var ElementPageAlias = qs.createObject();

ElementPageAlias.prototype = {
    _sources: {},
    _alias: null,
    _pattern: /^[-_a-zA-Z0-9\.]+$/,
    _parentVal: '',

    initialize: function (element, sources) {
        var that = this, defaultLang = qs.constant('DEFAULT_LANGUAGE');
        sources = sources || ['title'];
        sources = $.isArray(sources) ? sources : [sources];

        if (!(this._alias = document.getElementById(element))) {
            throw new Error('Element with id "source" not found !');
        }

        this._sources = {};
        _.forEach(sources, function (id) {
            var handle;
            if ((handle = (document.getElementById(id) || document.getElementById(id + '-' + id + '_' + defaultLang)))) {
                that._sources[id] = handle;
                that._addEvent(handle, 'blur', function () {that._onSourceBlur()});
            } else {
                throw new Error('Element with id "' + id + '" not found !');
            }
        });

        this._addEvent(this._alias, 'keypress', function () {that._onAliasKeypress()});
        this._addEvent(this._alias, 'keyup', function () {that._onAliasKeyup()});
    },

    _buildAlias: function (value) {
        if (!value || value == '') {
            return '';
        }
        return value.replace(/^\s+/, "").replace(/\s+$/, "").replace(/&+/, "-and-")
            .replace(/[^\sA-Za-z0-9_\.-]/g, "").replace(/\s+/g, "-").toLowerCase();
    },

    _getSourceValue: function () {
        var id, value = [];
        for (id in this._sources) {
            if (this._sources.hasOwnProperty(id)) {
                /* ящо хоча б одне поле з "sources" порожнє, то аліас формуватись немає (QSF-7 пункт 14) */
                if ('' == _.str.trim(this._sources[id].value)) {
                    return '';
                }
                value.push(this._sources[id].value);
            }
        }
        return value.join(' ');
    },

    _onSourceBlur: function () {
        var source = this._getSourceValue();
        if (source != '' && this._alias.value == '') {
            this._alias.value = this._buildAlias(source);
        }
    },

    _onAliasKeyup: function() {
        if (this._alias.value !== '' && !this._alias.value.match(this._pattern)) {
            this._alias.value = this._parentVal;
        }
    },

    _onAliasKeypress: function() {
        if (this._alias.value == '' || this._alias.value.match(this._pattern)) {
            this._parentVal = this._alias.value;
        }
    },

    _addEvent: function (obj, type, func) {
        if ('object' != typeof obj && !(obj = document.getElementById(obj))) {
            return;
        }
        if (obj.addEventListener) {
            obj.addEventListener(type, func, false);
        } else if (obj.attachEvent) {
            var f = function(e) {func.call(obj, e);};
            obj.attachEvent('on' + type, f);
        }
    }
};