'use strict'

/**

* Validate a topic to see if it's valid or not.

* A topic is valid if it follow below rules:

* - Rule #1: If any part of the topic is not `+` or `#`, then it must not contain `+` and '#'

* - Rule #2: Part `#` must be located at the end of the mailbox

*

* @param {String} topic - A topic

* @returns {Boolean} If the topic is valid, returns true. Otherwise, returns false.

*/

export function validateTopic (topic) {

var parts = topic.split('/')

for (var i = 0; i < parts.length; i++) {

if (parts[i] === '+') {

continue

}

if (parts[i] === '#') {

// for Rule #2

return i === parts.length - 1

}

if (parts[i].indexOf('+') !== -1 || parts[i].indexOf('#') !== -1) {

return false

}

}

return true

}

/**

* Validate an array of topics to see if any of them is valid or not

* @param {Array} topics - Array of topics

* @returns {String} If the topics is valid, returns null. Otherwise, returns the invalid one

*/

export function validateTopics (topics) {

if (topics.length === 0) {

return 'empty_topic_list'

}

for (var i = 0; i < topics.length; i++) {

if (!validateTopic(topics[i])) {

return topics[i]

}

}

return null

}