(function (factory) {
	var L, proj4;
	if (typeof define === 'function' && define.amd) {
		// AMD
		define(['leaflet', 'proj4'], factory);
	} else if (typeof module !== 'undefined') {
		// Node/CommonJS
		L = require('leaflet');
		proj4 = require('proj4');
		module.exports = factory(L, proj4);
	} else {
		// Browser globals
		if (typeof window.L === 'undefined' || typeof window.proj4 === 'undefined')
			throw 'Leaflet and proj4 must be loaded first';
		factory(window.L, window.proj4);
	}
}(function (L, proj4) {

	L.Proj = {};

	L.Proj._isProj4Obj = function(a) {
		return (typeof a.inverse !== 'undefined' &&
			typeof a.forward !== 'undefined');
	};

	L.Proj.Projection = L.Class.extend({
		initialize: function(code, def, bounds) {
			var isP4 = L.Proj._isProj4Obj(code);
			this._proj = isP4 ? code : this._projFromCodeDef(code, def);
			this.bounds = isP4 ? def : bounds;
		},

		project: function (latlng) {
			var point = this._proj.forward([latlng.lng, latlng.lat]);
			return new L.Point(point[0], point[1]);
		},

		unproject: function (point, unbounded) {
			var point2 = this._proj.inverse([point.x, point.y]);
			return new L.LatLng(point2[1], point2[0], unbounded);
		},

		_projFromCodeDef: function(code, def) {
			if (def) {
				proj4.defs(code, def);
			} else if (proj4.defs[code] === undefined) {
				var urn = code.split(':');
				if (urn.length > 3) {
					code = urn[urn.length - 3] + ':' + urn[urn.length - 1];
				}
				if (proj4.defs[code] === undefined) {
					throw 'No projection definition for code ' + code;
				}
			}

			return proj4(code);
		}
	});

	L.Proj.CRS = L.Class.extend({
		includes: L.CRS,

		options: {
			transformation: new L.Transformation(1, 0, -1, 0)
		},

		initialize: function(a, b, c) {
			var code,
			    proj,
			    def,
			    options;

			if (L.Proj._isProj4Obj(a)) {
				proj = a;
				code = proj.srsCode;
				options = b || {};

				this.projection = new L.Proj.Projection(proj, options.bounds);
			} else {
				code = a;
				def = b;
				options = c || {};
				this.projection = new L.Proj.Projection(code, def, options.bounds);
			}

			L.Util.setOptions(this, options);
			this.code = code;
			this.transformation = this.options.transformation;

			if (this.options.origin) {
				this.transformation =
					new L.Transformation(1, -this.options.origin[0],
						-1, this.options.origin[1]);
			}

			if (this.options.scales) {
				this._scales = this.options.scales;
			} else if (this.options.resolutions) {
				this._scales = [];
				for (var i = this.options.resolutions.length - 1; i >= 0; i--) {
					if (this.options.resolutions[i]) {
						this._scales[i] = 1 / this.options.resolutions[i];
					}
				}
			}

			this.infinite = !this.options.bounds;
		},

		scale: function(zoom) {
			var iZoom = Math.floor(zoom),
				baseScale,
				nextScale,
				scaleDiff,
				zDiff;
			if (zoom === iZoom) {
				return this._scales[zoom];
			} else {
				// Non-integer zoom, interpolate
				baseScale = this._scales[iZoom];
				nextScale = this._scales[iZoom + 1];
				scaleDiff = nextScale - baseScale;
				zDiff = (zoom - iZoom);
				return baseScale + scaleDiff * zDiff;
			}
		},
	});

	L.Proj.GeoJSON = L.GeoJSON.extend({
		initialize: function(geojson, options) {
			if (geojson.crs && geojson.crs.type === 'name') {
				var crs = new L.Proj.CRS(geojson.crs.properties.name);
				options = options || {};
				options.coordsToLatLng = function(coords) {
					var point = L.point(coords[0], coords[1]);
					return crs.projection.unproject(point);
				};
			}
			L.GeoJSON.prototype.initialize.call(this, geojson, options);
		}
	});

	L.Proj.geoJson = function(geojson, options) {
		return new L.Proj.GeoJSON(geojson, options);
	};

	return L.Proj;
}));