defmodule Dotzip do
  
  @moduledoc """
  Elixir Implementation of ZIP File Format. https://pkware.cachefly.net/webdocs/APPNOTE/APPNOTE-6.3.3.TXT
  """

  def decode(file) do
    {:ok, local, rest} = Dotzip.LocalFileHeader.decode(file)
    {:ok, central, r} = Dotzip.CentralDirectoryHeader.decode(rest)
    {:ok, e, rr} = Dotzip.EndCentralDirectory.decode(r)
    {local, central, e, rr}
  end
  
end

defmodule Dotzip.LocalFileHeader do
  
  defp signature(<< 0x50, 0x4b, 0x03, 0x04, rest::bitstring >>) do
    {:ok, %{}, rest}
  end

  defp version({:ok, data, << version::binary-size(2), rest::bitstring >>}) do
    {:ok, Map.put(data, :version, version), rest}
  end

  defp purpose_flag({:ok, data, << purpose_flag::binary-size(2), rest::bitstring >>}) do
    {:ok, Map.put(data, :purpose_flag, purpose_flag), rest}
  end

  defp compression_method({:ok, data, << compression_method::binary-size(2), rest::bitstring >>}) do
    {:ok, Map.put(data, :compression_method, compression_method), rest}
  end

  defp last_modification_time({:ok, data, << last_modification::little-size(16), rest::bitstring >>}) do
    {:ok, Map.put(data, :last_modification_time, last_modification), rest}
  end

  defp last_modification_date({:ok, data, << last_modification_date::little-size(16), rest::bitstring >>}) do
    {:ok, Map.put(data, :last_modification_date, last_modification_date), rest}
  end

  defp crc32({:ok, data, << crc32::binary-size(4), rest::bitstring >>}) do
   {:ok, Map.put(data, :crc32, crc32), rest} 
  end

  defp compressed_size({:ok, data, << compressed_size::little-size(32), rest::bitstring >>}) do
    {:ok, Map.put(data, :compressed_size, compressed_size), rest}
  end

  defp uncompressed_size({:ok, data, << uncompressed_size::little-size(32), rest::bitstring >>}) do
    {:ok, Map.put(data, :uncompressed_size, uncompressed_size), rest}
  end

  defp file_name_length({:ok, data, << file_name_length::little-size(16), rest::bitstring >>}) do
    {:ok, Map.put(data, :file_name_length, file_name_length), rest }
  end

  defp extra_field_length({:ok, data, << extra_field_length::little-size(16), rest::bitstring >>}) do
    {:ok, Map.put(data, :extra_field_length, extra_field_length), rest}
  end

  defp file_name({:ok, data, rest}) do
    %{ :file_name_length => file_name_length } = data
    <<file_name::binary-size(file_name_length), r::bitstring>> = rest
    {:ok, Map.put(data, :file_name, file_name), r}
  end

  defp extra_field({:ok, data, rest}) do
    %{ :extra_field_length => extra_field_length } = data
    <<extra_field::binary-size(extra_field_length), r::bitstring>> = rest
    {:ok, Map.put(data, :extra_field, extra_field), r}
  end

  defp content({:ok, data, rest}) do
    %{ :compressed_size => compressed_size } = data
    <<content::binary-size(compressed_size), r::bitstring>> = rest
    {:ok, Map.put(data, :content, content), r}
  end
  
  def decode(file) do
    {:ok, local_file_header, rest} = signature(file)
    |> version()
    |> purpose_flag()
    |> compression_method()
    |> last_modification_time()
    |> last_modification_date()
    |> crc32()
    |> compressed_size()
    |> uncompressed_size()
    |> file_name_length()
    |> extra_field_length()
    |> file_name()
    |> extra_field()
    |> content()
    end
  
end

defmodule Dotzip.CentralDirectoryHeader do

  defp signature(<< 0x50, 0x4b, 0x01, 0x02, rest::bitstring >>) do
    {:ok, %{}, rest}
  end

  defp version_made({:ok, data, << version::binary-size(2), rest::bitstring >>}) do
    {:ok, Map.put(data, :version_made, version), rest}
  end

  defp version_needed({:ok, data, << version::binary-size(2), rest::bitstring >>}) do
    {:ok, Map.put(data, :version_needed, version), rest}
  end
  
  defp purpose_flag({:ok, data, << purpose_flag::binary-size(2), rest::bitstring >>}) do
    {:ok, Map.put(data, :purpose_flag, purpose_flag), rest}
  end

  defp compression_method({:ok, data, << compression_method::binary-size(2), rest::bitstring >>}) do
    {:ok, Map.put(data, :compression_method, compression_method), rest}
  end

  defp last_modification_time({:ok, data, << last_modification::little-size(16), rest::bitstring >>}) do
    {:ok, Map.put(data, :last_modification_time, last_modification), rest}
  end

  defp last_modification_date({:ok, data, << last_modification_date::little-size(16), rest::bitstring >>}) do
    {:ok, Map.put(data, :last_modification_date, last_modification_date), rest}
  end

  defp crc32({:ok, data, << crc32::binary-size(4), rest::bitstring >>}) do
   {:ok, Map.put(data, :crc32, crc32), rest} 
  end

  defp compressed_size({:ok, data, << compressed_size::little-size(32), rest::bitstring >>}) do
    {:ok, Map.put(data, :compressed_size, compressed_size), rest}
  end

  defp uncompressed_size({:ok, data, << uncompressed_size::little-size(32), rest::bitstring >>}) do
    {:ok, Map.put(data, :uncompressed_size, uncompressed_size), rest}
  end

  defp file_name_length({:ok, data, << file_name_length::little-size(16), rest::bitstring >>}) do
    {:ok, Map.put(data, :file_name_length, file_name_length), rest }
  end

  defp extra_field_length({:ok, data, << extra_field_length::little-size(16), rest::bitstring >>}) do
    {:ok, Map.put(data, :extra_field_length, extra_field_length), rest}
  end

  defp file_comment_length({:ok, data, << file_comment_length::little-size(16), rest::bitstring >>}) do
    {:ok, Map.put(data, :file_comment_length, file_comment_length), rest}
  end

  defp disk_number_start({:ok, data, << disk_number_start::little-size(16), rest::bitstring >>}) do
    {:ok, Map.put(data, :disk_number_start, disk_number_start), rest}
  end

  defp internal_file_attributes({:ok, data, << internal_file_attributes::binary-size(2), rest::bitstring >>}) do
    {:ok, Map.put(data, :internal_file_attributes, internal_file_attributes), rest}
  end

  defp external_file_attributes({:ok, data, << external_file_attributes::binary-size(4), rest::bitstring >>}) do
    {:ok, Map.put(data, :external_file_attributes, external_file_attributes), rest}
  end

  defp relative_offset({:ok, data, << relative_offset::little-size(32), rest::bitstring >>}) do
    {:ok, Map.put(data, :relative_offset, relative_offset), rest}
  end

  defp file_name({:ok, data, rest}) do
    %{ :file_name_length => file_name_length } = data
    <<file_name::binary-size(file_name_length), r::bitstring>> = rest
    {:ok, Map.put(data, :file_name, file_name), r}
  end

  defp extra_field({:ok, data, rest}) do
    %{ :extra_field_length => extra_field_length } = data
    <<extra_field::binary-size(extra_field_length), r::bitstring>> = rest
    {:ok, Map.put(data, :extra_field, extra_field), r}
  end

  defp file_comment({:ok, data, rest}) do
    %{ :file_comment_length => file_comment_length } = data
    <<file_comment::binary-size(file_comment_length), r::bitstring>> = rest
    {:ok, Map.put(data, :file_comment, file_comment), r}
  end
  
  def decode(file) do
    {:ok, central_directory_header, rest} = signature(file)
    |> version_made()
    |> version_needed()
    |> purpose_flag()
    |> compression_method()
    |> last_modification_time()
    |> last_modification_date()
    |> crc32()
    |> compressed_size()
    |> uncompressed_size()
    |> file_name_length()
    |> extra_field_length()
    |> file_comment_length()
    |> disk_number_start()
    |> internal_file_attributes()
    |> external_file_attributes()
    |> relative_offset()
    |> file_name()
    |> extra_field()
    |> file_comment()
  end
  
end

defmodule Dotzip.EndCentralDirectory do
  
  defp signature(<< 0x50, 0x4b, 0x05, 0x06, rest::bitstring >>) do
    {:ok, %{}, rest}
  end

  defp number_disk({:ok, data, << number_disk::little-size(32), rest::bitstring >>}) do
    {:ok, Map.put(data, :number_disk, number_disk), rest}
  end

  def decode(file) do
    {:ok, end_central_directory, rest} = signature(file)
    |> number_disk()
  end
  
end