Umbraco-CMS/src/Umbraco.Infrastructure/Routing/NotFoundHandlerHelper.cs

using System;
using System.Linq;
using Microsoft.Extensions.Logging;
using Umbraco.Cms.Core.Configuration.Models;
using Umbraco.Cms.Core.Models;
using Umbraco.Cms.Core.Models.Entities;
using Umbraco.Cms.Core.Models.PublishedContent;
using Umbraco.Cms.Core.Services;
using Umbraco.Cms.Core.Xml;
using Umbraco.Extensions;

namespace Umbraco.Cms.Core.Routing
{
    /// <summary>
    /// Used to determine the node to display when content is not found based on the configured error404 elements in umbracoSettings.config
    /// </summary>
    internal class NotFoundHandlerHelper
    {
        internal static int? GetCurrentNotFoundPageId(
            ContentErrorPage[] error404Collection,
            IEntityService entityService,
            IPublishedContentQuery publishedContentQuery,
            string errorCulture,
            int? domainContentId)
        {
            if (error404Collection.Length > 1)
            {
                // test if a 404 page exists with current culture thread
                ContentErrorPage cultureErr = error404Collection.FirstOrDefault(x => x.Culture.InvariantEquals(errorCulture))
                    ?? error404Collection.FirstOrDefault(x => x.Culture == "default"); // there should be a default one!

                if (cultureErr != null)
                {
                    return GetContentIdFromErrorPageConfig(cultureErr, entityService, publishedContentQuery, domainContentId);
                }
            }
            else if (error404Collection.Length == 1)
            {
                return GetContentIdFromErrorPageConfig(error404Collection.First(), entityService, publishedContentQuery, domainContentId);
            }

            return null;
        }

        /// <summary>
        /// Returns the content id based on the configured ContentErrorPage section.
        /// </summary>
        internal static int? GetContentIdFromErrorPageConfig(
            ContentErrorPage errorPage,
            IEntityService entityService,
            IPublishedContentQuery publishedContentQuery,
            int? domainContentId)
        {
            if (errorPage.HasContentId)
            {
                return errorPage.ContentId;
            }

            if (errorPage.HasContentKey)
            {
                // need to get the Id for the GUID
                // TODO: When we start storing GUIDs into the IPublishedContent, then we won't have to look this up
                // but until then we need to look it up in the db. For now we've implemented a cached service for
                // converting Int -> Guid and vice versa.
                Attempt<int> found = entityService.GetId(errorPage.ContentKey, UmbracoObjectTypes.Document);
                if (found)
                {
                    return found.Result;
                }

                return null;
            }

            if (errorPage.ContentXPath.IsNullOrWhiteSpace() == false)
            {
                try
                {
                    // we have an xpath statement to execute
                    var xpathResult = UmbracoXPathPathSyntaxParser.ParseXPathQuery(
                        xpathExpression: errorPage.ContentXPath,
                        nodeContextId: domainContentId,
                        getPath: nodeid =>
                        {
                            IEntitySlim ent = entityService.Get(nodeid);
                            return ent.Path.Split(',').Reverse();
                        },
                        publishedContentExists: i => publishedContentQuery.Content(i) != null);

                    // now we'll try to execute the expression
                    IPublishedContent nodeResult = publishedContentQuery.ContentSingleAtXPath(xpathResult);
                    if (nodeResult != null)
                    {
                        return nodeResult.Id;
                    }
                }
                catch (Exception ex)
                {
                    StaticApplicationLogging.Logger.LogError(ex, "Could not parse xpath expression: {ContentXPath}", errorPage.ContentXPath);
                    return null;
                }
            }

            return null;
        }

    }
}