Make a move generator file

lib/chess/moves/generator.ex

@@ -0,0 +1,30 @@
+defmodule Chess.Moves.Generator do
+  @moduledoc false
+
+  def moves(_colour, _board, {0, _rank}, {-1, _}), do: []
+  def moves(_colour, _board, {_file, 0}, {_, -1}), do: []
+  def moves(_colour, _board, {7, _rank}, {1, _}), do: []
+  def moves(_colour, _board, {_file, 7}, {_, 1}), do: []
+  def moves(colour, board, {file, rank}, {fv, rv}) do
+    next_square = {file + fv, rank + rv}
+    cond do
+      can_take_piece?(colour, board, next_square) ->
+        [next_square]
+      obstruction?(board, next_square) ->
+        []
+      true ->
+        [next_square | moves(colour, board, next_square, {fv, rv})]
+    end
+  end
+
+  defp can_take_piece?(colour, board, {file, rank}) do
+    piece = board["#{file},#{rank}"]
+
+    piece && piece["colour"] != colour
+  end
+
+  defp obstruction?(board, {file, rank}) do
+    board
+    |> Map.has_key?("#{file},#{rank}")
+  end
+end

lib/chess/moves/rook.ex

@@ -1,6 +1,8 @@
 defmodule Chess.Moves.Rook do
   @moduledoc false
 
+  alias Chess.Moves.Generator
+
   def moves(board, {file, rank}) do
     moves_north(board, {file, rank}) ++
       moves_south(board, {file, rank}) ++
@@ -11,51 +13,24 @@ defmodule Chess.Moves.Rook do
   defp moves_north(board, {file, rank}) do
     board["#{file},#{rank}"]
     |> Map.get("colour")
-    |> _moves(board, {file, rank}, {0, +1})
+    |> Generator.moves(board, {file, rank}, {0, +1})
   end
 
   defp moves_south(board, {file, rank}) do
     board["#{file},#{rank}"]
     |> Map.get("colour")
-    |> _moves(board, {file, rank}, {0, -1})
+    |> Generator.moves(board, {file, rank}, {0, -1})
   end
 
   defp moves_east(board, {file, rank}) do
     board["#{file},#{rank}"]
     |> Map.get("colour")
-    |> _moves(board, {file, rank}, {+1, 0})
+    |> Generator.moves(board, {file, rank}, {+1, 0})
   end
 
   defp moves_west(board, {file, rank}) do
     board["#{file},#{rank}"]
     |> Map.get("colour")
-    |> _moves(board, {file, rank}, {-1, 0})
+    |> Generator.moves(board, {file, rank}, {-1, 0})
-  end
-
-  defp _moves(_colour, _board, {0, _rank}, {-1, _}), do: []
-  defp _moves(_colour, _board, {_file, 0}, {_, -1}), do: []
-  defp _moves(_colour, _board, {7, _rank}, {1, _}), do: []
-  defp _moves(_colour, _board, {_file, 7}, {_, 1}), do: []
-  defp _moves(colour, board, {file, rank}, {fv, rv}) do
-    next_square = {file + fv, rank + rv}
-    cond do
-      can_take_piece?(colour, board, next_square) ->
-        [next_square]
-      obstruction?(board, next_square) ->
-        []
-      true ->
-        [next_square | _moves(colour, board, next_square, {fv, rv})]
-    end
-  end
-
-  defp can_take_piece?(colour, board, {file, rank}) do
-    piece = board["#{file},#{rank}"]
-
-    piece && piece["colour"] != colour
-  end
-
-  defp obstruction?(board, {file, rank}) do
-    board
-    |> Map.has_key?("#{file},#{rank}")
   end
 end