/***
 * A convenient way to create DOM elements. ('cls' will be
 * automatically expanded to 'class', since 'class' may not appear as
 * a key of an object, even in quotes, in Safari.)
 *
 * DIV({cls: "mydiv", style: "color: blue;"}, [
 *   "Some text",
 *   A({href: "/some/location"}, ["A link"]),
 *   DIV({cls: "emptydiv"}),
 *   // if an object is inserted, the value of its 'element'
 *   // attribute will be used
 *   myView,
 *   DIV([
 *     "Both the attributes and the contents are optional",
 *     ["Lists", "are", "flattened"]
 *   })
 * ]);
 */

// XXX find a place to document the contract for *View classes -- they
// should have an attribute named 'element'

// XXX consider not requiring the contents to be wrapped in an
// array. eg: DIV({stuff: 12}, "thing1", "thing2"). backwards
// compatible with current behavior due to array flattening. could
// eliminate spurious wrapper div inserted by Layout.TwoColumnsFixedRight

// XXX allow style to be set as an object

var event_names = {
  blur: true,
  change: true,
  click: true,
  dblclick: true,
  error: true,
  focus: true,
  focusin: true,
  focusout: true,
  keydown: true,
  keypress: true,
  keyup: true,
  load: true,
  mousedown: true,
  mouseenter: true,
  mouseleave: true,
  mousemove: true,
  mouseout: true,
  mouseover: true,
  mouseup: true,
  resize: true,
  scroll: true,
  select: true,
  submit: true
};

var testDiv = document.createElement("div");
testDiv.innerHTML = '<a style="top:1px">a</a>';
var styleGetSetSupport = /top/.test(testDiv.firstChild.getAttribute("style"));

// All HTML4 elements, excluding deprecated elements
// http://www.w3.org/TR/html4/index/elements.html
// also excluding the following elements that seem unlikely to be
// used in the body:
// HEAD, HTML, LINK, MAP, META, NOFRAMES, NOSCRIPT, STYLE, TITLE
var tag_names =
  ('A ABBR ACRONYM B BDO BIG BLOCKQUOTE BR BUTTON CAPTION CITE CODE COL ' +
   'COLGROUP DD DEL DFN DIV DL DT EM FIELDSET FORM H1 H2 H3 H4 H5 H6 HR ' +
   'I IFRAME IMG INPUT INS KBD LABEL LEGEND LI OBJECT OL OPTGROUP OPTION ' +
   'P PARAM PRE Q S SAMP SCRIPT SELECT SMALL SPAN STRIKE STRONG SUB SUP ' +
   'TABLE TBODY TD TEXTAREA TFOOT TH THEAD TR TT U UL VAR').split(' ');

_.each(tag_names, function (tag) {
  var f = function (arg1, arg2) {
    var attrs, contents;
    if (arg2) {
      attrs = arg1;
      contents = arg2;
    } else {
      if (arg1 instanceof Array) {
        attrs = {};
        contents = arg1;
      } else {
        attrs = arg1;
        contents = [];
      }
    }
    var elt = document.createElement(tag);
    for (var a in attrs) {
      if (a === 'cls')
        elt.setAttribute('class', attrs[a]);
      else if (a === '_for')
        elt.setAttribute('for', attrs[a]);
      else if (a === 'style' && ! styleGetSetSupport)
        elt.style.cssText = String(attrs[a]);
      else if (event_names[a]) {
        if (typeof $ === "undefined")
          throw new Error("Event binding is supported only if " +
                          "jQuery or similar is available");
        ($(elt)[a])(attrs[a]);
      }
      else
        elt.setAttribute(a, attrs[a]);
    }
    var addChildren = function (children) {
      for (var i = 0; i < children.length; i++) {
        var c = children[i];
        if (!c && c !== '')
          throw new Error("Bad value for element body: " + c);
        else if (c instanceof Array)
          addChildren(c);
        else if (typeof c === "string")
          elt.appendChild(document.createTextNode(c));
        else if ('element' in c)
          addChildren([c.element]);
        else
          elt.appendChild(c);
      };
    };
    addChildren(contents);
    return elt;
  };
  // Put the function onto the package-scope variable with this name.
  eval(tag + " = f;");
});