.addedNodes.length; ++j) {
				var node = mutation.addedNodes[j];

				if (node instanceof HTMLImageElement) {
					this._onMutatedImage(node);
				} else if (node instanceof HTMLElement) {
					Array.prototype.forEach.call(
						node.querySelectorAll('img'),
						this._boundOnMutatedImage
					);

					// Check for, and remove, the "Google Maps can't load correctly" div.
					// You *are* loading correctly, you dumbwit.
					if (node.style.backgroundColor === 'white') {
						L.DomUtil.remove(node);
					}

					// Check for, and remove, the "For development purposes only" divs on the aerial/hybrid tiles.
					if (node.textContent.indexOf('For development purposes only') === 0) {
						L.DomUtil.remove(node);
					}

					// Check for, and remove, the "Sorry, we have no imagery here"
					// empty <div>s. The [style*="text-align: center"] selector
					// avoids matching the attribution notice.
					// This empty div doesn't have a reference to the tile
					// coordinates, so it's not possible to mark the tile as
					// failed.
					Array.prototype.forEach.call(
						node.querySelectorAll('div[draggable=false][style*="text-align: center"]'),
						L.DomUtil.remove
					);
				}
			}
		}
	},

	// Only images which 'src' attrib match this will be considered for moving around.
	// Looks like some kind of string-based protobuf, maybe??
	// Only the roads (and terrain, and vector-based stuff) match this pattern
	_roadRegexp: /!1i(\d+)!2i(\d+)!3i(\d+)!/,

	// On the other hand, raster imagery matches this other pattern
	_satRegexp: /x=(\d+)&y=(\d+)&z=(\d+)/,

	// On small viewports, when zooming in/out, a static image is requested
	// This will not be moved around, just removed from the DOM.
	_staticRegExp: /StaticMapService\.GetMapImage/,

	_onMutatedImage: function _onMutatedImage (imgNode) {
// 		if (imgNode.src) {
// 			console.log('caught mutated image: ', imgNode.src);
// 		}

		var coords,
		    match = imgNode.src.match(this._roadRegexp),
		    sublayer = 0;

		if (match) {
			coords = {
				z: match[1],
				x: match[2],
				y: match[3]
			};
			if (this._imagesPerTile > 1) {
				imgNode.style.zIndex = 1;
				sublayer = 1;
			}
		} else {
			match = imgNode.src.match(this._satRegexp);
			if (match) {
				coords = {
					x: match[1],
					y: match[2],
					z: match[3]
				};
			}
// 			imgNode.style.zIndex = 0;
			sublayer = 0;
		}

		if (coords) {
			var tileKey = this._tileCoordsToKey(coords);
			imgNode.style.position = 'absolute';
			imgNode.style.visibility = 'hidden';

			var key = tileKey + '/' + sublayer;
			// console.log('mutation for tile', key)
			//store img so it can also be used in subsequent tile requests
			this._freshTiles[key] = imgNode;

			if (key in this._tileCallbacks && this._tileCallbacks[key]) {
// console.log('Fullfilling callback ', key);
				//fullfill most recent tileCallback because there maybe callbacks that will never get a
				//corresponding mutation (because map moved to quickly...)
				this._tileCallbacks[key].pop()(imgNode);
				if (!this._tileCallbacks[key].length) { delete this._tileCallbacks[key]; }
			} else {
				if (this._tiles[tileKey]) {
					//we already have a tile in this position (mutation is probably a google layer being added)
					//replace it
					var c = this._tiles[tileKey].el,
					    oldImg = (sublayer === 0) ? c.firstChild : c.firstChild.nextSibling,
					    cloneImgNode = this._clone(imgNode);

					c.replaceChild(cloneImgNode, oldImg);
				}
			}
		} else if (imgNode.src.match(this._staticRegExp)) {
			imgNode.style.visibility = 'hidden';
		}
	},


	createTile: function (coords, done) {
		var key = this._tileCoordsToKey(coords),
		    tileContainer = L.DomUtil.create('div');

		tileContainer.dataset.pending = this._imagesPerTile;
		done = done.bind(this, null, tileContainer);

		for (var i = 0; i < this._imagesPerTile; ++i) {
			var key2 = key + '/' + i;
			if (key2 in this._freshTiles) {
				var imgNode = this._freshTiles[key2];
				tileContainer.appendChild(this._clone(imgNode));
				--tileContainer.dataset.pending;
// 				console.log('Got ', key2, ' from _freshTiles');
			} else {
				this._tileCallbacks[key2] = this._tileCallbacks[key2] || [];
				this._tileCallbacks[key2].push( (function (c/*, k2*/) {
					return function (imgNode) {
						c.appendChild(this._clone(imgNode));
						--c.dataset.pending;
						if (!parseInt(c.dataset.pending)) { done(); }
// 						console.log('Sent ', k2, ' to _tileCallbacks, still ', c.dataset.pending, ' images to go');
					}.bind(this);
				}.bind(this))(tileContainer/*, key2*/) );
			}
		}

		if (!parseInt(tileContainer.dataset.pending)) {
			L.Util.requestAnimFrame(done);
		}
		return tileContainer;
	},

	_clone: function (imgNode) {
		var clonedImgNode = imgNode.cloneNode(true);
		clonedImgNode.style.visibility = 'visible';
		return clonedImgNode;
	},

	_checkZoomLevels: function () {
		//setting the zoom level on the Google map may result in a different zoom level than the one requested
		//(it won't go beyond the level for which they have data).
		var zoomLevel = this._map.getZoom(),
		    gMapZoomLevel = this._mutant.getZoom();

		if (!zoomLevel || !gMapZoomLevel) return;

		if ((gMapZoomLevel !== zoomLevel) || //zoom levels are out of sync, Google doesn't have data
			(gMapZoomLevel > this.options.maxNativeZoom)) { //at current location, Google does have data (contrary to maxNativeZoom)
			//Update maxNativeZoom
			this._setMaxNativeZoom(gMapZoomLevel);
		}
	},

	_setMaxNativeZoom: function (zoomLevel) {
		if (zoomLevel != this.options.maxNativeZoom) {
			this.options.maxNativeZoom = zoomLevel;
			this._resetView();
		}
	},

	_reset: function () {
		this._initContainer();
	},

	_update: function () {
		// zoom level check needs to happen before super's implementation (tile addition/creation)
		// otherwise tiles may be missed if maxNativeZoom is not yet correctly determined
		if (this._mutant) {
			var center = this._map.getCenter(),
			   _center = new google.maps.LatLng(center.lat, center.lng);

			this._mutant.setCenter(_center);

			var zoom = this._map.getZoom(),
			    fractionalLevel = zoom !== Math.round(zoom),
			    mutantZoom = this._mutant.getZoom();

			//ignore fractional zoom levels
			if (!fractionalLevel && (zoom != mutantZoom)) {
				this._mutant.setZoom(zoom);

				if (this._mutantIsReady) this._checkZoomLevels();
				//else zoom level check will be done later by 'idle' handler
			}
		}

		L.GridLayer.prototype._update.call(this);
	},

	_resize: function () {
		var size = this._map.getSize();
		if (this._mutantContainer.style.width === size.x &&
			this._mutantContainer.style.height === size.y)
			return;
		this.setElementSize(this._mutantContainer, size);
		if (!this._mutant) return;
		google.maps.event.trigger(this._mutant, 'resize');
	},

	_handleZoomAnim: function () {
		if (!this._mutant) return;

		var center = this._map.getCenter(),
		   _center = new google.maps.LatLng(center.lat, center.lng);

		this._mutant.setCenter(_center);
		this._mutant.setZoom(Math.round(this._map.getZoom()));
		var gZoom = this._mutant.getZoom();

		// for (let key of Object.keys(this._freshTiles)) {
                // IE-compatible code, in ecmascript5:
		for (var key in Object.keys(this._freshTiles)) {
			if (gZoom != key.split(':')[2] /* tileZoom */) {
				delete this._freshTiles[key];
			}
		}
	},

	// Agressively prune _freshtiles when a tile with the same key is removed,
	// this prevents a problem where Leaflet keeps a loaded tile longer than
	// GMaps, so that GMaps makes two requests but Leaflet only consumes one,
	// polluting _freshTiles with stale data.
	_removeTile: function (key) {
		if (!this._mutant) return;

		//give time for animations to finish before checking it tile should be pruned
		setTimeout(this._pruneTile.bind(this, key), 1000);

		return L.GridLayer.prototype._removeTile.call(this, key);
	},

	_getLargeGMapBound: function (googleBounds) {
		var sw = googleBounds.getSouthWest(),
		    ne = googleBounds.getNorthEast(),
		    swLat = sw.lat(),
		    swLng = sw.lng(),
		    neLat = ne.lat(),
		    neLng = ne.lng(),
		    latDelta = Math.abs(neLat - swLat),
		    lngDelta = Math.abs(neLng - swLng);

		return L.latLngBounds([[swLat - latDelta, swLng - lngDelta], [neLat + latDelta, neLng + lngDelta]]);
	},

	_pruneTile: function (key) {
		var gZoom = this._mutant.getZoom(),
		    tileZoom = key.split(':')[2],
		    googleBounds = this._mutant.getBounds(),
		    gMapBounds = this._getLargeGMapBound(googleBounds);

		if (!googleBounds) {
			return;
		}

		for (var i=0; i<this._imagesPerTile; ++i) {
			var key2 = key + '/' + i;
			if (key2 in this._freshTiles) {
				var tileBounds = this._map && this._keyToBounds(key),
					stillVisible = this._map && tileBounds.overlaps(gMapBounds) && (tileZoom == gZoom);

				if (!stillVisible) delete this._freshTiles[key2];
//                              console.log('Prunning of ', key, (!stillVisible))
			}
		}
	}
});


// 🍂factory gridLayer.googleMutant(options)
// Returns a new `GridLayer.GoogleMutant` given its options
L.gridLayer.googleMutant = function (options) {
	return new L.GridLayer.GoogleMutant(options);
};
