(function($) {
    var CountTo = function(element, options) {
        this.$element = $(element);
        this.options = $.extend({}, CountTo.DEFAULTS, this.dataOptions(), options);
        this.init();
    };

    CountTo.DEFAULTS = {
        from: 0, // the number the element should start at
        to: 0, // the number the element should end at
        speed: 1000, // how long it should take to count between the target numbers
        refreshInterval: 100, // how often the element should be updated
        decimals: 0, // the number of decimal places to show
        formatter: formatter, // handler for formatting the value before rendering
        onUpdate: null, // callback method for every time the element is updated
        onComplete: null // callback method for when the element finishes updating
    };

    CountTo.prototype.init = function() {
        this.value = this.options.from;
        this.loops = Math.ceil(this.options.speed / this.options.refreshInterval);
        this.loopCount = 0;
        this.increment = (this.options.to - this.options.from) / this.loops;
    };

    CountTo.prototype.dataOptions = function() {
        var options = {
            from: this.$element.data('from'),
            to: this.$element.data('to'),
            speed: this.$element.data('speed'),
            refreshInterval: this.$element.data('refresh-interval'),
            decimals: this.$element.data('decimals')
        };

        var keys = Object.keys(options);

        for (var i in keys) {
            var key = keys[i];

            if (typeof(options[key]) === 'undefined') {
                delete options[key];
            }
        }

        return options;
    };

    CountTo.prototype.update = function() {
        this.value += this.increment;
        this.loopCount++;

        this.render();

        if (typeof(this.options.onUpdate) == 'function') {
            this.options.onUpdate.call(this.$element, this.value);
        }

        if (this.loopCount >= this.loops) {
            clearInterval(this.interval);
            this.value = this.options.to;

            if (typeof(this.options.onComplete) == 'function') {
                this.options.onComplete.call(this.$element, this.value);
            }
        }
    };

    CountTo.prototype.render = function() {
        var formattedValue = this.options.formatter.call(this.$element, this.value, this.options);
        this.$element.text(formattedValue);
    };

    CountTo.prototype.restart = function() {
        this.stop();
        this.init();
        this.start();
    };

    CountTo.prototype.start = function() {
        this.stop();
        this.render();
        this.interval = setInterval(this.update.bind(this), this.options.refreshInterval);
    };

    CountTo.prototype.stop = function() {
        if (this.interval) {
            clearInterval(this.interval);
        }
    };

    CountTo.prototype.toggle = function() {
        if (this.interval) {
            this.stop();
        } else {
            this.start();
        }
    };

    function formatter(value, options) {
        return value.toFixed(options.decimals);
    }

    $.fn.countTo = function(option) {
        return this.each(function() {
            var $this = $(this);
            var data = $this.data('countTo');
            var init = !data || typeof(option) === 'object';
            var options = typeof(option) === 'object' ? option : {};
            var method = typeof(option) === 'string' ? option : 'start';

            if (init) {
                if (data) data.stop();
                $this.data('countTo', data = new CountTo(this, options));
            }

            data[method].call(data);
        });
    };
}(jQuery));