Add initial SkyElement & city-list example

sky/framework/sky-element/TemplateBinding.sky

+<!--
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+-->
+<link rel="import" href="observe.sky" as="observe" />
+
+<script>
+Node.prototype.bind = function(name, observable, oneTime) {
+  var self = this;
+
+  if (oneTime) {
+    this[name] = observable;
+    return;
+  }
+
+  observable.open(function(value) {
+    self[name] = value;
+  });
+
+  return observable;
+};
+
+function sanitizeValue(value) {
+  return value == null ? '' : value;
+}
+
+function updateText(node, value) {
+  node.data = sanitizeValue(value);
+}
+
+function textBinding(node) {
+  return function(value) {
+    return updateText(node, value);
+  };
+}
+
+Text.prototype.bind = function(name, value, oneTime) {
+  if (name !== 'textContent')
+    return Node.prototype.bind.call(this, name, value, oneTime);
+
+  if (oneTime)
+    return updateText(this, value);
+
+  var observable = value;
+  updateText(this, observable.open(textBinding(this)));
+  return observable;
+}
+
+function updateAttribute(el, name, value) {
+  el.setAttribute(name, sanitizeValue(value));
+}
+
+function attributeBinding(el, name) {
+  return function(value) {
+    updateAttribute(el, name, value);
+  };
+}
+
+Element.prototype.bind = function(name, value, oneTime) {
+  if (name !== 'style' && name !== 'class')
+    return Node.prototype.bind.call(this, name, value, oneTime);
+
+  if (oneTime)
+    return updateAttribute(this, name, value);
+
+  var observable = value;
+  updateAttribute(this, name, observable.open(attributeBinding(this, name)));
+  return observable;
+}
+
+function getFragmentRoot(node) {
+  var p;
+  while (p = node.parentNode) {
+    node = p;
+  }
+
+  return node;
+}
+
+function searchRefId(node, id) {
+  if (!id)
+    return;
+
+  var ref;
+  var selector = '#' + id;
+  while (!ref) {
+    node = getFragmentRoot(node);
+
+    if (node.protoContent_)
+      ref = node.protoContent_.querySelector(selector);
+    else if (node.getElementById)
+      ref = node.getElementById(id);
+
+    if (ref || !node.templateCreator_)
+      break
+
+    node = node.templateCreator_;
+  }
+
+  return ref;
+}
+
+function getInstanceRoot(node) {
+  while (node.parentNode) {
+    node = node.parentNode;
+  }
+  return node.templateCreator_ ? node : null;
+}
+
+var BIND = 'bind';
+var REPEAT = 'repeat';
+var IF = 'if';
+
+var templateAttributeDirectives = {
+  'template': true,
+  'repeat': true,
+  'bind': true,
+  'ref': true
+};
+
+function isTemplate(el) {
+  if (el.isTemplate_ === undefined)
+    el.isTemplate_ = el.tagName == 'TEMPLATE';
+
+  return el.isTemplate_;
+}
+
+function mixin(to, from) {
+  Object.getOwnPropertyNames(from).forEach(function(name) {
+    Object.defineProperty(to, name,
+                          Object.getOwnPropertyDescriptor(from, name));
+  });
+}
+
+function getTemplateStagingDocument(template) {
+  if (!template.stagingDocument_) {
+    var owner = template.ownerDocument;
+    if (!owner.stagingDocument_) {
+      owner.stagingDocument_ = owner.implementation.createDocument('');
+      owner.stagingDocument_.isStagingDocument = true;
+      owner.stagingDocument_.stagingDocument_ = owner.stagingDocument_;
+    }
+
+    template.stagingDocument_ = owner.stagingDocument_;
+  }
+
+  return template.stagingDocument_;
+}
+
+var templateObserver;
+if (typeof MutationObserver == 'function') {
+  templateObserver = new MutationObserver(function(records) {
+    for (var i = 0; i < records.length; i++) {
+      records[i].target.refChanged_();
+    }
+  });
+}
+
+var contentDescriptor = {
+  get: function() {
+    return this.content_;
+  },
+  enumerable: true,
+  configurable: true
+};
+
+function ensureSetModelScheduled(template) {
+  if (!template.setModelFn_) {
+    template.setModelFn_ = function() {
+      template.setModelFnScheduled_ = false;
+      var map = getBindings(template,
+          template.delegate_ && template.delegate_.prepareBinding);
+      processBindings(template, map, template.model_);
+    };
+  }
+
+  if (!template.setModelFnScheduled_) {
+    template.setModelFnScheduled_ = true;
+    Observer.runEOM_(template.setModelFn_);
+  }
+}
+
+mixin(HTMLTemplateElement.prototype, {
+  bind: function(name, value, oneTime) {
+    if (name != 'ref')
+      return Element.prototype.bind.call(this, name, value, oneTime);
+
+    var self = this;
+    var ref = oneTime ? value : value.open(function(ref) {
+      self.setAttribute('ref', ref);
+      self.refChanged_();
+    });
+
+    this.setAttribute('ref', ref);
+    this.refChanged_();
+    if (oneTime)
+      return;
+
+    if (!this.bindings_) {
+      this.bindings_ = { ref: value };
+    } else {
+      this.bindings_.ref = value;
+    }
+
+    return value;
+  },
+
+  processBindingDirectives_: function(directives) {
+    if (this.iterator_)
+      this.iterator_.closeDeps();
+
+    if (!directives.if && !directives.bind && !directives.repeat) {
+      if (this.iterator_) {
+        this.iterator_.close();
+        this.iterator_ = undefined;
+      }
+
+      return;
+    }
+
+    if (!this.iterator_) {
+      this.iterator_ = new TemplateIterator(this);
+    }
+
+    this.iterator_.updateDependencies(directives, this.model_);
+
+    if (templateObserver) {
+      templateObserver.observe(this, { attributes: true,
+                                       attributeFilter: ['ref'] });
+    }
+
+    return this.iterator_;
+  },
+
+  createInstance: function(model, bindingDelegate, delegate_) {
+    if (bindingDelegate)
+      delegate_ = this.newDelegate_(bindingDelegate);
+    else if (!delegate_)
+      delegate_ = this.delegate_;
+
+    if (!this.refContent_)
+      this.refContent_ = this.ref_.content;
+    var content = this.refContent_;
+    if (content.firstChild === null)
+      return emptyInstance;
+
+    var map = getInstanceBindingMap(content, delegate_);
+    var stagingDocument = getTemplateStagingDocument(this);
+    var instance = stagingDocument.createDocumentFragment();
+    instance.templateCreator_ = this;
+    instance.protoContent_ = content;
+    instance.bindings_ = [];
+    instance.terminator_ = null;
+    var instanceRecord = instance.templateInstance_ = {
+      firstNode: null,
+      lastNode: null,
+      model: model
+    };
+
+    var i = 0;
+    var collectTerminator = false;
+    for (var child = content.firstChild; child; child = child.nextSibling) {
+      // The terminator of the instance is the clone of the last child of the
+      // content. If the last child is an active template, it may produce
+      // instances as a result of production, so simply collecting the last
+      // child of the instance after it has finished producing may be wrong.
+      if (child.nextSibling === null)
+        collectTerminator = true;
+
+      var clone = cloneAndBindInstance(child, instance, stagingDocument,
+                                       map.children[i++],
+                                       model,
+                                       delegate_,
+                                       instance.bindings_);
+      clone.templateInstance_ = instanceRecord;
+      if (collectTerminator)
+        instance.terminator_ = clone;
+    }
+
+    instanceRecord.firstNode = instance.firstChild;
+    instanceRecord.lastNode = instance.lastChild;
+    instance.templateCreator_ = undefined;
+    instance.protoContent_ = undefined;
+    return instance;
+  },
+
+  get model() {
+    return this.model_;
+  },
+
+  set model(model) {
+    this.model_ = model;
+    ensureSetModelScheduled(this);
+  },
+
+  get bindingDelegate() {
+    return this.delegate_ && this.delegate_.raw;
+  },
+
+  refChanged_: function() {
+    if (!this.iterator_ || this.refContent_ === this.ref_.content)
+      return;
+
+    this.refContent_ = undefined;
+    this.iterator_.valueChanged();
+    this.iterator_.updateIteratedValue(this.iterator_.getUpdatedValue());
+  },
+
+  clear: function() {
+    this.model_ = undefined;
+    this.delegate_ = undefined;
+    if (this.bindings_ && this.bindings_.ref)
+      this.bindings_.ref.close()
+    this.refContent_ = undefined;
+    if (!this.iterator_)
+      return;
+    this.iterator_.valueChanged();
+    this.iterator_.close()
+    this.iterator_ = undefined;
+  },
+
+  setDelegate_: function(delegate) {
+    this.delegate_ = delegate;
+    this.bindingMap_ = undefined;
+    if (this.iterator_) {
+      this.iterator_.instancePositionChangedFn_ = undefined;
+      this.iterator_.instanceModelFn_ = undefined;
+    }
+  },
+
+  newDelegate_: function(bindingDelegate) {
+    if (!bindingDelegate)
+      return;
+
+    function delegateFn(name) {
+      var fn = bindingDelegate && bindingDelegate[name];
+      if (typeof fn != 'function')
+        return;
+
+      return function() {
+        return fn.apply(bindingDelegate, arguments);
+      };
+    }
+
+    return {
+      bindingMaps: {},
+      raw: bindingDelegate,
+      prepareBinding: delegateFn('prepareBinding'),
+      prepareInstanceModel: delegateFn('prepareInstanceModel'),
+      prepareInstancePositionChanged:
+          delegateFn('prepareInstancePositionChanged')
+    };
+  },
+
+  set bindingDelegate(bindingDelegate) {
+    if (this.delegate_) {
+      throw Error('Template must be cleared before a new bindingDelegate ' +
+                  'can be assigned');
+    }
+
+    this.setDelegate_(this.newDelegate_(bindingDelegate));
+  },
+
+  get ref_() {
+    var ref = searchRefId(this, this.getAttribute('ref'));
+    if (!ref)
+      ref = this.instanceRef_;
+
+    if (!ref)
+      return this;
+
+    var nextRef = ref.ref_;
+    return nextRef ? nextRef : ref;
+  }
+});
+
+// Returns
+//   a) undefined if there are no mustaches.
+//   b) [TEXT, (ONE_TIME?, PATH, DELEGATE_FN, TEXT)+] if there is at least
+//      one mustache.
+function parseMustaches(s, name, node, prepareBindingFn) {
+  if (!s || !s.length)
+    return;
+
+  var tokens;
+  var length = s.length;
+  var startIndex = 0, lastIndex = 0, endIndex = 0;
+  var onlyOneTime = true;
+  while (lastIndex < length) {
+    var startIndex = s.indexOf('{{', lastIndex);
+    var oneTimeStart = s.indexOf('[[', lastIndex);
+    var oneTime = false;
+    var terminator = '}}';
+
+    if (oneTimeStart >= 0 &&
+        (startIndex < 0 || oneTimeStart < startIndex)) {
+      startIndex = oneTimeStart;
+      oneTime = true;
+      terminator = ']]';
+    }
+
+    endIndex = startIndex < 0 ? -1 : s.indexOf(terminator, startIndex + 2);
+
+    if (endIndex < 0) {
+      if (!tokens)
+        return;
+
+      tokens.push(s.slice(lastIndex)); // TEXT
+      break;
+    }
+
+    tokens = tokens || [];
+    tokens.push(s.slice(lastIndex, startIndex)); // TEXT
+    var pathString = s.slice(startIndex + 2, endIndex).trim();
+    tokens.push(oneTime); // ONE_TIME?
+    onlyOneTime = onlyOneTime && oneTime;
+    var delegateFn = prepareBindingFn &&
+                     prepareBindingFn(pathString, name, node);
+    // Don't try to parse the expression if there's a prepareBinding function
+    if (delegateFn == null) {
+      tokens.push(observe.Path.get(pathString)); // PATH
+    } else {
+      tokens.push(null);
+    }
+    tokens.push(delegateFn); // DELEGATE_FN
+    lastIndex = endIndex + 2;
+  }
+
+  if (lastIndex === length)
+    tokens.push(''); // TEXT
+
+  tokens.hasOnePath = tokens.length === 5;
+  tokens.isSimplePath = tokens.hasOnePath &&
+                        tokens[0] == '' &&
+                        tokens[4] == '';
+  tokens.onlyOneTime = onlyOneTime;
+
+  tokens.combinator = function(values) {
+    var newValue = tokens[0];
+
+    for (var i = 1; i < tokens.length; i += 4) {
+      var value = tokens.hasOnePath ? values : values[(i - 1) / 4];
+      if (value !== undefined)
+        newValue += value;
+      newValue += tokens[i + 3];
+    }
+
+    return newValue;
+  }
+
+  return tokens;
+};
+
+function processOneTimeBinding(name, tokens, node, model) {
+  if (tokens.hasOnePath) {
+    var delegateFn = tokens[3];
+    var value = delegateFn ? delegateFn(model, node, true) :
+                             tokens[2].getValueFrom(model);
+    return tokens.isSimplePath ? value : tokens.combinator(value);
+  }
+
+  var values = [];
+  for (var i = 1; i < tokens.length; i += 4) {
+    var delegateFn = tokens[i + 2];
+    values[(i - 1) / 4] = delegateFn ? delegateFn(model, node) :
+        tokens[i + 1].getValueFrom(model);
+  }
+
+  return tokens.combinator(values);
+}
+
+function processSinglePathBinding(name, tokens, node, model) {
+  var delegateFn = tokens[3];
+  var observer = delegateFn ? delegateFn(model, node, false) :
+      new observe.PathObserver(model, tokens[2]);
+
+  return tokens.isSimplePath ? observer :
+      new observe.ObserverTransform(observer, tokens.combinator);
+}
+
+function processBinding(name, tokens, node, model) {
+  if (tokens.onlyOneTime)
+    return processOneTimeBinding(name, tokens, node, model);
+
+  if (tokens.hasOnePath)
+    return processSinglePathBinding(name, tokens, node, model);
+
+  var observer = new observe.CompoundObserver();
+
+  for (var i = 1; i < tokens.length; i += 4) {
+    var oneTime = tokens[i];
+    var delegateFn = tokens[i + 2];
+
+    if (delegateFn) {
+      var value = delegateFn(model, node, oneTime);
+      if (oneTime)
+        observer.addPath(value)
+      else
+        observer.addObserver(value);
+      continue;
+    }
+
+    var path = tokens[i + 1];
+    if (oneTime)
+      observer.addPath(path.getValueFrom(model))
+    else
+      observer.addPath(model, path);
+  }
+
+  return new observe.ObserverTransform(observer, tokens.combinator);
+}
+
+function processBindings(node, bindings, model, instanceBindings) {
+  for (var i = 0; i < bindings.length; i += 2) {
+    var name = bindings[i]
+    var tokens = bindings[i + 1];
+    var value = processBinding(name, tokens, node, model);
+    var binding = node.bind(name, value, tokens.onlyOneTime);
+    if (binding && instanceBindings)
+      instanceBindings.push(binding);
+  }
+
+  if (!bindings.isTemplate)
+    return;
+
+  node.model_ = model;
+  var iter = node.processBindingDirectives_(bindings);
+  if (instanceBindings && iter)
+    instanceBindings.push(iter);
+}
+
+function parseWithDefault(el, name, prepareBindingFn) {
+  var v = el.getAttribute(name);
+  return parseMustaches(v == '' ? '{{}}' : v, name, el, prepareBindingFn);
+}
+
+function parseAttributeBindings(element, prepareBindingFn) {
+  var bindings = [];
+  var ifFound = false;
+  var bindFound = false;
+
+  for (var i = 0; i < element.attributes.length; i++) {
+    var attr = element.attributes[i];
+    var name = attr.name;
+    var value = attr.value;
+
+    if (isTemplate(element) &&
+        (name === IF || name === BIND || name === REPEAT)) {
+      continue;
+    }
+
+    var tokens = parseMustaches(value, name, element,
+                                prepareBindingFn);
+    if (!tokens)
+      continue;
+
+    bindings.push(name, tokens);
+  }
+
+  if (isTemplate(element)) {
+    bindings.isTemplate = true;
+    bindings.if = parseWithDefault(element, IF, prepareBindingFn);
+    bindings.bind = parseWithDefault(element, BIND, prepareBindingFn);
+    bindings.repeat = parseWithDefault(element, REPEAT, prepareBindingFn);
+
+    if (bindings.if && !bindings.bind && !bindings.repeat)
+      bindings.bind = parseMustaches('{{}}', BIND, element, prepareBindingFn);
+  }
+
+  return bindings;
+}
+
+function getBindings(node, prepareBindingFn) {
+  if (node instanceof Element) {
+    return parseAttributeBindings(node, prepareBindingFn);
+  }
+
+  if (node instanceof Text) {
+    var tokens = parseMustaches(node.data, 'textContent', node,
+                                prepareBindingFn);
+    if (tokens)
+      return ['textContent', tokens];
+  }
+
+  return [];
+}
+
+function cloneAndBindInstance(node, parent, stagingDocument, bindings, model,
+                              delegate,
+                              instanceBindings,
+                              instanceRecord) {
+  var clone = parent.appendChild(stagingDocument.importNode(node, false));
+
+  var i = 0;
+  for (var child = node.firstChild; child; child = child.nextSibling) {
+    cloneAndBindInstance(child, clone, stagingDocument,
+                          bindings.children[i++],
+                          model,
+                          delegate,
+                          instanceBindings);
+  }
+
+  if (bindings.isTemplate) {
+    clone.instanceRef_ = node;
+
+    if (delegate)
+      clone.setDelegate_(delegate);
+  }
+
+  processBindings(clone, bindings, model, instanceBindings);
+  return clone;
+}
+
+function createInstanceBindingMap(node, prepareBindingFn) {
+  var map = getBindings(node, prepareBindingFn);
+  map.children = {};
+  var index = 0;
+  for (var child = node.firstChild; child; child = child.nextSibling) {
+    map.children[index++] = createInstanceBindingMap(child, prepareBindingFn);
+  }
+
+  return map;
+}
+
+var contentUidCounter = 1;
+
+// TODO(rafaelw): Setup a MutationObserver on content which clears the id
+// so that bindingMaps regenerate when the template.content changes.
+function getContentUid(content) {
+  var id = content.id_;
+  if (!id)
+    id = content.id_ = contentUidCounter++;
+  return id;
+}
+
+// Each delegate is associated with a set of bindingMaps, one for each
+// content which may be used by a template. The intent is that each binding
+// delegate gets the opportunity to prepare the instance (via the prepare*
+// delegate calls) once across all uses.
+// TODO(rafaelw): Separate out the parse map from the binding map. In the
+// current implementation, if two delegates need a binding map for the same
+// content, the second will have to reparse.
+function getInstanceBindingMap(content, delegate_) {
+  var contentId = getContentUid(content);
+  if (delegate_) {
+    var map = delegate_.bindingMaps[contentId];
+    if (!map) {
+      map = delegate_.bindingMaps[contentId] =
+          createInstanceBindingMap(content, delegate_.prepareBinding) || [];
+    }
+    return map;
+  }
+
+  var map = content.bindingMap_;
+  if (!map) {
+    map = content.bindingMap_ =
+        createInstanceBindingMap(content, undefined) || [];
+  }
+  return map;
+}
+
+Object.defineProperty(Node.prototype, 'templateInstance', {
+  get: function() {
+    var instance = this.templateInstance_;
+    return instance ? instance :
+        (this.parentNode ? this.parentNode.templateInstance : undefined);
+  }
+});
+
+var emptyInstance = document.createDocumentFragment();
+emptyInstance.bindings_ = [];
+emptyInstance.terminator_ = null;
+
+function TemplateIterator(templateElement) {
+  this.closed = false;
+  this.templateElement_ = templateElement;
+  this.instances = [];
+  this.deps = undefined;
+  this.iteratedValue = [];
+  this.presentValue = undefined;
+  this.arrayObserver = undefined;
+}
+
+TemplateIterator.prototype = {
+  closeDeps: function() {
+    var deps = this.deps;
+    if (deps) {
+      if (deps.ifOneTime === false)
+        deps.ifValue.close();
+      if (deps.oneTime === false)
+        deps.value.close();
+    }
+  },
+
+  updateDependencies: function(directives, model) {
+    this.closeDeps();
+
+    var deps = this.deps = {};
+    var template = this.templateElement_;
+
+    var ifValue = true;
+    if (directives.if) {
+      deps.hasIf = true;
+      deps.ifOneTime = directives.if.onlyOneTime;
+      deps.ifValue = processBinding(IF, directives.if, template, model);
+
+      ifValue = deps.ifValue;
+
+      // oneTime if & predicate is false. nothing else to do.
+      if (deps.ifOneTime && !ifValue) {
+        this.valueChanged();
+        return;
+      }
+
+      if (!deps.ifOneTime)
+        ifValue = ifValue.open(this.updateIfValue, this);
+    }
+
+    if (directives.repeat) {
+      deps.repeat = true;
+      deps.oneTime = directives.repeat.onlyOneTime;
+      deps.value = processBinding(REPEAT, directives.repeat, template, model);
+    } else {
+      deps.repeat = false;
+      deps.oneTime = directives.bind.onlyOneTime;
+      deps.value = processBinding(BIND, directives.bind, template, model);
+    }
+
+    var value = deps.value;
+    if (!deps.oneTime)
+      value = value.open(this.updateIteratedValue, this);
+
+    if (!ifValue) {
+      this.valueChanged();
+      return;
+    }
+
+    this.updateValue(value);
+  },
+
+  /**
+   * Gets the updated value of the bind/repeat. This can potentially call
+   * user code (if a bindingDelegate is set up) so we try to avoid it if we
+   * already have the value in hand (from Observer.open).
+   */
+  getUpdatedValue: function() {
+    var value = this.deps.value;
+    if (!this.deps.oneTime)
+      value = value.discardChanges();
+    return value;
+  },
+
+  updateIfValue: function(ifValue) {
+    if (!ifValue) {
+      this.valueChanged();
+      return;
+    }
+
+    this.updateValue(this.getUpdatedValue());
+  },
+
+  updateIteratedValue: function(value) {
+    if (this.deps.hasIf) {
+      var ifValue = this.deps.ifValue;
+      if (!this.deps.ifOneTime)
+        ifValue = ifValue.discardChanges();
+      if (!ifValue) {
+        this.valueChanged();
+        return;
+      }
+    }
+
+    this.updateValue(value);
+  },
+
+  updateValue: function(value) {
+    if (!this.deps.repeat)
+      value = [value];
+    var observe = this.deps.repeat &&
+                  !this.deps.oneTime &&
+                  Array.isArray(value);
+    this.valueChanged(value, observe);
+  },
+
+  valueChanged: function(value, observeValue) {
+    if (!Array.isArray(value))
+      value = [];
+
+    if (value === this.iteratedValue)
+      return;
+
+    this.unobserve();
+    this.presentValue = value;
+    if (observeValue) {
+      this.arrayObserver = new observe.ArrayObserver(this.presentValue);
+      this.arrayObserver.open(this.handleSplices, this);
+    }
+
+    this.handleSplices(observe.ArrayObserver.calculateSplices(this.presentValue,
+                                                      this.iteratedValue));
+  },
+
+  getLastInstanceNode: function(index) {
+    if (index == -1)
+      return this.templateElement_;
+    var instance = this.instances[index];
+    var terminator = instance.terminator_;
+    if (!terminator)
+      return this.getLastInstanceNode(index - 1);
+
+    if (terminator.nodeType !== Node.ELEMENT_NODE ||
+        this.templateElement_ === terminator) {
+      return terminator;
+    }
+
+    var subtemplateIterator = terminator.iterator_;
+    if (!subtemplateIterator)
+      return terminator;
+
+    return subtemplateIterator.getLastTemplateNode();
+  },
+
+  getLastTemplateNode: function() {
+    return this.getLastInstanceNode(this.instances.length - 1);
+  },
+
+  insertInstanceAt: function(index, fragment) {
+    var previousInstanceLast = this.getLastInstanceNode(index - 1);
+    var parent = this.templateElement_.parentNode;
+    this.instances.splice(index, 0, fragment);
+
+    parent.insertBefore(fragment, previousInstanceLast.nextSibling);
+  },
+
+  extractInstanceAt: function(index) {
+    var previousInstanceLast = this.getLastInstanceNode(index - 1);
+    var lastNode = this.getLastInstanceNode(index);
+    var parent = this.templateElement_.parentNode;
+    var instance = this.instances.splice(index, 1)[0];
+
+    while (lastNode !== previousInstanceLast) {
+      var node = previousInstanceLast.nextSibling;
+      if (node == lastNode)
+        lastNode = previousInstanceLast;
+
+      instance.appendChild(parent.removeChild(node));
+    }
+
+    return instance;
+  },
+
+  getDelegateFn: function(fn) {
+    fn = fn && fn(this.templateElement_);
+    return typeof fn === 'function' ? fn : null;
+  },
+
+  handleSplices: function(splices) {
+    if (this.closed || !splices.length)
+      return;
+
+    var template = this.templateElement_;
+
+    if (!template.parentNode) {
+      this.close();
+      return;
+    }
+
+    observe.ArrayObserver.applySplices(this.iteratedValue, this.presentValue,
+                               splices);
+
+    var delegate = template.delegate_;
+    if (this.instanceModelFn_ === undefined) {
+      this.instanceModelFn_ =
+          this.getDelegateFn(delegate && delegate.prepareInstanceModel);
+    }
+
+    if (this.instancePositionChangedFn_ === undefined) {
+      this.instancePositionChangedFn_ =
+          this.getDelegateFn(delegate &&
+                             delegate.prepareInstancePositionChanged);
+    }
+
+    // Instance Removals
+    var instanceCache = new Map;
+    var removeDelta = 0;
+    for (var i = 0; i < splices.length; i++) {
+      var splice = splices[i];
+      var removed = splice.removed;
+      for (var j = 0; j < removed.length; j++) {
+        var model = removed[j];
+        var instance = this.extractInstanceAt(splice.index + removeDelta);
+        if (instance !== emptyInstance) {
+          instanceCache.set(model, instance);
+        }
+      }
+
+      removeDelta -= splice.addedCount;
+    }
+
+    // Instance Insertions
+    for (var i = 0; i < splices.length; i++) {
+      var splice = splices[i];
+      var addIndex = splice.index;
+      for (; addIndex < splice.index + splice.addedCount; addIndex++) {
+        var model = this.iteratedValue[addIndex];
+        var instance = instanceCache.get(model);
+        if (instance) {
+          instanceCache.delete(model);
+        } else {
+          if (this.instanceModelFn_) {
+            model = this.instanceModelFn_(model);
+          }
+
+          if (model === undefined) {
+            instance = emptyInstance;
+          } else {
+            instance = template.createInstance(model, undefined, delegate);
+          }
+        }
+
+        this.insertInstanceAt(addIndex, instance);
+      }
+    }
+
+    instanceCache.forEach(function(instance) {
+      this.closeInstanceBindings(instance);
+    }, this);
+
+    if (this.instancePositionChangedFn_)
+      this.reportInstancesMoved(splices);
+  },
+
+  reportInstanceMoved: function(index) {
+    var instance = this.instances[index];
+    if (instance === emptyInstance)
+      return;
+
+    this.instancePositionChangedFn_(instance.templateInstance_, index);
+  },
+
+  reportInstancesMoved: function(splices) {
+    var index = 0;
+    var offset = 0;
+    for (var i = 0; i < splices.length; i++) {
+      var splice = splices[i];
+      if (offset != 0) {
+        while (index < splice.index) {
+          this.reportInstanceMoved(index);
+          index++;
+        }
+      } else {
+        index = splice.index;
+      }
+
+      while (index < splice.index + splice.addedCount) {
+        this.reportInstanceMoved(index);
+        index++;
+      }
+
+      offset += splice.addedCount - splice.removed.length;
+    }
+
+    if (offset == 0)
+      return;
+
+    var length = this.instances.length;
+    while (index < length) {
+      this.reportInstanceMoved(index);
+      index++;
+    }
+  },
+
+  closeInstanceBindings: function(instance) {
+    var bindings = instance.bindings_;
+    for (var i = 0; i < bindings.length; i++) {
+      bindings[i].close();
+    }
+  },
+
+  unobserve: function() {
+    if (!this.arrayObserver)
+      return;
+
+    this.arrayObserver.close();
+    this.arrayObserver = undefined;
+  },
+
+  close: function() {
+    if (this.closed)
+      return;
+    this.unobserve();
+    for (var i = 0; i < this.instances.length; i++) {
+      this.closeInstanceBindings(this.instances[i]);
+    }
+
+    this.instances.length = 0;
+    this.closeDeps();
+    this.templateElement_.iterator_ = undefined;
+    this.closed = true;
+  }
+};
+</script>