var $ = require('jquery');


function infiniteLoad(options) {
    var defaults = {
        index: 0,
        isload: true,//是否正在加载
        isrun: true,//判断是否执行
        offset: {
            height: null,
            width: null
        }
    };

    this.registerEvent = {
        before: [],
        change: [],
        after: []
    };

    this.options = $.extend(true, {}, defaults, options);

    return this;
}

infiniteLoad.prototype.on = function(name, callback) {
    var g = this;
    var _e = g.registerEvent[name];

    if (_e) {
        _e.push(callback);
    }
    return _e;
};

infiniteLoad.prototype.off = function(name, callback) {
    var g = this;
    var _e = g.registerEvent[name];
    var e = [];

    $.each(_e, function(name, _callback) {
        if (_callback === callback) {
            e.push(name);
        }
    });

    $.each(e.reverse(), function(name, _callback) {
        _e.splice(_callback, 1);
    });
};

infiniteLoad.prototype.exect = function(key, params) {
    var g = this;
    var e;

    if (g.registerEvent[key] && g.registerEvent[key].length > 0) {
        for (e in g.registerEvent[key]) {
            if (g.registerEvent[key].hasOwnProperty(e)) {
                g.registerEvent[key][e](params);
            }
        }
    }
};

infiniteLoad.prototype.init = function() {
    var g = this;
    var p = this.options;

    function __loadMore() {

        if (p.isload && g.__directionCalculation()) {
            p.isload = false;
            p.index++;
            g.exect('after', p);
        }

        g.exect('change', p);
    }

    g.exect('before', p);

    $(window).scroll(__loadMore);
};

infiniteLoad.prototype.emit = function() {
    var p = this.options;

    p.isload = true;
};

infiniteLoad.prototype.__directionCalculation = function() {
    var p = this.options;

    if (p.offset.height() > 0 && $(window).scrollTop() + $(window).height() >= p.offset.height()) {
        return true;
    }

    if (p.offset.width() > 0 && $(window).scrollLeft() + $(window).width() >= p.offset.width()) {
        return true;
    }
    return false;
};

module.exports = infiniteLoad;