<!DOCTYPE html>
<html>
<head>
<meta http-equiv="refresh" content="3600">
<style>
html, body, iframe { margin: 0; padding: 0; border: none; width: 100%; height: 100%; }
</style>
</head>
<body>
<script>

const urls = [];
const CycleSeconds = 30;

const request = new XMLHttpRequest();
request.open('GET', '/data/manifest.json', true);
request.send(null);
request.onreadystatechange = function () {
    if (request.readyState != XMLHttpRequest.DONE)
        return;
    if (request.status !== 200) {
        alert('Failed with status: ' + request.status);
        return;
    }

    const manifest = JSON.parse(request.responseText);
    const dashboards = [];
    for (const dashboardName in manifest.dashboards)
        dashboards.push(dashboardName);

    for (const dashboardName of dashboards)
        urls.push('/v3/#/dashboard/' + dashboardName);

    loadURLAt(0);
}

let oldIframe = null;
function loadURLAt(i)
{
    const newIframe = document.createElement('iframe');
    document.body.appendChild(newIframe);
    newIframe.src = urls[i];
    newIframe.onload = () => {
        scrollUpIfNeeded(oldIframe).then(() => {
            showNewFrame(i, newIframe);
            setTimeout(() => scrollDownIfNeeded(newIframe), CycleSeconds * 1000 / 2);
        });
    }
}

function showNewFrame(i, iframe)
{
    if (oldIframe)
        document.body.removeChild(oldIframe);
    oldIframe = iframe;

    i = (i + 1) % urls.length;
    setTimeout(loadURLAt.bind(window, i), CycleSeconds * 1000);
}

function scrollUpIfNeeded(iframe)
{
    const diff = iframe ? iframe.scrollDiff : 0;
    if (!diff)
        return Promise.resolve();
    for (let i = 0; i < 500; i++)
        setTimeout(() => iframe.contentWindow.scrollTo(0, oldIframe.scrollDiff / 500 * (500 - i)), i);
    return new Promise((resolve) => setTimeout(resolve, 800));
}

function scrollDownIfNeeded(iframe)
{
    const viewportHeight = iframe.contentWindow.innerHeight;
    const contentHeight = iframe.contentDocument.body.offsetHeight;
    if (viewportHeight >= contentHeight)
        return;
    const diff = contentHeight - viewportHeight;
    for (let i = 0; i < 500; i++)
        setTimeout(() => iframe.contentWindow.scrollTo(0, diff / 500 * i), i);
    iframe.scrollDiff = diff;
}

</script>
</body>
</html>