[feat] prepare song for practise

Author: DanielCech

Sources/ScriptToolkit/FileExtension.swift

@@ -169,6 +169,50 @@ public extension File {
         return try File(path: newName)
     }
 
+    func prepareSongForPractise(outputFolder: Folder) throws {
+        print(name + ":")
+
+        let originalWavFile: File
+        if let ext = `extension`, ext.lowercased() != "wav" {
+            print("  Converting to wav")
+            originalWavFile = try convertToWav(newName: "wav-file.wav")
+        }
+        else {
+            originalWavFile = self
+        }
+
+        print("  Converting to 75% speed")
+        let file75 = try originalWavFile.slowDownAudio(newName: "tempo-75.wav", percent: 0.75)
+        print("  Converting to 90% speed")
+        let file90 = try originalWavFile.slowDownAudio(newName: "tempo-90.wav", percent: 0.9)
+
+        print("  Adding initial silence to 75% speed file")
+        let silencedFile75 = try file75.addSilence(newName: "silence-75.wav")
+        print("  Adding initial silence to 90% speed file")
+        let silencedFile90 = try file90.addSilence(newName: "silence-90.wav")
+        print("  Adding initial silence to 100% speed file")
+        let silencedFile100 = try originalWavFile.addSilence(newName: "silence-100.wav")
+
+        print("  Converting to M4A")
+        let silencedM4AFile75 = try silencedFile75.convertToM4A(newName: nameExcludingExtension + "@75.m4a")
+        let silencedM4AFile90 = try silencedFile90.convertToM4A(newName: nameExcludingExtension + "@90.m4a")
+        let silencedM4AFile100 = try silencedFile100.convertToM4A(newName: nameExcludingExtension + "@100.m4a")
+
+        // Move result to output dir
+        print("  Moving to destination folder")
+        try silencedM4AFile75.move(to: outputFolder)
+        try silencedM4AFile90.move(to: outputFolder)
+        try silencedM4AFile100.move(to: outputFolder)
+
+        // Clean up
+        try originalWavFile.delete()
+        try file75.delete()
+        try file90.delete()
+        try silencedFile75.delete()
+        try silencedFile90.delete()
+        try silencedFile100.delete()
+    }
+
     ////////////////////////////////////////////////////////////////////////////////
     // MARK: - PDF