// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Text;
using System.Text.Encodings.Web;
using System.Threading.Tasks;
using Microsoft.AspNet.Html;
using Microsoft.AspNet.Mvc.Internal;
using Microsoft.AspNet.Mvc.Logging;
using Microsoft.AspNet.Mvc.ModelBinding;
using Microsoft.AspNet.Mvc.Rendering;
using Microsoft.AspNet.Mvc.ViewEngines;
using Microsoft.AspNet.Mvc.ViewFeatures;
using Microsoft.AspNet.Mvc.ViewFeatures.Internal;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using Microsoft.Net.Http.Headers;

namespace Microsoft.AspNet.Mvc
{
    /// <summary>
    /// An <see cref="IActionResult"/> which renders a view component to the response.
    /// </summary>
    public class ViewComponentResult : ActionResult
    {
        /// <summary>
        /// Gets or sets the arguments provided to the view component.
        /// </summary>
        public object Arguments { get; set; }

        /// <summary>
        /// Gets or sets the <see cref="MediaTypeHeaderValue"/> representing the Content-Type header of the response.
        /// </summary>
        public MediaTypeHeaderValue ContentType { get; set; }

        /// <summary>
        /// Gets or sets the HTTP status code.
        /// </summary>
        public int? StatusCode { get; set; }

        /// <summary>
        /// Gets or sets the <see cref="ITempDataDictionary"/> for this result.
        /// </summary>
        public ITempDataDictionary TempData { get; set; }

        /// <summary>
        /// Gets or sets the name of the view component to invoke. Will be ignored if <see cref="ViewComponentType"/>
        /// is set to a non-<c>null</c> value.
        /// </summary>
        public string ViewComponentName { get; set; }

        /// <summary>
        /// Gets or sets the type of the view component to invoke.
        /// </summary>
        public Type ViewComponentType { get; set; }

        /// <summary>
        /// Gets or sets the <see cref="ViewDataDictionary"/> for this result.
        /// </summary>
        public ViewDataDictionary ViewData { get; set; }

        /// <summary>
        /// Gets or sets the <see cref="IViewEngine"/> used to locate views.
        /// </summary>
        /// <remarks>When <c>null</c>, an instance of <see cref="ICompositeViewEngine"/> from
        /// <c>ActionContext.HttpContext.RequestServices</c> is used.</remarks>
        public IViewEngine ViewEngine { get; set; }

        /// <inheritdoc />
        public override async Task ExecuteResultAsync(ActionContext context)
        {
            var response = context.HttpContext.Response;
            var services = context.HttpContext.RequestServices;

            var htmlHelperOptions = services.GetRequiredService<IOptions<MvcViewOptions>>().Value.HtmlHelperOptions;
            var viewComponentHelper = services.GetRequiredService<IViewComponentHelper>();

            var loggerFactory = services.GetRequiredService<ILoggerFactory>();
            var logger = loggerFactory.CreateLogger<ViewComponentResult>();
            var htmlEncoder = services.GetRequiredService<HtmlEncoder>();

            var viewData = ViewData;
            if (viewData == null)
            {
                var modelMetadataProvider = services.GetRequiredService<IModelMetadataProvider>();
                viewData = new ViewDataDictionary(modelMetadataProvider, context.ModelState);
            }

            var tempData = TempData;
            if (tempData == null)
            {
                var factory = services.GetRequiredService<ITempDataDictionaryFactory>();
                tempData = factory.GetTempData(context.HttpContext);
            }

            string resolvedContentType = null;
            Encoding resolvedContentTypeEncoding = null;
            ResponseContentTypeHelper.ResolveContentTypeAndEncoding(
                ContentType,
                response.ContentType,
                ViewExecutor.DefaultContentType,
                out resolvedContentType,
                out resolvedContentTypeEncoding);

            response.ContentType = resolvedContentType;

            if (StatusCode != null)
            {
                response.StatusCode = StatusCode.Value;
            }

            using (var writer = new HttpResponseStreamWriter(response.Body, resolvedContentTypeEncoding))
            {
                var viewContext = new ViewContext(
                    context,
                    NullView.Instance,
                    viewData,
                    tempData,
                    writer,
                    htmlHelperOptions);

                (viewComponentHelper as ICanHasViewContext)?.Contextualize(viewContext);
                var result = await GetViewComponentResult(viewComponentHelper, logger);

                result.WriteTo(writer, htmlEncoder);
            }
        }

        private Task<IHtmlContent> GetViewComponentResult(IViewComponentHelper viewComponentHelper, ILogger logger)
        {
            if (ViewComponentType == null && ViewComponentName == null)
            {
                throw new InvalidOperationException(Resources.FormatViewComponentResult_NameOrTypeMustBeSet(
                    nameof(ViewComponentName),
                    nameof(ViewComponentType)));
            }
            else if (ViewComponentType == null)
            {
                logger.ViewComponentResultExecuting(ViewComponentName);
                return viewComponentHelper.InvokeAsync(ViewComponentName, Arguments);
            }
            else
            {
                logger.ViewComponentResultExecuting(ViewComponentType);
                return viewComponentHelper.InvokeAsync(ViewComponentType, Arguments);
            }
        }
    }
}