support boards that wrap

lib/cartographer.ex

@@ -1,7 +1,7 @@
 defmodule Cartographer do
   alias Cartographer.Board
 
-  defdelegate new_board(height, width), to: Board
+  defdelegate new_board(height, width, wrap), to: Board
 
   defdelegate height(board), to: Board
 

lib/cartographer/board.ex

@@ -2,13 +2,18 @@ defmodule Cartographer.Board do
   defstruct(
     tiles: %{},
     height: nil,
-    width: nil
+    width: nil,
+    wrap: false
   )
 
-  def new_board(height, width) do
+  def new_board(height, width, :wrap), do: _new_board(height, width, true)
+  def new_board(height, width, :no_wrap), do: _new_board(height, width, false)
+
+  defp _new_board(height, width, wrap) do
     %__MODULE__{
       height: height,
       width: width,
+      wrap: wrap,
     }
   end
 
@@ -16,6 +21,15 @@ defmodule Cartographer.Board do
     x >= 0 and x < width and y >= 0 and y < height
   end
 
+  def teleport(%__MODULE__{:height => height, :width => width}, x, y) do
+    {_teleport(x, width), _teleport(y, height)}
+  end
+
+  defp _teleport(n, range) when n >= range, do: rem(n, range)
+  defp _teleport(n, range) when rem(n, range) == 0, do: 0
+  defp _teleport(n, range) when n < 0, do: range + rem(n, range)
+  defp _teleport(n, _range), do: n
+
   def coordinate_range(center_x, center_y, range) do
     for x <- (center_x - range)..(center_x + range), y <- (center_y - range)..(center_y + range), do: {x, y}
   end
@@ -29,12 +43,18 @@ defmodule Cartographer.Board do
     Map.get(board.tiles, {x, y})
   end
 
-  def get(board, center_x, center_y, range) do
+  def get(board = %{wrap: false}, center_x, center_y, range) do
     coordinate_range(center_x, center_y, range)
     |> Enum.filter(fn({x, y}) -> in_bounds(board, x, y) end)
     |> Enum.reduce(%{}, &(Map.put(&2, &1, Map.get(board.tiles, &1))))
   end
 
+  def get(board = %{wrap: true}, center_x, center_y, range) do
+    coordinate_range(center_x, center_y, range)
+    |> Enum.map(fn({x, y}) -> teleport(board, x, y) end)
+    |> Enum.reduce(%{}, &(Map.put(&2, &1, Map.get(board.tiles, &1))))
+  end
+
   def set(board, x, y, data) do
     in_bounds(board, x, y)
     |> _set(board, x, y, data)
@@ -50,10 +70,17 @@ defmodule Cartographer.Board do
 
   defp _set(_not_in_bounds, board, _x, _y, _data), do: board
 
-  def neighbors(board, center_x, center_y) do
+  def neighbors(board = %{wrap: false}, center_x, center_y) do
     coordinate_range(center_x, center_y, 1)
     |> List.delete({center_x, center_y})
     |> Enum.filter(fn({x, y}) -> in_bounds(board, x, y) end)
     |> Enum.reduce(%{}, &(Map.put(&2, &1, Map.get(board.tiles, &1))))
   end
+
+  def neighbors(board = %{wrap: true}, center_x, center_y) do
+    coordinate_range(center_x, center_y, 1)
+    |> List.delete({center_x, center_y})
+    |> Enum.map(fn({x, y}) -> teleport(board, x, y) end)
+    |> Enum.reduce(%{}, &(Map.put(&2, &1, Map.get(board.tiles, &1))))
+  end
 end