/**
 * hashgrid (jQuery version)
 * http://github.com/dotjay/hashgrid
 * Version 4, 29 Mar 2010
 * By Jon Gibbins, accessibility.co.uk
 *
 * // Using a basic #grid setup
 * var grid = new hashgrid();
 *
 * // Using #grid with a custom id (e.g. #mygrid)
 * var grid = new hashgrid("mygrid");
 *
 * // Using #grid with additional options
 * var grid = new hashgrid({
 *     id: 'mygrid',            // id for the grid container
 *     modifierKey: 'alt',      // optional 'ctrl', 'alt' or 'shift'
 *     showGridKey: 's',        // key to show the grid
 *     holdGridKey: 'enter',    // key to hold the grid in place
 *     foregroundKey: 'f',      // key to toggle foreground/background
 *     jumpGridsKey: 'd',       // key to cycle through the grid classes
 *     numberOfGrids: 2,        // number of grid classes used
 *     classPrefix: 'class',    // prefix for the grid classes
 *     cookiePrefix: 'mygrid'   // prefix for the cookie name
 * });
 */


/**
 * You can call hashgrid from your own code, but it's loaded here by
 * default for convenience.
 */
$(document).ready(function() {

  var grid = new hashgrid({
    numberOfGrids: 1
  });

});


/**
 * hashgrid overlay
 */
var hashgrid = function(set) {

  var options = {
    id: 'grid',             // id for the grid container
    modifierKey: null,      // optional 'ctrl', 'alt' or 'shift'
    showGridKey: 'g',       // key to show the grid
    holdGridKey: 'h',       // key to hold the grid in place
    foregroundKey: 'f',     // key to toggle foreground/background
    jumpGridsKey: 'j',      // key to cycle through the grid classes
    numberOfGrids: 1,       // number of grid classes used
    classPrefix: 'grid-',   // prefix for the grid classes
    cookiePrefix: 'hashgrid'// prefix for the cookie name
  };
  var overlayOn = false,
    sticky = false,
    overlayZState = 'B',
    overlayZBackground = -1,
    overlayZForeground = 9999,
    classNumber = 1;

  // Apply options
  if (typeof set == 'object') {
    var k;
    for (k in set) options[k] = set[k];
  }
  else if (typeof set == 'string') {
    options.id = set;
  }

  // Remove any conflicting overlay
  if ($('#' + options.id).length > 0) {
    $('#' + options.id).remove();
  }

  // Create overlay, hidden before adding to DOM
  var overlayEl = $('<div></div>');
  overlayEl
    .attr('id', options.id)
    .css('display', 'none');
  $("body").prepend(overlayEl);
  var overlay = $('#' + options.id);

  // Unless a custom z-index is set, ensure the overlay will be behind everything
  if (overlay.css('z-index') == 'auto') overlay.css('z-index', overlayZBackground);

  // Override the default overlay height with the actual page height
  var pageHeight = parseFloat($(document).height());
  overlay.height(pageHeight);

  // Add the first grid line so that we can measure it
  overlay.append('<div class="horiz first-line">');

  // Calculate the number of grid lines needed
  var overlayGridLines = overlay.children('.horiz'),
    overlayGridLineHeight = parseFloat(overlayGridLines.css('height')) + parseFloat(overlayGridLines.css('border-bottom-width'));

  // Break on zero line height
  if (overlayGridLineHeight <= 0) return true;

  // Add the remaining grid lines
  var i, numGridLines = Math.floor(pageHeight / overlayGridLineHeight);
  for (i = numGridLines - 1; i >= 1; i--) {
    overlay.append('<div class="horiz"></div>');
  }

  // Check for saved state
  var overlayCookie = readCookie(options.cookiePrefix + options.id);
  if (typeof overlayCookie == 'string') {
    var state = overlayCookie.split(',');
    state[2] = Number(state[2]);
    if ((typeof state[2] == 'number') && !isNaN(state[2])) {
      classNumber = state[2].toFixed(0);
      overlay.addClass(options.classPrefix + classNumber);
    }
    if (state[1] == 'F') {
      overlayZState = 'F';
      overlay.css('z-index', overlayZForeground);
    }
    if (state[0] == '1') {
      overlayOn = true;
      sticky = true;
      overlay.show();
    }
  }
  else {
    overlay.addClass(options.classPrefix + classNumber)
  }

  // Keyboard controls
  $(document).bind('keydown', keydownHandler);
  $(document).bind('keyup', keyupHandler);

  /**
   * Helpers
   */

  function getModifier(e) {
    if (options.modifierKey == null) return true; // Bypass by default
    var m = true;
    switch(options.modifierKey) {
      case 'ctrl':
        m = (e.ctrlKey ? e.ctrlKey : false);
        break;

      case 'alt':
        m = (e.altKey ? e.altKey : false);
        break;

      case 'shift':
        m = (e.shiftKey ? e.shiftKey : false);
        break;
    }
    return m;
  }

  function getKey(e) {
    var k = false, c = (e.keyCode ? e.keyCode : e.which);
    // Handle keywords
    if (c == 13) k = 'enter';
    // Handle letters
    else k = String.fromCharCode(c).toLowerCase();
    return k;
  }

  function saveState() {
    createCookie(options.cookiePrefix + options.id, (sticky ? '1' : '0') + ',' + overlayZState + ',' + classNumber, 1);
  }

  /**
   * Event handlers
   */

  function keydownHandler(e) {
    var source = e.target.tagName.toLowerCase();
    if ((source == 'input') || (source == 'textarea') || (source == 'select')) return true;
    var m = getModifier(e);
    if (!m) return true;
    var k = getKey(e);
    if (!k) return true;
    switch(k) {
      case options.showGridKey:
        if (!overlayOn) {
          overlay.show();
          overlayOn = true;
        }
        else if (sticky) {
          overlay.hide();
          overlayOn = false;
          sticky = false;
          saveState();
        }
        break;
      case options.holdGridKey:
        if (overlayOn && !sticky) {
          // Turn sticky overlay on
          sticky = true;
          saveState();
        }
        break;
      case options.foregroundKey:
        if (overlayOn) {
          // Toggle sticky overlay z-index
          if (overlay.css('z-index') == overlayZForeground) {
            overlay.css('z-index', overlayZBackground);
            overlayZState = 'B';
          }
          else {
            overlay.css('z-index', overlayZForeground);
            overlayZState = 'F';
          }
          saveState();
        }
        break;
      case options.jumpGridsKey:
        if (overlayOn && (options.numberOfGrids > 1)) {
          // Cycle through the available grids
          overlay.removeClass(options.classPrefix + classNumber);
          classNumber++;
          if (classNumber > options.numberOfGrids) classNumber = 1;
          overlay.addClass(options.classPrefix + classNumber);
          if (/webkit/.test( navigator.userAgent.toLowerCase() )) {
            forceRepaint();
          }
          saveState();
        }
        break;
    }
  }

  function keyupHandler(e) {
    var m = getModifier(e);
    if (!m) return true;
    var k = getKey(e);
    if (!k) return true;
    if ((k == options.showGridKey) && !sticky) {
      overlay.hide();
      overlayOn = false;
    }
  }

}


/**
 * Cookie functions
 *
 * By Peter-Paul Koch:
 * http://www.quirksmode.org/js/cookies.html
 */
function createCookie(name,value,days) {
  if (days) {
    var date = new Date();
    date.setTime(date.getTime()+(days*24*60*60*1000));
    var expires = "; expires="+date.toGMTString();
  }
  else var expires = "";
  document.cookie = name+"="+value+expires+"; path=/";
}

function readCookie(name) {
  var nameEQ = name + "=";
  var ca = document.cookie.split(';');
  for(var i=0;i < ca.length;i++) {
    var c = ca[i];
    while (c.charAt(0)==' ') c = c.substring(1,c.length);
    if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
  }
  return null;
}

function eraseCookie(name) {
  createCookie(name,"",-1);
}


/**
 * Forces a repaint (because WebKit has issues)
 * http://www.sitepoint.com/forums/showthread.php?p=4538763
 * http://www.phpied.com/the-new-game-show-will-it-reflow/
 */
function forceRepaint() {
  var ss = document.styleSheets[0];
  try {
    ss.addRule('.xxxxxx', 'position: relative');
    ss.removeRule(ss.rules.length - 1);
  } catch(e){}
}