Umbraco-CMS/src/Umbraco.Web.Website/ViewEngines/ProfilingViewEngineWrapperMvcViewOptionsSetup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.ViewEngines;
using Microsoft.Extensions.Options;
using Umbraco.Core.Logging;

namespace Umbraco.Web.Website.ViewEngines
{
    /// <summary>
    /// Wraps all view engines with a <see cref="ProfilingViewEngine"/>
    /// </summary>
    public class ProfilingViewEngineWrapperMvcViewOptionsSetup : IConfigureOptions<MvcViewOptions>
    {
        private readonly IProfiler _profiler;

        /// <summary>
        /// Initializes a new instance of the <see cref="ProfilingViewEngineWrapperMvcViewOptionsSetup"/> class.
        /// </summary>
        /// <param name="profiler">The <see cref="IProfiler"/></param>
        public ProfilingViewEngineWrapperMvcViewOptionsSetup(IProfiler profiler) => _profiler = profiler ?? throw new ArgumentNullException(nameof(profiler));

        /// <inheritdoc/>
        public void Configure(MvcViewOptions options)
        {
            if (options == null)
            {
                throw new ArgumentNullException(nameof(options));
            }

            WrapViewEngines(options.ViewEngines);
        }

        private void WrapViewEngines(IList<IViewEngine> viewEngines)
        {
            if (viewEngines == null || viewEngines.Count == 0)
            {
                return;
            }

            var originalEngines = viewEngines.ToList();
            viewEngines.Clear();
            foreach (IViewEngine engine in originalEngines)
            {
                IViewEngine wrappedEngine = engine is ProfilingViewEngine ? engine : new ProfilingViewEngine(engine, _profiler);
                viewEngines.Add(wrappedEngine);
            }
        }
    }
}