ex_midi

defmodule ExMidi.MidiSyx do
  import Bitwise

  @moduledoc """
  Read and write SYX (System Exclusive) file format.

  Handles both binary and plain text (hex) formats.
  """

  @midi :midi

  @doc "Read sysex messages from a SYX file."
  def read_file(path) do
    case File.read(path) do
      {:ok, data} ->
        if byte_size(data) == 0 do
          []
        else
          parser = ExMidi.MidiParser.new()

          parser =
            if binary_part(data, 0, 1) == <<0xF0>> do
              # Binary format — feed all bytes
              ExMidi.MidiParser.feed_bytes(parser, :binary.bin_to_list(data))
            else
              # Text format — parse hex
              text = to_string(data)
              hex_string = String.replace(text, ~r/\s/, "")

              bytes =
                for <<h::binary-size(2) <- hex_string>> do
                  {val, _} = Integer.parse(h, 16)
                  val
                end

              ExMidi.MidiParser.feed_bytes(parser, bytes)
            end

          {messages, _} = ExMidi.MidiParser.flush(parser)
          for {@midi, {:sys_ex, _}} = msg <- messages, do: msg
        end

      {:error, reason} ->
        {:error, reason}
    end
  end

  @doc "Write sysex messages to a SYX file."
  def write_file(path, messages, opts \\ []) do
    plaintext = Keyword.get(opts, :plaintext, false)
    sysex_data = for {@midi, {:sys_ex, data}} <- messages, do: data

    if plaintext do
      content =
        Enum.map_join(sysex_data, "\n", fn data ->
          hex = data |> Enum.map_join(" ", &String.pad_leading(Integer.to_string(&1, 16), 2, "0"))
          "F0 #{hex} F7"
        end)

      File.write(path, content <> "\n")
    else
      # Binary format: wrap each sysex data with F0...F7
      content =
        Enum.map(sysex_data, fn data ->
          Enum.reduce(data, <<0xF0>>, fn b, acc -> acc <> <<b &&& 0xFF>> end) <> <<0xF7>>
        end)

      File.write(path, content)
    end
  end
end