'use strict';

!function($) {

/**
 * Magellan module.
 * @module foundation.magellan
 */

class Magellan {
  /**
   * Creates a new instance of Magellan.
   * @class
   * @fires Magellan#init
   * @param {Object} element - jQuery object to add the trigger to.
   * @param {Object} options - Overrides to the default plugin settings.
   */
  constructor(element, options) {
    this.$element = element;
    this.options  = $.extend({}, Magellan.defaults, this.$element.data(), options);

    this._init();
    this.calcPoints();

    Foundation.registerPlugin(this, 'Magellan');
  }

  /**
   * Initializes the Magellan plugin and calls functions to get equalizer functioning on load.
   * @private
   */
  _init() {
    var id = this.$element[0].id || Foundation.GetYoDigits(6, 'magellan');
    var _this = this;
    this.$targets = $('[data-magellan-target]');
    this.$links = this.$element.find('a');
    this.$element.attr({
      'data-resize': id,
      'data-scroll': id,
      'id': id
    });
    this.$active = $();
    this.scrollPos = parseInt(window.pageYOffset, 10);

    this._events();
  }

  /**
   * Calculates an array of pixel values that are the demarcation lines between locations on the page.
   * Can be invoked if new elements are added or the size of a location changes.
   * @function
   */
  calcPoints() {
    var _this = this,
        body = document.body,
        html = document.documentElement;

    this.points = [];
    this.winHeight = Math.round(Math.max(window.innerHeight, html.clientHeight));
    this.docHeight = Math.round(Math.max(body.scrollHeight, body.offsetHeight, html.clientHeight, html.scrollHeight, html.offsetHeight));

    this.$targets.each(function(){
      var $tar = $(this),
          pt = Math.round($tar.offset().top - _this.options.threshold);
      $tar.targetPoint = pt;
      _this.points.push(pt);
    });
  }

  /**
   * Initializes events for Magellan.
   * @private
   */
  _events() {
    var _this = this,
        $body = $('html, body'),
        opts = {
          duration: _this.options.animationDuration,
          easing:   _this.options.animationEasing
        };
    $(window).one('load', function(){
      if(_this.options.deepLinking){
        if(location.hash){
          _this.scrollToLoc(location.hash);
        }
      }
      _this.calcPoints();
      _this._updateActive();
    });

    this.$element.on({
      'resizeme.zf.trigger': this.reflow.bind(this),
      'scrollme.zf.trigger': this._updateActive.bind(this)
    }).on('click.zf.magellan', 'a[href^="#"]', function(e) {
        e.preventDefault();
        var arrival   = this.getAttribute('href');
        _this.scrollToLoc(arrival);
      });
    $(window).on('popstate', function(e) {
      if(_this.options.deepLinking) {
        _this.scrollToLoc(window.location.hash);
      }
    });
  }

  /**
   * Function to scroll to a given location on the page.
   * @param {String} loc - a properly formatted jQuery id selector. Example: '#foo'
   * @function
   */
  scrollToLoc(loc) {
    // Do nothing if target does not exist to prevent errors
    if (!$(loc).length) {return false;}
    this._inTransition = true;
    var _this = this,
        scrollPos = Math.round($(loc).offset().top - this.options.threshold / 2 - this.options.barOffset);

    $('html, body').stop(true).animate(
      { scrollTop: scrollPos },
      this.options.animationDuration,
      this.options.animationEasing,
      function() {_this._inTransition = false; _this._updateActive()}
    );
  }

  /**
   * Calls necessary functions to update Magellan upon DOM change
   * @function
   */
  reflow() {
    this.calcPoints();
    this._updateActive();
  }

  /**
   * Updates the visibility of an active location link, and updates the url hash for the page, if deepLinking enabled.
   * @private
   * @function
   * @fires Magellan#update
   */
  _updateActive(/*evt, elem, scrollPos*/) {
    if(this._inTransition) {return;}
    var winPos = /*scrollPos ||*/ parseInt(window.pageYOffset, 10),
        curIdx;

    if(winPos + this.winHeight === this.docHeight){ curIdx = this.points.length - 1; }
    else if(winPos < this.points[0]){ curIdx = undefined; }
    else{
      var isDown = this.scrollPos < winPos,
          _this = this,
          curVisible = this.points.filter(function(p, i){
            return isDown ? p - _this.options.barOffset <= winPos : p - _this.options.barOffset - _this.options.threshold <= winPos;
          });
      curIdx = curVisible.length ? curVisible.length - 1 : 0;
    }

    this.$active.removeClass(this.options.activeClass);
    this.$active = this.$links.filter('[href="#' + this.$targets.eq(curIdx).data('magellan-target') + '"]').addClass(this.options.activeClass);

    if(this.options.deepLinking){
      var hash = "";
      if(curIdx != undefined){
        hash = this.$active[0].getAttribute('href');
      }
      if(hash !== window.location.hash) {
        if(window.history.pushState){
          window.history.pushState(null, null, hash);
        }else{
          window.location.hash = hash;
        }
      }
    }

    this.scrollPos = winPos;
    /**
     * Fires when magellan is finished updating to the new active element.
     * @event Magellan#update
     */
    this.$element.trigger('update.zf.magellan', [this.$active]);
  }

  /**
   * Destroys an instance of Magellan and resets the url of the window.
   * @function
   */
  destroy() {
    this.$element.off('.zf.trigger .zf.magellan')
        .find(`.${this.options.activeClass}`).removeClass(this.options.activeClass);

    if(this.options.deepLinking){
      var hash = this.$active[0].getAttribute('href');
      window.location.hash.replace(hash, '');
    }

    Foundation.unregisterPlugin(this);
  }
}

/**
 * Default settings for plugin
 */
Magellan.defaults = {
  /**
   * Amount of time, in ms, the animated scrolling should take between locations.
   * @option
   * @example 500
   */
  animationDuration: 500,
  /**
   * Animation style to use when scrolling between locations.
   * @option
   * @example 'ease-in-out'
   */
  animationEasing: 'linear',
  /**
   * Number of pixels to use as a marker for location changes.
   * @option
   * @example 50
   */
  threshold: 50,
  /**
   * Class applied to the active locations link on the magellan container.
   * @option
   * @example 'active'
   */
  activeClass: 'active',
  /**
   * Allows the script to manipulate the url of the current page, and if supported, alter the history.
   * @option
   * @example true
   */
  deepLinking: false,
  /**
   * Number of pixels to offset the scroll of the page on item click if using a sticky nav bar.
   * @option
   * @example 25
   */
  barOffset: 0
}

// Window exports
Foundation.plugin(Magellan, 'Magellan');

}(jQuery);