Rooks can be obstructed

lib/chess/moves/rook.ex

@@ -8,23 +8,54 @@ defmodule Chess.Moves.Rook do
       moves_west(board, {file, rank})
   end
 
-  defp moves_north(_board, {_file, 7}), do: []
   defp moves_north(board, {file, rank}) do
-    [{file, rank + 1} | moves_north(board, {file, rank + 1})]
+    board["#{file},#{rank}"]
+    |> Map.get("colour")
+    |> _moves(board, {file, rank}, {0, +1})
   end
 
-  defp moves_south(_board, {_file, 0}), do: []
   defp moves_south(board, {file, rank}) do
-    [{file, rank - 1} | moves_south(board, {file, rank - 1})]
+    board["#{file},#{rank}"]
+    |> Map.get("colour")
+    |> _moves(board, {file, rank}, {0, -1})
   end
 
-  defp moves_east(_board, {7, _rank}), do: []
   defp moves_east(board, {file, rank}) do
-    [{file + 1, rank} | moves_east(board, {file + 1, rank})]
+    board["#{file},#{rank}"]
+    |> Map.get("colour")
+    |> _moves(board, {file, rank}, {+1, 0})
   end
 
-  defp moves_west(_board, {0, _rank}), do: []
   defp moves_west(board, {file, rank}) do
-    [{file - 1, rank} | moves_west(board, {file - 1, rank})]
+    board["#{file},#{rank}"]
+    |> Map.get("colour")
+    |> _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

test/chess/moves/rook_test.exs

@@ -25,6 +25,34 @@ defmodule Chess.Moves.RookTest do
     assert Enum.sort(moves) == expected_moves
   end
 
+  test "rook is obstructed by another piece of the same colour" do
+    board = %{
+      "0,0" => %{"type" => "rook", "colour" => "white"},
+      "0,5" => %{"type" => "king", "colour" => "white"},
+    }
+    moves = Moves.available(board, {0, 0})
+
+    expected_moves = Enum.sort([
+      {0, 1}, {0, 2}, {0, 3}, {0, 4},
+      {1, 0}, {2, 0}, {3, 0}, {4, 0}, {5, 0}, {6, 0}, {7, 0},
+    ])
+    assert Enum.sort(moves) == expected_moves
+  end
+
+  test "rook can take a piece of the opposite colour" do
+    board = %{
+      "0,0" => %{"type" => "rook", "colour" => "white"},
+      "0,5" => %{"type" => "knight", "colour" => "black"},
+    }
+    moves = Moves.available(board, {0, 0})
+
+    expected_moves = Enum.sort([
+      {0, 1}, {0, 2}, {0, 3}, {0, 4}, {0, 5},
+      {1, 0}, {2, 0}, {3, 0}, {4, 0}, {5, 0}, {6, 0}, {7, 0},
+    ])
+    assert Enum.sort(moves) == expected_moves
+  end
+
   def board do
     Chess.Board.default
   end