/* MIT/X Consortium License
 *
 * Copyright (c) 2011-2012 Stefan Bolte <portix@gmx.net>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

MouseAutoScroll = (function() {
  const SCROLL_ICON="transparent url(data:image/png;base64,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) no-repeat scroll center";
  const SIZE = 32;
  const OFFSET = 5;
  var doc;
  Math.sign = function(x) { return x >=0 ? 1  : -1; };
  var span = null;
  var x = 0;
  var y = 0;
  var ev = null;
  var timerId = 0;
  var cursorStyle = null;
  function startTimer() {
    timerId = window.setInterval(timer, 40);
  }
  function stopTimer () {
    window.clearInterval(timerId);
    timerId = 0;
  }
  function timer () {
    if (ev) {
      var scrollY = (ev.y - y);
      var scrollX = (ev.x - x);
      var b = scrollY > 0
        && doc.documentElement.scrollHeight == (window.innerHeight + window.pageYOffset);
      var r = scrollX > 0
        && doc.documentElement.scrollWidth == (window.innerWidth + window.pageXOffset);
      var l = scrollX < 0 && window.pageXOffset == 0;
      var t = scrollY < 0 && window.pageYOffset == 0;
      var offX = Math.abs(scrollX) < OFFSET;
      var offY = Math.abs(scrollY) < OFFSET;
      if ( timerId != 0
          && (( b && r ) || ( b && l) || ( b && offX )
            || ( t && r ) || ( t && l) || ( t && offX )
            || (offY && r) || (offY && l) )) {
              stopTimer();
              return;
            }
      window.scrollBy(scrollX - Math.sign(scrollX) * OFFSET,
          scrollY - Math.sign(scrollY) * OFFSET);
    }
  }
  function mouseMove (e) {
    if (timerId == 0) {
      startTimer();
    }
    ev = e;
  }
  function init (e) {
    doc = e.target.ownerDocument;
    if (window.innerHeight >= doc.documentElement.scrollHeight
        && window.innerWidth >= doc.documentElement.scrollWidth) {
          return;
        }
    span = doc.createElement("div");
    span.style.width = SIZE + "px";
    span.style.height = SIZE + "px";
    span.style.background = SCROLL_ICON;
    span.style.left = e.x - (SIZE / 2) + "px";
    span.style.top  = e.y - (SIZE / 2) + "px";
    span.style.position = "fixed";
    span.style.fontSize = SIZE + "px";
    span.style.opacity = 0.6;
    cursorStyle = doc.defaultView.getComputedStyle(doc.body, null).cursor;
    doc.body.style.cursor = "move";
    doc.body.appendChild(span);
    doc.addEventListener('mousemove', mouseMove, false);
    span = span;
  }
  function clear (e) {
    doc.body.style.cursor = cursorStyle;
    span.parentNode.removeChild(span);
    doc.removeEventListener('mousemove', mouseMove, false);
    stopTimer();
    if (span)
      span =  null;
    if (ev)
      ev = null;
  }
  function mouseUp (e) { /* Simulate click, click event does not work during scrolling */
    if (Math.abs(e.x - x) < 5 && Math.abs(e.y - y) < 5) {
      init(e);
      window.removeEventListener('mouseup', mouseUp, false);
    }
  }
  function mouseDown (e) {
    var t = e.target;
    if (e.button == 0) {
      if (span) {
        clear();
      }
    } else if (e.button == 1) {
      if (span) {
        clear();
      }
      else if (!t.hasAttribute("href")
          && !t.hasAttribute("onmousedown")
          && !(t.hasAttribute("onclick"))) {
        x = e.x;
        y = e.y;
        window.addEventListener('mouseup', mouseUp, false);
      }
    }
  }
  window.addEventListener('mousedown', mouseDown, false);
})();