// ==UserScript==
// @name			Ladda nästa sida
// @description		        Laddar nästa sida automatiskt på Flashback
// @author			Paul Dawson /mod av Anteus, PM-fix GrooveMerchant
// @include			https://www.flashback.org/t*
// @include			https://www.flashback.org/p*
// @exclude			https://www.flashback.org/private.php*
// @version 0.0.1.20140604203842
// @namespace https://greasyfork.org/users/2463
// @downloadURL https://update.greasyfork.icu/scripts/2092/Ladda%20n%C3%A4sta%20sida.user.js
// @updateURL https://update.greasyfork.icu/scripts/2092/Ladda%20n%C3%A4sta%20sida.meta.js
// ==/UserScript==

var nextURL = null; // the URL for next, or null for pending/none
var nextLinkNode = null; // the node of the "Next" link
var mainTable = null;
window.addEventListener("load", init, false);

// Check the scroll position on a timer because we can't use onscroll (bug 189308).
// If we do switch to onscroll, remember to call testScrollPosition after changing the page.
setInterval(testScrollPosition, 100);

function init() 
{ 
  mainTable = findMainTable(document);
  nextLinkNode = findNextLink(document);
  setNextURL(document);
}

function testScrollPosition() 
{
  if ((nextURL != null) && ((document.documentElement.offsetHeight - document.documentElement.scrollTop) < (2.5 * window.innerHeight))) {
    // We're near the bottom of the page; one press of pgdn could get close to the bottom of the page.
    // (At about 1.9 * window.innerHeight, one press of pgdn would actually hit the bottom of the page.)
    pullMore();
  }
}

function pullMore()
{
  var iframe = document.createElement("iframe");
  iframe.addEventListener("load", whee, false);
  iframe.width = 1;
  iframe.height = 1;
  iframe.style.visibility = "hidden";
  iframe.src = nextURL;
  document.body.appendChild(iframe);

  // Don't pull this more than once.
  nextURL = null;

  function whee() {
    var iframeDoc = iframe.contentDocument;

    // Update nextURL for when we reach the bottom of the page again.
    setNextURL(iframeDoc);

    // Update the "Next" link in the page to make it a little less confusing.
    // Commented out because updating the "Next" link at the top of the page but not the one at
    // the bottom of the page is no good.
    // nextLinkNode.href = nextURL || "javascript:alert('No more!')";

    // no quick reply on Invision boards
    // removeQuickReply(mainTable);

    // Move posts into the main page's table.
    siphon(findMainTable(iframeDoc), mainTable);

    // Get rid of the iframe to free memory once it's GCed and so on.
    // Use a setTimeout to work around bug 305471 and to spread out the CPU usage to keep Firefox responsive.
    setTimeout( function() { iframe.parentNode.removeChild(iframe); }, 1500);
  }
}

function findMainTable(doc)
{
  // posts are contained in a div#posts (very sensible)

  for (var div,i=0; div=doc.getElementsByTagName("div")[i]; ++i) {
    if (div.id == "posts") {
      return div;
    }
  }

  return null;
}

function findNextLink(doc)
{
  for (var link,i=0; link=doc.links[i]; ++i)
    if ((link.innerHTML == ">" || link.text == ">") && link.getAttribute("href").indexOf("t") != -1) {
      return link;
    }
  return null;
}

function setNextURL(doc)
{
  var nextLink = findNextLink(doc)

  if (nextLink)
    nextURL = nextLink.href;
}

// Active topics have a "Quick Reply" textarea at the bottom of each page.
// This function removes it so you only have to see the last "Quick Reply" box on the page.
function removeQuickReply(table)
{
  var lastRow = lastRowOf(table);
  if (lastRow.getElementsByTagName("textarea")[0] != null) {
    lastRow.parentNode.removeChild(lastRow);
    
    // Remove the second-to-last row too.
    var lastRow = lastRowOf(table);
    lastRow.parentNode.removeChild(lastRow);
  }
}

function lastRowOf(table)
{
  return table.tBodies[0].rows[table.tBodies[0].rows.length - 1];
}

function siphon(sourceTable, destTable)
{
  var child;
  while ((child = sourceTable.childNodes[0]))
    destTable.appendChild(child);
}