From 6522724606707dcc77ecc155e76173cd01a74e47 Mon Sep 17 00:00:00 2001
From: konstantin <konstantin.klein@hochfrequenz.de>
Date: Fri, 14 Apr 2023 10:37:18 +0200
Subject: [PATCH] Add Extension Method to Load Requested MAUS or Fallback (#97)

---
 .../Interfaces/TemplateLoaderExtensions.cs    | 49 +++++++++++++
 EDILibraryTests/EDILibraryTests.csproj        |  1 +
 .../TemplateLoaderExtensionTests.cs           | 73 +++++++++++++++++++
 3 files changed, 123 insertions(+)
 create mode 100644 EDILibrary/Interfaces/TemplateLoaderExtensions.cs
 create mode 100644 EDILibraryTests/TemplateLoaderExtensionTests.cs

diff --git a/EDILibrary/Interfaces/TemplateLoaderExtensions.cs b/EDILibrary/Interfaces/TemplateLoaderExtensions.cs
new file mode 100644
index 0000000..e10648b
--- /dev/null
+++ b/EDILibrary/Interfaces/TemplateLoaderExtensions.cs
@@ -0,0 +1,49 @@
+using System;
+using System.Linq;
+using System.Threading.Tasks;
+using EDILibrary.MAUS;
+
+namespace EDILibrary.Interfaces
+{
+    /// <summary>
+    /// Extension methods for any <see cref="ITemplateLoader"/>
+    /// </summary>
+    public static class TemplateLoaderExtensions
+    {
+        /// <summary>
+        /// Calls the <see cref="ITemplateLoader.LoadMausTemplate"/> for all <see cref="EdifactFormatVersion"/>s younger than <paramref name="formatVersion"/> until a maus is found.
+        /// </summary>
+        /// <param name="loader"></param>
+        /// <param name="format"></param>
+        /// <param name="formatVersion"></param>
+        /// <param name="pid"></param>
+        /// <returns>
+        /// The MAUS matching the params or any maus younger than <paramref name="formatVersion"/> plus the actual format version of the loaded maus.
+        /// The latter can be used to e.g. log a warning in the application if the requested maus was not found and a fallback is used.
+        /// </returns>
+        public static async Task<Tuple<Anwendungshandbuch, EdifactFormatVersion?>> LoadMausTemplateOrFallback(this ITemplateLoader loader, EdifactFormat format, EdifactFormatVersion formatVersion, string pid)
+        {
+            var originalRequestedTemplate = await loader.LoadMausTemplate(format, formatVersion, pid);
+            if (originalRequestedTemplate is not null)
+            {
+                return new Tuple<Anwendungshandbuch, EdifactFormatVersion?>(originalRequestedTemplate, formatVersion);
+            }
+            foreach (var olderFormatVersion in Enum.GetValues<EdifactFormatVersion>().Where(fv => fv < formatVersion).OrderByDescending(fv => fv))
+            {
+                var olderMaus = await loader.LoadMausTemplate(format, olderFormatVersion, pid);
+                if (olderMaus != null)
+                {
+                    // Using the {PID} maus from format version {olderFormatVersion} as fallback for the requested {formatVersion} (DEV-20190), pid, olderFormatVersion, formatVersion);
+                    return new Tuple<Anwendungshandbuch, EdifactFormatVersion?>(olderMaus, olderFormatVersion);
+                }
+
+                if (olderFormatVersion == EdifactFormatVersion.FV1710)
+                {
+                    // No fallback found. This is not necessarily a problem.
+                    // No maus and no fallback found for {Pid}, {FormatVersion}
+                }
+            }
+            return new Tuple<Anwendungshandbuch, EdifactFormatVersion?>(null, null);
+        }
+    }
+}
diff --git a/EDILibraryTests/EDILibraryTests.csproj b/EDILibraryTests/EDILibraryTests.csproj
index 7d50ab4..53c4b57 100644
--- a/EDILibraryTests/EDILibraryTests.csproj
+++ b/EDILibraryTests/EDILibraryTests.csproj
@@ -5,6 +5,7 @@
     </PropertyGroup>
 
     <ItemGroup>
+        <PackageReference Include="FluentAssertions" Version="6.10.0" />
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.5.0" />
         <PackageReference Include="Moq" Version="4.18.4" />
         <PackageReference Include="MSTest.TestAdapter" Version="3.0.2" />
diff --git a/EDILibraryTests/TemplateLoaderExtensionTests.cs b/EDILibraryTests/TemplateLoaderExtensionTests.cs
new file mode 100644
index 0000000..6562292
--- /dev/null
+++ b/EDILibraryTests/TemplateLoaderExtensionTests.cs
@@ -0,0 +1,73 @@
+using System;
+using System.Linq;
+using System.Threading.Tasks;
+using EDILibrary;
+using EDILibrary.Interfaces;
+using EDILibrary.MAUS;
+using FluentAssertions;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Moq;
+
+
+namespace EDILibraryTests
+{
+    [TestClass]
+    public class TemplateLoaderExtensionTests
+    {
+        /// <summary>
+        /// In case the requested template exists, it should be loaded directly; Without using any fallback
+        /// </summary>
+        [TestMethod]
+        public async Task TestLoadingRegularTemplateIfExists()
+        {
+            var loaderMock = new Mock<ITemplateLoader>();
+            loaderMock.Setup(l => l.LoadMausTemplate(EdifactFormat.MSCONS, EdifactFormatVersion.FV2304, "13002")).ReturnsAsync(new Anwendungshandbuch()).Verifiable();
+
+            var loaderUnderTest = loaderMock.Object;
+            var (actualMaus, actualFormatVersion) = await loaderUnderTest.LoadMausTemplateOrFallback(EdifactFormat.MSCONS, EdifactFormatVersion.FV2304, "13002");
+            actualMaus.Should().NotBeNull();
+            actualFormatVersion.Should().Be(EdifactFormatVersion.FV2304);
+
+            loaderMock.VerifyAll();
+            loaderMock.VerifyNoOtherCalls();
+        }
+
+        /// <summary>
+        /// In case an older template exists, it should be returned instead of the requested one
+        /// </summary>
+        [TestMethod]
+        public async Task TestLoadingFallbackTemplateIfExists()
+        {
+            var loaderMock = new Mock<ITemplateLoader>();
+            loaderMock.Setup(l => l.LoadMausTemplate(EdifactFormat.MSCONS, EdifactFormatVersion.FV2304, "13002")).ReturnsAsync((Anwendungshandbuch)null).Verifiable();
+            loaderMock.Setup(l => l.LoadMausTemplate(EdifactFormat.MSCONS, EdifactFormatVersion.FV2210, "13002")).ReturnsAsync((Anwendungshandbuch)null).Verifiable();
+            loaderMock.Setup(l => l.LoadMausTemplate(EdifactFormat.MSCONS, EdifactFormatVersion.FV2110, "13002")).ReturnsAsync(new Anwendungshandbuch()).Verifiable();
+
+            var loaderUnderTest = loaderMock.Object;
+            var (actualMaus, actualFormatVersion) = await loaderUnderTest.LoadMausTemplateOrFallback(EdifactFormat.MSCONS, EdifactFormatVersion.FV2304, "13002");
+            actualMaus.Should().NotBeNull();
+            actualFormatVersion.Should().Be(EdifactFormatVersion.FV2110);
+
+            loaderMock.VerifyAll();
+            loaderMock.VerifyNoOtherCalls();
+        }
+
+        /// <summary>
+        /// If not even a fallback exists, only null should be returned
+        /// </summary>
+        [TestMethod]
+        public async Task TestLoadingNothingIfNotEvenAFallbackExists()
+        {
+            var loaderMock = new Mock<ITemplateLoader>();
+            loaderMock.Setup(l => l.LoadMausTemplate(EdifactFormat.MSCONS, It.IsAny<EdifactFormatVersion>(), "13002")).ReturnsAsync((Anwendungshandbuch)null).Verifiable();
+
+
+            var loaderUnderTest = loaderMock.Object;
+            var (actualMaus, actualFormatVersion) = await loaderUnderTest.LoadMausTemplateOrFallback(EdifactFormat.MSCONS, EdifactFormatVersion.FV2304, "13002");
+            actualMaus.Should().BeNull();
+            actualFormatVersion.Should().BeNull();
+
+            loaderMock.VerifyAll();
+        }
+    }
+}