app.js

'use strict';

const app = (mainCallback) => {
	const MARKDOWN_LINK_MATCH_REGEXP = /\[([^\]]+)\]\([^\)]+\)/g,
		MARKDOWN_INLINE_CODE_START_END_REGEXP = /^`[^`]+`$/,

		CODE_BLOCK_INDENT_REGEXP = /^ {4,}|\t/,
		CODE_BLOCK_FENCED_REGEXP = /^``` *([a-z]+)?$/,

		HEADER_HASH_REGEXP = /^(#{1,6})( +.+)$/,
		HEADER_UNDERLINE_REGEXP = /^(=+|-+)$/;

	function $(id) {
		return document.getElementById(id);
	}

	function markdownStripMeta(text) {
		// attempt to strip out [links](#url) segments, leaving just [links]
		// note: very basic, won't handle repeated [] or () segments in link values well
		text = text.replace(
			MARKDOWN_LINK_MATCH_REGEXP,
			(match,linkLabel) => linkLabel
		);

		// if text starts and ends with a *single set* of inline code backticks, remove them
		if (MARKDOWN_INLINE_CODE_START_END_REGEXP.test(text)) {
			return text.slice(1,-1);
		}

		return text;
	}

	function headerListFromMarkdown(markdown) {
		const markdownLineList = markdown.trim().split(/\r?\n/),
			headerList = [];

		let codeBlockFenceActive = false,
			lineItemPrevious;

		function addItem(level,text) {
			headerList.push({
				level: level,
				text: text
			});

			lineItemPrevious = undefined;
		}

		// work over each markdown line
		for (const lineItem of markdownLineList) {
			// indented code block line? if so, skip.
			if (CODE_BLOCK_INDENT_REGEXP.test(lineItem)) {
				continue;
			}

			const lineItemTrim = lineItem.trim();

			// fenced code block start/end?
			if (CODE_BLOCK_FENCED_REGEXP.test(lineItemTrim)) {
				codeBlockFenceActive = !codeBlockFenceActive;
				continue;
			}

			if (codeBlockFenceActive) {
				// skip all lines within a fenced code block
				continue;
			}

			// line match hash header style?
			const headerHashMatch = HEADER_HASH_REGEXP.exec(lineItemTrim);
			if (headerHashMatch) {
				addItem(
					headerHashMatch[1].length, // heading level
					markdownStripMeta(headerHashMatch[2].trim())
				);

				continue;
			}

			// line match underline header style?
			if (
				lineItemPrevious &&
				HEADER_UNDERLINE_REGEXP.test(lineItemTrim)
			) {
				addItem(
					// '=' = level 1 header, '-' = level 2
					(lineItemTrim[0] == '=') ? 1 : 2,
					markdownStripMeta(lineItemPrevious)
				);

				continue;
			}

			lineItemPrevious = lineItemTrim;
		}

		return headerList;
	}

	function indentWith(style) {
		// tab mode
		if (style == 'tab') {
			return '\t';
		}

		// spaces mode
		const match = /^space-([0-9])$/.exec(style);
		return ' '.repeat((match) ? match[1] : 1);
	}

	function buildPageAnchor(text) {
		return stripPunctuation(text)
			.replace(/ /g,'-')
			.toLowerCase();
	}

	function buildTOCMarkdown(headerList,indentWith,skipFirst) {
		const pageAnchorSeenCollection = {};
		let currentHeaderLevel = -1,
			currentIndent = -1,
			markdownTOC = '';

		for (const headerItem of headerList) {
			// skip the first heading found?
			if (skipFirst) {
				skipFirst = false;
				continue;
			}

			// raise/lower indent level for next TOC item
			const headerLevel = headerItem.level;
			if (headerLevel > currentHeaderLevel) {
				currentIndent++;

			} else if (headerLevel < currentHeaderLevel) {
				currentIndent -= (currentHeaderLevel - headerLevel);
				currentIndent = Math.max(currentIndent,0);
			}

			currentHeaderLevel = headerLevel;

			let pageAnchor = buildPageAnchor(headerItem.text);
			if (pageAnchorSeenCollection[pageAnchor] === undefined) {
				// new page anchor
				pageAnchorSeenCollection[pageAnchor] = 1;

			} else {
				// add increment to an already seen pageAnchor name
				pageAnchor = `${pageAnchor}-${pageAnchorSeenCollection[pageAnchor]++}`;
			}

			// build TOC line
			markdownTOC += (
				indentWith.repeat(currentIndent) +
				`- [${headerItem.text}](#${pageAnchor})\n`
			);
		}

		return markdownTOC;
	}

	function copyFormElementToClipboard(el) {
		// select element, copy content to clipboard then un-focus/select
		el.select();
		document.execCommand('copy');
		window.getSelection().removeAllRanges();
		el.blur();
	}

	function stripPunctuation(text) {
		let result = '';
		for (const char of text) {
			if ((char == '-') || (char == '_') || !isPunctuation(char.charCodeAt())) {
				result += char;
			}
		}

		return result;
	}

	function isPunctuation(charCode) {
		return (
			// simple characters
			((charCode >= 33) && (charCode <= 47)) ||
			((charCode >= 58) && (charCode <= 64)) ||
			((charCode >= 91) && (charCode <= 96)) ||
			((charCode >= 123) && (charCode <= 126)) ||

			// extended characters
			(charCode == 161) || (charCode == 167) || (charCode == 171) || (charCode == 182) ||
			(charCode == 183) || (charCode == 187) || (charCode == 191) || (charCode == 894) ||
			(charCode == 903) ||
			((charCode >= 1370) && (charCode <= 1375)) ||
			(charCode == 1417) || (charCode == 1418) || (charCode == 1470) || (charCode == 1472) ||
			(charCode == 1475) || (charCode == 1478) || (charCode == 1523) || (charCode == 1524) ||
			(charCode == 1545) || (charCode == 1546) || (charCode == 1548) || (charCode == 1549) ||
			(charCode == 1563) || (charCode == 1566) || (charCode == 1567) ||
			((charCode >= 1642) && (charCode <= 1645)) ||
			(charCode == 1748) ||
			((charCode >= 1792) && (charCode <= 1805)) ||
			((charCode >= 2039) && (charCode <= 2041)) ||
			((charCode >= 2096) && (charCode <= 2110)) ||
			(charCode == 2142) || (charCode == 2404) || (charCode == 2405) || (charCode == 2416) ||
			(charCode == 2800) || (charCode == 3572) || (charCode == 3663) || (charCode == 3674) ||
			(charCode == 3675) ||
			((charCode >= 3844) && (charCode <= 3858)) ||
			(charCode == 3860) ||
			((charCode >= 3898) && (charCode <= 3901)) ||
			(charCode == 3973) ||
			((charCode >= 4048) && (charCode <= 4052)) ||
			(charCode == 4057) || (charCode == 4058) ||
			((charCode >= 4170) && (charCode <= 4175)) ||
			(charCode == 4347) ||
			((charCode >= 4960) && (charCode <= 4968)) ||
			(charCode == 5120) || (charCode == 5741) || (charCode == 5742) || (charCode == 5787) ||
			(charCode == 5788) ||
			((charCode >= 5867) && (charCode <= 5869)) ||
			(charCode == 5941) || (charCode == 5942) ||
			((charCode >= 6100) && (charCode <= 6102)) ||
			((charCode >= 6104) && (charCode <= 6106)) ||
			((charCode >= 6144) && (charCode <= 6154)) ||
			(charCode == 6468) || (charCode == 6469) || (charCode == 6686) || (charCode == 6687) ||
			((charCode >= 6816) && (charCode <= 6822)) ||
			((charCode >= 6824) && (charCode <= 6829)) ||
			((charCode >= 7002) && (charCode <= 7008)) ||
			((charCode >= 7164) && (charCode <= 7167)) ||
			((charCode >= 7227) && (charCode <= 7231)) ||
			(charCode == 7294) || (charCode == 7295) ||
			((charCode >= 7360) && (charCode <= 7367)) ||
			(charCode == 7379) ||
			((charCode >= 8208) && (charCode <= 8231)) ||
			((charCode >= 8240) && (charCode <= 8259)) ||
			((charCode >= 8261) && (charCode <= 8273)) ||
			((charCode >= 8275) && (charCode <= 8286)) ||
			(charCode == 8317) || (charCode == 8318) || (charCode == 8333) || (charCode == 8334) ||
			((charCode >= 8968) && (charCode <= 8971)) ||
			(charCode == 9001) || (charCode == 9002) ||
			((charCode >= 10088) && (charCode <= 10101)) ||
			(charCode == 10181) || (charCode == 10182) ||
			((charCode >= 10214) && (charCode <= 10223)) ||
			((charCode >= 10627) && (charCode <= 10648)) ||
			((charCode >= 10712) && (charCode <= 10715)) ||
			(charCode == 10748) || (charCode == 10749) ||
			((charCode >= 11513) && (charCode <= 11516)) ||
			(charCode == 11518) || (charCode == 11519) || (charCode == 11632) ||
			((charCode >= 11776) && (charCode <= 11822)) ||
			((charCode >= 11824) && (charCode <= 11842)) ||
			((charCode >= 12289) && (charCode <= 12291)) ||
			((charCode >= 12296) && (charCode <= 12305)) ||
			((charCode >= 12308) && (charCode <= 12319)) ||
			(charCode == 12336) || (charCode == 12349) || (charCode == 12448) || (charCode == 12539) ||
			(charCode == 42238) || (charCode == 42239) ||
			((charCode >= 42509) && (charCode <= 42511)) ||
			(charCode == 42611) || (charCode == 42622) ||
			((charCode >= 42738) && (charCode <= 42743)) ||
			((charCode >= 43124) && (charCode <= 43127)) ||
			(charCode == 43214) || (charCode == 43215) ||
			((charCode >= 43256) && (charCode <= 43258)) ||
			(charCode == 43310) || (charCode == 43311) ||
			(charCode == 43359) ||
			((charCode >= 43457) && (charCode <= 43469)) ||
			(charCode == 43486) || (charCode == 43487) ||
			((charCode >= 43612) && (charCode <= 43615)) ||
			(charCode == 43742) || (charCode == 43743) || (charCode == 43760) || (charCode == 43761) ||
			(charCode == 44011) || (charCode == 64830) || (charCode == 64831) ||
			((charCode >= 65040) && (charCode <= 65049)) ||
			((charCode >= 65072) && (charCode <= 65106)) ||
			((charCode >= 65108) && (charCode <= 65121)) ||
			(charCode == 65123) || (charCode == 65128) || (charCode == 65130) || (charCode == 65131) ||
			((charCode >= 65281) && (charCode <= 65283)) ||
			((charCode >= 65285) && (charCode <= 65290)) ||
			((charCode >= 65292) && (charCode <= 65295)) ||
			(charCode == 65306) || (charCode == 65307) || (charCode == 65311) || (charCode == 65312) ||
			((charCode >= 65339) && (charCode <= 65341)) ||
			(charCode == 65343) || (charCode == 65371) || (charCode == 65373) ||
			((charCode >= 65375) && (charCode <= 65381)) ||
			((charCode >= 65792) && (charCode <= 65794)) ||
			(charCode == 66463) || (charCode == 66512) || (charCode == 66927) || (charCode == 67671) ||
			(charCode == 67871) || (charCode == 67903) ||
			((charCode >= 68176) && (charCode <= 68184)) ||
			(charCode == 68223) ||
			((charCode >= 68336) && (charCode <= 68342)) ||
			((charCode >= 68409) && (charCode <= 68415)) ||
			((charCode >= 68505) && (charCode <= 68508)) ||
			((charCode >= 69703) && (charCode <= 69709)) ||
			(charCode == 69819) || (charCode == 69820) ||
			((charCode >= 69822) && (charCode <= 69825)) ||
			((charCode >= 69952) && (charCode <= 69955)) ||
			(charCode == 70004) || (charCode == 70005) ||
			((charCode >= 70085) && (charCode <= 70088)) ||
			(charCode == 70093) ||
			((charCode >= 70200) && (charCode <= 70205)) ||
			(charCode == 70854) ||
			((charCode >= 71105) && (charCode <= 71113)) ||
			((charCode >= 71233) && (charCode <= 71235)) ||
			((charCode >= 74864) && (charCode <= 74868)) ||
			(charCode == 92782) || (charCode == 92783) || (charCode == 92917) ||
			((charCode >= 92983) && (charCode <= 92987)) ||
			(charCode == 92996) || (charCode == 113823)
		);
	}

	function init() {
		const tableOfContentsEl = $('table-of-contents');

		// determine if clipboard is available to browser
		if (
			document.queryCommandSupported &&
			document.queryCommandSupported('copy')
		) {
			const copyClipboardEl = $('copy-clipboard');

			// display copy to clipboard button, add click handler
			copyClipboardEl.parentNode.classList.remove('hide');
			copyClipboardEl.addEventListener(
				'click',
				copyFormElementToClipboard.bind(null,tableOfContentsEl)
			);
		}

		// add click handler to 'Generate' button
		$('generate').addEventListener('click',() => {
			tableOfContentsEl.value = buildTOCMarkdown(
				headerListFromMarkdown($('markdown-source').value),
				indentWith($('indent-style').value),
				$('skip-first-heading').checked
			);
		});
	}

	(mainCallback || (() => {
		if (document.readyState == 'loading') {
			document.addEventListener('DOMContentLoaded',init);
			return;
		}

		// DOM already ready
		init();
	}))({
		stripPunctuation: stripPunctuation
	});
};

// export app() for Node.js
if ((typeof module != 'undefined') && module.exports) {
	module.exports = app;
}

// test if we are a browser
if (typeof window != 'undefined') {
	app();
}