Add MP3Gain normalization tool

Sources/TonUinoLogic.swift

@@ -425,6 +425,93 @@ struct SDCardCleaner {
     }
 }
 
+struct MP3GainNormalizer {
+    private let fileManager: FileManager
+
+    init(fileManager: FileManager) {
+        self.fileManager = fileManager
+    }
+
+    func normalize(rootURL: URL) -> [ExportMessage] {
+        guard let mp3gainURL = mp3gainExecutableURL() else {
+            return [.error("mp3gain wurde nicht gefunden. Erwartet z. B. /opt/homebrew/bin/mp3gain.")]
+        }
+
+        do {
+            let mp3Files = try MP3FileFinder(fileManager: fileManager).mp3Files(in: rootURL)
+            guard !mp3Files.isEmpty else {
+                return [.warning("Keine MP3-Dateien für MP3Gain gefunden.")]
+            }
+
+            var messages: [ExportMessage] = []
+            var processed = 0
+
+            for batch in mp3Files.chunked(into: 50) {
+                let result = runMP3Gain(executableURL: mp3gainURL, files: batch)
+                messages.append(contentsOf: result.messages)
+                if result.success {
+                    processed += batch.count
+                }
+            }
+
+            messages.insert(.info("MP3Gain abgeschlossen: \(processed) von \(mp3Files.count) Datei(en) verarbeitet."), at: 0)
+            return messages
+        } catch {
+            return [.error("MP3Gain-Dateisuche fehlgeschlagen: \(error.localizedDescription)")]
+        }
+    }
+
+    private func runMP3Gain(executableURL: URL, files: [URL]) -> (success: Bool, messages: [ExportMessage]) {
+        let process = Process()
+        process.executableURL = executableURL
+        process.arguments = ["-r", "-k", "-d", "4"] + files.map { $0.path(percentEncoded: false) }
+
+        let outputPipe = Pipe()
+        let errorPipe = Pipe()
+        process.standardOutput = outputPipe
+        process.standardError = errorPipe
+
+        do {
+            try process.run()
+            process.waitUntilExit()
+        } catch {
+            return (false, [.error("mp3gain konnte nicht gestartet werden: \(error.localizedDescription)")])
+        }
+
+        let output = outputPipe.readString()
+        let errorOutput = errorPipe.readString()
+        var messages: [ExportMessage] = []
+
+        if process.terminationStatus == 0 {
+            messages.append(.info("MP3Gain Batch verarbeitet: \(files.count) Datei(en)"))
+        } else {
+            messages.append(.error("MP3Gain beendet mit Code \(process.terminationStatus)."))
+        }
+
+        if !output.isEmpty {
+            messages.append(.info(output))
+        }
+
+        if !errorOutput.isEmpty {
+            messages.append(process.terminationStatus == 0 ? .warning(errorOutput) : .error(errorOutput))
+        }
+
+        return (process.terminationStatus == 0, messages)
+    }
+
+    private func mp3gainExecutableURL() -> URL? {
+        let candidates = [
+            "/opt/homebrew/bin/mp3gain",
+            "/usr/local/bin/mp3gain",
+            "/usr/bin/mp3gain"
+        ]
+
+        return candidates
+            .map(URL.init(fileURLWithPath:))
+            .first { fileManager.isExecutableFile(atPath: $0.path(percentEncoded: false)) }
+    }
+}
+
 struct SDCardValidator {
     private let fileManager: FileManager
 
@@ -1253,6 +1340,18 @@ private extension Array where Element == ExportMessage {
     }
 }
 
+private extension Array {
+    func chunked(into size: Int) -> [[Element]] {
+        guard size > 0 else {
+            return [self]
+        }
+
+        return stride(from: 0, to: count, by: size).map {
+            Array(self[$0..<Swift.min($0 + size, count)])
+        }
+    }
+}
+
 private extension Array where Element == URL {
     func sortedByLocalizedName() -> [URL] {
         sorted {