Umbraco-CMS/src/Umbraco.Web.Common/Templates/TemplateRenderer.cs

using System;
using System.Globalization;
using System.IO;
using System.Linq;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Controllers;
using Microsoft.AspNetCore.Mvc.ModelBinding;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewEngines;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;
using Umbraco.Core;
using Umbraco.Core.Configuration.Models;
using Umbraco.Core.Configuration.UmbracoSettings;
using Umbraco.Core.Services;
using Umbraco.Core.Strings;
using Umbraco.Extensions;
using Umbraco.Web.Models;
using Umbraco.Web.Routing;
using Umbraco.Web.Templates;

namespace Umbraco.Web.Common.Templates
{
    /// <summary>
    /// This is used purely for the RenderTemplate functionality in Umbraco
    /// </summary>
    /// <remarks>
    /// This allows you to render an MVC template based purely off of a node id and an optional alttemplate id as string output.
    /// </remarks>
    internal class TemplateRenderer : ITemplateRenderer
    {
        private readonly IUmbracoContextAccessor _umbracoContextAccessor;
        private readonly IPublishedRouter _publishedRouter;
        private readonly IFileService _fileService;
        private readonly ILocalizationService _languageService;
        private readonly WebRoutingSettings _webRoutingSettings;
        private readonly IShortStringHelper _shortStringHelper;
        private readonly IHttpContextAccessor _httpContextAccessor;
        private readonly ICompositeViewEngine _viewEngine;

        public TemplateRenderer(IUmbracoContextAccessor umbracoContextAccessor,
            IPublishedRouter publishedRouter,
            IFileService fileService,
            ILocalizationService textService,
            IOptions<WebRoutingSettings> webRoutingSettings,
            IShortStringHelper shortStringHelper,
            IHttpContextAccessor httpContextAccessor,
            ICompositeViewEngine viewEngine)
        {
            _umbracoContextAccessor = umbracoContextAccessor ?? throw new ArgumentNullException(nameof(umbracoContextAccessor));
            _publishedRouter = publishedRouter ?? throw new ArgumentNullException(nameof(publishedRouter));
            _fileService = fileService ?? throw new ArgumentNullException(nameof(fileService));
            _languageService = textService ?? throw new ArgumentNullException(nameof(textService));
            _webRoutingSettings = webRoutingSettings.Value ?? throw new ArgumentNullException(nameof(webRoutingSettings));
            _shortStringHelper = shortStringHelper ?? throw new ArgumentNullException(nameof(shortStringHelper));
            _httpContextAccessor = httpContextAccessor ?? throw new ArgumentNullException(nameof(httpContextAccessor));
            _viewEngine = viewEngine ?? throw new ArgumentNullException(nameof(viewEngine));
        }

        public void Render(int pageId, int? altTemplateId, StringWriter writer)
        {
            if (writer == null) throw new ArgumentNullException(nameof(writer));

            var umbracoContext = _umbracoContextAccessor.GetRequiredUmbracoContext();
            // instantiate a request and process
            // important to use CleanedUmbracoUrl - lowercase path-only version of the current url, though this isn't going to matter
            // terribly much for this implementation since we are just creating a doc content request to modify it's properties manually.
            var contentRequest = _publishedRouter.CreateRequest(umbracoContext);

            var doc = contentRequest.UmbracoContext.Content.GetById(pageId);

            if (doc == null)
            {
                writer.Write("<!-- Could not render template for Id {0}, the document was not found -->", pageId);
                return;
            }

            //in some cases the UmbracoContext will not have a PublishedRequest assigned to it if we are not in the
            //execution of a front-end rendered page. In this case set the culture to the default.
            //set the culture to the same as is currently rendering
            if (umbracoContext.PublishedRequest == null)
            {
                var defaultLanguage = _languageService.GetAllLanguages().FirstOrDefault();
                contentRequest.Culture = defaultLanguage == null
                    ? CultureInfo.CurrentUICulture
                    : defaultLanguage.CultureInfo;
            }
            else
            {
                contentRequest.Culture = umbracoContext.PublishedRequest.Culture;
            }

            //set the doc that was found by id
            contentRequest.PublishedContent = doc;
            //set the template, either based on the AltTemplate found or the standard template of the doc
            var templateId = _webRoutingSettings.DisableAlternativeTemplates || !altTemplateId.HasValue
                ? doc.TemplateId
                : altTemplateId.Value;
            if (templateId.HasValue)
                contentRequest.TemplateModel = _fileService.GetTemplate(templateId.Value);

            //if there is not template then exit
            if (contentRequest.HasTemplate == false)
            {
                if (altTemplateId.HasValue == false)
                {
                    writer.Write("<!-- Could not render template for Id {0}, the document's template was not found with id {0}-->", doc.TemplateId);
                }
                else
                {
                    writer.Write("<!-- Could not render template for Id {0}, the altTemplate was not found with id {0}-->", altTemplateId);
                }
                return;
            }

            //First, save all of the items locally that we know are used in the chain of execution, we'll need to restore these
            //after this page has rendered.
            SaveExistingItems(out var oldPublishedRequest);

            try
            {
                //set the new items on context objects for this templates execution
                SetNewItemsOnContextObjects(contentRequest);

                //Render the template
                ExecuteTemplateRendering(writer, contentRequest);
            }
            finally
            {
                //restore items on context objects to continuing rendering the parent template
                RestoreItems(oldPublishedRequest);
            }

        }

        private void ExecuteTemplateRendering(TextWriter sw, IPublishedRequest request)
        {
            var httpContext = _httpContextAccessor.GetRequiredHttpContext();

            var viewResult = _viewEngine.GetView(null, $"~/Views/{request.TemplateAlias}.cshtml", false);

            if (viewResult.Success == false)
            {
                throw new InvalidOperationException($"A view with the name {request.TemplateAlias} could not be found");
            }

            var modelMetadataProvider = httpContext.RequestServices.GetRequiredService<IModelMetadataProvider>();
            var tempDataProvider = httpContext.RequestServices.GetRequiredService<ITempDataProvider>();

            var viewData = new ViewDataDictionary(modelMetadataProvider, new ModelStateDictionary())
            {
                Model = request.PublishedContent
            };

            var writer = new StringWriter();
            var viewContext = new ViewContext(
                new ActionContext(httpContext, httpContext.GetRouteData(), new ControllerActionDescriptor()),
                viewResult.View,
                viewData,
                new TempDataDictionary(httpContext, tempDataProvider),
                writer,
                new HtmlHelperOptions()
            );


            viewResult.View.RenderAsync(viewContext).GetAwaiter().GetResult();

            var output = writer.GetStringBuilder().ToString();

            sw.Write(output);
        }

        private void SetNewItemsOnContextObjects(IPublishedRequest request)
        {
            //now, set the new ones for this page execution
            _umbracoContextAccessor.UmbracoContext.PublishedRequest = request;
        }

        /// <summary>
        /// Save all items that we know are used for rendering execution to variables so we can restore after rendering
        /// </summary>
        private void SaveExistingItems(out IPublishedRequest oldPublishedRequest)
        {
            //Many objects require that these legacy items are in the http context items... before we render this template we need to first
            //save the values in them so that we can re-set them after we render so the rest of the execution works as per normal
            oldPublishedRequest = _umbracoContextAccessor.UmbracoContext.PublishedRequest;
        }

        /// <summary>
        /// Restores all items back to their context's to continue normal page rendering execution
        /// </summary>
        private void RestoreItems(IPublishedRequest oldPublishedRequest)
        {
            _umbracoContextAccessor.UmbracoContext.PublishedRequest = oldPublishedRequest;
        }
    }
}