fix: maintain passed in streams position

src/StreamShorts.Console/Commands/DefaultCommand.cs

@@ -52,7 +52,7 @@ internal class DefaultCommand(
       .Spinner(Spinner.Known.Dots)
       .StartAsync("Extracting audio...", async ctx =>
       {
-        audioStream = await _audioExtractor.ExtractMp3FromMp4Async(videoStream).ConfigureAwait(false);
+        audioStream = await _audioExtractor.ExtractMp3FromMp4Async(videoStream);
       });
 
     if (audioStream is null)

src/StreamShorts.Library/Media/IAudioService.cs

@@ -11,6 +11,9 @@ internal interface IAudioService
   /// </summary>
   /// <param name="mp3">The input MP3 stream.</param>
   /// <returns>The output WAV stream.</returns>
+  /// <exception cref="ArgumentNullException">Thrown when the MP3 stream is null.</exception>
+  /// <exception cref="ArgumentException">Thrown when the MP3 stream is not readable or seekable.</exception>
+  /// <remarks>The method will preserve the passed MP3 stream's data and position.</remarks
   Stream ConvertMp3ToWav16(Stream mp3);
 
   /// <summary>
@@ -19,6 +22,9 @@ internal interface IAudioService
   /// param name="wavStream">The input WAV stream.</param>
   /// <param name="segmentDuration">The duration of each segment.</param>
   /// <returns>The number of segments.</returns>
+  /// <exception cref="ArgumentNullException">Thrown when the WAV stream is null.</exception>
+  /// <exception cref="ArgumentException">Thrown when the WAV stream is not readable or seekable.</exception>
+  /// <remarks>The method will preserve the passed WAV stream's data and position.</remarks>
   int GetNumberOfWavSegments(Stream wavStream, TimeSpan segmentDuration);
 
   /// <summary>
@@ -28,5 +34,8 @@ internal interface IAudioService
   /// <param name="segmentNumber">The segment number to retrieve.</param>
   /// <param name="segmentDuration">The duration of each segment.</param>
   /// <returns>The segment stream.</returns>
+  /// <exception cref="ArgumentNullException">Thrown when the WAV stream is null.</exception>
+  /// <exception cref="ArgumentException">Thrown when the WAV stream is not readable or seekable.</exception>
+  /// <remarks>The method will preserve the passed WAV stream's data and position.</remarks>
   Stream GetWavSegment(Stream wavStream, int segmentNumber, TimeSpan segmentDuration);
 }

src/StreamShorts.Library/Media/NAudioService.cs

@@ -11,35 +11,77 @@ internal class NAudioService : IAudioService
 {
   public Stream ConvertMp3ToWav16(Stream mp3)
   {
-    using var reader = new Mp3FileReader(mp3);
-    var outFormat = new WaveFormat(16000, reader.WaveFormat.Channels);
-    using var resampler = new MediaFoundationResampler(reader, outFormat);
-    var waveStream = new MemoryStream();
-    WaveFileWriter.WriteWavFileToStream(waveStream, resampler);
-    waveStream.Position = 0;
-    return waveStream;
+    return UseStream(mp3, stream =>
+    {
+      using var reader = new Mp3FileReader(mp3);
+      var outFormat = new WaveFormat(16000, reader.WaveFormat.Channels);
+      using var resampler = new MediaFoundationResampler(reader, outFormat);
+      var waveStream = new MemoryStream();
+      WaveFileWriter.WriteWavFileToStream(waveStream, resampler);
+      waveStream.Position = 0;
+      return waveStream;
+    });
   }
 
   public int GetNumberOfWavSegments(Stream wavStream, TimeSpan segmentDuration)
   {
-    using var waveReader = new WaveFileReader(wavStream);
-    var totalDuration = waveReader.TotalTime;
-    var segmentCount = (int)Math.Ceiling(totalDuration.TotalMilliseconds / segmentDuration.TotalMilliseconds);
-    wavStream.Position = 0;
-    return segmentCount;
+    return UseStream(wavStream, stream =>
+    {
+      using var waveReader = new WaveFileReader(wavStream);
+      var totalDuration = waveReader.TotalTime;
+      var segmentCount = (int)Math.Ceiling(totalDuration.TotalMilliseconds / segmentDuration.TotalMilliseconds);
+      return segmentCount;
+    });
   }
 
   public Stream GetWavSegment(Stream wavStream, int segmentNumber, TimeSpan segmentDuration)
   {
-    using var segmentWaveReader = new WaveFileReader(wavStream);
-    var segment = segmentWaveReader.ToSampleProvider()
-      .Skip(segmentNumber * segmentDuration)
-      .Take(segmentDuration);
-    var segmentProvider = segment.ToWaveProvider16();
-    var segmentStream = new MemoryStream();
-    WaveFileWriter.WriteWavFileToStream(segmentStream, segmentProvider);
-    segmentStream.Position = 0;
-    wavStream.Position = 0;
-    return segmentStream;
+    return UseStream(wavStream, stream =>
+    {
+      using var segmentWaveReader = new WaveFileReader(wavStream);
+      var segment = segmentWaveReader.ToSampleProvider()
+        .Skip(segmentNumber * segmentDuration)
+        .Take(segmentDuration);
+      var segmentProvider = segment.ToWaveProvider16();
+      var segmentStream = new MemoryStream();
+      WaveFileWriter.WriteWavFileToStream(segmentStream, segmentProvider);
+      segmentStream.Position = 0;
+      return segmentStream;
+    });
+  }
+
+  private static T UseStream<T>(Stream stream, Func<Stream, T> action)
+  {
+    ValidateStream(stream);
+
+    var originalPosition = stream.Position;
+
+    try
+    {
+      stream.Position = 0;
+      return action(stream);
+    }
+    finally
+    {
+      stream.Position = originalPosition;
+    }
+  }
+
+  private static void ValidateStream(Stream stream)
+  {
+    if (stream == null)
+    {
+      throw new ArgumentNullException(nameof(stream), $"{nameof(stream)} cannot be null");
+    }
+
+    if (stream.CanRead is false)
+    {
+      throw new ArgumentException($"{nameof(stream)} must be readable", nameof(stream));
+    }
+
+    if (stream.CanSeek is false)
+    {
+      throw new ArgumentException($"{nameof(stream)} must be seekable", nameof(stream));
+    }
   }
 }