FileSystem: Add API to create a file using a path

Just like creating a folder from `FileSystem`, you can now create a file
using just a path, and any intermediate parent folders in that path will
also be created.

Sources/Files.swift

@@ -164,20 +164,9 @@ public class FileSystem {
 
         /// The folder that the item is contained in, or `nil` if this item is the root folder of the file system
         public var parent: Folder? {
-            guard path != "/" else {
-                return nil
+            return fileManager.parentPath(for: path).flatMap { parentPath in
+                return try? Folder(path: parentPath, using: fileManager)
             }
-
-            var pathComponents = path.pathComponents
-
-            switch kind {
-            case .file:
-                pathComponents.removeLast()
-            case .folder:
-                pathComponents.removeLast(2)
-            }
-
-            return try? Folder(path: pathComponents.joined(separator: "/"), using: fileManager)
         }
 
         /// A string describing the item
@@ -312,18 +301,45 @@ public class FileSystem {
         self.fileManager = fileManager
     }
 
+    /**
+     *  Create a new file at a given path
+     *
+     *  - parameter path: The path at which a file should be created. If the path is missing intermediate
+     *                    parent folders, those will be created as well.
+     *
+     *  - throws: `File.Error.writeFailed`
+     *
+     *  - returns: The file that was created
+     */
+    @discardableResult public func createFile(at path: String, contents: Data = Data()) throws -> File {
+        let path = fileManager.absolutePath(for: path)
+
+        guard let parentPath = fileManager.parentPath(for: path) else {
+            throw File.Error.writeFailed
+        }
+
+        do {
+            let name = path.substring(from: path.index(path.startIndex, offsetBy: parentPath.characters.count))
+            return try createFolder(at: parentPath).createFile(named: name, contents: contents)
+        } catch {
+            throw File.Error.writeFailed
+        }
+    }
+
     /**
      *  Create a new folder at a given path
      *
      *  - parameter path: The path at which a folder should be created. If the path is missing intermediate
      *                    parent folders, those will be created as well.
      *
      *  - throws: `Folder.Error.creatingFolderFailed`
+     *
+     *  - returns: The folder that was created
      */
     @discardableResult public func createFolder(at path: String) throws -> Folder {
         do {
-            let absolutePath = fileManager.absolutePath(for: path)
-            try fileManager.createDirectory(atPath: absolutePath, withIntermediateDirectories: true, attributes: nil)
+            let path = fileManager.absolutePath(for: path)
+            try fileManager.createDirectory(atPath: path, withIntermediateDirectories: true, attributes: nil)
             return try Folder(path: path, using: fileManager)
         } catch {
             throw Folder.Error.creatingFolderFailed
@@ -827,6 +843,22 @@ private extension FileManager {
 
         return currentDirectoryPath + "/" + path
     }
+
+    func parentPath(for path: String) -> String? {
+        guard path != "/" else {
+            return nil
+        }
+
+        var pathComponents = path.pathComponents
+
+        if path.hasSuffix("/") {
+            pathComponents.removeLast(2)
+        } else {
+            pathComponents.removeLast()
+        }
+
+        return pathComponents.joined(separator: "/")
+    }
 }
 
 private extension String {

Tests/FilesTests/FilesTests.swift

@@ -411,6 +411,15 @@ class FilesTests: XCTestCase {
         }
     }
 
+    func testCreatingFileFromFileSystem() {
+        performTest {
+            let filePath = folder.path + "one/two/three"
+            let contents = Data()
+            try FileSystem().createFile(at: filePath, contents: contents)
+            try XCTAssertEqual(File(path: filePath).read(), contents)
+        }
+    }
+
     func testCreatingFolderFromFileSystem() {
         performTest {
             let folderPath = folder.path + "one/two/three"