protected virtual void RollOverRenameFiles()

in src/log4net/Appender/RollingFileAppender.cs [1306:1384]
61 lines of code
13 McCabe index (conditional complexity)

  protected virtual void RollOverRenameFiles(string baseFileName)
  {
    baseFileName.EnsureNotNull();
    // If maxBackups <= 0, then there is no file renaming to be done.
    if (MaxSizeRollBackups == 0)
    {
      return;
    }
    if (CountDirection < 0)
    {
      // Delete the oldest file, to keep Windows happy.
      if (CurrentSizeRollBackups == MaxSizeRollBackups)
      {
        DeleteFile(CombinePath(baseFileName, "." + MaxSizeRollBackups));
        CurrentSizeRollBackups--;
      }

      // Map {(maxBackupIndex - 1), ..., 2, 1} to {maxBackupIndex, ..., 3, 2}
      for (int i = CurrentSizeRollBackups; i >= 1; i--)
      {
        RollFile(CombinePath(baseFileName, "." + i), CombinePath(baseFileName, "." + (i + 1)));
      }

      CurrentSizeRollBackups++;

      // Rename fileName to fileName.1
      RollFile(baseFileName, CombinePath(baseFileName, ".1"));
    }
    else
    {
      //countDirection >= 0
      if (CurrentSizeRollBackups >= MaxSizeRollBackups && MaxSizeRollBackups > 0)
      {
        //delete the first and keep counting up.
        int oldestFileIndex = CurrentSizeRollBackups - MaxSizeRollBackups;

        // If static then there is 1 file without a number, therefore 1 less archive
        if (StaticLogFileName)
        {
          oldestFileIndex++;
        }

        // If using a static log file then the base for the numbered sequence is the baseFileName passed in
        // If not using a static log file then the baseFileName will already have a numbered postfix which
        // we must remove, however it may have a date postfix which we must keep!
        string archiveFileBaseName = baseFileName;
        if (!StaticLogFileName)
        {
          if (PreserveLogFileNameExtension)
          {
            string extension = Path.GetExtension(archiveFileBaseName);
            string baseName = Path.Combine(Path.GetDirectoryName(archiveFileBaseName), Path.GetFileNameWithoutExtension(archiveFileBaseName));
            int lastDotIndex = baseName.LastIndexOf(".", StringComparison.Ordinal);
            if (lastDotIndex >= 0)
            {
              archiveFileBaseName = baseName.Substring(0, lastDotIndex) + extension;
            }
          }
          else
          {
            int lastDotIndex = archiveFileBaseName.LastIndexOf(".", StringComparison.Ordinal);
            if (lastDotIndex >= 0)
            {
              archiveFileBaseName = archiveFileBaseName.Substring(0, lastDotIndex);
            }
          }
        }

        // Delete the archive file
        DeleteFile(CombinePath(archiveFileBaseName, "." + oldestFileIndex));
      }

      if (StaticLogFileName)
      {
        CurrentSizeRollBackups++;
        RollFile(baseFileName, CombinePath(baseFileName, "." + CurrentSizeRollBackups));
      }
    }
  }