L.Control.Attribution = L.Control.extend({
	options: {
		position: 'bottomright',
		prefix: 'Powered by <a href="http://leaflet.cloudmade.com">Leaflet</a>'
	},

	initialize: function (options) {
		L.Util.setOptions(this, options);

		this._attributions = {};
	},

	onAdd: function (map) {
		this._container = L.DomUtil.create('div', 'leaflet-control-attribution');
		L.DomEvent.disableClickPropagation(this._container);

		map
			.on('layeradd', this._onLayerAdd, this)
			.on('layerremove', this._onLayerRemove, this);

		this._update();

		return this._container;
	},

	onRemove: function (map) {
		map
			.off('layeradd', this._onLayerAdd)
			.off('layerremove', this._onLayerRemove);

	},

	setPrefix: function (prefix) {
		this.options.prefix = prefix;
		this._update();
		return this;
	},

	addAttribution: function (text) {
		if (!text) { return; }

		if (!this._attributions[text]) {
			this._attributions[text] = 0;
		}
		this._attributions[text]++;

		this._update();

		return this;
	},

	removeAttribution: function (text) {
		if (!text) { return; }

		this._attributions[text]--;
		this._update();

		return this;
	},

	_update: function () {
		if (!this._map) { return; }

		var attribs = [];

		for (var i in this._attributions) {
			if (this._attributions.hasOwnProperty(i) && this._attributions[i]) {
				attribs.push(i);
			}
		}

		var prefixAndAttribs = [];

		if (this.options.prefix) {
			prefixAndAttribs.push(this.options.prefix);
		}
		if (attribs.length) {
			prefixAndAttribs.push(attribs.join(', '));
		}

		this._container.innerHTML = prefixAndAttribs.join(' &#8212; ');
	},

	_onLayerAdd: function (e) {
		if (e.layer.getAttribution) {
			this.addAttribution(e.layer.getAttribution());
		}
	},

	_onLayerRemove: function (e) {
		if (e.layer.getAttribution) {
			this.removeAttribution(e.layer.getAttribution());
		}
	}
});

L.Map.mergeOptions({
	attributionControl: true
});

L.Map.addInitHook(function () {
	if (this.options.attributionControl) {
		this.attributionControl = (new L.Control.Attribution()).addTo(this);
	}
});

L.control.attribution = function (options) {
	return new L.Control.Attribution(options);
};
