refactor: Add MergeDirectory() method + tests

src/Common.Tests/Extensions/FileSystemExtensionsTest.cs

@@ -0,0 +1,116 @@
+using System.IO.Abstractions;
+using System.IO.Abstractions.TestingHelpers;
+using System.Text.RegularExpressions;
+using Common.Extensions;
+using FluentAssertions;
+using NUnit.Framework;
+
+namespace Common.Tests.Extensions;
+
+[TestFixture]
+[Parallelizable(ParallelScope.All)]
+public class FileSystemExtensionsTest
+{
+    private static IEnumerable<string> ReRootFiles(IFileSystem fs, IEnumerable<string> files,
+        string oldRoot, string newRoot)
+    {
+        return files.Select(x =>
+        {
+            var strippedPath = Regex.Replace(x, $"^{oldRoot}", newRoot);
+            return fs.Path.GetFullPath(strippedPath);
+        });
+    }
+
+    private static ICollection<string> NormalizePaths(IEnumerable<string> paths)
+        => paths.Select(NormalizePath).ToList();
+
+    private static string NormalizePath(string path)
+    {
+        if (MockUnixSupport.IsUnixPlatform())
+        {
+            return Regex.Replace(path, @"^C:\\", "/").Replace("\\", "/");
+        }
+
+        return Regex.Replace(path, @"^/", @"C:\").Replace("/", "\\");
+    }
+
+    private static MockFileSystem NewMockFileSystem(IEnumerable<string> files, string cwd)
+    {
+        return NewMockFileSystem(files, Array.Empty<string>(), cwd);
+    }
+
+    private static MockFileSystem NewMockFileSystem(IEnumerable<string> files, IEnumerable<string> dirs, string cwd)
+    {
+        var dirData = dirs.Select(x => (x, (MockFileData) new MockDirectoryData()));
+        var fileData = files.Select(x => (x, new MockFileData("")));
+
+        return new MockFileSystem(fileData.Concat(dirData)
+            .ToDictionary(x => x.Item1, y => y.Item2), NormalizePath(cwd));
+    }
+
+    [Test]
+    public void Merge_directories_works()
+    {
+        var files = NormalizePaths(new[]
+        {
+            @"path1\1\file1.txt",
+            @"path1\1\file2.txt",
+            @"path1\1\2\3\4\file3.txt",
+            @"path1\file4.txt"
+        });
+
+        var dirs = NormalizePaths(new[]
+        {
+            @"path1\empty1",
+            @"path1\empty2",
+            @"path1\1\2\empty3",
+            @"path1\1\2\3\4\empty4"
+        });
+
+        var fs = NewMockFileSystem(files, dirs, @"C:\root\path");
+
+        fs.MergeDirectory("path1", "path2");
+
+        fs.AllDirectories.Select(MockUnixSupport.Path).Should()
+            .NotContain(x => x.Contains("path1") || x.Contains("empty"));
+
+        fs.AllFiles.Should().BeEquivalentTo(ReRootFiles(fs, files, "path1", "path2"));
+    }
+
+    [Test]
+    public void Fail_if_file_already_exists()
+    {
+        var files = NormalizePaths(new[]
+        {
+            @"path1\1\file1.txt",
+            @"path1\1\file2.txt",
+            @"path2\1\file1.txt"
+        });
+
+        var fs = NewMockFileSystem(files, @"C:\root\path");
+
+        var act = () => fs.MergeDirectory("path1", "path2");
+
+        act.Should().Throw<IOException>();
+    }
+
+    [Test]
+    public void Fail_if_directory_exists_where_file_goes()
+    {
+        var files = NormalizePaths(new[]
+        {
+            @"path1\1\file1"
+        });
+
+        var dirs = NormalizePaths(new[]
+        {
+            @"path2\1\file1"
+        });
+
+        var fs = NewMockFileSystem(files, dirs, @"C:\root\path");
+
+        var act = () => fs.MergeDirectory("path1", "path2");
+
+        act.Should().Throw<IOException>();
+    }
+}

src/Common/Extensions/FileSystemExtensions.cs

@@ -0,0 +1,30 @@
+using System.IO.Abstractions;
+using System.Text.RegularExpressions;
+
+namespace Common.Extensions;
+
+public static class FileSystemExtensions
+{
+    public static void MergeDirectory(this IFileSystem fs, string targetDir, string destDir)
+    {
+        targetDir = fs.Path.GetFullPath(targetDir);
+        destDir = fs.Path.GetFullPath(destDir);
+
+        var directories = fs.DirectoryInfo.FromDirectoryName(targetDir)
+            .EnumerateDirectories("*", SearchOption.AllDirectories)
+            .Append(fs.DirectoryInfo.FromDirectoryName(targetDir))
+            .OrderByDescending(x => x.FullName.Count(y => y is '/' or '\\'));
+
+        foreach (var dir in directories)
+        {
+            foreach (var file in dir.EnumerateFiles())
+            {
+                var newPath = Regex.Replace(file.FullName, $"^{Regex.Escape(targetDir)}", destDir);
+                fs.Directory.CreateDirectory(fs.Path.GetDirectoryName(newPath));
+                file.MoveTo(newPath);
+            }
+
+            dir.Delete();
+        }
+    }
+}