From 8a5adc44f574d042ea612ebcc46beb42452f1a8f Mon Sep 17 00:00:00 2001
From: Dan Barber <github@danbarber.me>
Date: Wed, 14 Mar 2018 18:24:04 -0400
Subject: [PATCH] Bishops can be obstructed

---
 lib/chess/moves/bishop.ex        | 26 ++++++++++++++------------
 test/chess/moves/bishop_test.exs | 28 +++++++++++++++++++++++++++-
 2 files changed, 41 insertions(+), 13 deletions(-)

diff --git a/lib/chess/moves/bishop.ex b/lib/chess/moves/bishop.ex
index a46c9c7..59dee89 100644
--- a/lib/chess/moves/bishop.ex
+++ b/lib/chess/moves/bishop.ex
@@ -1,6 +1,8 @@
 defmodule Chess.Moves.Bishop do
   @moduledoc false
 
+  alias Chess.Moves.Generator
+
   def moves(board, {file, rank}) do
     moves_northeast(board, {file, rank}) ++
       moves_southeast(board, {file, rank}) ++
@@ -8,27 +10,27 @@ defmodule Chess.Moves.Bishop do
       moves_southwest(board, {file, rank})
   end
 
-  defp moves_northeast(_board, {7, _rank}), do: []
-  defp moves_northeast(_board, {_file, 7}), do: []
   defp moves_northeast(board, {file, rank}) do
-    [{file + 1, rank + 1} | moves_northeast(board, {file + 1, rank + 1})]
+    board["#{file},#{rank}"]
+    |> Map.get("colour")
+    |> Generator.moves(board, {file, rank}, {1, 1})
   end
 
-  defp moves_southeast(_board, {7, _rank}), do: []
-  defp moves_southeast(_board, {_file, 0}), do: []
   defp moves_southeast(board, {file, rank}) do
-    [{file + 1, rank - 1} | moves_southeast(board, {file + 1, rank - 1})]
+    board["#{file},#{rank}"]
+    |> Map.get("colour")
+    |> Generator.moves(board, {file, rank}, {1, -1})
   end
 
-  defp moves_northwest(_board, {0, _rank}), do: []
-  defp moves_northwest(_board, {_file, 7}), do: []
   defp moves_northwest(board, {file, rank}) do
-    [{file - 1, rank + 1} | moves_northwest(board, {file - 1, rank + 1})]
+    board["#{file},#{rank}"]
+    |> Map.get("colour")
+    |> Generator.moves(board, {file, rank}, {-1, 1})
   end
 
-  defp moves_southwest(_board, {0, _rank}), do: []
-  defp moves_southwest(_board, {_file, 0}), do: []
   defp moves_southwest(board, {file, rank}) do
-    [{file - 1, rank - 1} | moves_southwest(board, {file - 1, rank - 1})]
+    board["#{file},#{rank}"]
+    |> Map.get("colour")
+    |> Generator.moves(board, {file, rank}, {-1, -1})
   end
 end
diff --git a/test/chess/moves/bishop_test.exs b/test/chess/moves/bishop_test.exs
index 4bd3941..9ffa149 100644
--- a/test/chess/moves/bishop_test.exs
+++ b/test/chess/moves/bishop_test.exs
@@ -19,7 +19,33 @@ defmodule Chess.Moves.BishopTest do
     moves = Moves.available(board, {0, 0})
 
     expected_moves = Enum.sort([
-      {1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}, {7, 7}
+      {1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}, {7, 7},
+    ])
+    assert Enum.sort(moves) == expected_moves
+  end
+
+  test "bishops are blocked by pieces of their own colour" do
+    board = %{
+      "0,0" => %{"type" => "bishop", "colour" => "white"},
+      "5,5" => %{"type" => "king", "colour" => "white"},
+    }
+    moves = Moves.available(board, {0, 0})
+
+    expected_moves = Enum.sort([
+      {1, 1}, {2, 2}, {3, 3}, {4, 4},
+    ])
+    assert Enum.sort(moves) == expected_moves
+  end
+
+  test "bishops can take an opponents piece" do
+    board = %{
+      "0,0" => %{"type" => "bishop", "colour" => "white"},
+      "5,5" => %{"type" => "knight", "colour" => "black"},
+    }
+    moves = Moves.available(board, {0, 0})
+
+    expected_moves = Enum.sort([
+      {1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5},
     ])
     assert Enum.sort(moves) == expected_moves
   end