document.addEventListener("DOMContentLoaded", function(event) {
    var iframe = document.getElementById('partner_deltareisen');
    var partner_id = iframe.dataset.partner_id;

    var iframe_url = 'https://partner.deltareisen.cz';

    iframe.setAttribute('src', iframe_url + '/?ta_id=' + partner_id);

    var scroll_top = function (pos) {
        if (pos) { //set
            if ('scrollY' in window) {
                window.scroll(0, pos);
            } else {
                document.documentElement.scrollTop = pos;
            }
        } else { //get
            if ('scrollY' in window) {
                return window.scrollY;
            } else {
                return document.documentElement.scrollTop;
            }
        }
    };

    function scrollTo(Y) {
        var easingFunction = function (t) {
            return t < 0.5 ? 2 * t * t : -1 + (4 - 2 * t) * t;
        };
        var start = Date.now(),
            from = scroll_top();

        if (from === Y) {
            return;
        }

        function min(a, b) {
            return a < b ? a : b;
        }

        function scroll() {
            var currentTime = Date.now(),
                time = min(1, ((currentTime - start) / 500)),
                easedT = easingFunction(time);

            scroll_top((easedT * (Y - from)) + from);

            if (time < 1) requestAnimationFrame(scroll);
        }

        requestAnimationFrame(scroll);
    }

    var iframe_position = iframe.getBoundingClientRect().top + scroll_top();

    window.addEventListener && window.addEventListener("message", OnMessage, false) || window.attachEvent && window.attachEvent("onmessage", OnMessage);

    function OnMessage(e) { //Při přijetí zprávy z iframu
        switch (e.data.type) {
            case 'resize':
                iframe.style.height = e.data.value + 'px';
                break;
            case 'get_url_params':
                iframe.contentWindow.postMessage({
                    type: 'url_params',
                    value: location.search
                }, iframe_url);
                break;
            case 'set_url_params':
                history.pushState(null, null, e.data.value);
                break;
            case 'scroll_to_iframe_position':
                iframe.contentWindow.postMessage({ // Do iframu se nastaví pozice ze které se scroluje
                    type: 'last_scroll',
                    value: scroll_top() - iframe_position
                }, iframe_url);
                scrollTo(iframe_position + e.data.value);
                break;
        }
    }

    var last_call = (new Date());
    window.onscroll = function () {
        if (((new Date()) - last_call) > 50) { // nejvýše každých 50ms
            last_call = new Date();
            iframe.contentWindow.postMessage({ // V iframe se nastaví scroll ve které se nachází
                type: 'iframe_scroll',
                value: scroll_top() - iframe_position
            }, iframe_url);
        }
    };
});