/// <summary>
        /// Saves the blog post.
        /// </summary>
        /// <param name="request">The request.</param>
        /// <param name="childContentOptionValues">The child content option values.</param>
        /// <param name="principal">The principal.</param>
        /// <param name="errorMessages">The error messages.</param>
        /// <returns>
        /// Saved blog post entity
        /// </returns>
        /// <exception cref="System.ComponentModel.DataAnnotations.ValidationException"></exception>
        /// <exception cref="SecurityException">Forbidden: Access is denied.</exception>
        public BlogPost SaveBlogPost(BlogPostViewModel request, IList <ContentOptionValuesViewModel> childContentOptionValues, IPrincipal principal, out string[] errorMessages)
        {
            errorMessages = new string[0];
            string[] roles;
            if (request.DesirableStatus == ContentStatus.Published)
            {
                accessControlService.DemandAccess(principal, RootModuleConstants.UserRoles.PublishContent);
                roles = new[] { RootModuleConstants.UserRoles.PublishContent };
            }
            else
            {
                accessControlService.DemandAccess(principal, RootModuleConstants.UserRoles.EditContent);
                roles = new[] { RootModuleConstants.UserRoles.EditContent };
            }

            var isNew       = request.Id.HasDefaultValue();
            var userCanEdit = securityService.IsAuthorized(RootModuleConstants.UserRoles.EditContent);

            ValidateData(isNew, request);

            BlogPost        blogPost;
            BlogPostContent content;
            PageContent     pageContent;

            GetBlogPostAndContentEntities(request, principal, roles, ref isNew, out content, out pageContent, out blogPost);
            var beforeChange = new UpdatingBlogModel(blogPost);

            // Master page / layout
            Layout layout;
            Page   masterPage;
            Region region;

            LoadDefaultLayoutAndRegion(out layout, out masterPage, out region);

            if (masterPage != null)
            {
                var level = accessControlService.GetAccessLevel(masterPage, principal);
                if (level < AccessLevel.Read)
                {
                    var          message    = BlogGlobalization.SaveBlogPost_FailedToSave_InaccessibleMasterPage;
                    const string logMessage = "Failed to save blog post. Selected master page for page layout is inaccessible.";
                    throw new ValidationException(() => message, logMessage);
                }
            }

            if (pageContent.Region == null)
            {
                pageContent.Region = region;
            }

            // Load master pages for updating page's master path and page's children master path
            IList <Guid>       newMasterIds;
            IList <Guid>       oldMasterIds;
            IList <Guid>       childrenPageIds;
            IList <MasterPage> existingChildrenMasterPages;

            PrepareForUpdateChildrenMasterPages(isNew, blogPost, request, out newMasterIds, out oldMasterIds, out childrenPageIds, out existingChildrenMasterPages);

            // TODO: TEST AND TRY TO FIX IT: TRANSACTION HERE IS REQUIRED!
            // UnitOfWork.BeginTransaction(); // NOTE: this causes concurrent data exception.

            Redirect redirectCreated = null;

            if (!isNew && userCanEdit && !string.Equals(blogPost.PageUrl, request.BlogUrl) && !string.IsNullOrWhiteSpace(request.BlogUrl))
            {
                request.BlogUrl = urlService.FixUrl(request.BlogUrl);
                pageService.ValidatePageUrl(request.BlogUrl, request.Id);
                if (request.RedirectFromOldUrl)
                {
                    var redirect = redirectService.CreateRedirectEntity(blogPost.PageUrl, request.BlogUrl);
                    if (redirect != null)
                    {
                        repository.Save(redirect);
                        redirectCreated = redirect;
                    }
                }

                blogPost.PageUrl = urlService.FixUrl(request.BlogUrl);
            }

            // Push to change modified data each time.
            blogPost.ModifiedOn = DateTime.Now;

            if (userCanEdit)
            {
                blogPost.Title       = request.Title;
                blogPost.Description = request.IntroText;
                blogPost.Author      = request.AuthorId.HasValue ? repository.AsProxy <Author>(request.AuthorId.Value) : null;
                blogPost.Category    = request.CategoryId.HasValue ? repository.AsProxy <Category>(request.CategoryId.Value) : null;
                blogPost.Image       = (request.Image != null && request.Image.ImageId.HasValue) ? repository.AsProxy <MediaImage>(request.Image.ImageId.Value) : null;
                if (isNew || request.DesirableStatus == ContentStatus.Published)
                {
                    blogPost.ActivationDate = request.LiveFromDate;
                    blogPost.ExpirationDate = TimeHelper.FormatEndDate(request.LiveToDate);
                }
            }

            if (isNew)
            {
                if (!string.IsNullOrWhiteSpace(request.BlogUrl))
                {
                    blogPost.PageUrl = urlService.FixUrl(request.BlogUrl);
                    pageService.ValidatePageUrl(blogPost.PageUrl);
                }
                else
                {
                    blogPost.PageUrl = CreateBlogPermalink(request.Title, null, blogPost.Category != null ? (Guid?)blogPost.Category.Id : null);
                }

                blogPost.MetaTitle = request.MetaTitle ?? request.Title;
                if (masterPage != null)
                {
                    blogPost.MasterPage = masterPage;
                    masterPageService.SetPageMasterPages(blogPost, masterPage.Id);
                }
                else
                {
                    blogPost.Layout = layout;
                }
                UpdateStatus(blogPost, request.DesirableStatus);
                AddDefaultAccessRules(blogPost, principal, masterPage);
            }
            else if (request.DesirableStatus == ContentStatus.Published ||
                     blogPost.Status == PageStatus.Preview)
            {
                // Update only if publishing or current status is preview.
                // Else do not change, because it may change from published to draft status
                UpdateStatus(blogPost, request.DesirableStatus);
            }

            // Create content.
            var newContent = new BlogPostContent
            {
                Id               = content != null ? content.Id : Guid.Empty,
                Name             = request.Title,
                Html             = request.Content ?? string.Empty,
                EditInSourceMode = request.EditInSourceMode,
                ActivationDate   = request.LiveFromDate,
                ExpirationDate   = TimeHelper.FormatEndDate(request.LiveToDate)
            };

            // Preserve content if user is not authorized to change it.
            if (!userCanEdit)
            {
                if (content == null)
                {
                    throw new SecurityException("Forbidden: Access is denied."); // User has no rights to create new content.
                }

                var contentToPublish = (BlogPostContent)(content.History != null
                    ? content.History.FirstOrDefault(c => c.Status == ContentStatus.Draft) ?? content
                    : content);

                newContent.Name = contentToPublish.Name;
                newContent.Html = contentToPublish.Html;
            }

            content             = SaveContentWithStatusUpdate(isNew, newContent, request, principal);
            pageContent.Content = content;
            optionService.SaveChildContentOptions(content, childContentOptionValues, request.DesirableStatus);

            blogPost.PageUrlHash     = blogPost.PageUrl.UrlHash();
            blogPost.UseCanonicalUrl = request.UseCanonicalUrl;

            MapExtraProperties(isNew, blogPost, content, pageContent, request, principal);

            // Notify about page properties changing.
            var cancelEventArgs = Events.BlogEvents.Instance.OnBlogChanging(beforeChange, new UpdatingBlogModel(blogPost));

            if (cancelEventArgs.Cancel)
            {
                errorMessages = cancelEventArgs.CancellationErrorMessages.ToArray();
                return(null);
            }

            repository.Save(blogPost);
            repository.Save(content);
            repository.Save(pageContent);

            masterPageService.UpdateChildrenMasterPages(existingChildrenMasterPages, oldMasterIds, newMasterIds, childrenPageIds);

            pageContent.Content   = content;
            blogPost.PageContents = new [] { pageContent };



            IList <Tag> newTags = null;

            if (userCanEdit)
            {
                newTags = SaveTags(blogPost, request);
            }

            // Commit
            unitOfWork.Commit();

            // Notify about new created tags.
            Events.RootEvents.Instance.OnTagCreated(newTags);

            // Notify about new or updated blog post.
            if (isNew)
            {
                Events.BlogEvents.Instance.OnBlogCreated(blogPost);
            }
            else
            {
                Events.BlogEvents.Instance.OnBlogUpdated(blogPost);
            }

            // Notify about redirect creation.
            if (redirectCreated != null)
            {
                Events.PageEvents.Instance.OnRedirectCreated(redirectCreated);
            }

            return(blogPost);
        }