defmodule Triangles do
  def area({a,b}) when is_number(a) and is_number(b) do
    a * b * 0.5
  end
  def area(_) do
    "Unknown arguments"
  end

  @spec lines_lengths!(String.t) :: Stream.t
  def lines_lengths! filepath do
    File.stream!(filepath)
    |> Stream.map(&String.replace(&1, "\n", ""))
    |> Stream.map(&{&1, String.length(&1)})
    |> Stream.with_index
  end

  defp val {{_, val}, _} do
    val
  end

  def longest_line_length! filepath do
    lines_lengths!(filepath)
    |> Enum.reduce(
      {{"", 0},-1},
      &(if val(&1) > val(&2) do &1 else &2 end)
    )
  end

  def longest_line! filepath do
    longest_line_length! filepath
  end

  def words_per_line! filepath do
    lines_lengths!(filepath)
    |> Stream.map(
      fn {{conts,_},index} ->
        conts
        |> (&String.split(&1,~r/\W+/)).() # Anonymous function needs to be evaluated?
        |> Enum.filter(&(String.length(&1) > 0)) # filter out empty splits
        |> (&{{conts, length(&1)}, index}).()
      end
    )
  end
end

defmodule TrianglesTest do
  def test_lines_lengths! do
    Triangles.lines_lengths!("./test.exs")
    |> print_line_info("Length")
  end


  def test_longest_line_length! do
    {{_, length}, line} = Triangles.longest_line_length!("./test.exs")
    IO.puts("#{line + 1}. Length: #{length}")
  end

  def test_longest_line! do
    {{conts, _}, line} = Triangles.longest_line!("./test.exs")
    IO.puts("#{line + 1}. \"#{conts}\"")
  end

  def test_words_per_line! do
    Triangles.words_per_line!("./test.exs")
    |> print_line_info("Words")
  end

  defp print_line_info(stream, attr) do
    stream |> Enum.each(
        fn({{_, value}, line}) ->
          IO.puts "#{line + 1}. #{attr}: #{value}"
        end
      )
  end
end

TrianglesTest.test_longest_line_length!
TrianglesTest.test_longest_line!
TrianglesTest.test_words_per_line!

IO.puts [1,-1,1,-1,1,-1] |>
  Stream.filter(&(is_number(&1) and &1 > 0)) |>
  Enum.reduce(&(&1 + &2))