mqtt-pattern/index.js

Fast library for matching MQTT patterns with named wildcards

"use strict";
var SEPARATOR = "/";
var SINGLE = "+";
var ALL = "#";

module.exports = {
	matches: matches,
	extract: extract,
	exec: exec,
	fill: fill,
	clean: clean
};

function exec(pattern, topic) {
	return matches(pattern, topic) ? extract(pattern, topic) : null;
}

function matches(pattern, topic) {
	var patternSegments = pattern.split(SEPARATOR);
	var topicSegments = topic.split(SEPARATOR);

	var patternLength = patternSegments.length;
	var topicLength = topicSegments.length;
	var lastIndex = patternLength - 1;

	for(var i = 0; i < patternLength; i++){
		var currentPattern = patternSegments[i];
		var patternChar = currentPattern[0];
		var currentTopic = topicSegments[i];

		if(!currentTopic && !currentPattern)
			continue;

		if(!currentTopic && currentPattern !== ALL) return false;

		// Only allow # at end
		if(patternChar === ALL)
			return i === lastIndex;
		if(patternChar !== SINGLE && currentPattern !== currentTopic)
			return false;
	}

	return patternLength === topicLength;
}

function fill(pattern, params){
	var patternSegments = pattern.split(SEPARATOR);
	var patternLength = patternSegments.length;

	var result = [];

	for (var i = 0; i < patternLength; i++) {
		var currentPattern = patternSegments[i];
		var patternChar = currentPattern[0];
		var patternParam = currentPattern.slice(1);
		var paramValue = params[patternParam];

		if(patternChar === ALL){
			// Check that it isn't undefined
			if(paramValue !== void 0)
				result.push([].concat(paramValue).join(SEPARATOR)); // Ensure it's an array

			// Since # wildcards are always at the end, break out of the loop
			break;
		} else if (patternChar === SINGLE)
			// Coerce param into a string, missing params will be undefined
			result.push("" + paramValue);
		else result.push(currentPattern);
	}

	return result.join(SEPARATOR);
}


function extract(pattern, topic) {
	var params = {};
	var patternSegments = pattern.split(SEPARATOR);
	var topicSegments = topic.split(SEPARATOR);

	var patternLength = patternSegments.length;

	for(var i = 0; i < patternLength; i++){
		var currentPattern = patternSegments[i];
		var patternChar = currentPattern[0];

		if(currentPattern.length === 1)
			continue;

		if(patternChar === ALL){
			params[currentPattern.slice(1)] = topicSegments.slice(i);
			break;
		} else if(patternChar === SINGLE){
			params[currentPattern.slice(1)] = topicSegments[i];
		}
	}

	return params;
}


function clean(pattern) {
	var patternSegments = pattern.split(SEPARATOR);
	var patternLength = patternSegments.length;

	var cleanedSegments = [];

	for(var i = 0; i < patternLength; i++){
		var currentPattern = patternSegments[i];
		var patternChar = currentPattern[0];

		if(patternChar === ALL){
			cleanedSegments.push(ALL);
		} else if(patternChar === SINGLE){
			cleanedSegments.push(SINGLE);
		} else {
			cleanedSegments.push(currentPattern);
		}
	}

	return cleanedSegments.join('/');
}