Add support for HandleBars File (to read a file) (#278)

* HandleBarsFileFragment

* 1.0.17

* {{File}}

src/WireMock.Net/Handlers/IFileSystemHandler.cs

@@ -49,12 +49,19 @@ namespace WireMock.Handlers
         void WriteMappingFile([NotNull] string path, [NotNull] string text);
 
         /// <summary>
-        /// Read a response body file as text.
+        /// Read a response body file as byte[].
         /// </summary>
         /// <param name="path">The path or filename from the file to read.</param>
         /// <returns>The file content as bytes.</returns>
         byte[] ReadResponseBodyAsFile([NotNull] string path);
 
+        /// <summary>
+        /// Read a response body file as text.
+        /// </summary>
+        /// <param name="path">The path or filename from the file to read.</param>
+        /// <returns>The file content as text.</returns>
+        string ReadResponseBodyAsString([NotNull] string path);
+
         /// <summary>
         /// Delete a file.
         /// </summary>

src/WireMock.Net/Handlers/LocalFileSystemHandler.cs

@@ -68,6 +68,16 @@ namespace WireMock.Handlers
             return File.ReadAllBytes(Path.GetFileName(path) == path ? Path.Combine(GetMappingFolder(), path) : path);
         }
 
+        /// <inheritdoc cref="IFileSystemHandler.ReadResponseBodyAsString"/>
+        public string ReadResponseBodyAsString(string path)
+        {
+            Check.NotNullOrEmpty(path, nameof(path));
+
+            // In case the path is a filename, the path will be adjusted to the MappingFolder.
+            // Else the path will just be as-is.
+            return File.ReadAllText(Path.GetFileName(path) == path ? Path.Combine(GetMappingFolder(), path) : path);
+        }
+
         /// <inheritdoc cref="IFileSystemHandler.FileExists"/>
         public bool FileExists(string filename)
         {

src/WireMock.Net/ResponseBuilders/Response.cs

@@ -21,7 +21,8 @@ namespace WireMock.ResponseBuilders
     /// </summary>
     public class Response : IResponseBuilder
     {
-        private readonly IFileSystemHandler _fileSystemHandler = new LocalFileSystemHandler();
+        private readonly IFileSystemHandler _fileSystemHandler;
+        private readonly ResponseMessageTransformer _responseMessageTransformer;
         private HttpClient _httpClientForProxy;
 
         /// <summary>
@@ -93,6 +94,9 @@ namespace WireMock.ResponseBuilders
         private Response(ResponseMessage responseMessage)
         {
             ResponseMessage = responseMessage;
+
+            _fileSystemHandler = new LocalFileSystemHandler();
+            _responseMessageTransformer = new ResponseMessageTransformer(_fileSystemHandler);
         }
 
         /// <summary>
@@ -417,7 +421,7 @@ namespace WireMock.ResponseBuilders
 
             if (UseTransformer)
             {
-                return ResponseMessageTransformer.Transform(requestMessage, ResponseMessage);
+                return _responseMessageTransformer.Transform(requestMessage, ResponseMessage);
             }
 
             // Just return normal defined ResponseMessage

src/WireMock.Net/Transformers/HandleBarsFile.cs

@@ -0,0 +1,41 @@
+using HandlebarsDotNet;
+using System;
+using WireMock.Handlers;
+using WireMock.Validation;
+
+namespace WireMock.Transformers
+{
+    internal static class HandleBarsFile
+    {
+        public static void Register(IHandlebars handlebarsContext, IFileSystemHandler fileSystemHandler)
+        {
+            handlebarsContext.RegisterHelper("File", (writer, context, arguments) =>
+            {
+                string value = ParseArgumentAndReadFileFragment(handlebarsContext, context, fileSystemHandler, arguments);
+                writer.Write(value);
+            });
+
+            handlebarsContext.RegisterHelper("File", (writer, options, context, arguments) =>
+            {
+                string value = ParseArgumentAndReadFileFragment(handlebarsContext, context, fileSystemHandler, arguments);
+                options.Template(writer, value);
+            });
+        }
+
+        private static string ParseArgumentAndReadFileFragment(IHandlebars handlebarsContext, dynamic context, IFileSystemHandler fileSystemHandler, object[] arguments)
+        {
+            Check.Condition(arguments, args => args.Length == 1, nameof(arguments));
+            Check.NotNull(arguments[0], "arguments[0]");
+
+            switch (arguments[0])
+            {
+                case string path:
+                    var templateFunc = handlebarsContext.Compile(path);
+                    string transformed = templateFunc(context);
+                    return fileSystemHandler.ReadResponseBodyAsString(transformed);
+            }
+
+            throw new NotSupportedException($"The value '{arguments[0]}' with type '{arguments[0]?.GetType()}' cannot be used in Handlebars File.");
+        }
+    }
+}

src/WireMock.Net/Transformers/HandleBarsHelpers.cs

@@ -1,10 +1,11 @@
 using HandlebarsDotNet;
+using WireMock.Handlers;
 
 namespace WireMock.Transformers
 {
     internal static class HandlebarsHelpers
     {
-        public static void Register(IHandlebars handlebarsContext)
+        public static void Register(IHandlebars handlebarsContext, IFileSystemHandler fileSystemHandler)
         {
             HandleBarsRegex.Register(handlebarsContext);
 
@@ -15,6 +16,8 @@ namespace WireMock.Transformers
             HandleBarsRandom.Register(handlebarsContext);
 
             HandleBarsXeger.Register(handlebarsContext);
+
+            HandleBarsFile.Register(handlebarsContext, fileSystemHandler);
         }
     }
 }

src/WireMock.Net/Transformers/ResponseMessageTransformer.cs

@@ -1,14 +1,17 @@
 using HandlebarsDotNet;
+using JetBrains.Annotations;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using WireMock.Handlers;
 using WireMock.Util;
+using WireMock.Validation;
 
 namespace WireMock.Transformers
 {
-    internal static class ResponseMessageTransformer
+    internal class ResponseMessageTransformer
     {
         private static readonly HandlebarsConfiguration HandlebarsConfiguration = new HandlebarsConfiguration
         {
@@ -17,12 +20,14 @@ namespace WireMock.Transformers
 
         private static readonly IHandlebars HandlebarsContext = Handlebars.Create(HandlebarsConfiguration);
 
-        static ResponseMessageTransformer()
+        public ResponseMessageTransformer([NotNull] IFileSystemHandler fileSystemHandler)
         {
-            HandlebarsHelpers.Register(HandlebarsContext);
+            Check.NotNull(fileSystemHandler, nameof(fileSystemHandler));
+
+            HandlebarsHelpers.Register(HandlebarsContext, fileSystemHandler);
         }
 
-        public static ResponseMessage Transform(RequestMessage requestMessage, ResponseMessage original)
+        public ResponseMessage Transform(RequestMessage requestMessage, ResponseMessage original)
         {
             var responseMessage = new ResponseMessage { StatusCode = original.StatusCode };
 
@@ -90,14 +95,14 @@ namespace WireMock.Transformers
             };
         }
 
-        private static void WalkNode(JToken node, object template)
+        private static void WalkNode(JToken node, object context)
         {
             if (node.Type == JTokenType.Object)
             {
                 // In case of Object, loop all children. Do a ToArray() to avoid `Collection was modified` exceptions.
                 foreach (JProperty child in node.Children<JProperty>().ToArray())
                 {
-                    WalkNode(child.Value, template);
+                    WalkNode(child.Value, context);
                 }
             }
             else if (node.Type == JTokenType.Array)
@@ -105,7 +110,7 @@ namespace WireMock.Transformers
                 // In case of Array, loop all items. Do a ToArray() to avoid `Collection was modified` exceptions.
                 foreach (JToken child in node.Children().ToArray())
                 {
-                    WalkNode(child, template);
+                    WalkNode(child, context);
                 }
             }
             else if (node.Type == JTokenType.String)
@@ -118,7 +123,7 @@ namespace WireMock.Transformers
                 }
 
                 var templateForStringValue = HandlebarsContext.Compile(stringValue);
-                string transformedString = templateForStringValue(template);
+                string transformedString = templateForStringValue(context);
                 if (!string.Equals(stringValue, transformedString))
                 {
                     ReplaceNodeValue(node, transformedString);

src/WireMock.Net/WireMock.Net.csproj

@@ -62,7 +62,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
     </PackageReference>
     <PackageReference Include="System.Linq.Dynamic.Core" Version="1.0.12" />
-    <PackageReference Include="RandomDataGenerator.Net" Version="1.0.7" />
+    <PackageReference Include="RandomDataGenerator.Net" Version="1.0.8" />
     <PackageReference Include="JmesPath.Net" Version="1.0.125" />
   </ItemGroup>