// ==========================================================================
// Project:   metamorph
// Copyright: ©2011 My Company Inc. All rights reserved.
// ==========================================================================

(function(window) {

  var K = function(){},
      guid = 0,
      document = window.document,

      // Feature-detect the W3C range API, the extended check is for IE9 which only partially supports ranges
      supportsRange = ('createRange' in document) && (typeof Range !== 'undefined') && Range.prototype.createContextualFragment,

      // Internet Explorer prior to 9 does not allow setting innerHTML if the first element
      // is a "zero-scope" element. This problem can be worked around by making
      // the first node an invisible text node. We, like Modernizr, use ­
      needsShy = (function(){
        var testEl = document.createElement('div');
        testEl.innerHTML = "<div></div>";
        testEl.firstChild.innerHTML = "<script></script>";
        return testEl.firstChild.innerHTML === '';
      })();

  // Constructor that supports either Metamorph('foo') or new
  // Metamorph('foo');
  // 
  // Takes a string of HTML as the argument.

  var Metamorph = function(html) {
    var self;

    if (this instanceof Metamorph) {
      self = this;
    } else {
      self = new K();
    }

    self.innerHTML = html;
    var myGuid = 'metamorph-'+(guid++);
    self.start = myGuid + '-start';
    self.end = myGuid + '-end';

    return self;
  };

  K.prototype = Metamorph.prototype;

  var rangeFor, htmlFunc, removeFunc, outerHTMLFunc, appendToFunc, afterFunc, prependFunc, startTagFunc, endTagFunc;

  outerHTMLFunc = function() {
    return this.startTag() + this.innerHTML + this.endTag();
  };

  startTagFunc = function() {
    return "<script id='" + this.start + "' type='text/x-placeholder'></script>";
  };

  endTagFunc = function() {
    return "<script id='" + this.end + "' type='text/x-placeholder'></script>";
  };

  // If we have the W3C range API, this process is relatively straight forward.
  if (supportsRange) {

    // IE 9 supports ranges but doesn't define createContextualFragment
    if (!Range.prototype.createContextualFragment) {
      Range.prototype.createContextualFragment = function(html) {
        var frag = document.createDocumentFragment(),
             div = document.createElement("div");
        frag.appendChild(div);
        div.outerHTML = html;
        return frag;
      };
    }

    // Get a range for the current morph. Optionally include the starting and
    // ending placeholders.
    rangeFor = function(morph, outerToo) {
      var range = document.createRange();
      var before = document.getElementById(morph.start);
      var after = document.getElementById(morph.end);

      if (outerToo) {
        range.setStartBefore(before);
        range.setEndAfter(after);
      } else {
        range.setStartAfter(before);
        range.setEndBefore(after);
      }

      return range;
    };

    htmlFunc = function(html, outerToo) {
      // get a range for the current metamorph object
      var range = rangeFor(this, outerToo);

      // delete the contents of the range, which will be the
      // nodes between the starting and ending placeholder.
      range.deleteContents();

      // create a new document fragment for the HTML
      var fragment = range.createContextualFragment(html);

      // insert the fragment into the range
      range.insertNode(fragment);
    };

    removeFunc = function() {
      // get a range for the current metamorph object including
      // the starting and ending placeholders.
      var range = rangeFor(this, true);

      // delete the entire range.
      range.deleteContents();
    };

    appendToFunc = function(node) {
      var range = document.createRange();
      range.setStart(node);
      range.collapse(false);
      var frag = range.createContextualFragment(this.outerHTML());
      node.appendChild(frag);
    };

    afterFunc = function(html) {
      var range = document.createRange();
      var after = document.getElementById(this.end);

      range.setStartAfter(after);
      range.setEndAfter(after);

      var fragment = range.createContextualFragment(html);
      range.insertNode(fragment);
    };

    prependFunc = function(html) {
      var range = document.createRange();
      var start = document.getElementById(this.start);

      range.setStartAfter(start);
      range.setEndAfter(start);

      var fragment = range.createContextualFragment(html);
      range.insertNode(fragment);
    };

  } else {
    /**
     * This code is mostly taken from jQuery, with one exception. In jQuery's case, we
     * have some HTML and we need to figure out how to convert it into some nodes.
     *
     * In this case, jQuery needs to scan the HTML looking for an opening tag and use
     * that as the key for the wrap map. In our case, we know the parent node, and
     * can use its type as the key for the wrap map.
     **/
    var wrapMap = {
      select: [ 1, "<select multiple='multiple'>", "</select>" ],
      fieldset: [ 1, "<fieldset>", "</fieldset>" ],
      table: [ 1, "<table>", "</table>" ],
      tbody: [ 2, "<table><tbody>", "</tbody></table>" ],
      tr: [ 3, "<table><tbody><tr>", "</tr></tbody></table>" ],
      colgroup: [ 2, "<table><tbody></tbody><colgroup>", "</colgroup></table>" ],
      map: [ 1, "<map>", "</map>" ],
      _default: [ 0, "", "" ]
    };

    /**
     * Given a parent node and some HTML, generate a set of nodes. Return the first
     * node, which will allow us to traverse the rest using nextSibling.
     *
     * We need to do this because innerHTML in IE does not really parse the nodes.
     **/
    var firstNodeFor = function(parentNode, html) {
      var arr = wrapMap[parentNode.tagName.toLowerCase()] || wrapMap._default;
      var depth = arr[0], start = arr[1], end = arr[2];

      if (needsShy) { html = '&shy;'+html; }

      var element = document.createElement('div');
      element.innerHTML = start + html + end;

      for (var i=0; i<=depth; i++) {
        element = element.firstChild;
      }

      // Look for &shy; to remove it.
      if (needsShy) {
        var shyElement = element;

        // Sometimes we get nameless elements with the shy inside
        while (shyElement.nodeType === 1 && !shyElement.nodeName && shyElement.childNodes.length === 1) {
          shyElement = shyElement.firstChild;
        }

        // At this point it's the actual unicode character.
        if (shyElement.nodeType === 3 && shyElement.nodeValue.charAt(0) === "\u00AD") {
          shyElement.nodeValue = shyElement.nodeValue.slice(1);
        }
      }

      return element;
    };

    /**
     * In some cases, Internet Explorer can create an anonymous node in
     * the hierarchy with no tagName. You can create this scenario via:
     *
     *     div = document.createElement("div");
     *     div.innerHTML = "<table>&shy<script></script><tr><td>hi</td></tr></table>";
     *     div.firstChild.firstChild.tagName //=> ""
     *
     * If our script markers are inside such a node, we need to find that
     * node and use *it* as the marker.
     **/
    var realNode = function(start) {
      while (start.parentNode.tagName === "") {
        start = start.parentNode;
      }

      return start;
    };

    /**
     * When automatically adding a tbody, Internet Explorer inserts the
     * tbody immediately before the first <tr>. Other browsers create it
     * before the first node, no matter what.
     *
     * This means the the following code:
     *
     *     div = document.createElement("div");
     *     div.innerHTML = "<table><script id='first'></script><tr><td>hi</td></tr><script id='last'></script></table>
     *
     * Generates the following DOM in IE:
     *
     *     + div
     *       + table
     *         - script id='first'
     *         + tbody
     *           + tr
     *             + td
     *               - "hi"
     *           - script id='last'
     *
     * Which means that the two script tags, even though they were
     * inserted at the same point in the hierarchy in the original
     * HTML, now have different parents.
     *
     * This code reparents the first script tag by making it the tbody's
     * first child.
     **/
    var fixParentage = function(start, end) {
      if (start.parentNode !== end.parentNode) {
        end.parentNode.insertBefore(start, end.parentNode.firstChild);
      }
    };

    htmlFunc = function(html, outerToo) {
      // get the real starting node. see realNode for details.
      var start = realNode(document.getElementById(this.start));
      var end = document.getElementById(this.end);
      var parentNode = end.parentNode;
      var node, nextSibling, last;

      // make sure that the start and end nodes share the same
      // parent. If not, fix it.
      fixParentage(start, end);

      // remove all of the nodes after the starting placeholder and
      // before the ending placeholder.
      node = start.nextSibling;
      while (node) {
        nextSibling = node.nextSibling;
        last = node === end;

        // if this is the last node, and we want to remove it as well,
        // set the `end` node to the next sibling. This is because
        // for the rest of the function, we insert the new nodes
        // before the end (note that insertBefore(node, null) is
        // the same as appendChild(node)).
        //
        // if we do not want to remove it, just break.
        if (last) {
          if (outerToo) { end = node.nextSibling; } else { break; }
        }

        node.parentNode.removeChild(node);

        // if this is the last node and we didn't break before
        // (because we wanted to remove the outer nodes), break
        // now.
        if (last) { break; }

        node = nextSibling;
      }

      // get the first node for the HTML string, even in cases like
      // tables and lists where a simple innerHTML on a div would
      // swallow some of the content.
      node = firstNodeFor(start.parentNode, html);

      // copy the nodes for the HTML between the starting and ending
      // placeholder.
      while (node) {
        nextSibling = node.nextSibling;
        parentNode.insertBefore(node, end);
        node = nextSibling;
      }
    };

    // remove the nodes in the DOM representing this metamorph.
    //
    // this includes the starting and ending placeholders.
    removeFunc = function() {
      var start = realNode(document.getElementById(this.start));
      var end = document.getElementById(this.end);

      this.html('');
      start.parentNode.removeChild(start);
      end.parentNode.removeChild(end);
    };

    appendToFunc = function(parentNode) {
      var node = firstNodeFor(parentNode, this.outerHTML());

      while (node) {
        nextSibling = node.nextSibling;
        parentNode.appendChild(node);
        node = nextSibling;
      }
    };

    afterFunc = function(html) {
      // get the real starting node. see realNode for details.
      var end = document.getElementById(this.end);
      var parentNode = end.parentNode;
      var nextSibling;
      var node;

      // get the first node for the HTML string, even in cases like
      // tables and lists where a simple innerHTML on a div would
      // swallow some of the content.
      node = firstNodeFor(parentNode, html);

      // copy the nodes for the HTML between the starting and ending
      // placeholder.
      while (node) {
        nextSibling = node.nextSibling;
        parentNode.insertBefore(node, end.nextSibling);
        node = nextSibling;
      }
    };

    prependFunc = function(html) {
      var start = document.getElementById(this.start);
      var parentNode = start.parentNode;
      var nextSibling;
      var node;

      node = firstNodeFor(parentNode, html);
      var insertBefore = start.nextSibling;

      while (node) {
        nextSibling = node.nextSibling;
        parentNode.insertBefore(node, insertBefore);
        node = nextSibling;
      }
    }
  }

  Metamorph.prototype.html = function(html) {
    this.checkRemoved();
    if (html === undefined) { return this.innerHTML; }

    htmlFunc.call(this, html);

    this.innerHTML = html;
  };

  Metamorph.prototype.replaceWith = function(html) {
    this.checkRemoved();
    htmlFunc.call(this, html, true);
  };

  Metamorph.prototype.remove = removeFunc;
  Metamorph.prototype.outerHTML = outerHTMLFunc;
  Metamorph.prototype.appendTo = appendToFunc;
  Metamorph.prototype.after = afterFunc;
  Metamorph.prototype.prepend = prependFunc;
  Metamorph.prototype.startTag = startTagFunc;
  Metamorph.prototype.endTag = endTagFunc;

  Metamorph.prototype.isRemoved = function() {
    var before = document.getElementById(this.start);
    var after = document.getElementById(this.end);

    return !before || !after;
  };

  Metamorph.prototype.checkRemoved = function() {
    if (this.isRemoved()) {
      throw new Error("Cannot perform operations on a Metamorph that is not in the DOM.");
    }
  };

  window.Metamorph = Metamorph;
})(this);