index.js

'use strict';

const Promise = require('bluebird');
const _ = require('lodash');
const defaultOptions = {start: '[[', end: ']]'};

const xGetAttributes = new RegExp('(\\S+)\\s*=\\s*([\\\'\\"])(.*?)\\2|(\\S+)\\s*=\\s*(\\S+)|([^\\\'^\\"^\\s]+)(?:\\s|$)|([\\\'\\"])(.*?)\\7', 'g');

const xGetTagAttributesText = '{start}.*?\\s(.*?){end}';
const xStartTagContents = '{start}(.*){end}';
const xTagMatch = '{start}.*?{end}';
const xIsEndTag = '^{start}\/';
const xGetTagName = '{start}(?:\/|)(.*?)(?:\\s|{end})';
const xStart = /\{start\}/g;
const xEnd = /\{end\}/g;

/**
 * @typedef ShortcodeParserFinder
 * Regular expressions object to use in extracting tag and tag-attribute data.
 *
 * @property {RegExp} tagMatch				Expression for extracting a tag.
 * @property {RegExp} isEndTag				Expression to test if a tag is an
 *											end tag
 * @property {RegExp} getTagName			Expression to extract the tag name.
 * @property {Function} getAttributes		Method to extract the attributes in
 *											a given start tag string.
 * @property {RegExp} getStartTagContent	Expression for extracting the
 * 											contents of start tag.
 */


/**
 * Add slashes to every character in a string.  Can be used to ensure all of
 * contents is treated as text and not used as regular expression functionality
 * when creating a RegExp with the given content.
 *
 * @private
 * @param {string} txt		The string to add slashes to.
 * @returns {string}		New slashed string.
 */
function _addSlashToEachCharacter(txt) {
	return txt.split('').map(char=>'\\' + char).join('');
}

/**
 * Get the attributes in the given tag text. Will return an object of the tag
 * attributes with properties being equal to their names and property values
 * equalling their value. Also, assign numbered properties for attribute
 * positions.
 *
 * @private
 * @param {RegExp} getAttributes        The regular expression to use in getting
 *										the attributes.
 * @param {string} tag					The tag text from open tag start
 *										and close.
 * @returns {Object}					The attributes object.
 */
function _getAttribute(getAttributes, tag) {
	let results = getAttributes.exec(tag);

	let attributes = {};
	if (results) {
		let result;
		let count = 1;
		while (result = xGetAttributes.exec(results[1])) {
			if (!result[6] && (result[1] || result[4])) {
				attributes[count] = {};
				attributes[result[1] || result[4]] = result[3] || result[5];
				attributes[count][result[1] || result[4]] = result[3] || result[5];
			} else if (result[6] || result[8]) {
				attributes[count] = result[6] || result[8];
			}
			count++;
		}
	}

	return attributes;
}

/**
 * Safely create a regular expression from the given template with the given
 * start and end characters replaced in the regular expression.
 *
 * @private
 * @param {string} template			The regular expression template. The text
 *									{start} and {end} will be replaced with
 *									the given startChars and endChars.
 * @param {string} startChars		Tag start characters.
 * @param {string} endChars			Tag end characters.
 * @param {string} [options='']		The regular expression options to
 *									use (eg. 'g' or 'gi').
 * @returns {RegExp}
 */
function _createRegExp(template, startChars, endChars, options = '') {
	return new RegExp(template
		.replace(xStart, _addSlashToEachCharacter(startChars))
		.replace(xEnd, _addSlashToEachCharacter(endChars)
		), options);
}

/**
 * Get an object containing the regular expressions to use in extracting tag
 * and tag-attribute data. Construct these expressions to work with the given
 * start and end tag characters supplied in the options object.
 *
 * @private
 * @class ShortcodeParserFinder
 * @param {object} options				The options object.
 * @param {string} options.start		Start of tag characters.
 * @param {string} options.end			End of tag characters.
 * @returns {ShortcodeParserFinder}
 *
 */
function _createRegExpsObj(options) {
	return {
		tagMatch: _createRegExp(xTagMatch, options.start, options.end, 'g'),
		isEndTag: _createRegExp(xIsEndTag, options.start, options.end),
		getTagName: _createRegExp(xGetTagName, options.start, options.end),
		getAttributes: _getAttribute.bind({}, _createRegExp(xGetTagAttributesText, options.start, options.end)),
		getStartTagContent: _createRegExp(xStartTagContents, options.start, options.end)
	};
}

/**
 * Given an array of tags, remove end tags combining them with their start tag
 * and placing tag content in the tag object.
 *
 * @private
 * @param {string} txt					The text containing all the given tags.
 * @param {Array} tags					Array of tag objects.
 * @returns {ShortcodeParserTag[]}		New array with end tags removed and tag
 *										data updated with any tag content.
 */
function _fixEndTags(txt, tags) {
	return tags.map((result, n)=> {
		if (result.endTag) {
			for (let nn = n; nn >= 0; nn--) {
				if ((tags[nn].tagName === result.tagName) && (!tags[nn].endTag)) {
					tags[nn].content = txt.substring(tags[nn].end, result.start);
					tags[nn].fullMatch += (tags[nn].content + result.fullMatch);
					tags[nn].end = result.end;
					tags[nn].selfClosing = false;
				}
			}
		}
		return result;
	}).filter(result=>!result.endTag);
}

/**
 * @private
 * Fix overlapping tags, removing tags inside tags
 *
 * @param {ShortcodeParserTag[]} tags	Tags to filter.
 * @returns {ShortcodeParserTag[]}		Filtered tags.
 */
function _filterOverlappingTags(tags) {
	return tags.filter((tag, n)=> {
		if (n > 0) {
			for (let nn = (n - 1); nn >= 0; nn--) {
				if (tags[nn].end > tag.start) return false;
			}
		}
		return true;
	});
}

/**
 * @typedef ShortcodeParserTag.
 * @property {string} tagName			The name of tag.
 * @property {boolean} endTag			Is this an end tag.
 * @property {string} fullMatch			The full tag text and content.
 * @property {integer} start			Start character number in
 * 										original text.
 * @property {integer} end				end character number in
 *										original text.
 * @property {object} attributes		The tag attributes as an object.
 * @property {string} content			The content of tag when their is
 *										an opening and closing tag.
 * @property {boolean} selfClosing		Is this a self-closing tag?
 * @property {string} tagContents		Contents of starting tag.
 */

/**
 * Create new tag object, describing extracted tag.
 *
 * @private
 * @class ShortcodeParserTag
 * @param {ShortcodeParserFinder} finder	Finder object to apply.
 * @param {Array} result					Results of tag extraction.
 * @returns {ShortcodeParserTag}			New tag object.
 */
function ShortcodeParserTag(finder, result) {
	return {
		tagName: finder.getTagName.exec(result[0])[1],
		endTag: finder.isEndTag.test(result[0]),
		fullMatch: result[0],
		end: result.lastIndex,
		start: result.lastIndex - result[0].length,
		attributes: finder.getAttributes(result[0]),
		content: '',
		tagContents: finder.getStartTagContent.exec(result[0])[1],
		selfClosing: true
	};
}

/**
 * Extract tag strings from given text, return regular expression matches
 * (with some addtional data, such as lastIndex).
 *
 * @private
 * @param {string} txt						Text to extract tags from.
 * @param {ShortcodeParserFinder} finder	Finder object to apply.
 * @returns {Array}							Results array.
 */
function _extractTagStrings(txt, finder) {
	let results = [];
	let result;
	while (result = finder.tagMatch.exec(txt)) {
		result.lastIndex = finder.tagMatch.lastIndex;
		results.push(result);
	}
	return results;
}

/**
 * Parse string for tags that handlers have been added for. Return tags that
 * can be parsed.
 *
 * @private
 * @param {string} txt						Text to parse for tags.
 * @param {ShortcodeParserFinder} finder	Finder object to apply.
 * @param {ShortcodeParser} parserInstance	The parser instance.
 * @returns {ShortcodeParserTag[]}			Tags which can be handled.
 */
function _parse(txt, finder, parserInstance) {
	return _extractTagStrings(txt, finder).map(
		result=>ShortcodeParserTag(finder, result)
	);
}

/**
 *  @typedef ShortcodeParserReplacer
 *  @property {string} replacer				Text to replace tag with.
 *  @property {ShortcodeParserTag} tag		Tag to do replacement on.
 */

/**
 * Apply a handler function to a given tag with supplied parameters.
 *
 * @private
 * @param {Function} handler						Handler to apply.
 * @param {ShortcodeParserTag} tag					Tag to apply handler to.
 * @param {Array} params							Further parameters to pass
 * 													to the handler.
 * @returns {Promise.<ShortcodeParserReplacer>}
 */
function _applyHandler(handler, tag, params) {
	return Promise.resolve(handler.apply({}, params) || '').then(replacer=>{
		return {replacer, tag};
	});
}

/**
 * Test if given selector is selector for the given tag.
 *
 * @private
 * @param {RegExp|Function} selector		Selector to test.
 * @param {ShortcodeParserTag} tag			Tag to test against.
 * @returns {boolean}
 */
function _isSelectorMatch(selector, tag) {
	return ((_.isRegExp(selector) && selector.test(tag.tagContents)) || (_.isFunction(selector) && selector(tag.tagContents)));
}

/**
 * Create a new Shortcode parser instance.
 *
 * @class
 * @public
 * @param {Object} options			Options to ShortcodeParser function.
 * @returns {ShortcodeParser}		New instance of shortcode parser.
 */
function ShortcodeParser(options = defaultOptions) {
	const tags = new Map();
	const finder = _createRegExpsObj(Object.assign({}, defaultOptions, options));

	/**
	 * Run set handlers for given tags, replacing text content as the handler
	 * return content.
	 *
	 * @private
	 * @param {string} txt						The full text containing the tags to
	 *											do the replacements on.
	 * @param {ShortcodeParserTag[]} _tags		The tags to run handlers on.
	 * @param {Array} params					The parameters to pass on to the
	 *											tag handlers.
	 * @returns {Promise.<string>}				Promise resolving on completion of
	 *											tag replacements.
	 */
	function _runHandlers(txt, _tags, params) {
		return Promise.all(_tags.map(tag=>{
			let promise;
			if (exports.has(tag.tagName)) {
				let handler = exports.get(tag.tagName).bind({}, tag);
				promise = _applyHandler(handler, tag, params);
			} else {
				tags.forEach((handler, selector)=>{
					let _handler = handler.bind({}, tag);
					if (!promise && _isSelectorMatch(selector, tag)) promise = _applyHandler(_handler, tag, params);
				});
			}
			return promise;
		})).filter(
			result=>result
		).mapSeries(result=>{
			txt = txt.replace(result.tag.fullMatch, result.replacer);
		}).then(()=>txt);
	}

	const exports = {
		/**
		 * Add a new handler to the parser for given tag name.
		 *
		 * @public
		 * @memberof ShortcodeParser
		 * @param {string|Function|RegExp} name			Tag name to set handler for.
		 * @param {function} handler					Handler function to fire on tag.
		 * @param {boolean} [throwOnAlreadySet=true]	Throw error if tage already exists?
		 * @return {function}							The handler function returned.
		 */
		add: (name, handler, throwOnAlreadySet=true)=> {
			if (exports.has(name) && throwOnAlreadySet) throw new Error(`Tag '${name}' already exists`);
			if (!_.isFunction(handler)) throw new TypeError(`Cannot assign a non function as handler method for '${name}'`);
			if (!_.isString(name) && !_.isRegExp(name) && !_.isFunction(name)) throw new TypeError('Cannot add handler if the reference is not a string, regular expression or function. Reference of type: ' + (typeof name) + ', was given.');
			tags.set(name, handler);
			return exports.get(name);
		},

		/**
		 * Test if a handler for given tag name.
		 *
		 * @public
		 * @memberof ShortcodeParser
		 * @param {string} name			The tag to look for a handler on.
		 * @returns {boolean}			Does it exist?
		 */
		has: name=>tags.has(name),

		/**
		 * Delete the handler for given tag name.
		 *
		 * @public
		 * @memberof ShortcodeParser
		 * @param {string} name			The tagname to delete the handler for.
		 * @returns {boolean}
		 */
		delete: name=> {
			if (!exports.has(name)) throw new RangeError(`Tag '${name}' does not exist`);
			return tags.delete(name);
		},

		/**
		 * Get the handler function for given tag name.
		 *
		 * @public
		 * @memberof ShortcodeParser
		 * @param {string} name			Tag name to get the handler for.
		 * @returns {function}			The handler for the given tag name.
		 */
		get: name=> {
			if (!exports.has(name)) throw new RangeError(`Tag '${name}' does not exist`);
			return tags.get(name);
		},

		/**
		 * Parse given text for tags, running handlers where handlers are
		 * defined and returning parsed text.
		 *
		 * @public
		 * @memberof ShortcodeParser
		 * @param {string} txt				Text to parse.
		 * @param {Array} [params=[]]		Parameters to pass to the handlers.
		 * @returns {Promise.<string>}		Promise resolving to new
		 *									parsed text.
		 */
		parse: (txt, ...params)=> {
			let tags = _filterOverlappingTags(_fixEndTags(txt, _parse(txt, finder, exports)));

			return _runHandlers(txt, tags, params).then(parsedTxt=> {
				if (txt !== parsedTxt) return exports.parse(parsedTxt, finder, exports);
				return parsedTxt;
			});
		}
	};

	return Object.freeze(exports);
}


module.exports = ShortcodeParser;