Improve asset handling

CHDataManagement/Generator/KnownHeaderElement.swift

@@ -0,0 +1,60 @@
+
+enum KnownHeaderElement: Int {
+
+    case codeHightlighting = 4
+
+    case modelViewer = 3
+
+    /// CSS File to style the audio player
+    case audioPlayerCss = 1
+
+    /// JavaScript file for the audio player
+    case audioPlayerJs = 2
+
+    func header(content: Content) -> HeaderElement? {
+        switch self {
+        case .codeHightlighting:
+            if let file = content.settings.pages.codeHighlightingJsFile {
+                return HeaderElement.js(file: file, defer: true)
+            }
+        case .modelViewer:
+            if let file = content.settings.pages.modelViewerJsFile {
+                return HeaderElement.jsModule(file)
+            }
+        case .audioPlayerCss:
+            if let file = content.settings.pages.audioPlayerCssFile {
+                return .css(file: file, order: HeaderElement.audioPlayerCssOrder)
+            }
+        case .audioPlayerJs:
+            if let file = content.settings.pages.audioPlayerJsFile {
+                return .js(file: file, defer: true)
+            }
+        }
+        return nil
+    }
+}
+
+extension KnownHeaderElement: Comparable {
+
+    static func < (lhs: KnownHeaderElement, rhs: KnownHeaderElement) -> Bool {
+        lhs.rawValue < rhs.rawValue
+    }
+
+
+}
+
+extension KnownHeaderElement: CustomStringConvertible {
+
+    var description: String {
+        switch self {
+        case .codeHightlighting:
+            return "code-highlighting"
+        case .modelViewer:
+            return "model-viewer"
+        case .audioPlayerCss:
+            return "audio-player-css"
+        case .audioPlayerJs:
+            return "audio-player-js"
+        }
+    }
+}