/*
 * Copyright (C) 2007, 2013, 2015 Apple Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

WebInspector.TreeOutline = class TreeOutline extends WebInspector.Object
{
    constructor(listNode)
    {
        super();

        this.element = listNode;

        this.children = [];
        this.selectedTreeElement = null;
        this._childrenListNode = listNode;
        this._childrenListNode.removeChildren();
        this._knownTreeElements = [];
        this._treeElementsExpandedState = [];
        this.allowsRepeatSelection = false;
        this.root = true;
        this.hasChildren = false;
        this.expanded = true;
        this.selected = false;
        this.treeOutline = this;

        this._childrenListNode.tabIndex = 0;
        this._childrenListNode.addEventListener("keydown", this._treeKeyDown.bind(this), true);
    }

    // Methods

    appendChild(child)
    {
        console.assert(child);
        if (!child)
            return;

        var lastChild = this.children[this.children.length - 1];
        if (lastChild) {
            lastChild.nextSibling = child;
            child.previousSibling = lastChild;
        } else {
            child.previousSibling = null;
            child.nextSibling = null;
        }

        var isFirstChild = !this.children.length;

        this.children.push(child);
        this.hasChildren = true;
        child.parent = this;
        child.treeOutline = this.treeOutline;
        child.treeOutline._rememberTreeElement(child);

        var current = child.children[0];
        while (current) {
            current.treeOutline = this.treeOutline;
            current.treeOutline._rememberTreeElement(current);
            current = current.traverseNextTreeElement(false, child, true);
        }

        if (child.hasChildren && child.treeOutline._treeElementsExpandedState[child.identifier] !== undefined)
            child.expanded = child.treeOutline._treeElementsExpandedState[child.identifier];

        if (this._childrenListNode)
            child._attach();

        if (this.treeOutline.onadd)
            this.treeOutline.onadd(child);

        if (isFirstChild && this.expanded)
            this.expand();
    }

    insertChild(child, index)
    {
        console.assert(child);
        if (!child)
            return;

        var previousChild = (index > 0 ? this.children[index - 1] : null);
        if (previousChild) {
            previousChild.nextSibling = child;
            child.previousSibling = previousChild;
        } else {
            child.previousSibling = null;
        }

        var nextChild = this.children[index];
        if (nextChild) {
            nextChild.previousSibling = child;
            child.nextSibling = nextChild;
        } else {
            child.nextSibling = null;
        }

        var isFirstChild = !this.children.length;

        this.children.splice(index, 0, child);
        this.hasChildren = true;
        child.parent = this;
        child.treeOutline = this.treeOutline;
        child.treeOutline._rememberTreeElement(child);

        var current = child.children[0];
        while (current) {
            current.treeOutline = this.treeOutline;
            current.treeOutline._rememberTreeElement(current);
            current = current.traverseNextTreeElement(false, child, true);
        }

        if (child.hasChildren && child.treeOutline._treeElementsExpandedState[child.identifier] !== undefined)
            child.expanded = child.treeOutline._treeElementsExpandedState[child.identifier];

        if (this._childrenListNode)
            child._attach();

        if (this.treeOutline.onadd)
            this.treeOutline.onadd(child);

        if (isFirstChild && this.expanded)
            this.expand();
    }

    removeChildAtIndex(childIndex, suppressOnDeselect, suppressSelectSibling)
    {
        console.assert(childIndex >= 0 && childIndex < this.children.length);
        if (childIndex < 0 || childIndex >= this.children.length)
            return;

        var child = this.children[childIndex];
        this.children.splice(childIndex, 1);

        var parent = child.parent;
        if (child.deselect(suppressOnDeselect)) {
            if (child.previousSibling && !suppressSelectSibling)
                child.previousSibling.select(true, false);
            else if (child.nextSibling && !suppressSelectSibling)
                child.nextSibling.select(true, false);
            else if (!suppressSelectSibling)
                parent.select(true, false);
        }

        if (child.previousSibling)
            child.previousSibling.nextSibling = child.nextSibling;
        if (child.nextSibling)
            child.nextSibling.previousSibling = child.previousSibling;

        if (child.treeOutline) {
            child.treeOutline._forgetTreeElement(child);
            child.treeOutline._forgetChildrenRecursive(child);
        }

        child._detach();
        child.treeOutline = null;
        child.parent = null;
        child.nextSibling = null;
        child.previousSibling = null;

        if (this.treeOutline && this.treeOutline.onremove)
            this.treeOutline.onremove(child);
    }

    removeChild(child, suppressOnDeselect, suppressSelectSibling)
    {
        console.assert(child);
        if (!child)
            return;

        var childIndex = this.children.indexOf(child);
        console.assert(childIndex !== -1);
        if (childIndex === -1)
            return;

        this.removeChildAtIndex(childIndex, suppressOnDeselect, suppressSelectSibling);

        if (!this.children.length) {
            if (this._listItemNode)
                this._listItemNode.classList.remove("parent");
            this.hasChildren = false;
        }
    }

    removeChildren(suppressOnDeselect)
    {
        var treeOutline = this.treeOutline;

        for (var i = 0; i < this.children.length; ++i) {
            var child = this.children[i];
            child.deselect(suppressOnDeselect);

            if (child.treeOutline) {
                child.treeOutline._forgetTreeElement(child);
                child.treeOutline._forgetChildrenRecursive(child);
            }

            child._detach();
            child.treeOutline = null;
            child.parent = null;
            child.nextSibling = null;
            child.previousSibling = null;

            if (treeOutline && treeOutline.onremove)
                treeOutline.onremove(child);
        }

        this.children = [];
    }

    removeChildrenRecursive(suppressOnDeselect)
    {
        var childrenToRemove = this.children;

        var treeOutline = this.treeOutline;

        var child = this.children[0];
        while (child) {
            if (child.children.length)
                childrenToRemove = childrenToRemove.concat(child.children);
            child = child.traverseNextTreeElement(false, this, true);
        }

        for (var i = 0; i < childrenToRemove.length; ++i) {
            child = childrenToRemove[i];
            child.deselect(suppressOnDeselect);

            if (child.treeOutline)
                child.treeOutline._forgetTreeElement(child);

            child._detach();
            child.children = [];
            child.treeOutline = null;
            child.parent = null;
            child.nextSibling = null;
            child.previousSibling = null;

            if (treeOutline && treeOutline.onremove)
                treeOutline.onremove(child);
        }

        this.children = [];
    }

    _rememberTreeElement(element)
    {
        if (!this._knownTreeElements[element.identifier])
            this._knownTreeElements[element.identifier] = [];

        // check if the element is already known
        var elements = this._knownTreeElements[element.identifier];
        if (elements.indexOf(element) !== -1)
            return;

        // add the element
        elements.push(element);
    }

    _forgetTreeElement(element)
    {
        if (this.selectedTreeElement === element)
            this.selectedTreeElement = null;
        if (this._knownTreeElements[element.identifier])
            this._knownTreeElements[element.identifier].remove(element, true);
    }

    _forgetChildrenRecursive(parentElement)
    {
        var child = parentElement.children[0];
        while (child) {
            this._forgetTreeElement(child);
            child = child.traverseNextTreeElement(false, parentElement, true);
        }
    }

    getCachedTreeElement(representedObject)
    {
        if (!representedObject)
            return null;

        if (representedObject.__treeElementIdentifier) {
            // If this representedObject has a tree element identifier, and it is a known TreeElement
            // in our tree we can just return that tree element.
            var elements = this._knownTreeElements[representedObject.__treeElementIdentifier];
            if (elements) {
                for (var i = 0; i < elements.length; ++i)
                    if (elements[i].representedObject === representedObject)
                        return elements[i];
            }
        }
        return null;
    }

    findTreeElement(representedObject, isAncestor, getParent)
    {
        if (!representedObject)
            return null;

        var cachedElement = this.getCachedTreeElement(representedObject);
        if (cachedElement)
            return cachedElement;

        // The representedObject isn't known, so we start at the top of the tree and work down to find the first
        // tree element that represents representedObject or one of its ancestors.
        var item;
        var found = false;
        for (var i = 0; i < this.children.length; ++i) {
            item = this.children[i];
            if (item.representedObject === representedObject || (isAncestor && isAncestor(item.representedObject, representedObject))) {
                found = true;
                break;
            }
        }

        if (!found)
            return null;

        // Make sure the item that we found is connected to the root of the tree.
        // Build up a list of representedObject's ancestors that aren't already in our tree.
        var ancestors = [];
        var currentObject = representedObject;
        while (currentObject) {
            ancestors.unshift(currentObject);
            if (currentObject === item.representedObject)
                break;
            currentObject = getParent(currentObject);
        }

        // For each of those ancestors we populate them to fill in the tree.
        for (var i = 0; i < ancestors.length; ++i) {
            // Make sure we don't call findTreeElement with the same representedObject
            // again, to prevent infinite recursion.
            if (ancestors[i] === representedObject)
                continue;

            // FIXME: we could do something faster than findTreeElement since we will know the next
            // ancestor exists in the tree.
            item = this.findTreeElement(ancestors[i], isAncestor, getParent);
            if (item)
                item.onpopulate();
        }

        return this.getCachedTreeElement(representedObject);
    }

    _treeElementDidChange(treeElement)
    {
        if (treeElement.treeOutline !== this)
            return;

        if (this.onchange)
            this.onchange(treeElement);
    }

    treeElementFromNode(node)
    {
        var listNode = node.enclosingNodeOrSelfWithNodeNameInArray(["ol", "li"]);
        if (listNode)
            return listNode.parentTreeElement || listNode.treeElement;
        return null;
    }

    treeElementFromPoint(x, y)
    {
        var node = this._childrenListNode.ownerDocument.elementFromPoint(x, y);
        if (!node)
            return null;

        return this.treeElementFromNode(node);
    }

    _treeKeyDown(event)
    {
        if (event.target !== this._childrenListNode)
            return;

        if (!this.selectedTreeElement || event.shiftKey || event.metaKey || event.ctrlKey)
            return;

        var handled = false;
        var nextSelectedElement;
        if (event.keyIdentifier === "Up" && !event.altKey) {
            nextSelectedElement = this.selectedTreeElement.traversePreviousTreeElement(true);
            while (nextSelectedElement && !nextSelectedElement.selectable)
                nextSelectedElement = nextSelectedElement.traversePreviousTreeElement(true);
            handled = nextSelectedElement ? true : false;
        } else if (event.keyIdentifier === "Down" && !event.altKey) {
            nextSelectedElement = this.selectedTreeElement.traverseNextTreeElement(true);
            while (nextSelectedElement && !nextSelectedElement.selectable)
                nextSelectedElement = nextSelectedElement.traverseNextTreeElement(true);
            handled = nextSelectedElement ? true : false;
        } else if (event.keyIdentifier === "Left") {
            if (this.selectedTreeElement.expanded) {
                if (event.altKey)
                    this.selectedTreeElement.collapseRecursively();
                else
                    this.selectedTreeElement.collapse();
                handled = true;
            } else if (this.selectedTreeElement.parent && !this.selectedTreeElement.parent.root) {
                handled = true;
                if (this.selectedTreeElement.parent.selectable) {
                    nextSelectedElement = this.selectedTreeElement.parent;
                    while (nextSelectedElement && !nextSelectedElement.selectable)
                        nextSelectedElement = nextSelectedElement.parent;
                    handled = nextSelectedElement ? true : false;
                } else if (this.selectedTreeElement.parent)
                    this.selectedTreeElement.parent.collapse();
            }
        } else if (event.keyIdentifier === "Right") {
            if (!this.selectedTreeElement.revealed()) {
                this.selectedTreeElement.reveal();
                handled = true;
            } else if (this.selectedTreeElement.hasChildren) {
                handled = true;
                if (this.selectedTreeElement.expanded) {
                    nextSelectedElement = this.selectedTreeElement.children[0];
                    while (nextSelectedElement && !nextSelectedElement.selectable)
                        nextSelectedElement = nextSelectedElement.nextSibling;
                    handled = nextSelectedElement ? true : false;
                } else {
                    if (event.altKey)
                        this.selectedTreeElement.expandRecursively();
                    else
                        this.selectedTreeElement.expand();
                }
            }
        } else if (event.keyCode === 8 /* Backspace */ || event.keyCode === 46 /* Delete */) {
            if (this.selectedTreeElement.ondelete)
                handled = this.selectedTreeElement.ondelete();
            if (!handled && this.treeOutline.ondelete)
                handled = this.treeOutline.ondelete(this.selectedTreeElement);
        } else if (isEnterKey(event)) {
            if (this.selectedTreeElement.onenter)
                handled = this.selectedTreeElement.onenter();
            if (!handled && this.treeOutline.onenter)
                handled = this.treeOutline.onenter(this.selectedTreeElement);
        } else if (event.keyIdentifier === "U+0020" /* Space */) {
            if (this.selectedTreeElement.onspace)
                handled = this.selectedTreeElement.onspace();
            if (!handled && this.treeOutline.onspace)
                handled = this.treeOutline.onspace(this.selectedTreeElement);
        }

        if (nextSelectedElement) {
            nextSelectedElement.reveal();
            nextSelectedElement.select(false, true);
        }

        if (handled) {
            event.preventDefault();
            event.stopPropagation();
        }
    }

    expand()
    {
        // this is the root, do nothing
    }

    collapse()
    {
        // this is the root, do nothing
    }

    revealed()
    {
        return true;
    }

    reveal()
    {
        // this is the root, do nothing
    }

    select()
    {
        // this is the root, do nothing
    }

    revealAndSelect(omitFocus)
    {
        // this is the root, do nothing
    }
};

WebInspector.TreeOutline._knownTreeElementNextIdentifier = 1;

WebInspector.TreeElement = class TreeElement extends WebInspector.Object
{
    constructor(title, representedObject, hasChildren)
    {
        super();

        this._title = title;
        this.representedObject = (representedObject || {});

        if (this.representedObject.__treeElementIdentifier)
            this.identifier = this.representedObject.__treeElementIdentifier;
        else {
            this.identifier = WebInspector.TreeOutline._knownTreeElementNextIdentifier++;
            this.representedObject.__treeElementIdentifier = this.identifier;
        }

        this._hidden = false;
        this._selectable = true;
        this.expanded = false;
        this.selected = false;
        this.hasChildren = hasChildren;
        this.children = [];
        this.treeOutline = null;
        this.parent = null;
        this.previousSibling = null;
        this.nextSibling = null;
        this._listItemNode = null;
    }

    // Methods

    appendChild() { return WebInspector.TreeOutline.prototype.appendChild.apply(this, arguments); }
    insertChild() { return WebInspector.TreeOutline.prototype.insertChild.apply(this, arguments); }
    removeChild() { return WebInspector.TreeOutline.prototype.removeChild.apply(this, arguments); }
    removeChildAtIndex() { return WebInspector.TreeOutline.prototype.removeChildAtIndex.apply(this, arguments); }
    removeChildren() { return WebInspector.TreeOutline.prototype.removeChildren.apply(this, arguments); }
    removeChildrenRecursive() { return WebInspector.TreeOutline.prototype.removeChildrenRecursive.apply(this, arguments); }

    get arrowToggleWidth()
    {
        return 10;
    }

    get selectable()
    {
        if (this._hidden)
            return false;
        return this._selectable;
    }

    set selectable(x)
    {
        this._selectable = x;
    }

    get listItemElement()
    {
        return this._listItemNode;
    }

    get childrenListElement()
    {
        return this._childrenListNode;
    }

    get title()
    {
        return this._title;
    }

    set title(x)
    {
        this._title = x;
        this._setListItemNodeContent();
        this.didChange();
    }

    get titleHTML()
    {
        return this._titleHTML;
    }

    set titleHTML(x)
    {
        this._titleHTML = x;
        this._setListItemNodeContent();
        this.didChange();
    }

    get tooltip()
    {
        return this._tooltip;
    }

    set tooltip(x)
    {
        this._tooltip = x;
        if (this._listItemNode)
            this._listItemNode.title = x ? x : "";
        this.didChange();
    }

    get hasChildren()
    {
        return this._hasChildren;
    }

    set hasChildren(x)
    {
        if (this._hasChildren === x)
            return;

        this._hasChildren = x;

        if (!this._listItemNode)
            return;

        if (x)
            this._listItemNode.classList.add("parent");
        else {
            this._listItemNode.classList.remove("parent");
            this.collapse();
        }

        this.didChange();
    }

    get hidden()
    {
        return this._hidden;
    }

    set hidden(x)
    {
        if (this._hidden === x)
            return;

        this._hidden = x;

        if (x) {
            if (this._listItemNode)
                this._listItemNode.classList.add("hidden");
            if (this._childrenListNode)
                this._childrenListNode.classList.add("hidden");
        } else {
            if (this._listItemNode)
                this._listItemNode.classList.remove("hidden");
            if (this._childrenListNode)
                this._childrenListNode.classList.remove("hidden");
        }

        if (this.treeOutline && this.treeOutline.onhidden)
            this.treeOutline.onhidden(this, x);
    }

    get shouldRefreshChildren()
    {
        return this._shouldRefreshChildren;
    }

    set shouldRefreshChildren(x)
    {
        this._shouldRefreshChildren = x;
        if (x && this.expanded)
            this.expand();
    }

    _fireDidChange()
    {
        delete this._didChangeTimeoutIdentifier;

        if (this.treeOutline)
            this.treeOutline._treeElementDidChange(this);
    }

    didChange()
    {
        if (!this.treeOutline)
            return;

        // Prevent telling the TreeOutline multiple times in a row by delaying it with a timeout.
        if (!this._didChangeTimeoutIdentifier)
            this._didChangeTimeoutIdentifier = setTimeout(this._fireDidChange.bind(this), 0);
    }

    _setListItemNodeContent()
    {
        if (!this._listItemNode)
            return;

        if (!this._titleHTML && !this._title)
            this._listItemNode.removeChildren();
        else if (typeof this._titleHTML === "string")
            this._listItemNode.innerHTML = this._titleHTML;
        else if (typeof this._title === "string")
            this._listItemNode.textContent = this._title;
        else {
            this._listItemNode.removeChildren();
            if (this._title.parentNode)
                this._title.parentNode.removeChild(this._title);
            this._listItemNode.appendChild(this._title);
        }
    }

    _attach()
    {
        if (!this._listItemNode || this.parent._shouldRefreshChildren) {
            if (this._listItemNode && this._listItemNode.parentNode)
                this._listItemNode.parentNode.removeChild(this._listItemNode);

            this._listItemNode = this.treeOutline._childrenListNode.ownerDocument.createElement("li");
            this._listItemNode.treeElement = this;
            this._setListItemNodeContent();
            this._listItemNode.title = this._tooltip ? this._tooltip : "";

            if (this.hidden)
                this._listItemNode.classList.add("hidden");
            if (this.hasChildren)
                this._listItemNode.classList.add("parent");
            if (this.expanded)
                this._listItemNode.classList.add("expanded");
            if (this.selected)
                this._listItemNode.classList.add("selected");

            this._listItemNode.addEventListener("mousedown", WebInspector.TreeElement.treeElementMouseDown);
            this._listItemNode.addEventListener("click", WebInspector.TreeElement.treeElementToggled);
            this._listItemNode.addEventListener("dblclick", WebInspector.TreeElement.treeElementDoubleClicked);

            if (this.onattach)
                this.onattach(this);
        }

        var nextSibling = null;
        if (this.nextSibling && this.nextSibling._listItemNode && this.nextSibling._listItemNode.parentNode === this.parent._childrenListNode)
            nextSibling = this.nextSibling._listItemNode;
        this.parent._childrenListNode.insertBefore(this._listItemNode, nextSibling);
        if (this._childrenListNode)
            this.parent._childrenListNode.insertBefore(this._childrenListNode, this._listItemNode.nextSibling);
        if (this.selected)
            this.select();
        if (this.expanded)
            this.expand();
    }

    _detach()
    {
        if (this.ondetach)
            this.ondetach(this);
        if (this._listItemNode && this._listItemNode.parentNode)
            this._listItemNode.parentNode.removeChild(this._listItemNode);
        if (this._childrenListNode && this._childrenListNode.parentNode)
            this._childrenListNode.parentNode.removeChild(this._childrenListNode);
    }

    static treeElementMouseDown(event)
    {
        var element = event.currentTarget;
        if (!element || !element.treeElement || !element.treeElement.selectable)
            return;

        if (element.treeElement.isEventWithinDisclosureTriangle(event)) {
            event.preventDefault();
            return;
        }

        element.treeElement.selectOnMouseDown(event);
    }

    static treeElementToggled(event)
    {
        var element = event.currentTarget;
        if (!element || !element.treeElement)
            return;

        var toggleOnClick = element.treeElement.toggleOnClick && !element.treeElement.selectable;
        var isInTriangle = element.treeElement.isEventWithinDisclosureTriangle(event);
        if (!toggleOnClick && !isInTriangle)
            return;

        if (element.treeElement.expanded) {
            if (event.altKey)
                element.treeElement.collapseRecursively();
            else
                element.treeElement.collapse();
        } else {
            if (event.altKey)
                element.treeElement.expandRecursively();
            else
                element.treeElement.expand();
        }
        event.stopPropagation();
    }

    static treeElementDoubleClicked(event)
    {
        var element = event.currentTarget;
        if (!element || !element.treeElement)
            return;

        if (element.treeElement.isEventWithinDisclosureTriangle(event))
            return;

        if (element.treeElement.ondblclick)
            element.treeElement.ondblclick.call(element.treeElement, event);
        else if (element.treeElement.hasChildren && !element.treeElement.expanded)
            element.treeElement.expand();
    }

    collapse()
    {
        if (this._listItemNode)
            this._listItemNode.classList.remove("expanded");
        if (this._childrenListNode)
            this._childrenListNode.classList.remove("expanded");

        this.expanded = false;
        if (this.treeOutline)
            this.treeOutline._treeElementsExpandedState[this.identifier] = false;

        if (this.oncollapse)
            this.oncollapse(this);

        if (this.treeOutline && this.treeOutline.oncollapse)
            this.treeOutline.oncollapse(this);
    }

    collapseRecursively()
    {
        var item = this;
        while (item) {
            if (item.expanded)
                item.collapse();
            item = item.traverseNextTreeElement(false, this, true);
        }
    }

    expand()
    {
        if (this.expanded && !this._shouldRefreshChildren && this._childrenListNode)
            return;

        // Set this before onpopulate. Since onpopulate can add elements and call onadd, this makes
        // sure the expanded flag is true before calling those functions. This prevents the possibility
        // of an infinite loop if onpopulate or onadd were to call expand.

        this.expanded = true;
        if (this.treeOutline)
            this.treeOutline._treeElementsExpandedState[this.identifier] = true;

        // If there are no children, return. We will be expanded once we have children.
        if (!this.hasChildren)
            return;

        if (this.treeOutline && (!this._childrenListNode || this._shouldRefreshChildren)) {
            if (this._childrenListNode && this._childrenListNode.parentNode)
                this._childrenListNode.parentNode.removeChild(this._childrenListNode);

            this._childrenListNode = this.treeOutline._childrenListNode.ownerDocument.createElement("ol");
            this._childrenListNode.parentTreeElement = this;
            this._childrenListNode.classList.add("children");

            if (this.hidden)
                this._childrenListNode.classList.add("hidden");

            this.onpopulate();

            for (var i = 0; i < this.children.length; ++i)
                this.children[i]._attach();

            delete this._shouldRefreshChildren;
        }

        if (this._listItemNode) {
            this._listItemNode.classList.add("expanded");
            if (this._childrenListNode && this._childrenListNode.parentNode !== this._listItemNode.parentNode)
                this.parent._childrenListNode.insertBefore(this._childrenListNode, this._listItemNode.nextSibling);
        }

        if (this._childrenListNode)
            this._childrenListNode.classList.add("expanded");

        if (this.onexpand)
            this.onexpand(this);

        if (this.treeOutline && this.treeOutline.onexpand)
            this.treeOutline.onexpand(this);
    }

    expandRecursively(maxDepth)
    {
        var item = this;
        var info = {};
        var depth = 0;

        // The Inspector uses TreeOutlines to represents object properties, so recursive expansion
        // in some case can be infinite, since JavaScript objects can hold circular references.
        // So default to a recursion cap of 3 levels, since that gives fairly good results.
        if (maxDepth === undefined)
            maxDepth = 3;

        while (item) {
            if (depth < maxDepth)
                item.expand();
            item = item.traverseNextTreeElement(false, this, (depth >= maxDepth), info);
            depth += info.depthChange;
        }
    }

    hasAncestor(ancestor)
        {
        if (!ancestor)
            return false;

        var currentNode = this.parent;
        while (currentNode) {
            if (ancestor === currentNode)
                return true;
            currentNode = currentNode.parent;
        }

        return false;
    }

    reveal()
    {
        var currentAncestor = this.parent;
        while (currentAncestor && !currentAncestor.root) {
            if (!currentAncestor.expanded)
                currentAncestor.expand();
            currentAncestor = currentAncestor.parent;
        }

        if (this.onreveal)
            this.onreveal(this);
    }

    revealed(ignoreHidden)
    {
        if (!ignoreHidden && this.hidden)
            return false;

        var currentAncestor = this.parent;
        while (currentAncestor && !currentAncestor.root) {
            if (!currentAncestor.expanded)
                return false;
            if (!ignoreHidden && currentAncestor.hidden)
                return false;
            currentAncestor = currentAncestor.parent;
        }

        return true;
    }

    selectOnMouseDown(event)
    {
        this.select(false, true);
    }

    select(omitFocus, selectedByUser, suppressOnSelect, suppressOnDeselect)
    {
        if (!this.treeOutline || !this.selectable)
            return;

        if (this.selected && !this.treeOutline.allowsRepeatSelection)
            return;

        if (!omitFocus)
            this.treeOutline._childrenListNode.focus();

        // Focusing on another node may detach "this" from tree.
        var treeOutline = this.treeOutline;
        if (!treeOutline)
            return;

        treeOutline.processingSelectionChange = true;

        if (!this.selected) {
            if (treeOutline.selectedTreeElement)
                treeOutline.selectedTreeElement.deselect(suppressOnDeselect);

            this.selected = true;
            treeOutline.selectedTreeElement = this;

            if (this._listItemNode)
                this._listItemNode.classList.add("selected");
        }

        if (this.onselect && !suppressOnSelect)
            this.onselect(this, selectedByUser);

        if (treeOutline.onselect && !suppressOnSelect)
            treeOutline.onselect(this, selectedByUser);

        treeOutline.processingSelectionChange = false;
    }

    revealAndSelect(omitFocus, selectedByUser, suppressOnSelect, suppressOnDeselect)
    {
        this.reveal();
        this.select(omitFocus, selectedByUser, suppressOnSelect, suppressOnDeselect);
    }

    deselect(suppressOnDeselect)
    {
        if (!this.treeOutline || this.treeOutline.selectedTreeElement !== this || !this.selected)
            return false;

        this.selected = false;
        this.treeOutline.selectedTreeElement = null;

        if (this._listItemNode)
            this._listItemNode.classList.remove("selected");

        if (this.ondeselect && !suppressOnDeselect)
            this.ondeselect(this);

        if (this.treeOutline.ondeselect && !suppressOnDeselect)
            this.treeOutline.ondeselect(this);

        return true;
    }

    onpopulate()
    {
        // Overriden by subclasses.
    }

    traverseNextTreeElement(skipUnrevealed, stayWithin, dontPopulate, info)
    {
        function shouldSkip(element) {
            return skipUnrevealed && !element.revealed(true);
        }

        var depthChange = 0;
        var element = this;

        if (!dontPopulate)
            element.onpopulate();

        do {
            if (element.hasChildren && element.children[0] && (!skipUnrevealed || element.expanded)) {
                element = element.children[0];
                depthChange += 1;
            } else {
                while (element && !element.nextSibling && element.parent && !element.parent.root && element.parent !== stayWithin) {
                    element = element.parent;
                    depthChange -= 1;
                }

                if (element)
                    element = element.nextSibling;
            }
        } while (element && shouldSkip(element));

        if (info)
            info.depthChange = depthChange;

        return element;
    }

    traversePreviousTreeElement(skipUnrevealed, dontPopulate)
    {
        function shouldSkip(element) {
            return skipUnrevealed && !element.revealed(true);
        }

        var element = this;

        do {
            if (element.previousSibling) {
                element = element.previousSibling;

                while (element && element.hasChildren && element.expanded && !shouldSkip(element)) {
                    if (!dontPopulate)
                        element.onpopulate();
                    element = element.children.lastValue;
                }
            } else
                element = element.parent && element.parent.root ? null : element.parent;
        } while (element && shouldSkip(element));

        return element;
    }

    isEventWithinDisclosureTriangle(event)
    {
        if (!document.contains(this._listItemNode))
            return false;

        // FIXME: We should not use getComputedStyle(). For that we need to get rid of using ::before for disclosure triangle. (http://webk.it/74446)
        var computedLeftPadding = window.getComputedStyle(this._listItemNode).getPropertyCSSValue("padding-left").getFloatValue(CSSPrimitiveValue.CSS_PX);
        var left = this._listItemNode.totalOffsetLeft + computedLeftPadding;
        return event.pageX >= left && event.pageX <= left + this.arrowToggleWidth && this.hasChildren;
    }
};
