From bffdc71f4c8359e9d418bb5e6eef4ee12286e72b Mon Sep 17 00:00:00 2001
From: Dan Pettersson <dan82pettersson@gmail.com>
Date: Sat, 15 Jul 2017 07:06:53 +0200
Subject: [PATCH] Creating the AureliaBindTagHelper to render Aurelia bindings
 for ASP.NET MVC model members

---
 .../TagHelpers/AureliaBindTagHelper.cs        | 139 ++++++++++++++++++
 src/FooBar.Web/Views/Home/Person.cshtml       |  15 +-
 2 files changed, 148 insertions(+), 6 deletions(-)
 create mode 100644 src/FooBar.Web/TagHelpers/AureliaBindTagHelper.cs

diff --git a/src/FooBar.Web/TagHelpers/AureliaBindTagHelper.cs b/src/FooBar.Web/TagHelpers/AureliaBindTagHelper.cs
new file mode 100644
index 0000000..cae551b
--- /dev/null
+++ b/src/FooBar.Web/TagHelpers/AureliaBindTagHelper.cs
@@ -0,0 +1,139 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc.ViewFeatures;
+using Microsoft.AspNetCore.Razor.TagHelpers;
+
+namespace FooBar.Web.TagHelpers
+{
+	[HtmlTargetElement(Attributes = VkAuBindPrefix + "*")]
+	public class AureliaBindTagHelper : TagHelper
+	{
+		private const string VkAuBindPrefix = "th-au-bind-";
+		private const string VkAuValueConvertersPrefix = "th-au-value-converters-";
+		private const string VkAuBindingBehaviorsPrefix = "th-au-binding-behaviors-";
+
+		private IDictionary<string, ModelExpression> _allModels;
+		/// <summary>
+		/// If attribute is foo and MVC Model member is Bar; th-au-bind-foo="Bar"
+		/// To change binding type from default .bind; th-au-bind-foo.one-time="Bar" (other possibles are .one-way and .two-way) 
+		/// </summary>
+		[HtmlAttributeName("th-au-all-models", DictionaryAttributePrefix = VkAuBindPrefix)]
+		public IDictionary<string, ModelExpression> AllModels {
+			get {
+				return _allModels ??
+					   (_allModels = new Dictionary<string, ModelExpression>(StringComparer.OrdinalIgnoreCase));
+			}
+			set {
+				_allModels = value;
+			}
+		}
+
+		private IDictionary<string, string> _allValueConverters;
+		/// <summary>
+		/// Aurelia Value Converters to use for each binding. If multiple separate with |.
+		/// To set for attribute foo: th-au-value-converters-foo="conv1"
+		/// </summary>
+		[HtmlAttributeName("th-au-all-value-converters", DictionaryAttributePrefix = VkAuValueConvertersPrefix)]
+		public IDictionary<string, string> AllValueConverters {
+			get {
+				return _allValueConverters ??
+					   (_allValueConverters = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase));
+			}
+			set {
+				_allValueConverters = value;
+			}
+		}
+
+		private IDictionary<string, string> _allBindingBehaviors;
+		/// <summary>
+		/// Aurelia Binding Behaviours to use for each binding. If multiple separate with &.
+		/// To set for attribute foo: th-au-binding-behaviors-foo="beh1"
+		/// </summary>
+		[HtmlAttributeName("th-au-all-binding-behaviors", DictionaryAttributePrefix = VkAuBindingBehaviorsPrefix)]
+		public IDictionary<string, string> AllBindingBehaviors {
+			get {
+				return _allBindingBehaviors ??
+					   (_allBindingBehaviors = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase));
+			}
+			set {
+				_allBindingBehaviors = value;
+			}
+		}
+
+		public override void Process(TagHelperContext context, TagHelperOutput output)
+		{
+			foreach (KeyValuePair<string, ModelExpression> item in AllModels)
+			{
+				string attributeName = item.Key;
+				string bindType = "bind";
+				if (attributeName.Contains("."))
+				{
+					var parts = attributeName.Split('.');
+					attributeName = parts[0];
+					bindType = parts[1];
+				}
+
+				string expression = BuildExpression(item.Value);
+
+				string valueConverters = "";
+				if (AllValueConverters.ContainsKey(attributeName))
+				{
+					valueConverters = AllValueConverters[attributeName];
+				}
+
+				string bindingBehaviors = "";
+				if (AllBindingBehaviors.ContainsKey(attributeName))
+				{
+					bindingBehaviors = AllBindingBehaviors[attributeName];
+				}
+
+				expression = AddConvertersAndBehaviors(expression, valueConverters, bindingBehaviors);
+
+				output.Attributes.SetAttribute(attributeName + "." + bindType, expression);
+			}
+		}
+
+		public static string BuildExpression(ModelExpression model)
+		{
+			string name = model.Name;
+
+			if (String.IsNullOrEmpty(name))
+			{
+				throw new InvalidOperationException("AureliaGenericBindTagHelper could not resolve name from the given ModelExpression.");
+			}
+
+			string result = string.Empty;
+			string[] parts = name.Split('.');
+			for (int i = 0; i < parts.Length; i++)
+			{
+				if (i > 0)
+				{
+					result += ".";
+				}
+				string part = parts[i][0].ToString().ToLowerInvariant() + parts[i].Substring(1); //Make camelCase;
+				result += part;
+			}
+			result = "data." + result; //"data" is by convention the name of any MVC Model added as data to a client side model.
+			return result;
+		}
+
+		public static string AddConvertersAndBehaviors(string bindExpression, string valueConverters, string bindingBehaviors)
+		{
+			string result = bindExpression;
+
+			if (!String.IsNullOrWhiteSpace(valueConverters))
+			{
+				result += " | " + valueConverters;
+			}
+
+			if (!String.IsNullOrWhiteSpace(bindingBehaviors))
+			{
+				result += " & " + bindingBehaviors;
+			}
+
+			return result;
+		}
+	}
+}
\ No newline at end of file
diff --git a/src/FooBar.Web/Views/Home/Person.cshtml b/src/FooBar.Web/Views/Home/Person.cshtml
index adfc48a..b050860 100644
--- a/src/FooBar.Web/Views/Home/Person.cshtml
+++ b/src/FooBar.Web/Views/Home/Person.cshtml
@@ -1,5 +1,5 @@
 @{
-    ViewData["Title"] = "Person";
+	ViewData["Title"] = "Person";
 }
 
 @model FooBar.Web.Models.PersonModel
@@ -7,7 +7,7 @@
 <div th-aurelia-enhance-module="app/views/home/home-person" th-aurelia-enhance-data="@Model">
 	<h1>Edit Person</h1>
 
-	@if(ViewData.ContainsKey("Feedback"))
+	@if (ViewData.ContainsKey("Feedback"))
 	{
 		<div class="alert alert-info">
 			@ViewData["Feedback"]
@@ -17,17 +17,20 @@
 	<form asp-action="Person" data-ajax="true">
 		<div class="form-group">
 			<label asp-for="FirstName"></label>
-			<input asp-for="FirstName" class="form-control" value.bind="data.firstName" />
+			<input asp-for="FirstName" class="form-control" th-au-bind-value="FirstName" />
 		</div>
 
 		<div class="form-group">
 			<label asp-for="LastName"></label>
-			<input asp-for="LastName" class="form-control" value.bind="data.lastName" />
+			<input asp-for="LastName" class="form-control" th-au-bind-value="LastName" />
 		</div>
 
 		<div class="form-group">
 			<label>Full name</label>
-			<div>${data.firstName} ${data.lastName}</div>
+			<div>
+				<span th-au-bind-textcontent="FirstName"></span>
+				<span th-au-bind-textcontent="LastName"></span>
+			</div>
 		</div>
 
 		<div class="form-group">
@@ -37,7 +40,7 @@
 
 		<div class="form-group">
 			<label asp-for="Age"></label>
-			<input asp-for="Age" class="form-control" value.bind="data.age" />
+			<input asp-for="Age" class="form-control" th-au-bind-value="Age" />
 		</div>
 
 		<div class="form-group">