SequenceDiagram/web/lib/editor.js

(function () {
	'use strict';

	var ComponentsLibrary = [
		{
			code: '{Agent1} -> {Agent2}: {Message}',
			title: 'Simple arrow (synchronous)',
		},
		{
			code: '{Agent1} --> {Agent2}: {Message}',
			title: 'Arrow with dotted line (response)',
		},
		{
			code: '{Agent1} ->> {Agent2}: {Message}',
			title: 'Open arrow (asynchronous)',
		},
		{
			code: '{Agent1} -x {Agent2}: {Message}',
			title: 'Lost message',
		},
		{
			code: '{Agent1} ~> {Agent2}: {Message}',
			title: 'Wavy line',
		},
		{
			code: '{Agent1} -> {Agent1}: {Message}',
			title: 'Self-connection',
		},
		{
			code: '{Agent1} -> ...{id}\n...{id} -> {Agent2}: {Message}',
			preview: (
				'begin A, B\n' +
				'A -> ...x\n' +
				'...x -> B: Message'
			),
			title: 'Asynchronous message',
		},
		{
			code: '* -> {Agent1}: {Message}',
			title: 'Found message',
		},
		{
			code: (
				'{Agent1} -> {Agent2}\n' +
				'& {Agent1} -> {Agent3}: {Broadcast}'
			),
			title: 'Broadcast message',
		},
		{
			code: (
				'{Agent1} -> +{Agent2}: {Request}\n' +
				'{Agent1} <-- -{Agent2}: {Response}'
			),
			title: 'Request/response pair',
		},
		{
			code: (
				'{Agent1} -> *{Agent2}: {Request}\n' +
				'{Agent1} <-- !{Agent2}: {Response}'
			),
			title: 'Inline agent creation / destruction',
		},
		{
			code: (
				'{Agent1} -> {Agent2}: {Request}\n' +
				'{Agent1} <-- {Agent2}: {Response}\n' +
				'end {Agent2}'
			),
			preview: (
				'begin A\n' +
				'::\n' +
				'A -> B: Request\n' +
				'A <-- B: Response\n' +
				'end B'
			),
			title: 'Agent creation / destruction',
		},
		{
			code: 'autolabel "[<inc>] <label>"',
			preview: (
				'autolabel "[<inc>] <label>"\n' +
				'A -> B: Foo\n' +
				'A <- B: Bar\n' +
				'A -> B: Baz'
			),
			title: 'Numbered labels',
		},
		{
			code: (
				'if {Condition1}\n' +
				'  {Agent1} -> {Agent2}\n' +
				'else if {Condition2}\n' +
				'  {Agent1} -> {Agent2}\n' +
				'else\n' +
				'  {Agent1} -> {Agent2}\n' +
				'end'
			),
			preview: (
				'begin A, B\n' +
				'if Condition1\n' +
				'  A -> B\n' +
				'else if Condition2\n' +
				'  A -> B\n' +
				'else\n' +
				'  A -> B\n' +
				'end'
			),
			title: 'Conditional blocks',
		},
		{
			code: (
				'repeat {Condition}\n' +
				'  {Agent1} -> {Agent2}\n' +
				'end'
			),
			preview: (
				'begin A, B\n' +
				'repeat Condition\n' +
				'  A -> B\n' +
				'end'
			),
			title: 'Repeated block',
		},
		{
			code: (
				'begin reference: {Label} as {Name}\n' +
				'{Agent1} -> {Name}\n' +
				'end {Name}'
			),
			preview: (
				'begin A\n' +
				'begin reference: "See 1.3" as myRef\n' +
				'A -> myRef\n' +
				'myRef -> A\n' +
				'end myRef'
			),
			title: 'Reference',
		},
		{
			code: (
				'begin reference over {Covered}: {Label} as {Name}\n' +
				'{Agent1} -> {Name}\n' +
				'end {Name}'
			),
			preview: (
				'begin A, B, C\n' +
				'begin reference over B, C: "See 1.3" as myRef\n' +
				'A -> myRef\n' +
				'myRef -> A\n' +
				'end myRef'
			),
			title: 'Reference over agents',
		},
		{
			code: (
				'group {Label}\n' +
				'  {Agent1} -> {Agent2}\n' +
				'end'
			),
			preview: (
				'begin A, B\n' +
				'group Label\n' +
				'  A -> B\n' +
				'end'
			),
			title: 'Group',
		},
		{
			code: 'note over {Agent1}: {Message}',
			title: 'Note over agent',
		},
		{
			code: 'note over {Agent1}, {Agent2}: {Message}',
			title: 'Note over multiple agents',
		},
		{
			code: 'note left of {Agent1}: {Message}',
			title: 'Note left of agent',
		},
		{
			code: 'note right of {Agent1}: {Message}',
			title: 'Note right of agent',
		},
		{
			code: 'note between {Agent1}, {Agent2}: {Message}',
			title: 'Note between agents',
		},
		{
			code: (
				'{Agent1} -> {Agent2}\n' +
				'& note right of {Agent2}: {Message}'
			),
			title: 'Inline note',
		},
		{
			code: 'state over {Agent1}: {State}',
			title: 'State over agent',
		},
		{
			code: '[ -> {Agent1}: {Message1}\n{Agent1} -> ]: {Message2}',
			title: 'Arrows to/from the sides',
		},
		{
			code: '{Agent1} -~ ]: {Message1}\n{Agent1} <-~ ]: {Message2}',
			title: 'Fading arrows',
		},
		{
			code: 'text right: {Message}',
			preview: (
				'A -> B\n' +
				'simultaneously:\n' +
				'text right: "Message\\non the\\nside"'
			),
			title: 'Text beside the diagram',
		},
		{
			code: 'divider space with height 10: {message}',
			preview: (
				'begin A, B, C, D, E, F\n' +
				'divider space with height 30: message'
			),
			title: 'Vertical space divider',
		},
		{
			code: 'divider line with height 10: {message}',
			preview: (
				'begin A, B, C, D, E, F\n' +
				'divider line with height 30: message'
			),
			title: 'Line divider',
		},
		{
			code: 'divider delay with height 10: {message}',
			preview: (
				'begin A, B, C, D, E, F\n' +
				'divider delay with height 30: message'
			),
			title: 'Delay divider',
		},
		{
			code: 'divider tear with height 10: {message}',
			preview: (
				'begin A, B, C, D, E, F\n' +
				'divider tear with height 30: message'
			),
			title: 'Tear divider',
		},
		{
			code: 'title {Title}',
			preview: 'headers box\ntitle Title\nA -> B',
			title: 'Title',
		},
		{
			code: '**{text}**',
			preview: 'A -> B: **bold**',
			surround: true,
			title: 'Bold markdown',
		},
		{
			code: '_{text}_',
			preview: 'A -> B: _italic_',
			surround: true,
			title: 'Italic markdown',
		},
		{
			code: '~{text}~',
			preview: 'A -> B: ~strikeout~',
			surround: true,
			title: 'Strikeout markdown',
		},
		{
			code: '<u>{text}</u>',
			preview: 'A -> B: <u>underline</u>',
			surround: true,
			title: 'Underline markdown',
		},
		{
			code: '<o>{text}</o>',
			preview: 'A -> B: <o>overline</o>',
			surround: true,
			title: 'Overline markdown',
		},
		{
			code: '<sup>{text}</sup>',
			preview: 'A -> B: super<sup>script</sup>',
			surround: true,
			title: 'Superscript markdown',
		},
		{
			code: '<sub>{text}</sub>',
			preview: 'A -> B: sub<sub>script</sub>',
			surround: true,
			title: 'Subscript markdown',
		},
		{
			code: '`{text}`',
			preview: 'A -> B: `mono`',
			surround: true,
			title: 'Monospace markdown',
		},
		{
			code: '<red>{text}</red>',
			preview: 'A -> B: <red>red</red>',
			surround: true,
			title: 'Red markdown',
		},
		{
			code: '<highlight>{text}</highlight>',
			preview: 'A -> B: <highlight>highlight</highlight>',
			surround: true,
			title: 'Highlight markdown',
		},
		{
			code: '{Agent} is red',
			preview: 'headers box\nA is red\nbegin A',
			title: 'Red agent line',
		},
		{
			code: '{Agent} is a person',
			preview: 'headers box\nA is a person\nbegin A',
			title: 'Person indicator',
		},
		{
			code: '{Agent} is a database',
			preview: 'headers box\nA is a database\nbegin A',
			title: 'Database indicator',
		},
		{
			code: 'theme monospace',
			preview: 'headers box\ntitle mono\ntheme monospace\nA -> B',
			title: 'Monospace theme',
		},
		{
			code: 'theme chunky',
			preview: 'headers box\ntitle chunky\ntheme chunky\nA -> B',
			title: 'Chunky theme',
		},
		{
			code: 'theme sketch',
			preview: 'headers box\ntitle sketch\ntheme sketch\nA -> B',
			title: 'Sketch theme',
		},
		{
			code: 'terminators cross',
			preview: 'begin A\nterminators cross',
			title: 'Cross terminators',
		},
		{
			code: 'terminators fade',
			preview: 'begin A\nterminators fade',
			title: 'Fade terminators',
		},
		{
			code: 'terminators bar',
			preview: 'begin A\nterminators bar',
			title: 'Bar terminators',
		},
		{
			code: 'terminators box',
			preview: 'begin A\nterminators box',
			title: 'Box terminators',
		},
	];

	const VALID_HASH = /^[0-9]{1,2}$/;

	function getHash() {
		const full = window.location.hash;
		return full ? full.substr(1) : '';
	}

	class HashSlotNav {
		constructor(changeListener = () => null) {
			this.hash = getHash();
			window.addEventListener('hashchange', () => {
				// Only trigger listener if change wasn't caused by us
				if(getHash() !== this.hash) {
					changeListener();
				}
			});
		}

		getRawHash() {
			return getHash();
		}

		maxSlots() {
			// Capacity of localStorage is limited
			// So avoid allowing too many documents
			// (also acts as a fail-safe if anything gets loop-ey)
			return 100;
		}

		getSlot() {
			const hash = getHash();
			if(VALID_HASH.test(hash)) {
				return Number(hash);
			}
			return null;
		}

		setSlot(v) {
			this.hash = v.toFixed(0);
			window.location.hash = this.hash;
		}
	}

	function make(value, document) {
		if(typeof value === 'string') {
			return document.createTextNode(value);
		} else if(typeof value === 'number') {
			return document.createTextNode(value.toString(10));
		} else if(typeof value === 'object' && value.element) {
			return value.element;
		} else {
			return value;
		}
	}

	function unwrap(node) {
		if(node === null) {
			return null;
		} else if(node.element) {
			return node.element;
		} else {
			return node;
		}
	}

	class WrappedElement {
		constructor(element) {
			this.element = element;
		}

		addBefore(child = null, before = null) {
			if(child === null) {
				return this;
			} else if(Array.isArray(child)) {
				for(const c of child) {
					this.addBefore(c, before);
				}
			} else {
				const childElement = make(child, this.element.ownerDocument);
				this.element.insertBefore(childElement, unwrap(before));
			}
			return this;
		}

		add(...child) {
			return this.addBefore(child, null);
		}

		del(child = null) {
			if(child !== null) {
				this.element.removeChild(unwrap(child));
			}
			return this;
		}

		attr(key, value) {
			this.element.setAttribute(key, value);
			return this;
		}

		attrs(attrs) {
			for(const k in attrs) {
				if(Object.prototype.hasOwnProperty.call(attrs, k)) {
					this.element.setAttribute(k, attrs[k]);
				}
			}
			return this;
		}

		styles(styles) {
			for(const k in styles) {
				if(Object.prototype.hasOwnProperty.call(styles, k)) {
					this.element.style[k] = styles[k];
				}
			}
			return this;
		}

		setClass(cls) {
			return this.attr('class', cls);
		}

		addClass(cls) {
			const classes = this.element.getAttribute('class');
			if(!classes) {
				return this.setClass(cls);
			}
			const list = classes.split(' ');
			if(list.includes(cls)) {
				return this;
			}
			list.push(cls);
			return this.attr('class', list.join(' '));
		}

		delClass(cls) {
			const classes = this.element.getAttribute('class');
			if(!classes) {
				return this;
			}
			const list = classes.split(' ');
			const p = list.indexOf(cls);
			if(p !== -1) {
				list.splice(p, 1);
				this.attr('class', list.join(' '));
			}
			return this;
		}

		text(text) {
			this.element.textContent = text;
			return this;
		}

		on(event, callback, options = {}) {
			if(Array.isArray(event)) {
				for(const e of event) {
					this.on(e, callback, options);
				}
			} else {
				this.element.addEventListener(event, callback, options);
			}
			return this;
		}

		off(event, callback, options = {}) {
			if(Array.isArray(event)) {
				for(const e of event) {
					this.off(e, callback, options);
				}
			} else {
				this.element.removeEventListener(event, callback, options);
			}
			return this;
		}

		val(value) {
			this.element.value = value;
			return this;
		}

		select(start, end = null) {
			this.element.selectionStart = start;
			this.element.selectionEnd = (end === null) ? start : end;
			return this;
		}

		focus() {
			this.element.focus();
			return this;
		}

		focussed() {
			return this.element === this.element.ownerDocument.activeElement;
		}

		empty() {
			while(this.element.childNodes.length > 0) {
				this.element.removeChild(this.element.lastChild);
			}
			return this;
		}

		attach(parent) {
			unwrap(parent).appendChild(this.element);
			return this;
		}

		detach() {
			if(this.element.parentNode) {
				this.element.parentNode.removeChild(this.element);
			}
			return this;
		}
	}

	class DOMWrapper {
		constructor(document) {
			if(!document) {
				throw new Error('Missing document!');
			}
			this.document = document;
			this.wrap = this.wrap.bind(this);
			this.el = this.el.bind(this);
			this.txt = this.txt.bind(this);
		}

		wrap(element) {
			if(element.element) {
				return element;
			} else {
				return new WrappedElement(element);
			}
		}

		el(tag, namespace = null) {
			let element = null;
			if(namespace === null) {
				element = this.document.createElement(tag);
			} else {
				element = this.document.createElementNS(namespace, tag);
			}
			return new WrappedElement(element);
		}

		txt(content = '') {
			return this.document.createTextNode(content);
		}
	}

	DOMWrapper.WrappedElement = WrappedElement;

	DOMWrapper.WrappedElement.prototype.fastClick = function() {
		const pt = {x: -1, y: 0};
		return this
			.on('touchstart', (e) => {
				const [touch] = e.touches;
				pt.x = touch.pageX;
				pt.y = touch.pageY;
			}, {passive: true})
			.on('touchend', (e) => {
				if(
					pt.x === -1 ||
					e.touches.length !== 0 ||
					e.changedTouches.length !== 1
				) {
					pt.x = -1;
					return;
				}
				const [touch] = e.changedTouches;
				if(
					Math.abs(pt.x - touch.pageX) < 10 &&
					Math.abs(pt.y - touch.pageY) < 10
				) {
					e.preventDefault();
					e.target.click();
				}
				pt.x = -1;
			});
	};

	function split(nodes, options) {
		const filteredNodes = [];
		const filteredOpts = {
			direction: options.direction,
			minSize: [],
			sizes: [],
			snapOffset: options.snapOffset,
		};

		let total = 0;
		for(let i = 0; i < nodes.length; ++ i) {
			if(nodes[i]) {
				filteredNodes.push(nodes[i]);
				filteredOpts.minSize.push(options.minSize[i]);
				filteredOpts.sizes.push(options.sizes[i]);
				total += options.sizes[i];
			}
		}
		for(let i = 0; i < filteredNodes.length; ++ i) {
			filteredOpts.minSize[i] *= 100 / total;
			filteredOpts.sizes[i] *= 100 / total;

			const percent = filteredOpts.sizes[i] + '%';
			if(filteredOpts.direction === 'vertical') {
				nodes[i].styles({
					boxSizing: 'border-box',
					height: percent,
					width: '100%',
				});
			} else {
				nodes[i].styles({
					boxSizing: 'border-box',
					display: 'inline-block',
					height: '100%',
					verticalAlign: 'top', // Safari fix
					width: percent,
				});
			}
		}

		if(filteredNodes.length < 2) {
			return;
		}

		// Load on demand for progressive enhancement
		// (failure to load external module will not block functionality)
		options.require(['split'], (Split) => {
			// Patches for:
			// https://github.com/nathancahill/Split.js/issues/97
			// https://github.com/nathancahill/Split.js/issues/111
			const parent = nodes[0].element.parentNode;
			const oldAEL = parent.addEventListener;
			const oldREL = parent.removeEventListener;
			parent.addEventListener = (event, callback) => {
				if(event === 'mousemove' || event === 'touchmove') {
					window.addEventListener(event, callback, {passive: true});
				} else {
					oldAEL.call(parent, event, callback);
				}
			};
			parent.removeEventListener = (event, callback) => {
				if(event === 'mousemove' || event === 'touchmove') {
					window.removeEventListener(event, callback);
				} else {
					oldREL.call(parent, event, callback);
				}
			};

			let oldCursor = null;
			const cursor = (filteredOpts.direction === 'vertical') ?
				'row-resize' : 'col-resize';

			return new Split(
				filteredNodes.map((node) => node.element),
				Object.assign({
					cursor,
					direction: 'vertical',
					gutterSize: 0,
					onDragEnd: () => {
						document.body.style.cursor = oldCursor;
						oldCursor = null;
					},
					onDragStart: () => {
						oldCursor = document.body.style.cursor;
						document.body.style.cursor = cursor;
					},
				}, filteredOpts)
			);
		});
	}

	DOMWrapper.WrappedElement.prototype.split = function(nodes, options) {
		this.add(nodes);
		split(nodes, options);
		return this;
	};

	function hasDroppedFile(event, mime) {
		if(!event.dataTransfer.items && event.dataTransfer.files.length === 0) {
			// Work around Safari not supporting dataTransfer.items
			return [...event.dataTransfer.types].includes('Files');
		}

		const items = (event.dataTransfer.items || event.dataTransfer.files);
		return (items.length === 1 && items[0].type === mime);
	}

	function getDroppedFile(event, mime) {
		const items = (event.dataTransfer.items || event.dataTransfer.files);
		if(items.length !== 1 || items[0].type !== mime) {
			return null;
		}
		const [item] = items;
		if(item.getAsFile) {
			return item.getAsFile();
		} else {
			return item;
		}
	}

	function getFileContent(file) {
		return new Promise((resolve) => {
			const reader = new FileReader();
			reader.addEventListener('loadend', () => {
				resolve(reader.result);
			}, {once: true});
			reader.readAsText(file);
		});
	}

	class EventObject {
		constructor() {
			this.listeners = new Map();
			this.forwards = new Set();
		}

		addEventListener(type, callback) {
			const l = this.listeners.get(type);
			if(l) {
				l.push(callback);
			} else {
				this.listeners.set(type, [callback]);
			}
		}

		removeEventListener(type, fn) {
			const l = this.listeners.get(type);
			if(!l) {
				return;
			}
			const i = l.indexOf(fn);
			if(i !== -1) {
				l.splice(i, 1);
			}
		}

		on(type, fn) {
			this.addEventListener(type, fn);
			return this;
		}

		off(type, fn) {
			this.removeEventListener(type, fn);
			return this;
		}

		countEventListeners(type) {
			return (this.listeners.get(type) || []).length;
		}

		removeAllEventListeners(type) {
			if(type) {
				this.listeners.delete(type);
			} else {
				this.listeners.clear();
			}
		}

		addEventForwarding(target) {
			this.forwards.add(target);
		}

		removeEventForwarding(target) {
			this.forwards.delete(target);
		}

		removeAllEventForwardings() {
			this.forwards.clear();
		}

		trigger(type, params = []) {
			(this.listeners.get(type) || []).forEach(
				(listener) => listener(...params)
			);
			this.forwards.forEach((fwd) => fwd.trigger(type, params));
		}
	}

	const PARAM_PATTERN = /\{[^}]+\}/g;

	function addNewline(value) {
		if(value.length > 0 && value.charAt(value.length - 1) !== '\n') {
			return value + '\n';
		}
		return value;
	}

	function findPos(content, index) {
		let p = 0;
		let line = 0;
		for(;;) {
			const nextLn = content.indexOf('\n', p) + 1;
			if(index < nextLn || nextLn === 0) {
				return {ch: index - p, line};
			}
			p = nextLn;
			++ line;
		}
	}

	function cmInRange(pos, {from, to}) {
		return !(
			pos.line < from.line || (pos.line === from.line && pos.ch < from.ch) ||
			pos.line > to.line || (pos.line === to.line && pos.ch > to.ch)
		);
	}

	function findNextToken(block, skip) {
		PARAM_PATTERN.lastIndex = 0;
		for(let m = null; (m = PARAM_PATTERN.exec(block));) {
			if(!skip.includes(m[0])) {
				return m[0];
			}
		}
		return null;
	}

	function lineWithinRange(doc, ln, start, end) {
		const full = doc.getLine(ln);
		const begin = (ln === start.line) ? start.ch : 0;
		return {
			chOffset: begin,
			line: (ln === end.line) ? full.slice(begin, end.ch) : full.slice(begin),
		};
	}

	class CodeEditor extends EventObject {
		constructor(dom, container, {
			mode = '',
			require = null,
			value = '',
		}) {
			super();

			this.mode = mode;
			this.require = require || (() => null);

			this.marker = null;

			this.isAutocompleting = false;
			this.enhanced = false;

			this.code = dom.el('textarea')
				.setClass('editor-simple')
				.val(value)
				.on('input', () => this.trigger('change'))
				.on('focus', () => this.trigger('focus'))
				.attach(container);

			this._enhance();
		}

		markLineHover(ln = null) {
			this.unmarkLineHover();
			if(ln !== null && this.enhanced) {
				this.marker = this.code.markText(
					{ch: 0, line: ln},
					{ch: 0, line: ln + 1},
					{
						className: 'hover',
						clearOnEnter: true,
						inclusiveLeft: false,
						inclusiveRight: false,
					}
				);
			}
		}

		unmarkLineHover() {
			if(this.marker) {
				this.marker.clear();
				this.marker = null;
			}
		}

		selectLine(ln = null) {
			if(ln === null) {
				return;
			}
			if(this.enhanced) {
				this.code.setSelection(
					{ch: 0, line: ln},
					{ch: 0, line: ln + 1},
					{bias: -1, origin: '+focus'}
				);
				this.code.focus();
			}
		}

		enterParams(start, end, block) {
			const doc = this.code.getDoc();
			const endBookmark = doc.setBookmark(end);
			const done = [];

			const keydown = (cm, event) => {
				switch(event.keyCode) {
				case 13:
				case 9:
					if(!this.isAutocompleting) {
						event.preventDefault();
					}
					this.advanceParams();
					break;
				case 27:
					if(!this.isAutocompleting) {
						event.preventDefault();
						this.cancelParams();
					}
					break;
				}
			};

			const move = () => {
				if(this.paramMarkers.length === 0) {
					return;
				}
				const m = this.paramMarkers[0].find();
				const [r] = doc.listSelections();
				if(!cmInRange(r.anchor, m) || !cmInRange(r.head, m)) {
					this.cancelParams();
					this.code.setSelection(r.anchor, r.head);
				}
			};

			this.paramMarkers = [];
			this.cancelParams = () => {
				this.code.off('keydown', keydown);
				this.code.off('cursorActivity', move);
				this.paramMarkers.forEach((m) => m.clear());
				this.paramMarkers = null;
				this.code.setCursor(endBookmark.find());
				endBookmark.clear();
				this.cancelParams = null;
				this.advanceParams = null;
			};
			this.advanceParams = () => {
				this.paramMarkers.forEach((m) => m.clear());
				this.paramMarkers.length = 0;
				this.nextParams(start, endBookmark, block, done);
			};

			this.code.on('keydown', keydown);
			this.code.on('cursorActivity', move);

			this.advanceParams();
		}

		nextParams(start, endBookmark, block, done) {
			const tok = findNextToken(block, done);
			if(!tok) {
				this.cancelParams();
				return;
			}
			done.push(tok);

			const doc = this.code.getDoc();
			const ranges = [];
			const end = endBookmark.find();
			for(let ln = start.line; ln <= end.line; ++ ln) {
				const {chOffset, line} = lineWithinRange(doc, ln, start, end);
				for(let p = 0; (p = line.indexOf(tok, p)) !== -1; p += tok.length) {
					const anchor = {ch: chOffset + p, line: ln};
					const head = {ch: chOffset + p + tok.length, line: ln};
					ranges.push({anchor, head});
					this.paramMarkers.push(doc.markText(anchor, head, {
						className: 'param',
						clearWhenEmpty: false,
						inclusiveLeft: true,
						inclusiveRight: true,
					}));
				}
			}

			if(ranges.length > 0) {
				doc.setSelections(ranges, 0);
			} else {
				this.cancelParams();
			}
		}

		hasSelection() {
			const from = this.code.getCursor('from');
			const to = this.code.getCursor('to');
			return from.line !== to.line || from.ch !== to.ch;
		}

		internalAddSurroundCode(block) {
			if(this.enhanced) {
				if(this.hasSelection()) {
					this.code.replaceSelection(
						block.replace(/\{.*\}/, this.code.getSelection()),
						'end',
						'library'
					);
				} else {
					const cur = this.code.getCursor('head');
					this.code.replaceSelection(block, null, 'library');
					const end = {ch: cur.ch + block.length, line: cur.line};
					this.enterParams(cur, end, block);
				}
			} else {
				const value = this.value();
				const s1 = this.code.element.selectionStart;
				const s2 = this.code.element.selectionEnd;
				const wrapped = block.replace(/\{.*\}/, value.substring(s1, s2));
				this.code
					.val(value.substr(0, s1) + wrapped + value.substr(s2))
					.select(s1 + wrapped.length);
				this.trigger('change');
			}
		}

		internalAddIndependentCode(block) {
			if(this.enhanced) {
				const cur = this.code.getCursor('head');
				const pos = {ch: 0, line: cur.line + ((cur.ch > 0) ? 1 : 0)};
				let replaced = addNewline(block);
				if(pos.line >= this.code.lineCount()) {
					replaced = '\n' + replaced;
				}
				this.code.replaceRange(replaced, pos, null, 'library');
				const lines = block.split('\n').length;
				const end = {ch: 0, line: pos.line + lines};
				this.enterParams(pos, end, block);
			} else {
				const value = this.value();
				const cur = this.code.element.selectionStart;
				const pos = ('\n' + value + '\n').indexOf('\n', cur);
				const replaced = (
					addNewline(value.substr(0, pos)) +
					addNewline(block)
				);
				this.code
					.val(replaced + value.substr(pos))
					.select(replaced.length);
				this.trigger('change');
			}
		}

		addCodeBlock(block, surround = false) {
			this.code.focus();

			if(surround) {
				this.internalAddSurroundCode(block);
			} else {
				this.internalAddIndependentCode(block);
			}
		}

		value() {
			if(this.enhanced) {
				return this.code.getDoc().getValue();
			} else {
				return this.code.element.value;
			}
		}

		setValue(code) {
			if(this.enhanced) {
				const doc = this.code.getDoc();
				doc.setValue(code);
				doc.clearHistory();
			} else {
				this.code.val(code);
			}
		}

		_enhance() {
			// Load on demand for progressive enhancement
			// (failure to load external module will not block functionality)
			this.require([
				'cm/lib/codemirror',
				'cm/addon/hint/show-hint',
				'cm/addon/edit/trailingspace',
				'cm/addon/comment/comment',
			], (CodeMirror) => {
				const globals = {};
				this.trigger('enhance', [CodeMirror, globals]);

				const oldCode = this.code;

				const {selectionStart, selectionEnd, value} = oldCode.element;
				const focussed = oldCode.focussed();

				const code = new CodeMirror(oldCode.element.parentNode, {
					extraKeys: {
						'Cmd-/': (cm) => cm.toggleComment({padding: ''}),
						'Cmd-Enter': 'autocomplete',
						'Ctrl-/': (cm) => cm.toggleComment({padding: ''}),
						'Ctrl-Enter': 'autocomplete',
						'Ctrl-Space': 'autocomplete',
						'Shift-Tab': (cm) => cm.execCommand('indentLess'),
						'Tab': (cm) => cm.execCommand('indentMore'),
					},
					globals,
					lineNumbers: true,
					mode: this.mode,
					showTrailingSpace: true,
					value,
				});
				oldCode.detach();

				code.getDoc().setSelection(
					findPos(value, selectionStart),
					findPos(value, selectionEnd)
				);

				let lastKey = 0;
				code.on('keydown', (cm, event) => {
					lastKey = event.keyCode;
				});

				code.on('change', (cm, change) => {
					this.trigger('change');

					if(change.origin === '+input') {
						if(lastKey === 13) {
							lastKey = 0;
							return;
						}
					} else if(change.origin !== 'complete') {
						return;
					}
					CodeMirror.commands.autocomplete(cm, null, {
						completeSingle: false,
					});
				});

				code.on('focus', () => this.trigger('focus'));

				code.on('cursorActivity', () => {
					const from = code.getCursor('from');
					const to = code.getCursor('to');
					this.trigger('cursorActivity', [from, to]);
				});

				/*
				 * See https://github.com/codemirror/CodeMirror/issues/3092
				 * startCompletion will fire even if there are no completions, so
				 * we cannot rely on it. Instead we hack the hints function to
				 * propagate 'shown' as 'hint-shown', which we pick up here
				 */
				code.on('hint-shown', () => {
					this.isAutocompleting = true;
				});

				code.on('endCompletion', () => {
					this.isAutocompleting = false;
				});

				if(focussed) {
					code.focus();
				}

				this.code = code;
				this.enhanced = true;
			});
		}
	}

	function toCappedFixed(v, cap) {
		const s = v.toString();
		const p = s.indexOf('.');
		if(p === -1 || s.length - p - 1 <= cap) {
			return s;
		}
		return v.toFixed(cap);
	}

	function valid(v = null) {
		return v !== null && !Number.isNaN(v);
	}

	class URLExporter {
		constructor(renderBase = '', editBase = '') {
			this.renderBase = renderBase;
			this.editBase = editBase;
		}

		setRenderBase(renderBase) {
			this.renderBase = renderBase;
		}

		setEditBase(editBase) {
			this.editBase = editBase;
		}

		_convertCode(code, keepBlankLines = false) {
			let lines = code
				.split('\n')
				.map(encodeURIComponent);

			if(keepBlankLines) {
				// Always trim trailing blank lines
				while(lines.length > 0 && lines[lines.length - 1] === '') {
					-- lines.length;
				}
			} else {
				lines = lines.filter((ln) => ln !== '');
			}

			return lines.join('/');
		}

		_convertWidthHeight(width, height) {
			let opts = '';
			if(valid(width)) {
				opts += 'w' + toCappedFixed(Math.max(width, 0), 4);
			}
			if(valid(height)) {
				opts += 'h' + toCappedFixed(Math.max(height, 0), 4);
			}
			return opts + '/';
		}

		_convertZoom(zoom) {
			if(zoom === 1) {
				return '';
			}
			return 'z' + toCappedFixed(Math.max(zoom, 0), 4) + '/';
		}

		_convertSize({height, width, zoom}) {
			if(valid(width) || valid(height)) {
				return this._convertWidthHeight(width, height);
			}
			if(valid(zoom)) {
				return this._convertZoom(zoom);
			}
			return '';
		}

		getRenderURL(code, size = {}) {
			return (
				this.renderBase +
				this._convertSize(size) +
				this._convertCode(code) +
				'.svg'
			);
		}

		getEditURL(code) {
			return (
				this.editBase +
				'#edit:' +
				this._convertCode(code, true)
			);
		}
	}

	class VoidStorage {
		constructor() {
			this.value = '';
		}

		set(value) {
			this.value = value;
		}

		get() {
			return this.value;
		}

		remove() {
			this.value = '';
		}
	}

	const DELAY_AGENTCHANGE = 500;
	const DELAY_STAGECHANGE = 250;
	const PNG_RESOLUTION = 4;

	function simplifyPreview(code) {
		return 'headers fade\nterminators fade\n' + code
			.replace(/\{Agent([0-9]*)\}/g, (match, num) => {
				if(typeof num === 'undefined') {
					return 'A';
				} else {
					return String.fromCharCode('A'.charCodeAt(0) + Number(num) - 1);
				}
			})
			.replace(/[{}]/g, '');
	}

	function fetchResource(path) {
		if(typeof fetch === 'undefined') {
			return Promise.reject(new Error());
		}
		return fetch(path)
			.then((response) => {
				if(!response.ok) {
					throw new Error(response.statusText);
				}
				return response;
			});
	}

	function setDocumentTitle(diagramTitle) {
		let title = diagramTitle.trim();
		if(title.length > 20) {
			title = title.substr(0, 18).trim() + '\u2026';
		}
		document.title = (title ? `${title} \u2014 ` : '') + 'Sequence Diagram';
	}

	class Interface {
		constructor({
			sequenceDiagram,
			defaultCode = '',
			library = [],
			links = [],
			require = null,
			storage = new VoidStorage(),
			touchUI = false,
		}) {
			this.diagram = sequenceDiagram;
			this.defaultCode = defaultCode;
			this.storage = storage;
			this.library = library;
			this.links = links;
			this.minScale = 1.5;
			this.require = require || (() => null);
			this.touchUI = touchUI;

			this.debounced = null;
			this.latestSeq = null;
			this.renderedSeq = null;
			this.pngDirty = true;
			this.updatingPNG = false;

			this.marker = null;

			this._downloadSVGClick = this._downloadSVGClick.bind(this);
			this._downloadPNGClick = this._downloadPNGClick.bind(this);
			this._downloadPNGFocus = this._downloadPNGFocus.bind(this);
			this._downloadURLClick = this._downloadURLClick.bind(this);
			this._hideDropStyle = this._hideDropStyle.bind(this);

			this.diagram
				.on('render', () => {
					this.updateMinSize(this.diagram.getSize());
					setDocumentTitle(this.diagram.getTitle());
					this.pngDirty = true;
				})
				.on('mouseover', (element) => this.code.markLineHover(element.ln))
				.on('mouseout', () => this.code.unmarkLineHover())
				.on('click', (element) => {
					this.code.unmarkLineHover();
					this.code.selectLine(element.ln);
					this._hideURLBuilder();
				})
				.on('dblclick', (element) => {
					this.diagram.toggleCollapsed(element.ln);
					this._hideURLBuilder();
				});
		}

		buildURLBuilder() {
			const copied = this.dom.el('div').setClass('copied')
				.add('Copied to Clipboard');
			this.urlOutput = this.dom.el('input').setClass('output')
				.attr('readonly', 'readonly')
				.on('focus', () => {
					this.urlOutput.select(0, this.urlOutput.element.value.length);
				});

			const copy = this.dom.el('button').setClass('copy')
				.attr('title', 'Copy to clipboard')
				.fastClick()
				.on('click', () => {
					if(this.touchUI) {
						this.urlOutput.styles({display: 'block'});
					}
					this.urlOutput
						.focus()
						.select(0, this.urlOutput.element.value.length)
						.element.ownerDocument.execCommand('copy');
					copy.focus();
					this.container.delClass('keyinput');
					if(this.touchUI) {
						this.urlOutput.styles({display: 'none'});
					}
					copied.styles({
						'display': 'block',
						'opacity': 1,
						'transition': 'none',
					});
					setTimeout(() => copied.styles({
						'opacity': 0,
						'transition': 'opacity 0.5s linear',
					}), 1000);
					setTimeout(() => copied.styles({'display': 'none'}), 1500);
				});

			const updateMode = () => {
				this.renderOpts.styles({
					'display': this.modeEdit.element.checked ? 'none' : 'block',
				});
				this._refreshURL();
			};

			this.modeRender = this.dom.el('input').attrs({
				'checked': 'checked',
				'name': 'export-mode',
				'type': 'radio',
				'value': 'render',
			}).on('change', updateMode);

			this.modeEdit = this.dom.el('input').attrs({
				'name': 'export-mode',
				'type': 'radio',
				'value': 'edit',
			}).on('change', updateMode);

			this.modeMarkdown = this.dom.el('input').attrs({
				'name': 'export-mode',
				'type': 'radio',
				'value': 'markdown',
			}).on('change', updateMode);

			this.urlWidth = this.dom.el('input').attrs({
				'min': 0,
				'placeholder': 'auto',
				'step': 'any',
				'type': 'number',
			}).on('input', () => {
				this.urlZoom.val('1');
				this._refreshURL();
			});

			this.urlHeight = this.dom.el('input').attrs({
				'min': 0,
				'placeholder': 'auto',
				'step': 'any',
				'type': 'number',
			}).on('input', () => {
				this.urlZoom.val('1');
				this._refreshURL();
			});

			this.urlZoom = this.dom.el('input').attrs({
				'min': 0,
				'step': 'any',
				'type': 'number',
				'value': 1,
			}).on('input', () => {
				this.urlWidth.val('');
				this.urlHeight.val('');
				this._refreshURL();
			});

			this.renderOpts = this.dom.el('div').add(
				this.dom.el('label').add('width ', this.urlWidth),
				', ',
				this.dom.el('label').add('height ', this.urlHeight),
				this.dom.el('span').setClass('or').add('or'),
				this.dom.el('label').add('zoom ', this.urlZoom)
			);

			const urlOpts = this.dom.el('div').setClass('config').add(
				this.dom.el('div').setClass('export-mode').add(
					this.dom.el('label').add(this.modeRender, 'View'),
					this.dom.el('label').add(this.modeEdit, 'Edit'),
					this.dom.el('label').add(this.modeMarkdown, 'Markdown')
				),
				this.renderOpts,
				this.urlOutput,
				copy,
				copied
			);

			const urlBuilder = this.dom.el('div').setClass('urlbuilder')
				.styles({'display': 'none'})
				.add(
					this.dom.el('div').setClass('message')
						.add('Loading\u2026')
				);

			const ownURL = (typeof window === 'undefined') ? 'http://localhost' : window.location.href;
			this.renderService = new URLExporter();
			this.renderService.setEditBase(new URL('.', ownURL).href);

			const relativePath = 'render/';
			fetchResource(relativePath)
				.then((response) => response.text())
				.then((content) => {
					let path = content.trim();
					if(!path || path.startsWith('<')) {
						path = relativePath;
					}
					this.renderService.setRenderBase(new URL(path, ownURL).href);
					urlBuilder.empty().add(urlOpts);
					this._refreshURL();
				})
				.catch(() => {
					urlBuilder.empty().add(
						this.dom.el('div').setClass('message')
							.add('No online rendering service available.')
					);
				});

			return urlBuilder;
		}

		_refreshURL() {
			const code = this.code.value();
			const viewOpts = {
				height: Number.parseFloat(this.urlHeight.element.value),
				width: Number.parseFloat(this.urlWidth.element.value),
				zoom: Number.parseFloat(this.urlZoom.element.value || '1'),
			};

			let url = '';
			if(this.modeMarkdown.element.checked) {
				const edit = this.renderService.getEditURL(code);
				const view = this.renderService.getRenderURL(code, viewOpts);
				const title = this.diagram.getTitle()
					.replace(/[^a-zA-Z0-9 \-_'"]/g, '')
					.trim();
				url = `[![${title}](${view})](${edit})`;
			} else if(this.modeEdit.element.checked) {
				url = this.renderService.getEditURL(code);
			} else {
				url = this.renderService.getRenderURL(code, viewOpts);
			}
			this.urlOutput.val(url);
		}

		_showURLBuilder() {
			if(this.builderVisible) {
				return;
			}
			this.builderVisible = true;
			if(this.touchUI) {
				this.urlBuilder.styles({
					'bottom': '-210px',
					'display': 'block',
				});
			} else {
				this.urlBuilder.styles({
					'display': 'block',
					'height': '0px',
					'padding': '0px',
					'width': this.optsHold.element.clientWidth + 'px',
				});
			}
			clearTimeout(this.builderTm);
			this.builderTm = setTimeout(() => {
				if(this.touchUI) {
					this.urlBuilder.styles({'bottom': 0});
				} else {
					this.urlBuilder.styles({
						'height': '150px',
						'padding': '10px',
						'width': '400px',
					});
					this.optsHold.styles({
						'box-shadow': '10px 10px 25px 12px rgba(0,0,0,0.3)',
					});
				}
			}, 0);

			this._refreshURL();
		}

		_hideURLBuilder() {
			if(!this.builderVisible) {
				return;
			}
			this.builderVisible = false;
			if(this.touchUI) {
				this.urlBuilder.styles({
					'bottom': (-this.urlBuilder.element.clientHeight - 60) + 'px',
				});
			} else {
				this.urlBuilder.styles({
					'height': '0px',
					'padding': '0px',
					'width': '0px',
				});
				this.optsHold.styles({
					'box-shadow': 'none',
				});
			}
			this.container.delClass('keyinput');
			clearTimeout(this.builderTm);
			this.builderTm = setTimeout(() => {
				this.urlBuilder.styles({'display': 'none'});
			}, 200);
		}

		buildOptionsDownloads() {
			this.downloadPNG = this.dom.el('a')
				.text('Export PNG')
				.attrs({
					'download': 'SequenceDiagram.png',
					'href': '#',
				})
				.on(['focus', 'mouseover', 'mousedown'], this._downloadPNGFocus)
				// Exploit delay between touchend and click on mobile
				.on('touchend', this._downloadPNGFocus)
				.on('click', this._downloadPNGClick);

			this.downloadSVG = this.dom.el('a')
				.text('SVG')
				.attrs({
					'download': 'SequenceDiagram.svg',
					'href': '#',
				})
				.fastClick()
				.on('click', this._downloadSVGClick);

			this.downloadURL = this.dom.el('a')
				.text('URL')
				.attrs({'href': '#'})
				.fastClick()
				.on('click', this._downloadURLClick);

			this.urlBuilder = this.buildURLBuilder();

			this.optsHold = this.dom.el('div').setClass('options downloads').add(
				this.downloadPNG,
				this.downloadSVG,
				this.downloadURL,
				this.urlBuilder
			);

			return this.optsHold;
		}

		buildLibrary(container) {
			const diagrams = this.library.map((lib) => {
				const holdInner = this.dom.el('div')
					.attr('title', lib.title || lib.code);

				const hold = this.dom.el('div')
					.setClass('library-item')
					.add(holdInner)
					.fastClick()
					.on('click', () => this.code.addCodeBlock(
						lib.code,
						lib.surround
					))
					.attach(container);

				return this.diagram.clone({
					code: simplifyPreview(lib.preview || lib.code),
					container: holdInner.element,
					render: false,
				}).on('error', (sd, e) => {
					window.console.warn('Failed to render preview', e);
					hold.attr('class', 'library-item broken');
					holdInner.text(lib.code);
				});
			});

			try {
				this.diagram.renderAll(diagrams);
			} catch(ignore) {
				// Ignore
			}

			return container;
		}

		buildCodePane() {
			const container = this.dom.el('div').setClass('pane-code');

			this.code = new CodeEditor(this.dom, container, {
				mode: 'sequence',
				require: this.require,
				value: this.storage.get() || this.defaultCode,
			});

			this.code
				.on('enhance', (CM, globals) => {
					this.diagram.registerCodeMirrorMode(CM);
					globals.themes = this.diagram.getThemeNames();
				})
				.on('change', () => this.update(false))
				.on('cursorActivity', (from, to) => {
					this.diagram.setHighlight(Math.min(from.line, to.line));
				})
				.on('focus', () => this._hideURLBuilder());

			return container;
		}

		buildLibPane() {
			if(this.library.length === 0) {
				return null;
			}

			return this.dom.el('div').setClass('pane-library')
				.add(this.dom.el('div').setClass('pane-library-scroller')
					.add(this.buildLibrary(
						this.dom.el('div').setClass('pane-library-inner')
					)));
		}

		buildViewPane() {
			this.viewPaneInner = this.dom.el('div').setClass('pane-view-inner')
				.add(this.diagram.dom())
				.on('touchstart', () => this._hideURLBuilder(), {passive: true})
				.on('mousedown', () => this._hideURLBuilder());

			this.errorMsg = this.dom.el('div').setClass('msg-error');

			return this.dom.el('div').setClass('pane-view')
				.add(
					this.dom.el('div').setClass('pane-view-scroller')
						.add(this.viewPaneInner),
					this.errorMsg
				);
		}

		build(container) {
			this.dom = new DOMWrapper(container.ownerDocument);

			this.container = this.dom.wrap(container)
				.on('dragover', (event) => {
					event.preventDefault();
					if(hasDroppedFile(event, 'image/svg+xml')) {
						event.dataTransfer.dropEffect = 'copy';
						this._showDropStyle();
					} else {
						event.dataTransfer.dropEffect = 'none';
					}
				})
				.on('dragleave', this._hideDropStyle)
				.on('dragend', this._hideDropStyle)
				.on('drop', (event) => {
					event.preventDefault();
					this._hideDropStyle();
					const file = getDroppedFile(event, 'image/svg+xml');
					if(file) {
						this.loadFile(file);
					}
				})
				.on('focusin', () => this.container.addClass('keyinput'))
				.on('focusout', () => this.container.delClass('keyinput'));

			const codePane = this.buildCodePane();
			const libPane = this.buildLibPane();
			const viewPane = this.buildViewPane();

			const links = this.links.map((link) => this.dom.el('a')
				.attrs({'href': link.href, 'target': '_blank'})
				.text(this.touchUI ? link.touchLabel : link.label));

			if(this.touchUI) {
				this.buildOptionsDownloads();
				this.container
					.addClass('touch')
					.add(
						this.dom.el('div').setClass('pane-hold')
							.split([viewPane, codePane], {
								direction: 'vertical',
								minSize: [10, 10],
								require: this.require,
								sizes: [80, 20],
								snapOffset: 20,
							}),
						libPane.styles({'display': 'none', 'top': '100%'}),
						this.urlBuilder,
						this.dom.el('div').setClass('optbar')
							.add(
								...links,
								this.downloadPNG.text('PNG'),
								this.downloadSVG.text('SVG'),
								this.downloadURL.text('URL')
							)
					);
			} else {
				this.container
					.add(
						this.dom.el('div').setClass('pane-hold')
							.split([
								this.dom.el('div').setClass('pane-side')
									.split([codePane, libPane], {
										direction: 'vertical',
										minSize: [100, 5],
										require: this.require,
										sizes: [70, 30],
										snapOffset: 5,
									}),
								viewPane,
							], {
								direction: 'horizontal',
								minSize: [10, 10],
								require: this.require,
								sizes: [30, 70],
								snapOffset: 70,
							}),
						this.dom.el('div').setClass('options links').add(links),
						this.buildOptionsDownloads()
					);
			}

			if(typeof window !== 'undefined') {
				window.addEventListener('keydown', (e) => {
					if(e.keyCode === 27) {
						this._hideURLBuilder();
					}
				});
			}

			// Delay first update 1 frame to ensure render target is ready
			// (prevents initial incorrect font calculations for custom fonts)
			setTimeout(this.update.bind(this), 0);
		}

		updateMinSize({width, height}) {
			this.viewPaneInner.styles({
				'minHeight': Math.ceil(height * this.minScale) + 'px',
				'minWidth': Math.ceil(width * this.minScale) + 'px',
			});
		}

		redrawDebounced(sequence, delay) {
			if(delay <= 0) {
				this.redraw(sequence);
			} else {
				clearTimeout(this.debounced);
				this.latestSeq = sequence;
				this.debounced = setTimeout(() => this.redraw(sequence), delay);
			}
		}

		redraw(sequence) {
			clearTimeout(this.debounced);
			this.debounced = null;
			this.renderedSeq = sequence;
			this.diagram.render(sequence);
		}

		markError(error) {
			if(typeof error === 'object' && error.message) {
				this.errorMsg.text(error.message);
			} else {
				this.errorMsg.text(error);
			}
			this.errorMsg.addClass('error');
		}

		markOK() {
			this.errorMsg.text('').delClass('error');
		}

		loadFile(file) {
			return getFileContent(file).then((svg) => {
				const code = this.diagram.extractCodeFromSVG(svg);
				if(code) {
					this.code.setValue(code);
					this.diagram.expandAll({render: false});
					this.update(true);
					this.diagram.setHighlight(null);
				}
			});
		}

		update(immediate = true) {
			this._hideURLBuilder();
			const src = this.code.value();
			this.storage.set(src);
			let sequence = null;
			try {
				sequence = this.diagram.process(src);
			} catch(e) {
				this.markError(e);
				return;
			}
			this.markOK();

			let delay = 0;
			if(!immediate && this.renderedSeq) {
				const old = this.renderedSeq;
				if(sequence.agents.length !== old.agents.length) {
					delay = DELAY_AGENTCHANGE;
				} else if(sequence.stages.length !== old.stages.length) {
					delay = DELAY_STAGECHANGE;
				}
			}

			this.redrawDebounced(sequence, delay);
		}

		forceRender() {
			if(this.debounced) {
				clearTimeout(this.debounced);
				this.redraw(this.latestSeq);
			}
		}

		updatePNGLink() {
			this.forceRender();
			if(this.updatingPNG || !this.pngDirty) {
				return false;
			}
			this.pngDirty = false;
			this.updatingPNG = true;
			this.diagram.getPNG({resolution: PNG_RESOLUTION})
				.then(({url, latest}) => {
					if(latest) {
						this.downloadPNG.attr('href', url);
						this.updatingPNG = false;
					}
				});
			return true;
		}

		_showDropStyle() {
			this.container.addClass('drop-target');
		}

		_hideDropStyle() {
			this.container.delClass('drop-target');
		}

		_downloadPNGFocus() {
			this.updatePNGLink();
		}

		_downloadPNGClick(e) {
			if(this.updatingPNG) {
				e.preventDefault();
			} else if(this.updatePNGLink()) {
				e.preventDefault();
			}
			this._hideURLBuilder();
		}

		_downloadSVGClick() {
			this.forceRender();
			const url = this.diagram.getSVGSynchronous();
			this.downloadSVG.attr('href', url);
			this._hideURLBuilder();
		}

		_downloadURLClick(e) {
			e.preventDefault();

			if(this.builderVisible) {
				this._hideURLBuilder();
			} else {
				this._showURLBuilder();
			}
		}
	}

	class LocalStorage {
		constructor(id) {
			this.id = id;
		}

		set(value) {
			try {
				window.localStorage.setItem(this.id, value);
			} catch(ignore) {
				// Ignore
			}
		}

		get() {
			try {
				return window.localStorage.getItem(this.id) || '';
			} catch(e) {
				return '';
			}
		}

		remove() {
			try {
				window.localStorage.removeItem(this.id);
			} catch(e) {
				// Ignore
			}
		}
	}

	class MultiLocalStorage {
		constructor(slotManager, slotStorage) {
			this.slotManager = slotManager;
			this.slotStorage = slotStorage;
			this.slot = this.slotManager.getSlot();
			this.value = this.get();
			this.originalValue = this.value;
			this.loadTime = Date.now();
			this.internalStorageListener = this.internalStorageListener.bind(this);

			window.addEventListener('storage', this.internalStorageListener);
			this.checkSlot();
		}

		getCurrentValue() {
			// If the page just loaded, clone the original document
			// (works around glitches with CodeMirror when duplicating tabs)
			if(Date.now() < this.loadTime + 500) {
				return this.originalValue;
			}
			return this.value;
		}

		key() {
			return this.slotStorage.getSlotKey(this.slot);
		}

		checkSlot() {
			const key = this.key();
			window.localStorage.removeItem(`chk-${key}`);
			window.localStorage.removeItem(`res-${key}`);
			window.localStorage.removeItem(`ack-${key}`);

			// Check if any other tabs are viewing the same document
			window.localStorage.setItem(`chk-${key}`, '1');
		}

		cloneSlot() {
			const slotLimit = this.slotManager.maxSlots();
			const newSlot = this.slotStorage.nextAvailableSlot(slotLimit);
			if(!newSlot) {
				return;
			}

			const value = this.getCurrentValue();
			this.slotStorage.set(newSlot, value);
			this.slot = newSlot;
			this.slotManager.setSlot(newSlot);

			// Force editor to load corrected content if needed
			if(value !== this.value) {
				document.location.reload();
			}
		}

		// eslint-disable-next-line complexity
		internalStorageListener({ storageArea, key, newValue }) {
			if(storageArea !== window.localStorage) {
				return;
			}

			const ownKey = this.key();
			if(key === ownKey && newValue !== this.value) {
				if(newValue === null) {
					// Somebody deleted our document; put it back
					// (a nicer explanation for the deleter may be nice, but later)
					window.localStorage.setItem(ownKey, this.value);
				}
				// Another tab unexpectedly changed a value we own
				// Remind them that we own the document
				window.localStorage.removeItem(`res-${ownKey}`);
				window.localStorage.setItem(`res-${ownKey}`, '1');
			}

			if(key === `chk-${ownKey}` && newValue) {
				// Another tab is checking if our slot is in use; reply yes
				window.localStorage.setItem(`res-${ownKey}`, '1');
			}

			if(key === `res-${ownKey}` && newValue) {
				// Another tab owns our slot; clone the document
				window.localStorage.removeItem(`chk-${ownKey}`);
				window.localStorage.removeItem(`res-${ownKey}`);
				window.localStorage.setItem(`ack-${ownKey}`, '1');
				this.cloneSlot();
			}

			if(key === `ack-${ownKey}` && newValue) {
				// Another tab has acknowledged us as the owner of the document
				// Restore 'correct' value in case it was clobbered accidentally
				window.localStorage.removeItem(`ack-${ownKey}`, '1');
				window.localStorage.setItem(ownKey, this.value);
			}
		}

		set(value) {
			this.value = value;
			this.slotStorage.set(this.slot, value);
		}

		get() {
			return this.slotStorage.get(this.slot);
		}

		remove() {
			this.slotStorage.remove(this.slot);
		}

		close() {
			window.removeEventListener('storage', this.internalStorageListener);
		}
	}

	var SequenceDiagram = window.SequenceDiagram;

	const VALID_SLOT_KEY = /^s[0-9]+$/;

	class SlotLocalStores {
		getSlotKey(slot) {
			return `s${slot}`;
		}

		getAllSlots() {
			const result = [];
			try {
				for(const key in window.localStorage) {
					if(VALID_SLOT_KEY.test(key)) {
						result.push(Number(key.substr(1)));
					}
				}
			} catch(e) {
				// Ignore
			}
			return result;
		}

		nextAvailableSlot(limit = Number.MAX_SAFE_INTEGER) {
			try {
				for(let i = 1; i < limit; ++ i) {
					if(window.localStorage.getItem(this.getSlotKey(i)) === null) {
						return i;
					}
				}
				return null;
			} catch(e) {
				return null;
			}
		}

		set(slot, value) {
			try {
				window.localStorage.setItem(this.getSlotKey(slot), value);
			} catch(ignore) {
				// Ignore
			}
		}

		get(slot) {
			try {
				return window.localStorage.getItem(this.getSlotKey(slot)) || '';
			} catch(e) {
				return '';
			}
		}

		remove(slot) {
			try {
				window.localStorage.removeItem(this.getSlotKey(slot));
			} catch(ignore) {
				// Ignore
			}
		}
	}

	var requestSlot = (hashNav, slotStorage) => {
		if(hashNav.getSlot() !== null) {
			return Promise.resolve();
		}

		const slots = slotStorage.getAllSlots().sort((a, b) => (a - b));
		if(!slots.length) {
			hashNav.setSlot(1);
			return Promise.resolve();
		}

		const dom = new DOMWrapper(window.document);
		const container = dom.el('div').setClass('pick-document')
			.add(dom.el('h1').text('Available documents on this computer:'))
			.add(dom.el('p').text('(right-click to delete)'))
			.attach(document.body);

		function remove(slot) {
			// eslint-disable-next-line no-alert
			if(window.confirm('Delete this document?')) {
				slotStorage.remove(slot);
				window.location.reload();
			}
		}

		const diagram = new SequenceDiagram();
		return new Promise((resolve) => {
			const diagrams = slots.map((slot) => {
				const code = slotStorage.get(slot);

				const holdInner = dom.el('div')
					.attr('title', code.trim());

				const hold = dom.el('a')
					.attr('href', `#${slot}`)
					.setClass('pick-document-item')
					.add(holdInner)
					.fastClick()
					.on('click', (e) => {
						e.preventDefault();
						resolve(slot);
					})
					.on('contextmenu', (e) => {
						e.preventDefault();
						remove(slot);
					})
					.attach(container);

				return diagram.clone({
					code,
					container: holdInner.element,
					render: false,
				}).on('error', (sd, e) => {
					window.console.warn('Failed to render preview', e);
					hold.attr('class', 'pick-document-item broken');
					holdInner.text(code);
				});
			});

			try {
				diagram.renderAll(diagrams);
			} catch(ignore) {
				// Ignore
			}

			if(slots.length < hashNav.maxSlots()) {
				dom.el('div')
					.setClass('pick-document-item new')
					.add(dom.el('div').attr('title', 'New document'))
					.on('click', () => resolve(slotStorage.nextAvailableSlot()))
					.attach(container);
			}
		}).then((slot) => {
			container.detach();
			hashNav.setSlot(slot);
		});
	};

	const require = window.requirejs;

	const paths = {};
	const hashes = {};
	const metaTags = window.document.getElementsByTagName('meta');

	for(let i = 0; i < metaTags.length; ++ i) {
		const metaTag = metaTags[i];
		const name = metaTag.getAttribute('name');
		if(name && name.startsWith('cdn-')) {
			const module = name.substr('cdn-'.length);
			let src = metaTag.getAttribute('content');
			if(src.endsWith('.mjs')) {
				src = src.substr(0, src.length - '.mjs'.length);
			} else if(src.endsWith('.js')) {
				src = src.substr(0, src.length - '.js'.length);
			}
			paths[module] = src;
			const integrity = metaTag.getAttribute('data-integrity');
			if(integrity) {
				hashes[module] = integrity;
			}
		}
	}

	require.config({
		hashes,
		onNodeCreated: (node, config, module) => {
			if(config.hashes[module]) {
				// Thanks, https://stackoverflow.com/a/37065379/1180785
				node.setAttribute('integrity', config.hashes[module]);
				node.setAttribute('crossorigin', 'anonymous');
			}
		},
		paths,
	});

	const defaultCode = (
		'title Labyrinth\n' +
		'\n' +
		'Bowie -> Goblin: You remind me of the babe\n' +
		'Goblin -> Bowie: What babe?\n' +
		'Bowie -> Goblin: The babe with the power\n' +
		'Goblin -> Bowie: What power?\n' +
		'note right of Bowie, Goblin: Most people get muddled here!\n' +
		'Bowie -> Goblin: "The power of voodoo"\n' +
		'Goblin -> Bowie: "Who-do?"\n' +
		'Bowie -> Goblin: You do!\n' +
		'Goblin -> Bowie: Do what?\n' +
		'Bowie -> Goblin: Remind me of the babe!\n' +
		'\n' +
		'Bowie -> Audience: Sings\n' +
		'\n' +
		'terminators box\n'
	);

	function migrateOldDocument(slotStorage) {
		const oldStorage = new LocalStorage('src');
		const doc = oldStorage.get();
		if(doc) {
			const newSlot = slotStorage.nextAvailableSlot();
			slotStorage.set(newSlot, doc);
			oldStorage.remove();
		}
	}

	function loadHashDocument(hashNav, slotStorage) {
		const editPrefix = 'edit:';
		const hash = hashNav.getRawHash();
		if(!hash.startsWith(editPrefix)) {
			return;
		}

		let doc = hash
			.substr(editPrefix.length)
			.split('/')
			.map(decodeURIComponent)
			.join('\n');

		if(!doc) {
			return;
		}

		if(!doc.endsWith('\n')) {
			doc += '\n';
		}

		const newSlot = slotStorage.nextAvailableSlot();
		slotStorage.set(newSlot, doc);
		hashNav.setSlot(newSlot);
	}

	window.addEventListener('load', () => {
		const loader = window.document.getElementById('loader');
		const [nav] = loader.getElementsByTagName('nav');
		const linkElements = nav.getElementsByTagName('a');
		const links = [];
		for(let i = 0; i < linkElements.length; ++ i) {
			const element = linkElements[i];
			links.push({
				href: element.getAttribute('href'),
				label: element.textContent,
				touchLabel: element.dataset.touch,
			});
		}

		const slotStorage = new SlotLocalStores();
		migrateOldDocument(slotStorage);

		const hashNav = new HashSlotNav(() => {
			// If the slot is changed by the user, reload to force a document load
			window.location.reload();
		});
		loadHashDocument(hashNav, slotStorage);

		loader.parentNode.removeChild(loader);

		requestSlot(hashNav, slotStorage).then(() => {
			const ui = new Interface({
				defaultCode,
				library: ComponentsLibrary,
				links,
				require,
				sequenceDiagram: new SequenceDiagram(),
				storage: new MultiLocalStorage(hashNav, slotStorage),
				touchUI: ('ontouchstart' in window),
			});
			ui.build(window.document.body);
		});
	});

}());