//Target the first letter of the first element found in the wrapper
;(function ( $, window, document, undefined ) {
    //defaults
    var pluginName = 'extLinks',
        defaults = {
          addIcon : true,
          newTab: true,
          skipSelectors : { //defines the selector to skip when parsing the wrapper
            classes : [],
            ids : []
          },
          skipChildTags : ['IMG']//skip those tags if they are direct children of the current link element
        };


    function Plugin( element, options ) {
      this.$_el     = $(element);
      this.options  = $.extend( {}, defaults, options) ;
      this._href    = $.trim( this.$_el.attr( 'href' ) );
      this.init();
    }


    Plugin.prototype.init = function() {
      var $_external_icon = this.$_el.next('.tc-external');
      //if not eligible, then remove any remaining icon element and return
      //important => the element to remove is right after the current link element ( => use of '+' CSS operator )
      if ( ! this._is_eligible() ) {
        if ( $_external_icon.length )
          $_external_icon.remove();
        return;
      }

      //add the icon link, if not already there
      if ( this.options.addIcon && 0 === $_external_icon.length ) {
        this.$_el.after('<span class="tc-external">');
      }

      //add the target _blank, if not already there
      if ( this.options.newTab && '_blank' != this.$_el.attr('target') )
        this.$_el.attr('target' , '_blank');
    };


    /*
    * @return boolean
    */
    Plugin.prototype._is_eligible = function() {
      var self = this;
      if ( ! this._is_external( this._href ) )
        return;

      //is first child tag allowed ?
      if ( ! this._is_first_child_tag_allowed () )
        return;

      //are ids and classes selectors allowed ?
      //all type of selectors (in the array) must pass the filter test
      if ( 2 != ( ['ids', 'classes'].filter( function( sel_type) { return self._is_selector_allowed(sel_type); } ) ).length )
        return;

      return true;
    };


    /********
    * HELPERS
    *********/
    /*
    * @params string : ids or classes
    * @return boolean
    */
    Plugin.prototype._is_selector_allowed = function( requested_sel_type ) {
      var sel_type = 'ids' == requested_sel_type ? 'id' : 'class',
          _selsToSkip   = this.options.skipSelectors[requested_sel_type];

      //check if option is well formed
      if ( 'object' != typeof(this.options.skipSelectors) || ! this.options.skipSelectors[requested_sel_type] || ! $.isArray( this.options.skipSelectors[requested_sel_type] ) || 0 === this.options.skipSelectors[requested_sel_type].length )
        return true;

      //has a forbidden parent?
      if ( this.$_el.parents( _selsToSkip.map( function( _sel ){ return 'id' == sel_type ? '#' + _sel : '.' + _sel; } ).join(',') ).length > 0 )
        return false;

      //has requested sel ?
      if ( ! this.$_el.attr( sel_type ) )
        return true;

      var _elSels       = this.$_el.attr( sel_type ).split(' '),
          _filtered     = _elSels.filter( function(classe) { return -1 != $.inArray( classe , _selsToSkip ) ;});

      //check if the filtered selectors array with the non authorized selectors is empty or not
      //if empty => all selectors are allowed
      //if not, at least one is not allowed
      return 0 === _filtered.length;
    };



    /*
    * @return boolean
    */
    Plugin.prototype._is_first_child_tag_allowed = function() {
      //has children ?
      if ( 0 === this.$_el.children().length )
        return true;

      var tagName     = this.$_el.children().first()[0].tagName,
          _tagToSkip  = this.options.skipChildTags;

      //check if tag to skip option is an array
      if ( ! $.isArray( _tagToSkip ) )
        return true;

      //make sure tags in option are all in uppercase
      _tagToSkip = _tagToSkip.map( function( _tag ) { return _tag.toUpperCase(); });
      return -1 == $.inArray( tagName , _tagToSkip );
    };



    /*
    * @return boolean
    */
    Plugin.prototype._is_external = function( _href  ) {
      //gets main domain and extension, no matter if it is a n level sub domain
      //works also with localhost or numeric urls
      var _main_domain = (location.host).split('.').slice(-2).join('.'),
          _reg = new RegExp( _main_domain );

      _href = $.trim( _href );

      if ( _href !== '' && _href != '#' && this._isValidURL( _href ) )
        return ! _reg.test( _href );
      return;
    };


    /*
    * @return boolean
    */
    Plugin.prototype._isValidURL = function( _url ){
      var _pattern = /(ftp|http|https):\/\/(\w+:{0,1}\w*@)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%@!\-\/]))?/;
      return _pattern.test( _url );
    };


    // prevents against multiple instantiations
    $.fn[pluginName] = function ( options ) {
      return this.each(function () {
        if (!$.data(this, 'plugin_' + pluginName)) {
            $.data(this, 'plugin_' + pluginName,
            new Plugin( this, options ));
        }
      });
    };

})( jQuery, window, document );
