From e2826fdbce90b0c06d6a43ce7d9b2872ce587c7d Mon Sep 17 00:00:00 2001
From: Dan Barber <github@danbarber.me>
Date: Sat, 7 Apr 2018 13:08:18 -0400
Subject: [PATCH] Split out game status checks and add piece colour search

---
 lib/chess/board.ex        | 27 +++++++++++-----------
 lib/chess/game.ex         | 21 +++++++++++++++++
 test/chess/board_test.exs | 47 +++++++++------------------------------
 test/chess/game_test.ex   | 43 +++++++++++++++++++++++++++++++++++
 4 files changed, 89 insertions(+), 49 deletions(-)
 create mode 100644 lib/chess/game.ex
 create mode 100644 test/chess/game_test.ex

diff --git a/lib/chess/board.ex b/lib/chess/board.ex
index cb86af5..c89af74 100644
--- a/lib/chess/board.ex
+++ b/lib/chess/board.ex
@@ -1,8 +1,6 @@
 defmodule Chess.Board do
   @moduledoc false
 
-  alias Chess.Moves.Piece
-
   def transform(board) do
     Enum.map(0..7, fn (rank) ->
       Enum.map(0..7, fn (file) ->
@@ -16,7 +14,15 @@ defmodule Chess.Board do
     |> Enum.filter(fn({_index, piece}) ->
       match?(%{"type" => ^type, "colour" => ^colour}, piece)
     end)
-    |> Enum.map(fn({index, _piece}) -> index_to_tuple(index) end)
+    |> indexes_to_tuples
+  end
+
+  def search(board, %{"colour" => colour}) do
+    board
+    |> Enum.filter(fn({_index, piece}) ->
+      match?(%{"colour" => ^colour}, piece)
+    end)
+    |> indexes_to_tuples
   end
 
   def piece(board, {file, rank}) do
@@ -32,16 +38,6 @@ defmodule Chess.Board do
     Map.put(board, "#{to_file},#{to_rank}", piece)
   end
 
-  def king_in_check?(board, colour) do
-    king =
-      board
-      |> search(%{"type" => "king", "colour" => colour})
-      |> List.first
-
-    board
-    |> Piece.attacked?(king)
-  end
-
   def default do
     %{
       "0,7" => %{"type" => "rook",   "colour" => "black"},
@@ -82,6 +78,11 @@ defmodule Chess.Board do
     }
   end
 
+  defp indexes_to_tuples(list) do
+    list
+    |> Enum.map(fn({index, _piece}) -> index_to_tuple(index) end)
+  end
+
   defp index_to_tuple(index) do
     index
     |> String.split(",")
diff --git a/lib/chess/game.ex b/lib/chess/game.ex
new file mode 100644
index 0000000..56075d0
--- /dev/null
+++ b/lib/chess/game.ex
@@ -0,0 +1,21 @@
+defmodule Chess.Game do
+  @moduledoc false
+
+  alias Chess.Board
+  alias Chess.Moves.Piece
+
+  def player_checkmated?(board, colour) do
+    board
+    |> Board.search(%{"colour" => colour})
+  end
+
+  def king_in_check?(board, colour) do
+    king =
+      board
+      |> Board.search(%{"type" => "king", "colour" => colour})
+      |> List.first
+
+    board
+    |> Piece.attacked?(king)
+  end
+end
diff --git a/test/chess/board_test.exs b/test/chess/board_test.exs
index f7be08b..b19f7b5 100644
--- a/test/chess/board_test.exs
+++ b/test/chess/board_test.exs
@@ -22,6 +22,17 @@ defmodule Chess.BoardTest do
     assert Board.search(board, piece) == expected_result
   end
 
+  test "finds pieces on the board with a partial search" do
+    board = Board.default
+
+    piece = %{"colour" => "white"}
+    expected_result = [
+      {0, 1}, {1, 1}, {2, 1}, {3, 1}, {4, 1}, {5, 1}, {6, 1}, {7, 1},
+      {0, 0}, {1, 0}, {2, 0}, {3, 0}, {4, 0}, {5, 0}, {6, 0}, {7, 0},
+    ] |> Enum.sort
+    assert Board.search(board, piece) == expected_result
+  end
+
   test "finds a single piece on the board" do
     board = Board.default
 
@@ -40,40 +51,4 @@ defmodule Chess.BoardTest do
       "5,2" => %{"type" => "queen", "colour" => "white"},
     }
   end
-
-  test "recognise when the king is in check" do
-    board = %{
-      "4,0" => %{"type" => "king", "colour" => "white"},
-      "4,7" => %{"type" => "queen", "colour" => "black"},
-    }
-
-    assert Board.king_in_check?(board, "white")
-  end
-
-  test "recognise when the king is not in check" do
-    board = %{
-      "5,0" => %{"type" => "king", "colour" => "white"},
-      "4,7" => %{"type" => "queen", "colour" => "black"},
-    }
-
-    refute Board.king_in_check?(board, "white")
-  end
-
-  test "recognize when the king is in check by a knight" do
-    board = %{
-      "4,0" => %{"type" => "king", "colour" => "white"},
-      "3,2" => %{"type" => "knight", "colour" => "black"},
-    }
-
-    assert Board.king_in_check?(board, "white")
-  end
-
-  test "recognize when the king is in check by a pawn" do
-    board = %{
-      "4,0" => %{"type" => "king", "colour" => "white"},
-      "3,1" => %{"type" => "pawn", "colour" => "black"},
-    }
-
-    assert Board.king_in_check?(board, "white")
-  end
 end
diff --git a/test/chess/game_test.ex b/test/chess/game_test.ex
new file mode 100644
index 0000000..4a634ea
--- /dev/null
+++ b/test/chess/game_test.ex
@@ -0,0 +1,43 @@
+defmodule Chess.GameTest do
+  @moduledoc false
+
+  use Chess.DataCase
+
+  alias Chess.Game
+
+  test "recognise when the king is in check" do
+    board = %{
+      "4,0" => %{"type" => "king", "colour" => "white"},
+      "4,7" => %{"type" => "queen", "colour" => "black"},
+    }
+
+    assert Game.king_in_check?(board, "white")
+  end
+
+  test "recognise when the king is not in check" do
+    board = %{
+      "5,0" => %{"type" => "king", "colour" => "white"},
+      "4,7" => %{"type" => "queen", "colour" => "black"},
+    }
+
+    refute Game.king_in_check?(board, "white")
+  end
+
+  test "recognize when the king is in check by a knight" do
+    board = %{
+      "4,0" => %{"type" => "king", "colour" => "white"},
+      "3,2" => %{"type" => "knight", "colour" => "black"},
+    }
+
+    assert Game.king_in_check?(board, "white")
+  end
+
+  test "recognize when the king is in check by a pawn" do
+    board = %{
+      "4,0" => %{"type" => "king", "colour" => "white"},
+      "3,1" => %{"type" => "pawn", "colour" => "black"},
+    }
+
+    assert Game.king_in_check?(board, "white")
+  end
+end