public Yield GetNavigationSiblings(DreamContext context, DreamMessage request, Result <DreamMessage> response)
        {
            CheckResponseCache(context, false);

            PageBE page = PageBL_GetPageFromUrl(context, false);

            if (page.Title.IsTalk)
            {
                page = PageBL.GetPageByTitle(page.Title.AsFront());
            }

            // build response
            IList <NavBE> list = NavBL.QueryNavSiblingsData(page, context.Culture);

            if (ShowDebug(context))
            {
                response.Return(DreamMessage.Ok(NavBL.ConvertNavPageListToDoc(list)));
            }
            else
            {
                XDoc doc = NavBL.ComputeNavigationDocument(list, page, (uint)page.ID, 0, true, context.GetParam("width", int.MaxValue));
                if (ShowXml(context))
                {
                    response.Return(DreamMessage.Ok(doc));
                }
                else
                {
                    XDoc result = new XDoc("tree");
                    result.Start("siblings");

                    // add name of sibling nodes
                    System.Text.StringBuilder nodes = new System.Text.StringBuilder();
                    ulong homepageId = DekiContext.Current.Instance.HomePageId;
                    foreach (NavBE sibling in list)
                    {
                        if ((sibling.ParentId == page.ParentID) && (sibling.Id != homepageId))
                        {
                            if (nodes.Length != 0)
                            {
                                nodes.Append(",");
                            }
                            nodes.AppendFormat("n{0}", sibling.Id);
                        }
                    }
                    result.Elem("nodes", nodes.ToString());

                    // add sibling nodes
                    result.Start("html");
                    result.Elem("pre", doc["siblings-pre"].Contents);
                    result.Elem("post", doc["siblings-post"].Contents);
                    result.End();
                    result.End();
                    response.Return(DreamMessage.Ok(result));
                }
            }
            yield break;
        }
        public Yield GetNavigationFull(DreamContext context, DreamMessage request, Result <DreamMessage> response)
        {
            CheckResponseCache(context, false);

            PageBE page = PageBL_GetPageFromUrl(context, false);

            if (page.Title.IsTalk)
            {
                page = PageBL.GetPageByTitle(page.Title.AsFront());
            }

            // check if requestest page exists, otherwise find nearest parent
            uint         new_page_id = NavBL.NEW_PAGE_ID;
            ulong        homepageId  = DekiContext.Current.Instance.HomePageId;
            List <NavBE> list;
            bool         expandableNav = context.GetParam("type", "compact").EqualsInvariantIgnoreCase("expandable");

            // check if a page was found
            if (page.ID == 0)
            {
                // find nearest ancestor and authorize access
                PageBE ancestor = page;
                while (!ancestor.Title.IsHomepage)
                {
                    // fetch ancestor page based on title
                    ulong id = DbUtils.CurrentSession.Nav_GetNearestParent(ancestor.Title);
                    ancestor = PageBL.GetPageById(id);
                    if (PermissionsBL.IsUserAllowed(DekiContext.Current.User, ancestor, Permissions.BROWSE))
                    {
                        break;
                    }

                    // determine parent page title
                    Title title = ancestor.Title.GetParent();
                    if (title == null)
                    {
                        // current ancestor was the homepage
                        break;
                    }
                    ancestor = new PageBE {
                        Title = title
                    };
                }
                if (ancestor.ID == 0)
                {
                    ancestor = PageBL.GetHomePage();
                }
                list = NavBL.QueryNavTreeData(ancestor, context.Culture, expandableNav).ToList();

                // find the nearest parent node and increase its child count
                foreach (NavBE nearestAncestors in list)
                {
                    if (nearestAncestors.Id == ancestor.ID)
                    {
                        nearestAncestors.ChildCount = nearestAncestors.ChildCount + 1;
                        break;
                    }
                }

                // for each missing node, generate a dummy page and insert it into result set
                ulong        ancestor_id       = ancestor.ID;
                string[]     ancestor_segments = ancestor.Title.AsUnprefixedDbSegments();
                string[]     new_page_segments = page.Title.AsUnprefixedDbSegments();
                List <NavBE> newNodes          = new List <NavBE>(32);
                for (int i = ancestor_segments.Length; i < new_page_segments.Length; ++i)
                {
                    string title = string.Join("/", new_page_segments, 0, i + 1);

                    // create dummy node with <page><page_id /><page_namespace /><page_title ><page_parent /><page_children /></page>
                    NavBE newPage = new NavBE {
                        Id         = new_page_id,
                        NameSpace  = (ushort)page.Title.Namespace,
                        Title      = title,
                        ParentId   = (ancestor_id == homepageId) ? 0 : ancestor_id,
                        ChildCount = (i == new_page_segments.Length - 1) ? 0 : 1
                    };
                    newNodes.Add(newPage);

                    // update page information
                    page.ID       = new_page_id;
                    page.ParentID = ancestor_id;
                    ancestor_id   = new_page_id++;
                }

                // check if we need to remove the children nodes of the ancestor
                ancestor_id = (ancestor.ID == homepageId) ? 0 : (uint)ancestor.ID;
                if (!expandableNav && (new_page_segments.Length - ancestor_segments.Length) > 1)
                {
                    // remove ancestor children and add new dummy nodes
                    for (int start = 0; start < list.Count; ++start)
                    {
                        // check if we found a matching child
                        if ((list[start].ParentId == ancestor_id) && (list[start].Id != homepageId))
                        {
                            // look for last child to remove so we can remove an entire range at once
                            int end = start + 1;
                            for (; (end < list.Count) && (list[end].ParentId == ancestor_id) && (list[end].Id != homepageId); ++end)
                            {
                            }
                            list.RemoveRange(start, end - start);
                            --start;
                        }
                    }
                }
                else
                {
                    // find where among the ancestor children we need to insert the dummy node
                    for (int index = 0; index < list.Count; ++index)
                    {
                        NavBE current = list[index];
                        if ((current.ParentId == ancestor_id) && (current.Id != homepageId))
                        {
                            string[] parts = Title.FromDbPath(NS.UNKNOWN, current.Title, current.DisplayName).AsUnprefixedDbSegments();
                            if ((parts.Length > 0) && (new_page_segments.Length > 0) && (string.Compare(parts[parts.Length - 1], new_page_segments[parts.Length - 1], true, context.Culture) > 0))
                            {
                                // found the spot
                                list.InsertRange(index, newNodes);
                                newNodes = null;
                                break;
                            }
                        }
                    }
                }

                // check if we didn't find the spot
                if (newNodes != null)
                {
                    // add new nodes to the end
                    list.AddRange(newNodes);
                }
            }
            else
            {
                list = NavBL.QueryNavTreeData(page, context.Culture, expandableNav).ToList();
            }

            // find first parent
            ulong parent_id    = homepageId;
            int   parent_index = -1;

            for (int i = 0; i < list.Count; ++i)
            {
                if (list[i].Id == parent_id)
                {
                    parent_index = i;
                    break;
                }
            }
            if (parent_index == -1)
            {
                throw new Exception("unexpected [homepage not found]");
            }

            // add any missing ancestor nodes (might have been removed by permission check or might simply not exist)
            string[] page_segments = page.Title.AsUnprefixedDbSegments();
            ushort   ns            = (ushort)page.Title.Namespace;

            for (int i = 0; i <= page_segments.Length; ++i)
            {
                string title = string.Join("/", page_segments, 0, i);

                // loop over all nodes
                bool found = false;
                for (int j = 0; j < list.Count; ++j)
                {
                    NavBE node = list[j];

                    // NOTE (steveb): we walk the path one parent at a time; however, there are a few special cases, because of namespaces
                    //      for instance, the parent page of User:Bob is the homepage (ditto for Template:Page), but the parent page of Admin:Config is Admin:

                    // check if we found a node matching the current title
                    if ((string.Compare(node.Title, title, true, context.Culture) == 0) && (((i == 0) && (ns != (ushort)NS.ADMIN)) ? (node.NameSpace == (ushort)NS.MAIN) : (node.NameSpace == ns)))
                    {
                        found = true;

                        // let's make sure node is pointing to right parent
                        node.ParentId = (parent_id == homepageId) ? 0 : parent_id;
                        parent_id     = node.Id;
                        parent_index  = j;
                        break;
                    }
                }
                if (!found)
                {
                    // node is missing, let's create a new one
                    NavBE newPage = new NavBE {
                        Id        = new_page_id,
                        NameSpace = (ushort)page.Title.Namespace,
                        Title     = title,
                        ParentId  = (parent_id == homepageId) ? 0 : parent_id, ChildCount = 1
                    };

                    // add new page after parent
                    list.Insert(parent_index + 1, newPage);
                    parent_id    = new_page_id++;
                    parent_index = parent_index + 1;
                }
            }

            // build response
            if (ShowDebug(context))
            {
                response.Return(DreamMessage.Ok(NavBL.ConvertNavPageListToDoc(list)));
            }
            else
            {
                XDoc result = expandableNav ? NavBL.ComputeExpandableNavigationDocument(list, page, 0, 0, false) : NavBL.ComputeNavigationDocument(list, page, 0, 0, false, context.GetParam("width", int.MaxValue));
                if (ShowXml(context))
                {
                    response.Return(DreamMessage.Ok(result));
                }
                else
                {
                    response.Return(DreamMessage.Ok(new XDoc("tree").Value(result.Contents)));
                }
            }
            yield break;
        }
        public Yield GetNavigationChildren(DreamContext context, DreamMessage request, Result <DreamMessage> response)
        {
            CheckResponseCache(context, false);

            PageBE page = PageBL_GetPageFromUrl(context, false);

            if (page.Title.IsTalk)
            {
                page = PageBL.GetPageByTitle(page.Title.AsFront());
            }

            // build response
            uint          exclude = context.GetParam <uint>("exclude", 0);
            IList <NavBE> list    = NavBL.QueryNavChildrenData(page, context.Culture);

            if (ShowDebug(context))
            {
                response.Return(DreamMessage.Ok(NavBL.ConvertNavPageListToDoc(list)));
            }
            else
            {
                bool expandableNav = context.GetParam("type", "compact").EqualsInvariantIgnoreCase("expandable");
                XDoc doc           = expandableNav ? NavBL.ComputeExpandableNavigationDocument(list, page, 0, exclude, true) : NavBL.ComputeNavigationDocument(list, page, 0, exclude, true, context.GetParam("width", int.MaxValue));
                if (ShowXml(context))
                {
                    response.Return(DreamMessage.Ok(doc));
                }
                else
                {
                    XDoc result = new XDoc("tree");
                    result.Start("children");

                    // add name of children nodes
                    System.Text.StringBuilder nodes = new System.Text.StringBuilder();
                    ulong homepageId = DekiContext.Current.Instance.HomePageId;
                    ulong parentId   = (page.ID == homepageId) ? 0 : page.ID;
                    foreach (NavBE child in list)
                    {
                        if ((child.ParentId == parentId) && (child.Id != homepageId))
                        {
                            if (nodes.Length != 0)
                            {
                                nodes.Append(",");
                            }
                            nodes.AppendFormat("n{0}", child.Id);
                        }
                    }
                    result.Elem("nodes", nodes.ToString());

                    // add <div> list
                    result.Start("html");
                    if (exclude != 0)
                    {
                        result.Start("pre").Value(doc["children-pre"].Contents).End();
                        result.Start("post").Value(doc["children-post"].Contents).End();
                    }
                    else
                    {
                        result.Value(doc.Contents);
                    }
                    result.End();
                    result.End();
                    response.Return(DreamMessage.Ok(result));
                }
            }
            yield break;
        }