plans.ex

defmodule Pyramid.Plans do
  defstruct height: nil, layers: nil
end

pyramix.ex

defmodule Pyramid do
  @moduledoc """
  Mario's Pyramid problem solution
  """
  def main(height) do
    #How to validate that input is > 0 without if?
    plans = %Pyramid.Plans{height: height}
    plans
    |> build_layers
    |> print_out
  end

  def print_out(%Pyramid.Plans{layers: layers}) do
    # Say I didn't want a newline at the very end, would the best way be to just
    # delete the last element of the flattened list?
    # List.flatten(layers)
    # |> Enum.join("")
    # |> IO.puts
    IO.puts(layers)
  end

  @doc """
  Builds a list consisting of the carachters needed for the layer of the Pyramid
  `blocks` is the number of blocks in the layer
  `height` is used to calculate the left padding

  ## Examples
    iex> Pyramid.build_layer(3, 5)
    [" ", " ", "#", "#", "#", "\\n"]
  """
  def build_layer(blocks, height) do
    # Cleaner
    Enum.map(1..height + 1, fn
      x when x <= (height - blocks) -> ' '
      x when x > height -> '\n'
      _ -> '#'
    end)
    # Messier
    # left_pad = height - blocks
    # padding = Enum.map(0..left_pad, fn(pos)-> " " end)
    # padding_plus_blocks = padding ++ Enum.map(1..blocks, fn()-> "#" end)
    # trimmed = List.delete_at(padding_plus_blocks, 0)
    # trimmed ++ ["\n"]
  end

  @doc """
  Builds a List of lists with each layer's representation in strings i.e.
  [[" ", "#", "\n"], ["#", "#", "\n"]]
  """
  def build_layers(%Pyramid.Plans{height: height} = plans) do

    layers =
      1..height
      # Can I do an (&build_layer/2) with args here instead of the full fn inside
      # the map?, should this somehow be done with recursion?
      |> Enum.map(fn(blocks_in_layer)-> build_layer(blocks_in_layer, height) end)
      %Pyramid.Plans{plans | layers: layers}
  end
end