diffusion/src/selectors/topic-selector.js

Diffusion JavaScript client

var util = require('topics/topic-path-utils');

/**
 * A {@link TopicSelector} is a value that identifies one or more topics.
 * @param {TopicSelector.Type} type - The type of this selector.
 * @param {String} prefix - The maximum topic path prefix from this selector.
 * @param {String} expression - The original expression of this selector.
 * @class TopicSelector
 */
function TopicSelector(type, prefix, expression) {
    /*
     * The type of this selector.
     */
    this.type = type;
    
    /*
     * The maximum topic path prefix from this selector.
     */
    this.prefix = prefix;
    
    /*
     * The original expression of this selector.
     */
    this.expression = expression;
}

/**
 * @readonly
 * @enum {String}
 */
TopicSelector.Prefix = {
    /** Prefix used for {@link TopicSelector.Type.PATH} expressions. */
    PATH : '>',
    /** Prefix used for {@link TopicSelector.Type.SPLIT_PATH_PATTERN} expressions. */
    SPLIT_PATH_PATTERN : '?',
    /** Prefix used for {@link TopicSelector.Type.FULL_PATH_PATTERN} expressions. */
    FULL_PATH_PATTERN : '*',
    /** Prefix used for {@link TopicSelector.Type.SELECTOR_SET} expressions. */
    SELECTOR_SET : '#'
};

/**
 * Topic Selector type.
 * 
 * @readonly
 * @enum {TopicSelector.Prefix}
 */
TopicSelector.Type = {
    /** A selector that selects a single topic. */
    PATH : TopicSelector.Prefix.PATH,
    /** A selector that is a split-path pattern. */
    SPLIT_PATH_PATTERN : TopicSelector.Prefix.SPLIT_PATH_PATTERN,
    /** A selector that is a full-path pattern. */
    FULL_PATH_PATTERN : TopicSelector.Prefix.FULL_PATH_PATTERN,
    /** A composite of multiple selectors. */
    SELECTOR_SET : TopicSelector.Prefix.SELECTOR_SET
};

/**
 * Evaluate this selector against a topic path.
 * 
 * @param {String} topicPath - The topic path
 * @returns {Boolean} If this selector selects the topic path
 */
TopicSelector.prototype.selects = function(topicPath) {
    var canonical = util.canonicalise(topicPath);
    return canonical.indexOf(this.prefix) === 0 && this.doSelects(canonical);
};

TopicSelector.prototype.toString = function() {
    return this.expression;
};

module.exports = TopicSelector;