railroad-diagrams.js

"use strict";
/*
Railroad Diagrams
by Tab Atkins Jr. (and others)
http://xanthir.com
http://twitter.com/tabatkins
http://github.com/tabatkins/railroad-diagrams

This document and all associated files in the github project are licensed under CC0: http://creativecommons.org/publicdomain/zero/1.0/
This means you can reuse, remix, or otherwise appropriate this project for your own use WITHOUT RESTRICTION.
(The actual legal meaning can be found at the above link.)
Don't ask me for permission to use any part of this project, JUST USE IT.
I would appreciate attribution, but that is not required by the license.
*/

/*
This file uses a module pattern to avoid leaking names into the global scope.
The only accidental leakage is the name "temp".
The exported names can be found at the bottom of this file;
simply change the names in the array of strings to change what they are called in your application.

As well, several configuration constants are passed into the module function at the bottom of this file.
At runtime, these constants can be found on the Diagram class.
*/

(function(options) {
	function subclassOf(baseClass, superClass) {
		baseClass.prototype = Object.create(superClass.prototype);
		baseClass.prototype.$super = superClass.prototype;
	}

	function unnull(/* children */) {
		return [].slice.call(arguments).reduce(function(sofar, x) { return sofar !== undefined ? sofar : x; });
	}

	function determineGaps(outer, inner) {
		var diff = outer - inner;
		switch(Diagram.INTERNAL_ALIGNMENT) {
			case 'left': return [0, diff]; break;
			case 'right': return [diff, 0]; break;
			case 'center':
			default: return [diff/2, diff/2]; break;
		}
	}

	function wrapString(value) {
		return ((typeof value) == 'string') ? new Terminal(value) : value;
	}

	function sum(iter, func) {
		if(!func) func = function(x) { return x; };
		return iter.map(func).reduce(function(a,b){return a+b}, 0);
	}

	function max(iter, func) {
		if(!func) func = function(x) { return x; };
		return Math.max.apply(null, iter.map(func));
	}

	function SVG(name, attrs, text) {
		attrs = attrs || {};
		text = text || '';
		var el = document.createElementNS("http://www.w3.org/2000/svg",name);
		for(var attr in attrs) {
			if(attr === 'xlink:href')
				el.setAttributeNS("http://www.w3.org/1999/xlink", 'href', attrs[attr]);
			else
				el.setAttribute(attr, attrs[attr]);
		}
		el.textContent = text;
		return el;
	}

	function FakeSVG(tagName, attrs, text){
		if(!(this instanceof FakeSVG)) return new FakeSVG(tagName, attrs, text);
		if(text) this.children = text;
		else this.children = [];
		this.tagName = tagName;
		this.attrs = unnull(attrs, {});
		return this;
	};
	FakeSVG.prototype.format = function(x, y, width) {
		// Virtual
	};
	FakeSVG.prototype.addTo = function(parent) {
		if(parent instanceof FakeSVG) {
			parent.children.push(this);
			return this;
		} else {
			var svg = this.toSVG();
			parent.appendChild(svg);
			return svg;
		}
	};
	FakeSVG.prototype.escapeString = function(string) {
		// Escape markdown and HTML special characters
		return string.replace(/[*_\`\[\]<&]/g, function(charString) {
			return '&#' + charString.charCodeAt(0) + ';';
		});
	};
	FakeSVG.prototype.toSVG = function() {
		var el = SVG(this.tagName, this.attrs);
		if(typeof this.children == 'string') {
			el.textContent = this.children;
		} else {
			this.children.forEach(function(e) {
				el.appendChild(e.toSVG());
			});
		}
		return el;
	};
	FakeSVG.prototype.toString = function(opt) {
        opt=opt||{};
		var str = '<' + this.tagName;
        var group = this.tagName == "g" || this.tagName == "svg";
        if(this.tagName == "svg" && opt.svgattr){
            str += ' '+opt.svgattr;
        }
		for(var attr in this.attrs) {
			str += ' ' + attr + '="' + (this.attrs[attr]+'').replace(/&/g, '&amp;').replace(/"/g, '&quot;') + '"';
		}
        str += '>';
        if(this.tagName == "svg" && opt.css){
            str += '\n<style><![CDATA[\n'+opt.css+'\n]]></style>';
        }
		if(group) str += "\n";
		if(typeof this.children == 'string') {
			str += FakeSVG.prototype.escapeString(this.children);
		} else {
			this.children.forEach(function(e) {
				str += e;
			});
		}
		str += '</' + this.tagName + '>\n';
		return str;
	}

	function Path(x,y) {
		if(!(this instanceof Path)) return new Path(x,y);
		FakeSVG.call(this, 'path');
		this.attrs.d = "M"+x+' '+y;
	}
	subclassOf(Path, FakeSVG);
	Path.prototype.m = function(x,y) {
		this.attrs.d += 'm'+x+' '+y;
		return this;
	}
	Path.prototype.h = function(val) {
		this.attrs.d += 'h'+val;
		return this;
	}
	Path.prototype.right = function(val) { return this.h(Math.max(0, val)); }
	Path.prototype.left = function(val) { return this.h(-Math.max(0, val)); }
	Path.prototype.v = function(val) {
		this.attrs.d += 'v'+val;
		return this;
	}
	Path.prototype.down = function(val) { return this.v(Math.max(0, val)); }
	Path.prototype.up = function(val) { return this.v(-Math.max(0, val)); }
	Path.prototype.arc = function(sweep){
		// 1/4 of a circle
		var x = Diagram.ARC_RADIUS;
		var y = Diagram.ARC_RADIUS;
		if(sweep[0] == 'e' || sweep[1] == 'w') {
			x *= -1;
		}
		if(sweep[0] == 's' || sweep[1] == 'n') {
			y *= -1;
		}
		if(sweep == 'ne' || sweep == 'es' || sweep == 'sw' || sweep == 'wn') {
			var cw = 1;
		} else {
			var cw = 0;
		}
		this.attrs.d += "a"+Diagram.ARC_RADIUS+" "+Diagram.ARC_RADIUS+" 0 0 "+cw+' '+x+' '+y;
		return this;
	}
	Path.prototype.arc_8 = function(start, dir) {
		// 1/8 of a circle
		const arc = Diagram.ARC_RADIUS;
		const s2 = 1/Math.sqrt(2) * arc;
		const s2inv = (arc - s2);
		let path = "a " + arc + " " + arc + " 0 0 " + (dir=='cw' ? "1" : "0") + " ";
		const sd = start+dir;
		const offset =
			sd == 'ncw'   ? [s2, s2inv] :
			sd == 'necw'  ? [s2inv, s2] :
			sd == 'ecw'   ? [-s2inv, s2] :
			sd == 'secw'  ? [-s2, s2inv] :
			sd == 'scw'   ? [-s2, -s2inv] :
			sd == 'swcw'  ? [-s2inv, -s2] :
			sd == 'wcw'   ? [s2inv, -s2] :
			sd == 'nwcw'  ? [s2, -s2inv] :
			sd == 'nccw'  ? [-s2, s2inv] :
			sd == 'nwccw' ? [-s2inv, s2] :
			sd == 'wccw'  ? [s2inv, s2] :
			sd == 'swccw' ? [s2, s2inv] :
			sd == 'sccw'  ? [s2, -s2inv] :
			sd == 'seccw' ? [s2inv, -s2] :
			sd == 'eccw'  ? [-s2inv, -s2] :
			sd == 'neccw' ? [-s2, -s2inv] : null
		;
		path += offset.join(" ");
		this.attrs.d += path;
		return this;
	}
	Path.prototype.l = function(x, y) {
		this.attrs.d += 'l'+x+' '+y;
		return this;
	}
	Path.prototype.format = function() {
		// All paths in this library start/end horizontally.
		// The extra .5 ensures a minor overlap, so there's no seams in bad rasterizers.
		this.attrs.d += 'h.5';
		return this;
	}

	function Diagram(items) {
		if(!(this instanceof Diagram)) return new Diagram([].slice.call(arguments));
		FakeSVG.call(this, 'svg', {class: Diagram.DIAGRAM_CLASS});
		this.items = items.map(wrapString);
		this.items.unshift(new Start);
		this.items.push(new End);
		this.up = this.down = this.height = this.width = 0;
		for(var i = 0; i < this.items.length; i++) {
			var item = this.items[i];
			this.width += item.width + (item.needsSpace?20:0);
			this.up = Math.max(this.up, item.up - this.height);
			this.height += item.height;
			this.down = Math.max(this.down - item.height, item.down);
		}
		this.formatted = false;
	}
	subclassOf(Diagram, FakeSVG);
	for(var option in options) {
		Diagram[option] = options[option];
	}
	Diagram.prototype.format = function(paddingt, paddingr, paddingb, paddingl) {
		paddingt = unnull(paddingt, 20);
		paddingr = unnull(paddingr, paddingt, 20);
		paddingb = unnull(paddingb, paddingt, 20);
		paddingl = unnull(paddingl, paddingr, 20);
		var x = paddingl;
		var y = paddingt;
		y += this.up;
		var g = FakeSVG('g', Diagram.STROKE_ODD_PIXEL_LENGTH ? {transform:'translate(.5 .5)'} : {});
		for(var i = 0; i < this.items.length; i++) {
			var item = this.items[i];
			if(item.needsSpace) {
				Path(x,y).h(10).addTo(g);
				x += 10;
			}
			item.format(x, y, item.width).addTo(g);
			x += item.width;
			y += item.height;
			if(item.needsSpace) {
				Path(x,y).h(10).addTo(g);
				x += 10;
			}
		}
		this.attrs.width = this.width + paddingl + paddingr;
		this.attrs.height = this.up + this.height + this.down + paddingt + paddingb;
		this.attrs.viewBox = "0 0 " + this.attrs.width + " " + this.attrs.height;
		g.addTo(this);
		this.formatted = true;
		return this;
	}
	Diagram.prototype.addTo = function(parent) {
		if(!parent) {
			var scriptTag = document.getElementsByTagName('script');
			scriptTag = scriptTag[scriptTag.length - 1];
			parent = scriptTag.parentNode;
		}
		return this.$super.addTo.call(this, parent);
	}
	Diagram.prototype.toSVG = function() {
		if (!this.formatted) {
			this.format();
		}
		return this.$super.toSVG.call(this);
	}
	Diagram.prototype.toString = function(opt) {
		if (!this.formatted) {
			this.format();
		}
		return this.$super.toString.call(this,opt);
	}

	function ComplexDiagram() {
		var diagram = new Diagram([].slice.call(arguments));
		var items = diagram.items;
		items.shift();
		items.pop();
		items.unshift(new Start("complex"));
		items.push(new End("complex"));
		diagram.items = items;
		return diagram;
	}

	function Sequence(items) {
		if(!(this instanceof Sequence)) return new Sequence([].slice.call(arguments));
		FakeSVG.call(this, 'g');
		this.items = items.map(wrapString);
		var numberOfItems = this.items.length;
		this.needsSpace = true;
		this.up = this.down = this.height = this.width = 0;
		for(var i = 0; i < this.items.length; i++) {
			var item = this.items[i];
			this.width += item.width + (item.needsSpace?20:0);
			this.up = Math.max(this.up, item.up - this.height);
			this.height += item.height;
			this.down = Math.max(this.down - item.height, item.down);
		}
		if(this.items[0].needsSpace) this.width -= 10;
		if(this.items[this.items.length-1].needsSpace) this.width -= 10;
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "sequence"
		}
	}
	subclassOf(Sequence, FakeSVG);
	Sequence.prototype.format = function(x,y,width) {
		// Hook up the two sides if this is narrower than its stated width.
		var gaps = determineGaps(width, this.width);
		Path(x,y).h(gaps[0]).addTo(this);
		Path(x+gaps[0]+this.width,y+this.height).h(gaps[1]).addTo(this);
		x += gaps[0];

		for(var i = 0; i < this.items.length; i++) {
			var item = this.items[i];
			if(item.needsSpace && i > 0) {
				Path(x,y).h(10).addTo(this);
				x += 10;
			}
			item.format(x, y, item.width).addTo(this);
			x += item.width;
			y += item.height;
			if(item.needsSpace && i < this.items.length-1) {
				Path(x,y).h(10).addTo(this);
				x += 10;
			}
		}
		return this;
	}

	function Stack(items) {
		if(!(this instanceof Stack)) return new Stack([].slice.call(arguments));
		FakeSVG.call(this, 'g');
		if( items.length === 0 ) {
			throw new RangeError("Stack() must have at least one child.");
		}
		this.items = items.map(wrapString);
		this.width = Math.max.apply(null, this.items.map(function(e) { return e.width + (e.needsSpace?20:0); }));
		//if(this.items[0].needsSpace) this.width -= 10;
		//if(this.items[this.items.length-1].needsSpace) this.width -= 10;
		if(this.items.length > 1){
			this.width += Diagram.ARC_RADIUS*2;
		}
		this.needsSpace = true;
		this.up = this.items[0].up;
		this.down = this.items[this.items.length-1].down;

		this.height = 0;
		var last = this.items.length - 1;
		for(var i = 0; i < this.items.length; i++) {
			var item = this.items[i];
			this.height += item.height;
			if(i > 0) {
				this.height += Math.max(Diagram.ARC_RADIUS*2, item.up + Diagram.VERTICAL_SEPARATION);
			}
			if(i < last) {
				this.height += Math.max(Diagram.ARC_RADIUS*2, item.down + Diagram.VERTICAL_SEPARATION);
			}
		}
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "stack"
		}
	}
	subclassOf(Stack, FakeSVG);
	Stack.prototype.format = function(x,y,width) {
		var gaps = determineGaps(width, this.width);
		Path(x,y).h(gaps[0]).addTo(this);
		x += gaps[0];
		var xInitial = x;
		if(this.items.length > 1) {
			Path(x, y).h(Diagram.ARC_RADIUS).addTo(this);
			x += Diagram.ARC_RADIUS;
		}

		for(var i = 0; i < this.items.length; i++) {
			var item = this.items[i];
			var innerWidth = this.width - (this.items.length>1 ? Diagram.ARC_RADIUS*2 : 0);
			item.format(x, y, innerWidth).addTo(this);
			x += innerWidth;
			y += item.height;

			if(i !== this.items.length-1) {
				Path(x, y)
					.arc('ne').down(Math.max(0, item.down + Diagram.VERTICAL_SEPARATION - Diagram.ARC_RADIUS*2))
					.arc('es').left(innerWidth)
					.arc('nw').down(Math.max(0, this.items[i+1].up + Diagram.VERTICAL_SEPARATION - Diagram.ARC_RADIUS*2))
					.arc('ws').addTo(this);
				y += Math.max(item.down + Diagram.VERTICAL_SEPARATION, Diagram.ARC_RADIUS*2) + Math.max(this.items[i+1].up + Diagram.VERTICAL_SEPARATION, Diagram.ARC_RADIUS*2);
				//y += Math.max(Diagram.ARC_RADIUS*4, item.down + Diagram.VERTICAL_SEPARATION*2 + this.items[i+1].up)
				x = xInitial+Diagram.ARC_RADIUS;
			}

		}

		if(this.items.length > 1) {
			Path(x,y).h(Diagram.ARC_RADIUS).addTo(this);
			x += Diagram.ARC_RADIUS;
		}
		Path(x,y).h(gaps[1]).addTo(this);

		return this;
	}

	function OptionalSequence(items) {
		if(!(this instanceof OptionalSequence)) return new OptionalSequence([].slice.call(arguments));
		FakeSVG.call(this, 'g');
		if( items.length === 0 ) {
			throw new RangeError("OptionalSequence() must have at least one child.");
		}
		if( items.length === 1 ) {
			return new Sequence(items);
		}
		var arc = Diagram.ARC_RADIUS;
		this.items = items.map(wrapString);
		this.needsSpace = false;
		this.width = 0;
		this.up = 0;
		this.height = sum(this.items, function(x){return x.height});
		this.down = this.items[0].down;
		var heightSoFar = 0;
		for(var i = 0; i < this.items.length; i++) {
			var item = this.items[i];
			this.up = Math.max(this.up, Math.max(arc*2, item.up + Diagram.VERTICAL_SEPARATION) - heightSoFar);
			heightSoFar += item.height;
			if(i > 0) {
				this.down = Math.max(this.height + this.down, heightSoFar + Math.max(arc*2, item.down + Diagram.VERTICAL_SEPARATION)) - this.height;
			}
			var itemWidth = (item.needsSpace?10:0) + item.width;
			if(i == 0) {
				this.width += arc + Math.max(itemWidth, arc);
			} else {
				this.width += arc*2 + Math.max(itemWidth, arc) + arc;
			}
		}
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "optseq"
		}
	}
	subclassOf(OptionalSequence, FakeSVG);
	OptionalSequence.prototype.format = function(x, y, width) {
		var arc = Diagram.ARC_RADIUS;
		var gaps = determineGaps(width, this.width);
		Path(x, y).right(gaps[0]).addTo(this);
		Path(x + gaps[0] + this.width, y + this.height).right(gaps[1]).addTo(this);
		x += gaps[0]
		var upperLineY = y - this.up;
		var last = this.items.length - 1;
		for(var i = 0; i < this.items.length; i++) {
			var item = this.items[i];
			var itemSpace = (item.needsSpace?10:0);
			var itemWidth = item.width + itemSpace;
			if(i == 0) {
				// Upper skip
				Path(x,y)
					.arc('se')
					.up(y - upperLineY - arc*2)
					.arc('wn')
					.right(itemWidth - arc)
					.arc('ne')
					.down(y + item.height - upperLineY - arc*2)
					.arc('ws')
					.addTo(this);
				// Straight line
				Path(x, y)
					.right(itemSpace + arc)
					.addTo(this);
				item.format(x + itemSpace + arc, y, item.width).addTo(this);
				x += itemWidth + arc;
				y += item.height;
				// x ends on the far side of the first element,
				// where the next element's skip needs to begin
			} else if(i < last) {
				// Upper skip
				Path(x, upperLineY)
					.right(arc*2 + Math.max(itemWidth, arc) + arc)
					.arc('ne')
					.down(y - upperLineY + item.height - arc*2)
					.arc('ws')
					.addTo(this);
				// Straight line
				Path(x,y)
					.right(arc*2)
					.addTo(this);
				item.format(x + arc*2, y, item.width).addTo(this);
				Path(x + item.width + arc*2, y + item.height)
					.right(itemSpace + arc)
					.addTo(this);
				// Lower skip
				Path(x,y)
					.arc('ne')
					.down(item.height + Math.max(item.down + Diagram.VERTICAL_SEPARATION, arc*2) - arc*2)
					.arc('ws')
					.right(itemWidth - arc)
					.arc('se')
					.up(item.down + Diagram.VERTICAL_SEPARATION - arc*2)
					.arc('wn')
					.addTo(this);
				x += arc*2 + Math.max(itemWidth, arc) + arc;
				y += item.height;
			} else {
				// Straight line
				Path(x, y)
					.right(arc*2)
					.addTo(this);
				item.format(x + arc*2, y, item.width).addTo(this);
				Path(x + arc*2 + item.width, y + item.height)
					.right(itemSpace + arc)
					.addTo(this);
				// Lower skip
				Path(x,y)
					.arc('ne')
					.down(item.height + Math.max(item.down + Diagram.VERTICAL_SEPARATION, arc*2) - arc*2)
					.arc('ws')
					.right(itemWidth - arc)
					.arc('se')
					.up(item.down + Diagram.VERTICAL_SEPARATION - arc*2)
					.arc('wn')
					.addTo(this);
			}
		}
		return this;
	}

	function AlternatingSequence(items) {
		if(!(this instanceof AlternatingSequence)) return new AlternatingSequence([].slice.call(arguments));
		FakeSVG.call(this, 'g');
		if( items.length === 1 ) {
			return new Sequence(items);
		}
		if( items.length !== 2 ) {
			throw new RangeError("AlternatingSequence() must have one or two children.");
		}
		this.items = items.map(wrapString);
		this.needsSpace = false;

		const arc = Diagram.ARC_RADIUS;
		const vert = Diagram.VERTICAL_SEPARATION;
		const max = Math.max;
		const first = this.items[0];
		const second = this.items[1];

		const arcX = 1 / Math.sqrt(2) * arc * 2;
		const arcY = (1 - 1 / Math.sqrt(2)) * arc * 2;
		const crossY = Math.max(arc, Diagram.VERTICAL_SEPARATION);
		const crossX = (crossY - arcY) + arcX;

		const firstOut = max(arc + arc, crossY/2 + arc + arc, crossY/2 + vert + first.down);
		this.up = firstOut + first.height + first.up;

		const secondIn = max(arc + arc, crossY/2 + arc + arc, crossY/2 + vert + second.up);
		this.down = secondIn + second.height + second.down;

		this.height = 0;

		const firstWidth = 2*(first.needsSpace?10:0) + first.width;
		const secondWidth = 2*(second.needsSpace?10:0) + second.width;
		this.width = 2*arc + max(firstWidth, crossX, secondWidth) + 2*arc;

		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "altseq"
		}
	}
	subclassOf(AlternatingSequence, FakeSVG);
	AlternatingSequence.prototype.format = function(x, y, width) {
		const arc = Diagram.ARC_RADIUS;
		const gaps = determineGaps(width, this.width);
		Path(x,y).right(gaps[0]).addTo(this);
		console.log(gaps);
		x += gaps[0];
		Path(x+this.width, y).right(gaps[1]).addTo(this);
		// bounding box
		//Path(x+gaps[0], y).up(this.up).right(this.width).down(this.up+this.down).left(this.width).up(this.down).addTo(this);
		const first = this.items[0];
		const second = this.items[1];

		// top
		const firstIn = this.up - first.up;
		const firstOut = this.up - first.up - first.height;
		Path(x,y).arc('se').up(firstIn-2*arc).arc('wn').addTo(this);
		first.format(x + 2*arc, y - firstIn, this.width - 4*arc).addTo(this);
		Path(x + this.width - 2*arc, y - firstOut).arc('ne').down(firstOut - 2*arc).arc('ws').addTo(this);

		// bottom
		const secondIn = this.down - second.down - second.height;
		const secondOut = this.down - second.down;
		Path(x,y).arc('ne').down(secondIn - 2*arc).arc('ws').addTo(this);
		second.format(x + 2*arc, y + secondIn, this.width - 4*arc).addTo(this);
		Path(x + this.width - 2*arc, y + secondOut).arc('se').up(secondOut - 2*arc).arc('wn').addTo(this);

		// crossover
		const arcX = 1 / Math.sqrt(2) * arc * 2;
		const arcY = (1 - 1 / Math.sqrt(2)) * arc * 2;
		const crossY = Math.max(arc, Diagram.VERTICAL_SEPARATION);
		const crossX = (crossY - arcY) + arcX;
		const crossBar = (this.width - 4*arc - crossX)/2;
		Path(x+arc, y - crossY/2 - arc).arc('ws').right(crossBar)
			.arc_8('n', 'cw').l(crossX - arcX, crossY - arcY).arc_8('sw', 'ccw')
			.right(crossBar).arc('ne').addTo(this);
		Path(x+arc, y + crossY/2 + arc).arc('wn').right(crossBar)
			.arc_8('s', 'ccw').l(crossX - arcX, -(crossY - arcY)).arc_8('nw', 'cw')
			.right(crossBar).arc('se').addTo(this);

		//Path(x+arc, y + crossoverSize/2 + arc).arc('wn').right(crossBar).addTo(this);
		//Path(x+2*arc+crossBar+crossoverSize, y - crossoverSize/2).right(crossBar).arc('ne').addTo(this);
		//Path(x+2*arc+crossBar, y + crossoverSize/2).l(crossoverSize, -crossoverSize).addTo(this);

		return this;
	}

	function Choice(normal, items) {
		if(!(this instanceof Choice)) return new Choice(normal, [].slice.call(arguments,1));
		FakeSVG.call(this, 'g');
		if( typeof normal !== "number" || normal !== Math.floor(normal) ) {
			throw new TypeError("The first argument of Choice() must be an integer.");
		} else if(normal < 0 || normal >= items.length) {
			throw new RangeError("The first argument of Choice() must be an index for one of the items.");
		} else {
			this.normal = normal;
		}
		var first = 0;
		var last = items.length - 1;
		this.items = items.map(wrapString);
		this.width = Math.max.apply(null, this.items.map(function(el){return el.width})) + Diagram.ARC_RADIUS*4;
		this.height = this.items[normal].height;
		this.up = this.items[first].up;
		for(var i = first; i < normal; i++) {
			if(i == normal-1) var arcs = Diagram.ARC_RADIUS*2;
			else var arcs = Diagram.ARC_RADIUS;
			this.up += Math.max(arcs, this.items[i].height + this.items[i].down + Diagram.VERTICAL_SEPARATION + this.items[i+1].up);
		}
		this.down = this.items[last].down;
		for(var i = normal+1; i <= last; i++) {
			if(i == normal+1) var arcs = Diagram.ARC_RADIUS*2;
			else var arcs = Diagram.ARC_RADIUS;
			this.down += Math.max(arcs, this.items[i-1].height + this.items[i-1].down + Diagram.VERTICAL_SEPARATION + this.items[i].up);
		}
		this.down -= this.items[normal].height; // already counted in Choice.height
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "choice"
		}
	}
	subclassOf(Choice, FakeSVG);
	Choice.prototype.format = function(x,y,width) {
		// Hook up the two sides if this is narrower than its stated width.
		var gaps = determineGaps(width, this.width);
		Path(x,y).h(gaps[0]).addTo(this);
		Path(x+gaps[0]+this.width,y+this.height).h(gaps[1]).addTo(this);
		x += gaps[0];

		var last = this.items.length -1;
		var innerWidth = this.width - Diagram.ARC_RADIUS*4;

		// Do the elements that curve above
		for(var i = this.normal - 1; i >= 0; i--) {
			var item = this.items[i];
			if( i == this.normal - 1 ) {
				var distanceFromY = Math.max(Diagram.ARC_RADIUS*2, this.items[this.normal].up + Diagram.VERTICAL_SEPARATION + item.down + item.height);
			}
			Path(x,y)
				.arc('se')
				.up(distanceFromY - Diagram.ARC_RADIUS*2)
				.arc('wn').addTo(this);
			item.format(x+Diagram.ARC_RADIUS*2,y - distanceFromY,innerWidth).addTo(this);
			Path(x+Diagram.ARC_RADIUS*2+innerWidth, y-distanceFromY+item.height)
				.arc('ne')
				.down(distanceFromY - item.height + this.height - Diagram.ARC_RADIUS*2)
				.arc('ws').addTo(this);
			distanceFromY += Math.max(Diagram.ARC_RADIUS, item.up + Diagram.VERTICAL_SEPARATION + (i == 0 ? 0 : this.items[i-1].down+this.items[i-1].height));
		}

		// Do the straight-line path.
		Path(x,y).right(Diagram.ARC_RADIUS*2).addTo(this);
		this.items[this.normal].format(x+Diagram.ARC_RADIUS*2, y, innerWidth).addTo(this);
		Path(x+Diagram.ARC_RADIUS*2+innerWidth, y+this.height).right(Diagram.ARC_RADIUS*2).addTo(this);

		// Do the elements that curve below
		for(var i = this.normal+1; i <= last; i++) {
			var item = this.items[i];
			if( i == this.normal + 1 ) {
				var distanceFromY = Math.max(Diagram.ARC_RADIUS*2, this.height + this.items[this.normal].down + Diagram.VERTICAL_SEPARATION + item.up);
			}
			Path(x,y)
				.arc('ne')
				.down(distanceFromY - Diagram.ARC_RADIUS*2)
				.arc('ws').addTo(this);
			item.format(x+Diagram.ARC_RADIUS*2, y+distanceFromY, innerWidth).addTo(this);
			Path(x+Diagram.ARC_RADIUS*2+innerWidth, y+distanceFromY+item.height)
				.arc('se')
				.up(distanceFromY - Diagram.ARC_RADIUS*2 + item.height - this.height)
				.arc('wn').addTo(this);
			distanceFromY += Math.max(Diagram.ARC_RADIUS, item.height + item.down + Diagram.VERTICAL_SEPARATION + (i == last ? 0 : this.items[i+1].up));
		}

		return this;
	}

	function MultipleChoice(normal, type, items) {
		if(!(this instanceof MultipleChoice)) return new MultipleChoice(normal, type, [].slice.call(arguments,2));
		FakeSVG.call(this, 'g');
		if( typeof normal !== "number" || normal !== Math.floor(normal) ) {
			throw new TypeError("The first argument of MultipleChoice() must be an integer.");
		} else if(normal < 0 || normal >= items.length) {
			throw new RangeError("The first argument of MultipleChoice() must be an index for one of the items.");
		} else {
			this.normal = normal;
		}
		if( type != "any" && type != "all" ) {
			throw new SyntaxError("The second argument of MultipleChoice must be 'any' or 'all'.");
		} else {
			this.type = type;
		}
		this.needsSpace = true;
		this.items = items.map(wrapString);
		this.innerWidth = max(this.items, function(x){return x.width});
		this.width = 30 + Diagram.ARC_RADIUS + this.innerWidth + Diagram.ARC_RADIUS + 20;
		this.up = this.items[0].up;
		this.down = this.items[this.items.length-1].down;
		this.height = this.items[normal].height;
		for(var i = 0; i < this.items.length; i++) {
			var item = this.items[i];
			if(i == normal - 1 || i == normal + 1) var minimum = 10 + Diagram.ARC_RADIUS;
			else var minimum = Diagram.ARC_RADIUS;
			if(i < normal) {
				this.up += Math.max(minimum, item.height + item.down + Diagram.VERTICAL_SEPARATION + this.items[i+1].up);
			} else if(i > normal) {
				this.down += Math.max(minimum, item.up + Diagram.VERTICAL_SEPARATION + this.items[i-1].down + this.items[i-1].height);
			}
		}
		this.down -= this.items[normal].height; // already counted in this.height
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "multiplechoice"
		}
	}
	subclassOf(MultipleChoice, FakeSVG);
	MultipleChoice.prototype.format = function(x, y, width) {
		var gaps = determineGaps(width, this.width);
		Path(x, y).right(gaps[0]).addTo(this);
		Path(x + gaps[0] + this.width, y + this.height).right(gaps[1]).addTo(this);
		x += gaps[0];

		var normal = this.items[this.normal];

		// Do the elements that curve above
		for(var i = this.normal - 1; i >= 0; i--) {
			var item = this.items[i];
			if( i == this.normal - 1 ) {
				var distanceFromY = Math.max(10 + Diagram.ARC_RADIUS, normal.up + Diagram.VERTICAL_SEPARATION + item.down + item.height);
			}
			Path(x + 30,y)
				.up(distanceFromY - Diagram.ARC_RADIUS)
				.arc('wn').addTo(this);
			item.format(x + 30 + Diagram.ARC_RADIUS, y - distanceFromY, this.innerWidth).addTo(this);
			Path(x + 30 + Diagram.ARC_RADIUS + this.innerWidth, y - distanceFromY + item.height)
				.arc('ne')
				.down(distanceFromY - item.height + this.height - Diagram.ARC_RADIUS - 10)
				.addTo(this);
			if(i != 0) {
				distanceFromY += Math.max(Diagram.ARC_RADIUS, item.up + Diagram.VERTICAL_SEPARATION + this.items[i-1].down + this.items[i-1].height);
			}
		}

		Path(x + 30, y).right(Diagram.ARC_RADIUS).addTo(this);
		normal.format(x + 30 + Diagram.ARC_RADIUS, y, this.innerWidth).addTo(this);
		Path(x + 30 + Diagram.ARC_RADIUS + this.innerWidth, y + this.height).right(Diagram.ARC_RADIUS).addTo(this);

		for(var i = this.normal+1; i < this.items.length; i++) {
			var item = this.items[i];
			if(i == this.normal + 1) {
				var distanceFromY = Math.max(10+Diagram.ARC_RADIUS, normal.height + normal.down + Diagram.VERTICAL_SEPARATION + item.up);
			}
			Path(x + 30, y)
				.down(distanceFromY - Diagram.ARC_RADIUS)
				.arc('ws')
				.addTo(this);
			item.format(x + 30 + Diagram.ARC_RADIUS, y + distanceFromY, this.innerWidth).addTo(this)
			Path(x + 30 + Diagram.ARC_RADIUS + this.innerWidth, y + distanceFromY + item.height)
				.arc('se')
				.up(distanceFromY - Diagram.ARC_RADIUS + item.height - normal.height)
				.addTo(this);
			if(i != this.items.length - 1) {
				distanceFromY += Math.max(Diagram.ARC_RADIUS, item.height + item.down + Diagram.VERTICAL_SEPARATION + this.items[i+1].up);
			}
		}
		var text = FakeSVG('g', {"class": "diagram-text"}).addTo(this)
		FakeSVG('title', {}, (this.type=="any"?"take one or more branches, once each, in any order":"take all branches, once each, in any order")).addTo(text)
		FakeSVG('path', {
			"d": "M "+(x+30)+" "+(y-10)+" h -26 a 4 4 0 0 0 -4 4 v 12 a 4 4 0 0 0 4 4 h 26 z",
			"class": "diagram-text"
			}).addTo(text)
		FakeSVG('text', {
			"x": x + 15,
			"y": y + 4,
			"class": "diagram-text"
			}, (this.type=="any"?"1+":"all")).addTo(text)
		FakeSVG('path', {
			"d": "M "+(x+this.width-20)+" "+(y-10)+" h 16 a 4 4 0 0 1 4 4 v 12 a 4 4 0 0 1 -4 4 h -16 z",
			"class": "diagram-text"
			}).addTo(text)
		FakeSVG('path', {
			"d": "M "+(x+this.width-13)+" "+(y-2)+" a 4 4 0 1 0 6 -1 m 2.75 -1 h -4 v 4 m 0 -3 h 2",
			"style": "stroke-width: 1.75"
		}).addTo(text)
		return this;
	};

	function Optional(item, skip) {
		if( skip === undefined )
			return Choice(1, Skip(), item);
		else if ( skip === "skip" )
			return Choice(0, Skip(), item);
		else
			throw "Unknown value for Optional()'s 'skip' argument.";
	}

	function OneOrMore(item, rep) {
		if(!(this instanceof OneOrMore)) return new OneOrMore(item, rep);
		FakeSVG.call(this, 'g');
		rep = rep || (new Skip);
		this.item = wrapString(item);
		this.rep = wrapString(rep);
		this.width = Math.max(this.item.width, this.rep.width) + Diagram.ARC_RADIUS*2;
		this.height = this.item.height;
		this.up = this.item.up;
		this.down = Math.max(Diagram.ARC_RADIUS*2, this.item.down + Diagram.VERTICAL_SEPARATION + this.rep.up + this.rep.height + this.rep.down);
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "oneormore"
		}
	}
	subclassOf(OneOrMore, FakeSVG);
	OneOrMore.prototype.needsSpace = true;
	OneOrMore.prototype.format = function(x,y,width) {
		// Hook up the two sides if this is narrower than its stated width.
		var gaps = determineGaps(width, this.width);
		Path(x,y).h(gaps[0]).addTo(this);
		Path(x+gaps[0]+this.width,y+this.height).h(gaps[1]).addTo(this);
		x += gaps[0];

		// Draw item
		Path(x,y).right(Diagram.ARC_RADIUS).addTo(this);
		this.item.format(x+Diagram.ARC_RADIUS,y,this.width-Diagram.ARC_RADIUS*2).addTo(this);
		Path(x+this.width-Diagram.ARC_RADIUS,y+this.height).right(Diagram.ARC_RADIUS).addTo(this);

		// Draw repeat arc
		var distanceFromY = Math.max(Diagram.ARC_RADIUS*2, this.item.height+this.item.down+Diagram.VERTICAL_SEPARATION+this.rep.up);
		Path(x+Diagram.ARC_RADIUS,y).arc('nw').down(distanceFromY-Diagram.ARC_RADIUS*2).arc('ws').addTo(this);
		this.rep.format(x+Diagram.ARC_RADIUS, y+distanceFromY, this.width - Diagram.ARC_RADIUS*2).addTo(this);
		Path(x+this.width-Diagram.ARC_RADIUS, y+distanceFromY+this.rep.height).arc('se').up(distanceFromY-Diagram.ARC_RADIUS*2+this.rep.height-this.item.height).arc('en').addTo(this);

		return this;
	}

	function ZeroOrMore(item, rep, skip) {
		return Optional(OneOrMore(item, rep), skip);
	}

	function Start(type) {
		if(!(this instanceof Start)) return new Start();
		FakeSVG.call(this, 'path');
		this.width = 20;
		this.height = 0;
		this.up = 10;
		this.down = 10;
		this.type = type || "simple";
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "start"
		}
	}
	subclassOf(Start, FakeSVG);
	Start.prototype.format = function(x,y) {
		if (this.type === "complex") {
			this.attrs.d = 'M '+x+' '+(y-10)+' v 20 m 0 -10 h 20.5';
		} else {
			this.attrs.d = 'M '+x+' '+(y-10)+' v 20 m 10 -20 v 20 m -10 -10 h 20.5';
		}
		return this;
	}

	function End(type) {
		if(!(this instanceof End)) return new End();
		FakeSVG.call(this, 'path');
		this.width = 20;
		this.height = 0;
		this.up = 10;
		this.down = 10;
		this.type = type || "simple";
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "end"
		}
	}
	subclassOf(End, FakeSVG);
	End.prototype.format = function(x,y) {
		if (this.type === "complex") {
			this.attrs.d = 'M '+x+' '+y+' h 20 m 0 -10 v 20';
		} else {
			this.attrs.d = 'M '+x+' '+y+' h 20 m -10 -10 v 20 m 10 -20 v 20';
		}
		return this;
	}

	function Terminal(text, href) {
		if(!(this instanceof Terminal)) return new Terminal(text, href);
		FakeSVG.call(this, 'g', {'class': 'terminal'});
		this.text = text;
		this.href = href;
		this.width = text.length * 8 + 20; /* Assume that each char is .5em, and that the em is 16px */
		this.height = 0;
		this.up = 11;
		this.down = 11;
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "terminal"
		}
	}
	subclassOf(Terminal, FakeSVG);
	Terminal.prototype.needsSpace = true;
	Terminal.prototype.format = function(x, y, width) {
		// Hook up the two sides if this is narrower than its stated width.
		var gaps = determineGaps(width, this.width);
		Path(x,y).h(gaps[0]).addTo(this);
		Path(x+gaps[0]+this.width,y).h(gaps[1]).addTo(this);
		x += gaps[0];

		FakeSVG('rect', {x:x, y:y-11, width:this.width, height:this.up+this.down, rx:10, ry:10}).addTo(this);
		var text = FakeSVG('text', {x:x+this.width/2, y:y+4}, this.text);
		if(this.href)
			FakeSVG('a', {'xlink:href': this.href}, [text]).addTo(this);
		else
			text.addTo(this);
		return this;
	}

	function NonTerminal(text, href) {
		if(!(this instanceof NonTerminal)) return new NonTerminal(text, href);
		FakeSVG.call(this, 'g', {'class': 'non-terminal'});
		this.text = text;
		this.href = href;
		this.width = text.length * 8 + 20;
		this.height = 0;
		this.up = 11;
		this.down = 11;
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "nonterminal"
		}
	}
	subclassOf(NonTerminal, FakeSVG);
	NonTerminal.prototype.needsSpace = true;
	NonTerminal.prototype.format = function(x, y, width) {
		// Hook up the two sides if this is narrower than its stated width.
		var gaps = determineGaps(width, this.width);
		Path(x,y).h(gaps[0]).addTo(this);
		Path(x+gaps[0]+this.width,y).h(gaps[1]).addTo(this);
		x += gaps[0];

		FakeSVG('rect', {x:x, y:y-11, width:this.width, height:this.up+this.down}).addTo(this);
		var text = FakeSVG('text', {x:x+this.width/2, y:y+4}, this.text);
		if(this.href)
			FakeSVG('a', {'xlink:href': this.href}, [text]).addTo(this);
		else
			text.addTo(this);
		return this;
	}

	function Comment(text, href) {
		if(!(this instanceof Comment)) return new Comment(text, href);
		FakeSVG.call(this, 'g');
		this.text = text;
		this.href = href;
		this.width = text.length * 7 + 10;
		this.height = 0;
		this.up = 11;
		this.down = 11;
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "comment"
		}
	}
	subclassOf(Comment, FakeSVG);
	Comment.prototype.needsSpace = true;
	Comment.prototype.format = function(x, y, width) {
		// Hook up the two sides if this is narrower than its stated width.
		var gaps = determineGaps(width, this.width);
		Path(x,y).h(gaps[0]).addTo(this);
		Path(x+gaps[0]+this.width,y+this.height).h(gaps[1]).addTo(this);
		x += gaps[0];

		var text = FakeSVG('text', {x:x+this.width/2, y:y+5, class:'comment'}, this.text);
		if(this.href)
			FakeSVG('a', {'xlink:href': this.href}, [text]).addTo(this);
		else
			text.addTo(this);
		return this;
	}

	function Skip() {
		if(!(this instanceof Skip)) return new Skip();
		FakeSVG.call(this, 'g');
		this.width = 0;
		this.height = 0;
		this.up = 0;
		this.down = 0;
		if(Diagram.DEBUG) {
			this.attrs['data-updown'] = this.up + " " + this.height + " " + this.down
			this.attrs['data-type'] = "skip"
		}
	}
	subclassOf(Skip, FakeSVG);
	Skip.prototype.format = function(x, y, width) {
		Path(x,y).right(width).addTo(this);
		return this;
	}

	var root;
	if (typeof define === 'function' && define.amd) {
		// AMD. Register as an anonymous module.
		root = {};
		define([], function() {
			return root;
		});
	} else if (typeof exports === 'object') {
		// CommonJS for node
		root = exports;
	} else {
		// Browser globals (root is window)
		root = this;
	}

	var temp = [Diagram, ComplexDiagram, Sequence, Stack, OptionalSequence, AlternatingSequence, Choice, MultipleChoice, Optional, OneOrMore, ZeroOrMore, Terminal, NonTerminal, Comment, Skip];
	/*
	These are the names that the internal classes are exported as.
	If you would like different names, adjust them here.
	*/
	['Diagram', 'ComplexDiagram', 'Sequence', 'Stack', 'OptionalSequence', 'AlternatingSequence', 'Choice', 'MultipleChoice', 'Optional', 'OneOrMore', 'ZeroOrMore', 'Terminal', 'NonTerminal', 'Comment', 'Skip']
		.forEach(function(e,i) { root[e] = temp[i]; });
}).call(this,
	{
	VERTICAL_SEPARATION: 8,
	ARC_RADIUS: 10,
	DIAGRAM_CLASS: 'railroad-diagram',
	STROKE_ODD_PIXEL_LENGTH: true,
	INTERNAL_ALIGNMENT: 'center'
	}
);