FormActionTagHelper.cs

// 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.Collections.Generic;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.Routing;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Razor.TagHelpers;
using Microsoft.AspNetCore.Routing;

namespace Microsoft.AspNetCore.Mvc.TagHelpers
{
    /// <summary>
    /// <see cref="ITagHelper"/> implementation targeting &lt;button&gt; elements and &lt;input&gt; elements with
    /// their <c>type</c> attribute set to <c>image</c> or <c>submit</c>.
    /// </summary>
    [HtmlTargetElement("button", Attributes = ActionAttributeName)]
    [HtmlTargetElement("button", Attributes = ControllerAttributeName)]
    [HtmlTargetElement("button", Attributes = AreaAttributeName)]
    [HtmlTargetElement("button", Attributes = PageAttributeName)]
    [HtmlTargetElement("button", Attributes = PageHandlerAttributeName)]
    [HtmlTargetElement("button", Attributes = FragmentAttributeName)]
    [HtmlTargetElement("button", Attributes = RouteAttributeName)]
    [HtmlTargetElement("button", Attributes = RouteValuesDictionaryName)]
    [HtmlTargetElement("button", Attributes = RouteValuesPrefix + "*")]
    [HtmlTargetElement("input", Attributes = ImageActionAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = ImageControllerAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = ImageAreaAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = ImagePageAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = ImagePageHandlerAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = ImageFragmentAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = ImageRouteAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = ImageRouteValuesDictionarySelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = ImageRouteValuesSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = SubmitActionAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = SubmitControllerAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = SubmitAreaAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = SubmitPageAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = SubmitPageHandlerAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = SubmitFragmentAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = SubmitRouteAttributeSelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = SubmitRouteValuesDictionarySelector, TagStructure = TagStructure.WithoutEndTag)]
    [HtmlTargetElement("input", Attributes = SubmitRouteValuesSelector, TagStructure = TagStructure.WithoutEndTag)]
    public class FormActionTagHelper : TagHelper
    {
        private const string ActionAttributeName = "asp-action";
        private const string AreaAttributeName = "asp-area";
        private const string ControllerAttributeName = "asp-controller";
        private const string PageAttributeName = "asp-page";
        private const string PageHandlerAttributeName = "asp-page-handler";
        private const string FragmentAttributeName = "asp-fragment";
        private const string RouteAttributeName = "asp-route";
        private const string RouteValuesDictionaryName = "asp-all-route-data";
        private const string RouteValuesPrefix = "asp-route-";
        private const string FormAction = "formaction";

        private const string ImageTypeSelector = "[type=image], ";
        private const string ImageActionAttributeSelector = ImageTypeSelector + ActionAttributeName;
        private const string ImageAreaAttributeSelector = ImageTypeSelector + AreaAttributeName;
        private const string ImagePageAttributeSelector = ImageTypeSelector + PageAttributeName;
        private const string ImagePageHandlerAttributeSelector = ImageTypeSelector + PageHandlerAttributeName;
        private const string ImageFragmentAttributeSelector = ImageTypeSelector + FragmentAttributeName;
        private const string ImageControllerAttributeSelector = ImageTypeSelector + ControllerAttributeName;
        private const string ImageRouteAttributeSelector = ImageTypeSelector + RouteAttributeName;
        private const string ImageRouteValuesDictionarySelector = ImageTypeSelector + RouteValuesDictionaryName;
        private const string ImageRouteValuesSelector = ImageTypeSelector + RouteValuesPrefix + "*";

        private const string SubmitTypeSelector = "[type=submit], ";
        private const string SubmitActionAttributeSelector = SubmitTypeSelector + ActionAttributeName;
        private const string SubmitAreaAttributeSelector = SubmitTypeSelector + AreaAttributeName;
        private const string SubmitPageAttributeSelector = SubmitTypeSelector + PageAttributeName;
        private const string SubmitPageHandlerAttributeSelector = SubmitTypeSelector + PageHandlerAttributeName;
        private const string SubmitFragmentAttributeSelector = SubmitTypeSelector + FragmentAttributeName;
        private const string SubmitControllerAttributeSelector = SubmitTypeSelector + ControllerAttributeName;
        private const string SubmitRouteAttributeSelector = SubmitTypeSelector + RouteAttributeName;
        private const string SubmitRouteValuesDictionarySelector = SubmitTypeSelector + RouteValuesDictionaryName;
        private const string SubmitRouteValuesSelector = SubmitTypeSelector + RouteValuesPrefix + "*";

        private IDictionary<string, string> _routeValues;

        /// <summary>
        /// Creates a new <see cref="FormActionTagHelper"/>.
        /// </summary>
        /// <param name="urlHelperFactory">The <see cref="IUrlHelperFactory"/>.</param>
        public FormActionTagHelper(IUrlHelperFactory urlHelperFactory)
        {
            UrlHelperFactory = urlHelperFactory;
        }

        /// <inheritdoc />
        public override int Order => -1000;

        /// <summary>
        /// Gets or sets the <see cref="Rendering.ViewContext"/> for the current request.
        /// </summary>
        [HtmlAttributeNotBound]
        [ViewContext]
        public ViewContext ViewContext { get; set; }

        protected IUrlHelperFactory UrlHelperFactory { get; }

        /// <summary>
        /// The name of the action method.
        /// </summary>
        [HtmlAttributeName(ActionAttributeName)]
        public string Action { get; set; }

        /// <summary>
        /// The name of the controller.
        /// </summary>
        [HtmlAttributeName(ControllerAttributeName)]
        public string Controller { get; set; }

        /// <summary>
        /// The name of the area.
        /// </summary>
        [HtmlAttributeName(AreaAttributeName)]
        public string Area { get; set; }

        /// <summary>
        /// The name of the page.
        /// </summary>
        [HtmlAttributeName(PageAttributeName)]
        public string Page { get; set; }

        /// <summary>
        /// The name of the page handler.
        /// </summary>
        [HtmlAttributeName(PageHandlerAttributeName)]
        public string PageHandler { get; set; }

        /// <summary>
        /// Gets or sets the URL fragment.
        /// </summary>
        [HtmlAttributeName(FragmentAttributeName)]
        public string Fragment { get; set; }

        /// <summary>
        /// Name of the route.
        /// </summary>
        /// <remarks>
        /// Must be <c>null</c> if <see cref="Action"/> or <see cref="Controller"/> is non-<c>null</c>.
        /// </remarks>
        [HtmlAttributeName(RouteAttributeName)]
        public string Route { get; set; }

        /// <summary>
        /// Additional parameters for the route.
        /// </summary>
        [HtmlAttributeName(RouteValuesDictionaryName, DictionaryAttributePrefix = RouteValuesPrefix)]
        public IDictionary<string, string> RouteValues
        {
            get
            {
                if (_routeValues == null)
                {
                    _routeValues = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
                }

                return _routeValues;
            }
            set
            {
                _routeValues = value;
            }
        }

        /// <inheritdoc />
        /// <remarks>Does nothing if user provides an <c>FormAction</c> attribute.</remarks>
        /// <exception cref="InvalidOperationException">
        /// Thrown if <c>FormAction</c> attribute is provided and <see cref="Action"/>, <see cref="Controller"/>,
        /// <see cref="Fragment"/> or <see cref="Route"/> are non-<c>null</c> or if the user provided <c>asp-route-*</c> attributes.
        /// Also thrown if <see cref="Route"/> and one or both of <see cref="Action"/> and <see cref="Controller"/>
        /// are non-<c>null</c>
        /// </exception>
        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            if (output == null)
            {
                throw new ArgumentNullException(nameof(output));
            }

            // If "FormAction" is already set, it means the user is attempting to use a normal button or input element.
            if (output.Attributes.ContainsName(FormAction))
            {
                if (Action != null ||
                    Controller != null ||
                    Area != null ||
                    Page != null ||
                    PageHandler != null ||
                    Fragment != null ||
                    Route != null ||
                    (_routeValues != null && _routeValues.Count > 0))
                {
                    // User specified a FormAction and one of the bound attributes; can't override that FormAction
                    // attribute.
                    throw new InvalidOperationException(
                        Resources.FormatFormActionTagHelper_CannotOverrideFormAction(
                            FormAction,
                            output.TagName,
                            RouteValuesPrefix,
                            ActionAttributeName,
                            ControllerAttributeName,
                            AreaAttributeName,
                            FragmentAttributeName,
                            RouteAttributeName,
                            PageAttributeName,
                            PageHandlerAttributeName));
                }

                return;
            }

            var routeLink = Route != null;
            var actionLink = Controller != null || Action != null;
            var pageLink = Page != null || PageHandler != null;

            if ((routeLink && actionLink) || (routeLink && pageLink) || (actionLink && pageLink))
            {
                var message = string.Join(
                    Environment.NewLine,
                    Resources.FormatCannotDetermineAttributeFor(FormAction, '<' + output.TagName + '>'),
                    RouteAttributeName,
                    ControllerAttributeName + ", " + ActionAttributeName,
                    PageAttributeName + ", " + PageHandlerAttributeName);

                throw new InvalidOperationException(message);
            }

            RouteValueDictionary routeValues = null;
            if (_routeValues != null && _routeValues.Count > 0)
            {
                routeValues = new RouteValueDictionary(_routeValues);
            }

            if (Area != null)
            {
                if (routeValues == null)
                {
                    routeValues = new RouteValueDictionary();
                }

                // Unconditionally replace any value from asp-route-area.
                routeValues["area"] = Area;
            }

            var urlHelper = UrlHelperFactory.GetUrlHelper(ViewContext);
            string url;
            if (pageLink)
            {
                url = urlHelper.Page(Page, PageHandler, routeValues, protocol: null, host: null, fragment: Fragment);
            }
            else if (routeLink)
            {
                url = urlHelper.RouteUrl(Route, routeValues, protocol: null, host: null, fragment: Fragment);
            }
            else
            {
                url = urlHelper.Action(Action, Controller, routeValues, protocol: null, host: null, fragment: Fragment);
            }

            output.Attributes.SetAttribute(FormAction, url);
        }
    }
}