// Set date and time when you want to stop this loop
var endLoopAt = new Date('July 08, 2016 08:24:00');

// Create a sandboxed environment
var sandBoxedIframe = document.createElement("iframe");
sandBoxedIframe.onload = checkAndUpvote;
document.body.appendChild(sandBoxedIframe);

// Used to check if last updated link is same as one being checked now
var lastUpdatedFirstPostLink = "";

function checkAndUpvote() {
    // Get document of sandboxed iframe
    var rootDoc = sandBoxedIframe.contentWindow.document;
    // get all posts
    var posts = rootDoc.querySelectorAll("#siteTable > .thing");
    // get top most item from posts
    var mostRecent = posts[0].querySelector(".first > a");
    // get url to comments for the mostRecent post
    var commentUrl = mostRecent.getAttribute("href");
    // Return if this one is same as the one checked in last run
    if(commentUrl === lastUpdatedFirstPostLink) {
        return;
    }
    // else update the env
    lastUpdatedFirstPostLink = commentUrl;
    console.log("Proceeding to upvote first reply!!!");

    // Create another sandboxed env for the new post
    var postIframe = document.createElement("iframe");

    // Tell the iframe to do this when post page loads inside sandbox
    postIframe.onload = function() {
        // Wait for 2 seconds after the post page has loaded
        setTimeout(function() {
            // Get document of target post page
            var postDocRoot = postIframe.contentWindow.document;
            // Get all replies to the post
            var replies = postDocRoot.querySelectorAll(".sitetable .thing");
            // get upvote button for top most reply
            var firstReply_UpvoteButton = replies[1].querySelector(".midcol .up");
            // Create click event to trigger upon upvote button
            var clickToUpvoteEvent = new MouseEvent("click");
            // Trigger the click event
            firstReply_UpvoteButton.dispatchEvent(clickToUpvoteEvent);
        }, 2000);

        // After 30 seconds remove the post sandbox
        setTimeout(function() {
            document.body.removeChild(postIframe);
        }, 30 * 1000);
    };

    // load the comment page for the post
    postIframe.src = commentUrl;
    // Add it to body
    document.body.appendChild(postIframe);
}

var loop = setInterval(function() {
    // If time right now is more than time it's supposed to end, then end it
    if(Date.now() > endLoopAt.getTime()) {
        clearInterval(loop);
        console.log("End time reached. No more loops will be run again");
        return;
    }

    // else refresh the page, which will fire refreshAndUpvote
    console.log("Running loop!!");
    // This will refresh the sandboxed page to update new posts
    sandBoxedIframe.src = "https://www.reddit.com/r/webdev/";
}, 30 * 60 * 1000);