text_file_utils.ex

defmodule TextFileUtils do
  def fix_line_breaks(file_path) do
    {:ok, file} = File.open(file_path)
    out_file_path = "/tmp/fixed_file_#{:erlang.system_time}.tmp"
    {:ok, out_file} = File.open(out_file_path, [:write])
    process_file(file, out_file, "")
    File.close(file)
    File.close(out_file)
    out_file_path
  end

  defp process_file(in_file, out_file, last) do
    c = IO.read(in_file, 1)
    case {last, c} do
      {"\r", "\n"} ->
        #windows case
        IO.write(out_file, "\n")
      {"\r", _} ->
        # weird osx excel case, only \r
        IO.write(out_file, "\n")
        IO.write(out_file, c)
      {_, "\n" = c} ->
        # unix case, only newline
        IO.write(out_file, "\n")
      {_, "\r" = c} ->
        # we skip it
      {_, :eof} ->
        nil
      {_, c} ->
        IO.write(out_file, c)
    end

    if c != :eof do
      process_file(in_file, out_file, c)
    end
  end
end