Clean code for file type detection

WebsiteGenerator/Files/FileSystem.swift

@@ -261,7 +261,8 @@ final class FileSystem {
 
         // Ensure that image file is supported
         let ext = destinationUrl.pathExtension.lowercased()
-        guard MediaType.isProcessableImage(ext) else {
+        guard ImageType(fileExtension: ext) != nil else {
+            // TODO: This should never be reached, since extensions are checked before
             log.add(info: "Copying image", source: image.source)
             do {
                 let sourceUrl = input.appendingPathComponent(image.source)
@@ -303,7 +304,7 @@ final class FileSystem {
         }
 
         let destinationExtension = destinationUrl.pathExtension.lowercased()
-        guard let type = MediaType.supportedImage(destinationExtension) else {
+        guard let type = ImageType(fileExtension: destinationExtension)?.fileType else {
             log.add(error: "No image type for extension \(destinationExtension)",
                     source: destination)
             return

WebsiteGenerator/Files/ImageType.swift

@@ -0,0 +1,27 @@
+import Foundation
+import AppKit
+
+enum ImageType: CaseIterable {
+    case jpg
+    case png
+
+    init?(fileExtension: String) {
+        switch fileExtension {
+        case "jpg", "jpeg":
+            self = .jpg
+        case "png":
+            self = .png
+        default:
+            return nil
+        }
+    }
+
+    var fileType: NSBitmapImageRep.FileType {
+        switch self {
+        case .jpg:
+            return .jpeg
+        case .png:
+            return .png
+        }
+    }
+}

WebsiteGenerator/Files/MediaType.swift

@@ -1,39 +0,0 @@
-import Foundation
-import AppKit
-
-private let supportedImageExtensions: [String : NSBitmapImageRep.FileType] = [
-    "jpg" : .jpeg,
-    "jpeg" : .jpeg,
-    "png" : .png,
-]
-
-private let supportedVideoExtensions: Set<String> = [
-    "mp4", "mov", "m4v"
-]
-
-enum MediaType {
-    case image
-    case video
-    case file
-    case svg
-
-    init(fileExtension: String) {
-        if supportedImageExtensions[fileExtension] != nil {
-            self = .image
-        } else if supportedVideoExtensions.contains(fileExtension) {
-            self = .video
-        } else if fileExtension == "svg" {
-            self = .svg
-        } else {
-            self = .file
-        }
-    }
-
-    static func isProcessableImage(_ fileExtension: String) -> Bool {
-        supportedImage(fileExtension) != nil
-    }
-
-    static func supportedImage(_ fileExtension: String) -> NSBitmapImageRep.FileType? {
-        supportedImageExtensions[fileExtension]
-    }
-}

WebsiteGenerator/Files/VideoType.swift

@@ -1,6 +1,6 @@
 import Foundation
 
-enum VideoType: String {
+enum VideoType: String, CaseIterable {
     case mp4
     case m4v